Citation
Development of a toxic bait for control of mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus)

Material Information

Title:
Development of a toxic bait for control of mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus)
Creator:
Kepner, Rodney Leon, 1957-
Publication Date:
Language:
English
Physical Description:
vi, 81 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Corn cobs ( jstor )
Dyes ( jstor )
Insects ( jstor )
Molasses ( jstor )
Mortality ( jstor )
Pastures ( jstor )
Plugs ( jstor )
Rain ( jstor )
Soybeans ( jstor )
Stimulants ( jstor )
Crickets -- Control ( lcsh )
Dissertations, Academic -- Entomology and Nematology -- UF
Entomology and Nematology thesis Ph. D
Mole crickets -- Control ( lcsh )
City of Gainesville ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 1985.
Bibliography:
Bibliography: leaves 74-80.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Rodney Leon Kepner.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
The University of Florida George A. Smathers Libraries respect the intellectual property rights of others and do not claim any copyright interest in this item. This item may be protected by copyright but is made available here under a claim of fair use (17 U.S.C. §107) for non-profit research and educational purposes. Users of this work have responsibility for determining copyright status prior to reusing, publishing or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder. The Smathers Libraries would like to learn more about this item and invite individuals or organizations to contact the RDS coordinator (ufdissertations@uflib.ufl.edu) with any additional information they can provide.
Resource Identifier:
020913125 ( ALEPH )
13351056 ( OCLC )

Downloads

This item has the following downloads:


Full Text

PAGE 1

DEVELOPMENT OF A TOXIC BAIT FOR CONTROL OF MOLE CRICKETS (ORTHOPTERA: GRYLLOTALPIDAE: Scapteriscus) BY RODNEY LEON KEPNER A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1985

PAGE 2

ACKNOWLEDGEMENTS I am deeply indebted to Dr. S. S. J. Yu, Associate Professor of Entomology and Nematology and chairman of my supervisory committee, for his constant encouragement and guidance throughout the course of my research. I would like to also thank the other members of my supervisory committee. Dr. S. H. Kerr and Dr. M. Wilcox, for their constructive review of this dissertation. I wish to thank A. J. Thompson for his cooperation and assistance in field trials. I thank Greg Piepel, Partha Lahiri and Will Hudson for their assistance in statistical analysis. I am grateful to Jane Medley for her help with illustrations and Glinda Burnett for typing this dissertation. Finally, I give special thanks to my parents for their endless encouragement, understanding and support that has made all my efforts at the University of Florida possible. ii

PAGE 3

TABLE OF CONTENTS Page ACKNOWLEDGEMENTS " . ii ABSTRACT v INTRODUCTION 1 LITERATURE REVIEW 3 MATERIALS AND METHODS 9 Test Insects 9 Feeding Stimulants 9 Agar Plug Assay 9 Dye Impregnated Bait Assay 11 Carriers 19 Acceptance Trials 19 Efficacy Tests 20 Toxicants 20 Field Tests 21 Field Bucket Trials 21 Field Tests 22 Field Persistence 22 Bait Weathering 22 Chemical Analysis 24 Bioassays 26 Bait Acceptance 26 RESULTS 27 Feeding Stimulants 27 iii

PAGE 4

Agar Plug Assay 27 Dye Impregnated Bait Assay 41 Carriers 41 Bait Acceptance 41 Carrier Efficacy Trials 48 Toxicant 48 Field Tests 48 Field Bucket Trials 48 Field Tests 52 Field Persistence 52 Chemical Analysis 52 Bioassay 58 Bait Acceptance 58 DISCUSSION 62 APPENDIX 70 REFERENCES 74 BIOGRAPHICAL SKETCH 81 iv

PAGE 5

Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fullfillment of the Requirements for the Degree of Doctor of Philosophy DEVELOPMENT OF A TOXIC BAIT FOR CONTROL OF MOLE CRICKETS (ORTHOPTERA: GRYLLOTALPIDAE: Scapteriscus ) By Rodney Leon Kepner August, 1985 Chairman: Dr. S. J. Yu Major Department: Entomology and Nematology Several species of mole crickets in the genus Scapteriscus are considered the most destructive insect pests of turf and pasture grass in Florida. In pasture situations, chemical control is limited to treatments with toxic baits. However, treatments with available formulations have not always been effective and reports of poor control are numerous. Studies were conducted to develop an effective bait formulation for control of pest mole cricket species in Florida. Specific aspects investigated were feeding stimulants, carriers, toxicants, application rates, and field persistence. Bait composition studies showed that mole crickets, Scapteriscus vicinus and S^. acletus share similar responses to several feeding stimulants and bait carriers. Crude cottonseed oil or refined soybean oil, in combination with sucrose, were the most effective feeding stimulants tested. Other materials found significantly stimulating include Coax, malt extract, and brewers concentrate. Molasses and amyl V

PAGE 6

acetate, though presently reconnnended as bait attractants, did not enhance bait consumption by either species. Laying mash and finely cracked corn were the most acceptable bait carriers evaluated. Toxicity trials with malathion bait formulations established that a 4% bait was significantly more efficacious than the 2% bait presently recommended. A malathion 4% bait formulated from crude cottonseed oil (5%) and sucrose (10%) on a laying mash carrier was significantly more efficacious than several commercial bait formulations in small-scale field trials. Malathion bait was highly efficacious (>80% control) at 0.56, 1.12, and 2.24 kg Al/ha indicating that substantial reductions (50-75%) in the use of malathion can be made compared to current label recommended rates (1.12-2.24 kg Al/ha) . Full-scale field trials at 0.56 and 1.12 kg Al/ha in heavily infested bahiagrass pastures gave >90% control lasting as long as two months. Field tests suggest that season long control may be achieved with a single application. Field persistence studies determined that malathion bait retained half its malathion content and effectiveness for as long as 28 days. Loss of bait efficacy was due to loss of bait acceptability rather than bait toxicity. Rainfall and evaporation were major factors responsible for loss of malathion residues from the bait formulation. vi

PAGE 7

INTRODUCTION Several species of mole crickets in the genus Scapteriscus are considered major pests of turf, pasturegrass , and vegetable and field crops throughout the southeastern United States. In 1980, $11.7 million was spent in Florida on insecticides alone in an attempt to control these pests. It is estimated that in the same year mole crickets caused $35 million damage based on total costs of control and losses (Southern, 1983). Although they cause damage in vegetable and tobacco seed beds, mole crickets are considered the most destructive insect pests of turf and pasturegrass in Florida. Bahiagrass is one of the most popular pasture and turf grasses and is the preferred host for mole crickets. There are approximately 400,000 hectares of turf and 4.4 million hectares of pasturegrass in Florida. Statewide surveys have indicated that as much as 30% of bahiagrass has been heavily damaged by mole crickets, and in several areas virtually 100% of the bahiagrass in pastures has been severely damaged (Reinert and Short, 1981; Reinert et al. , 1981). In some instances, cattle producers have had to reduce their number of cattle by up to 30% due to this loss of forage (J. Rawls, personal communication) . With turfgrass a highly valued commodity in a touristoriented economy and pasturegrass integral to a large livestock industry, mole crickets are one of Florida's most serious economic pests. Presently chemical treatments are the only effective method of controlling mole crickets. Control consists of soil treatments with 1

PAGE 8

2 insecticidal granules or sprays and surface applications with toxic baits. In pasture situations, chemical control is limited to baits since irrigation and/or soil incorporation are not practical. Baits offer the most cost effective and ecologically sound use of insecticides available. But control by baiting has not always been effective, and complaints of poor control are numerous (Koehler et al. , 1979). With the cost of chemical control increasingly more expensive, growers cannot afford ineffective treatments and be left with no alternatives. The objective of this research was to develop an optimal bait formulation for control of mole crickets. Specific aspects to be studied were feeding stimulants, carriers, toxicants, application rates and field persistence.

PAGE 9

LITERATURE REVIEW Three pest species of mole crickets are known to occur in Florida. There is the tawny mole cricket, Scapteriscus vicinus (Scudder) , the southern mole cricket, S^. acletus (Rehn and Hebard) , and the short winged mole cricket, S. abbreviatus (Scudder). A fourth species, the northern mole cricket, Neocurtilla hexadactyla (Perty) , is native to Florida and is not of pest status. The genus Scapteriscus is not considered native to the United States. Walker and Nickle (1981) examined the introduction of pest mole cricket species and concluded that S^. vicinus and S^. acletus were introduced into Brunswick, Georgia, ca. 1899 and 1904, respectively. Subsequent introductions and spread have resulted in infestations throughout much of the southeastern United States. Scapteriscus abbreviatus was introduced at several ports along coastal Florida between 1899 and 1912. Due to their flightless nature, dispersal has been limited and this species is not found far from initial ports of entry. Much of the mole cricket literature has been concerned with control. Numerous remedial control measures of limited value have been proposed by Barrett (1902), Worsham and Reed (1912), and Van Zwaluwenburg (1918). These include such methods as protective barriers around plants, light and pitfall traps, cultivation, and flooding. More recently sound trapping has been proposed for controlling mole crickets (Ulagaraj and Walker, 1973), but recent studies have shown little promise (Ngo and Beck, 1982). 3

PAGE 10

4 Chemical control has been the most effective method for controlling mole crickets throughout the literature. Repellents such as sulfur and naphthalene have offered satisfactory control though naphthalene treatments were short lived (Barrett, 1902; Worsham and Reed, 1912; Van Zwaluwenburg , 1918; Kelsheimer, 1945). Soil applications of kerosine and orthodichlorobenzene have been shown effective but were phytotoxic at effective doses (Barrett, 1902; Van Zwaluwenburg, 1918; Callan, 1945). Fumigation with carbon bisulfide or sodium and calcium cyanide was employed with moderate success until the 1940s (Barrett, 1902; Van Zwaluwenburg, 1918; Thomas, 1926; Watson, 1939; Brooks, 1947). More recently ethylene dibromide was found effective on mole crickets (D. E. Short, personal communication) but all uses were cancelled by the Environmental Protection Agency in 1984. After the development of synthetic insecticides in the 1940s, chemical control almost exclusively consisted of soil treatments with chlorinated hydrocarbon insecticides such as DDT (Kelsheimer, 1945) and chlordane (Kelsheimer, 1947). Later, soil applications with lindane (Hayslip, 1948), aldrin (Kelsheimer and Kerr, 1957), parathion (Guthrie et al., 1958), heptachlor (Tappan, 1963) and kepone (Kerr, 1966) were recommended and used effectively to control mole crickets. Due to problems with environmental persistence, these compounds were removed from use in the early 1970s. Presently propoxur, diazinon, ethoprop, and isofenphos are the only soil treatments registered for mole crickets in Florida (Kepner, 1984). However, their use is limited to non-forage crops . Poison baits are one of the oldest and most widely recommended methods for controlling mole crickets. Their use has been documented as

PAGE 11

5 early as 1902 in Puerto Rico (Barrett, 1902) and 1909 in Georgia (Worsham, 1909). Recommended formulations have changed over the years but baits are generally composed of three basic components: toxicants, carriers and attractants (feeding stimulants, true attractants) . A major portion of the literature concerning mole cricket baits pertains to toxicants. Paris green (Barrett, 1902; Van Zwaluwenburg , 1918), lead arsenate (Worsham and Reed, 1912; Watson, 1925), calcium arsenate (More, 1924; Thomas 1926; Watson, 1934), barium fluosilicate (Kassab, 1939; Callan, 1945), sodium fluosilicate (Annand, 1942), chlordane (Wisecup and Hayslip, 1953; Kelsheimer and Kerr, 1957), toxaphene (Habeck and Kuitert, 1964) and kepone (Beck and Skinner, 1967) have all been effective in bait formulations until restricted from use. Presently propoxur 2% bait, chlorpyrifos 0.5% bait, malathion 2% bait, trichlorfon 5% bait, and carbaryl 20% bait are labeled for mole crickets in Florida (Kepner, 1984). The latter three are the only chemical treatments registered for control in pastures. The efficacy of bait toxicants has generally been based on counting post-treatment surface mortality (Habeck and Kuitert, 1964; Beck and Skinner, 1967; Short and Driggers, 1973; Koehler and Short, 1976a; 1976b; Short and Koehler, 1977). Worsham and Reed (1912) first observed that the majority of mole crickets killed by baiting died below the surface and that true bait efficacy is difficult to evaluate using surface mortality. Ulagaraj (1974), Walker (1979), and Green et al. (1984) have all demonstrated that surface counts do not reveal the true efficacy of bait treatments due to this high percentage of subsurface mortality. Green et al. (1984) evaluated a variety of insecticides in bait form using total surface/subsurface mortality and determined that

PAGE 12

6 diazinon, trlchlorfon, and chlorpyrlfos were the most toxic to S. vlcinus and acletus . Ismalov and Rustamova (1981) also used total mortality to evaluate baits and found cypermethrin, fenvalerate and deltamethrin highly effective against the mole cricket Gryllotalpa gryllotalpa . Numerous materials have been added as attractants to poison baits in hopes of luring crickets and ensuring bait consumption. Barrett (1902) believed that the addition of sugar water slightly enhanced bait efficacy and Worsham and Reed (1912) advocated the addition of "syrup" (molasses) to make baits more tempting. Molasses was first added to insecticidal baits in the 1890s to adhere arsenic to wheat bran for grasshopper control but later was believed to have attractive properties (Morrill, 1919). Molasses has been a standard component in mole cricket baits since the early 1900s (Watson, 1921; More, 1924; Thomas, 1928; Schroeder, 1941; Wisecup and Hayslip, 1953; Koehler and Short, 1976b). Grasshopper bait formulations incorporating citrus pulp (juice) as an attractant were used to control mole crickets until the 1930s (Watson, 1915; 1925; 1934; 1938). Citrus juice was believed to be an attractive flavoring for mole crickets (Watson, 1925). Meat scraps were also found to be a promising bait attractant (Annand, 1941). There are conflicting reports throughout the literature concerning the advantage of incorporating various materials as attractants in mole cricket baits. Van Zwaluwenburg (1918) claimed that the addition of salt, molasses, citrus juice, or honey did not increase bait efficacy and only made baits unnecessarily attractive to ants, fowl, and domestic animals. Schroeder (1941) claimed that the addition of molasses and other sweeteners did not enhance the efficacy of bran bait sufficiently

PAGE 13

7 to justify additional costs based on field tests. Hayslip (1943) claimed that honey, corn and cane syrup increased the attractiveness of some baits but not of wheat bran. Wisecup and Hayslip (1953) found that stable manure, tankage, dried blood, and meat scraps, although believed attractive to mole crickets, did not increase the effectiveness of wheat bran baits. Presently, amyl acetate (Koehler and Short, 1976a) and molasses (Koehler and Short, 1976b) are used as bait attractants but little is known of their added effect. Recent research concerning bait additives has offered some preliminary results. Kepner (1981) evaluated over 45 different food type materials as attractants for both £. vicinus and S^. acletus . No materials were found attractive to S^. vicinus but rancid hamburger meat and fish meal were slightly attractive to S^. acletus . He concluded that olfactory perception was probably of limited importance in food location and that bait additives acted more as feeding stimulants rather than true attractants. Walker (1979) evaluated molasses and malt extract as feeding stimulants and demonstrated that they both induce feeding by S. acletus . In field trials, malt extract was shown to increase the efficacy of a sawdust-malathion 2% bait based on surface mortality (W. Stackhouse and S. Walker, personal communication). Research concerning bait carriers has also been limited. Materials such as chopped grass (Barrett, 1902), wheat bran, corn meal, cottonseed meal (Worsham and Reed, 1912), flour (Watson, 1915), egg mash (Watson, 1934), crushed rice (Kassab, 1939), lespezeda meal (Watson, 1939), commercial dog food (Watson, 1941), rice bran (Callan, 1945), oatmeal (Wisecup and Hayslip, 1953), horse manure (Chao, 1975), peanut hulls and wheat shorts (Koehler and Short, 1976a) have all been utilized as

PAGE 14

8 carriers but evidence of their relative acceptance by mole crickets is inadequate. Worsham and Reed (1912) believed that mole crickets preferred cottonseed meal baits to those of wheat bran or corn meal and Van Zwaluwenburg (1918) claimed that flour was preferred to all three materials. Madden (1937) refuted this later claim and established that wheat bran bait was more efficacious than flour bait. Watson (1934) believed that egg mash was a more effective carrier than wheat bran and Wisecup and Hayslip (1953) claimed that wheat bran was more efficacious than corn meal, rice flour, oatmeal and wheat flour. More recently, a malathion 2% bait formulated from either sawdust and malt, corn cob grits and malt, or corn cob grits and molasses sometimes proved equally efficacious compared to a standard bait formulated from laying mash and molasses in field tests (W. Stackhouse and S. Walker, personal communication). Ismalov and Rustamova (1981) found "vegetable baits" to be effective when formulated with pyrethroid insecticides.

PAGE 15

MATERIALS AND METHODS Test Insects All experiments utilized adult female S^. vicinus and S^. acletus or late instar S^. vicinus nymphs collected from the field. Adults were captured by sound trapping with an artificial cricket as described by Walker (1982). Late instar nymphs were collected from bahiagrass pastures by using linear pitfall traps modified from Lawrence (1982). All crickets were held in the laboratory for several days prior to testing in 13 or 19 1 plastic buckets filled with moist soil at a density of 30 and 50 crickets/bucket, respectively. Crickets were fed a diet of ground Purina Dog Chow and maintained at laboratory test conditions: 25 °C and a 14:10 light: dark photoperiod. Due to storage limitations, some insects were held outdoors in 1.5 m diameter plastic wading pools filled with soil at a density of 200 crickets/pool. When needed, crickets were flushed from the soil with water and then conditioned in the laboratory as just described. Feeding Stimulants Agar Plug Assay Several methods have been used to assay chemicals as feeding stimulants for insects. These generally involve the presentation of test chemicals in/on an inert medium such as elder pith (Cook, 1977; Norris and Baker, 1967; Ritter, 1967), filter paper (Thorsteinson and Nayar, 1963; Wensler and Dudzenski, 1972; Stacey et al., 1977), styropor 9

PAGE 16

10 (Meisner and Ascher, 1968; Meisner et al., 1972; Ascher and Nemny, 1981), or agar/cellulose (Hsiao and Fraenkel, 1968; Ma, 1972; Beck, 1956) . Feeding activity is usually based on some measurement of consumption. Preliminary studies determined that a 2% agar/2% cellulose medium was readily consumed by mole crickets when known feeding stimulants were incorporated. A method was therefore developed from that of Hsiao and Fraenkel (1968) that used agar plugs to evaluate various nutrient chemicals and bait additives as feeding stimulants for mole crickets. Agar plugs were prepared by mixing test compounds (w/v) in hot 2% agar/2% cellulose solution. Fifty ml of hot medium were poured into glass petri plates (20 x 100 mm) and allowed to gel on ice. Small plugs (12 mm diameter) were then cut with a cork borer and individually weighed (initial wet weight). Tween 80 (0.1%) was used as a surfactant in preparations with lipid soluble compounds. Crickets were placed in individual glass petri plates (20 x 100 mm) and starved 24 hours. Agar plugs were offered on 2.5 cm squares of aluminum foil in no-choice experiments for 18 hours. Water was made available throughout the entire test period in the form of moist cotton. After crickets had fed, plugs were dried on wax paper for 24 hours at 55 °C and final dry weight was determined. From controls, percent water content was determined and used to reexpress dried plug weight as final wet weight. This technique eliminated any weight loss caused by evaporation during testing. Feeding response was expressed as wet weight consumed per cricket. For each compound, treatments were replicated 10-15 times per concentration depending on availability of crickets. Each concentration was compared to the control by using the 2-sample t-test. Those feeding stimulants found most promising were further evaluated in comparison tests.

PAGE 17

11 Results were analyzed by analysis of variance and means separated by the Waller-Duncan K-ratio procedure. Dye Impregnated Bait Assay To further evaluate compounds found most promising in agar plug assays, a method was developed to test feeding stimulants on an actual bait carrier. A modification of the method described by Daum et al. (1969) was employed using a granular bait impregnated with 0.1% Calco Oil Red N-1700 dye. Bait consumption was based on the amount of dye ingested as determined photometrically. The absorbance spectrum for Calco dye was measured on a Beckman Model 5260 uv/vis spectrophotometer (Figure 1). A maximum absorbance of 516 nm was determined and this was used in all dye measurements. Bait was prepared by mixing 10 gms corn cob grits (12-14 mesh) with 10 mg dye dissolved in 10 ml acetone under a ventilated hood until all acetone had evaporated. Feeding stimulants, dissolved in 10 ml water, were then incorporated into the bait on a w/w basis and air dried for several hours prior to testing. Tween 80 (0.1%) was used as a surfactant in preparations containing lipid soluble compounds. Experiments were conducted in the laboratory in 473 ml plastic cups filled with 250 ml dry builders sand moistened with 60 ml distilled water. This technique was used to simulate as natural an environment as possible in the laboratory. Individual adult mole crickets were placed in cups and starved 24 hours. Plastic snap-sealing lids perforated with seven 6 mm diameter holes prevented escape and allowed for ventilation. Several hundred milligrams of bait were sprinkled over the sand surface in each cup. Crickets were allowed to feed beginning at darkness and were removed after eight hours and immediately frozen at -20 °C.

PAGE 18

12 30Nvaaosav

PAGE 19

13 Crickets were later dissected and the entire digestive tracts removed. Guts were macerated with forceps and the dye was extracted with three separate five ml aliquots of acetone shaken for 15 minutes each. The total extract was passed through Whatman No. 1 filter paper and the final volume determined. Color intensities were measured on a Turner Model 330 spectrophotometer at 516 nm and converted to micrograms dye by use of a standard curve (Figure 2) . Concentrations of dye in the bait were also measured in this way and results were used to express the amount of dye extracted as milligrams bait ingested per cricket. Each treatment was replicated four times with five crickets each. Results were analyzed by analysis of variance and means were separated by the Waller-Duncan K-ratio procedure. Effect of dye on feeding . The effect of dye concentration on feeding response of adult S^. acletus was evaluated. Corn cob grit baits incorporating 15% malt extract (w/w) and impregnated with 0.05, 0.1, 0.2 and 0.4% Calco dye were tested in sand-filled plastic cups as described above. Treatments were replicated four times with five crickets each. Mean bait consumption was determined and results were analyzed by regression analysis. There was no correlation between mean bait consumption and dye concentration. However, some mortality was observed at 0.4%. From these results 0.1% was selected for further studies. To determine if Calco dye had a repellant or stimulant effect on feeding, 0.1% dye was incorporated into agar /cellulose medium containing 5% crude cottonseed oil and 10% sucrose (w/v) . Feeding response of adult S_. acletus was measured by using the agar plug assay described earlier. The 0.1% concentration was found not to have any significant effect on agar consumption when compared to controls.

PAGE 20

1.0 5 10 CONCENTRATION (UG/ML) Figure 2. Standard curve and regression equation for Calco Oil Red N-1700.

PAGE 21

15 Egestion time. To determine how long crickets could be allowed to feed before dye was lost through egestion, twenty adult female S_. vicinus were individually placed in glass petri plates (100 x 20 mm) and starved 24 hours. Cracked corn bait (12-14 mesh) impregnated with 0.1% Calco dye, 5% crude cottonseed oil, and 10% sucrose (w/w) was offered beginning at darkness. Water was made available throughout the test period in the form of moist cotton. Crickets were allowed to feed undisturbed for 5 hours and then placed in clean petri plates. Plates were checked every hour up to 14 hours post-feeding for presence of fecal material. When feces were present, crickets were placed in clean plates and the hour noted. Fecal material was extracted with 4 ml acetone and the presence of dye determined photometrically. Crickets fed uncolored bait were used as controls. Dye was observed in feces no earlier than 9-10 hours post-feeding. Based on these observations, bait feeding experiments were terminated within 8 hours to prevent loss of dye through egestion. Duration of feeding . The duration of feeding In bait assays was determined. Cracked corn bait (12-14 mesh) impregnated with 0.1% Calco dye, 5% crude cottonseed oil, and 10% sucrose (wt/wt) was individually offered to 80 adult female ^. vicinus in sand-filled plastic cups. Four groups of five crickets each were randomly selected and removed at two hour intervals for up to eight hours post-feeding. Guts were dissected and bait consumption was measured as described earlier. Mole crickets reached maximum consumption within four hours after which no significant increase in feeding was observed. Based on these results, eight hours exposure allows adequate time for all crickets to feed and does not affect the amount of bait consumed.

PAGE 22

16 Metabolism of dye . House flies have been shown to metabolize azo dye with microsomal azoreductase which requires NADPH under anaerobic conditions (Shargel et al., 1972). Since Calco Oil Red N-1700 is an azo dye (Figure 3) , experiments were conducted to determine if Calco dye is metabolized by mole crickets. Adult S_. acletus were dissected and entire digestive tracts removed. Guts were washed free of contents and rinsed in ice cold 1.15% KCl. Pooled tissue samples from eight individuals were homogenized in 20 ml ice cold O.IM sodium phosphate buffer, pH 7.5, in a motor-driven tissue grinder for 30 seconds. The crude homogenate was filtered through cheese cloth and used immediately as an enzjnne source. Each of three incubation tubes contained a mixture of 5 ml crude homogenate (equivalent to two guts), 400 ug Calco dye dissolved in 0.1 ml methyl cellosolve, and an NADPH generating system consisting 1.8 umol of NADP, 18 umol of glucose-6-phosphate, and 1 unit of glucose-6-phosphate dehydrogenase. The mixtures were incubated at 30°C in an atmosphere of nitrogen for 60 minutes. The reaction was stopped with 10 ml ethyl acetate and the dye extracted by shaking the tubes for one hour. Extracts were measured at 516 nm in a Turner Model 330 spectrophotometer and the total amount of dye was compared to controls incubated with boiled enzyme. Crude whole gut homogenate metabolized approximately 15% of the azo dye. This indicates a potential loss of Calco dye in bait feeding experiments due to metabolism by azoreductase. Absorption of dye . Calco dye has been shown to be absorbed from the diet into fat body of boll weevils (Cast and Landin, 1966), tobacco budworm larvae (Hendricks and Graham, 1970), and pink bollworm larvae (Graham and Mangum, 1971). To determine if Calco dye is absorbed from

PAGE 24

18 bait ingested by mole crickets, adult S. acletus were fed a cracked corn bait (12-14 mesh) impregnated with 0.1% Calco dye, 5% crude cottonseed oil, and 10% sucrose (w/w) in sand-filled cups as described earlier. After eight hours feeding, the entire digestive tracts of five individuals were carefully dissected and discarded. The remaining carcasses were ground in 25 ml acetone in a large mortar and pestle. The ground tissue and acetone rinse were placed in a soxhlet extractor and the tissue extracted with 150 ml acetone for four hours. The solvent exchange rate was three times per hour. Cooled extract was condensed to 15 ml in a Rinco evaporator and then absorbance measured at 516 nm. Tissue extracts from treated crickets were compared to extracts from crickets fed uncolored bait. There was no evidence of dye in tissue from treated individuals indicating no significant loss of dye through absorption in mole crickets. Percent dye recovery . The percent recovery of Calco dye from a corn cob grit carrier was determined. To each of three tissue culture tubes were added 100 mg corn cob grits (12-14 mesh) and 100 ug Calco dye dissolved in 5 ml acetone. Contents were evaporated to dryness under a gentle stream of air. Calco dye was extracted with three separate five ml aliquots of acetone shaken for 15 minutes each. The total extract was passed through Whatman No. 1 filter paper and the total amount of dye measured on a Turner Model 330 spectrophotometer at 516 nm. Total dye extracted was compared to controls (100 ug dye in 5 ml acetone). Percent recovery for corn cob grits was 96.9% and final results for bait feeding experiments were corrected for this. To determine percent recovery from gut tissue, 5 macerated guts from adult acletus were added to the mixture. There was no difference

PAGE 25

19 in percent recovery when guts were present compared to controls without them. Results indicate there is no significant binding (adsorption) of dye by gut tissue in mole crickets. Carriers Acceptance Trials Carriers were evaluated by the dye impregnated bait assay described earlier. The only difference was that the feeding stimulant component remained constant. In addition to measuring bait consumption on a per cricket basis, percent acceptance was determined. Colored bait could easily be observed in the crop during dissections. The percentage of crickets with colored food present in the crop was used as a measure of percent acceptance. Ten different carrier-type materials (12-14 mesh) were evaluated for acceptance both with and without incorporation of a feeding stimulant. Four replicates of five crickets each were used per treatment. Percent dye recovery was determined for each carrier and corrected f or in the final results (see appendix) . Percent acceptance was transformed arcsin 100 prior to analysis. Results were analyzed by analysis of variance and means separated by Waller-Duncan K-ratio procedure. Based on feeding stimulant and carrier acceptance trials, both S. vicinus and S^. acletus show similar responses. Additionally, bait efficacy studies by Green et al. (1984) indicate these two species also share similar toxicity responses to a variety of insecticides. Therefore, based on these observations, only one species was used as a model for further laboratory studies. Scapteriscus acletus was chosen as the model since it is easy to work with and thrives in captivity.

PAGE 26

20 Efficacy Tests From bait acceptance trials, laying mash, cracked corn, and wheat bran were found to be the three most acceptable carriers tested for both species. To further differentiate among these materials, efficacy was tested by the method of Green et al. (1984). A malathion 2% bait was formulated from each of the three carriers with technical grade malathion (96% active ingredient), crude cottonseed oil (5%) and sucrose (10%). Experiments were conducted in 473 ml plastic cups filled with 250 ml dry builders sand moistened with 60 ml water. Individual adult female S^. acletus were introduced into cups and starved 24 hours. Baits were offered on the sand surface at a rate of 2.24 kg Al/ha and treatments were replicated three times with 10 crickets each. Cups were covered with plastic snap-sealing lids perforated with seven 6 mm diameter holes to prevent escape and allow for ventilation. Tests were conducted for 72 hours and total mortality (surface/subsurface) determined. Crickets offered non-toxic bait were used as controls and mortality was corrected by Abbott's formula (Abbott, 1925). Analysis of variance was performed on the arcsinN/%/100 transformation and means were separated by the Waller-Duncan K-ratio procedure. Toxicants Malathion was chosen as an optimal toxicant due to its known toxicity to mole crickets, low cost, low mammalian toxicity, short environmental persistence, and its present registration for mole crickets on turf and pasture. A dose-mortality curve for adult female S. acletus was determined by the testing procedures described in carrier efficacy trials. Based on feeding stimulant and carrier evaluations, malathion bait was formulated on a laying mash carrier (12-14 mesh)

PAGE 27

21 impregnated with 5% crude cottonseed oil and 10% sucrose. Each treatment was applied at 56 kg formulation/ha and replicated four times with 10 crickets each. Probit analysis was performed and a log dose-probit regression equation determined by using the SAS Probit procedure (Ray, 1982). Field Tests Field Bucket Trials From toxicant studies, a malathion 4% bait was found to give 80-90% control. To evaluate the effect of application rate and compare malathion A% bait to several commercial bait formulations under field conditions, efficacy was tested outdoors in 19 1 plastic flower pots (30 cm dia.) by the method of Green et al. (1984). Several drainage holes in the bottom of each bucket were covered with 18 mesh aluminum screen to prevent escape. Buckets, buried at ground level, were filled with top soil and covered with 18 mesh fiberglass screen secured with a large rubber band. Eight adult female S^. acletus , were introduced into individual buckets and starved 24 hours. The malathion 4% bait was tested at rates of 0.56, 1.12, and 2.24 kg Al/ha and commercial baits were tested at label recommended rates. Treatments were replicated four times and total mortality (surface/subsurface) was determined after 72 hours. Several crickets often found missing from buckets were assumed dead based on studies by Green et al. (1984). Four untreated buckets were used as controls and mortality was corrected by Abbott's formula (Abbott, 1925). Analysis of variance was performed on the arcsin V'%/100 transformation and means were separated by the Waller-Duncan K-ratio procedure.

PAGE 28

22 Field Tests The malathion A% bait was tested in several heavily infested bahlagrass pastures at the A. J. Thompson farm near Grove Park, Florida. Linear pitfall traps (Figure 4), modified from Lawrence (1982), were used to monitor mole cricket population levels before and after treatments. Each trap consisted of a central 19 1 plastic bucket partially buried in the soil. Four 3 m long sections of 7.6 cm diameter plastic drainage pipe were buried at soil level radiating out from the central bucket at 90° angles. A 2.5 cm slot was cut along the length of each pipe and served as a pitfall. End caps and a bucket lid prevented crickets from escaping and kept soil from drying out. Crickets caught in the trap worked themselves into the central bucket and were counted the following day. A malathion 4% bait was prepared by mixing 1.9 1 malathion 5EC (4%), 1.5 1 crude cottonseed oil (5%), and 4.5 1 sugar water (600 gm sucrose/1 water) (10%) in a small hand sprayer. This mixture was sprayed onto 22.7 kg of laying mash in a slowly turning cement mixer. Bait was broadcast at rates of 0.56 and 1.12 kg Al/ha with a tractor mounted fertilizer spreader. Two or three traps were placed in each of three 4 ha fields and monitored for a 2-3 week period both before and after treatment. Relative mole cricket populat ion levels were based on mean 24 hour catch. Field Persistence Bait Weathering Malathion bait was weathered in 60 x 60 cm trays constructed of fine nylon cloth stretched over a frame of 5 x 5 x 60 cm pine boards

PAGE 29

23

PAGE 30

24 (Figure 5). A 4% bait was prepared as described in carrier efficacy trials. Trays were placed flat on a 10 cm layer of clean yellow sand and bait was spread in a thin monolayer in each of the trays. This allowed the bait to be in direct contact with the soil yet allowed for 2 easy collection of clean samples. A 3700 cm section of 6 mm hardware cloth was placed over the top of each tray to prevent birds and other small animals from consuming bait. To eliminate the effect of rainfall, half the trays were covered with clear polyethylene plastic (4 mil) secured over a 1.25 cm PVC pipe frame. A 15 cm gap was left between the ground and the bottom edge of the plastic to allow for ventilation. Samples were collected weekly for eight weeks and environmental conditions were monitored from a weather station on the University of Florida Agronomy farm a few hundred meters from the test site. Fresh bait and weekly samples were held at -20 °C until analysis. Chemical Analysis A 500 mg sample of bait was dried in an oven at 70°C for 24 hours to determine dry weight. Malathion was extracted with 10 ml reagent grade acetone by shaking the mixture for one hour. A 100 ul aliquot was diluted 5000X in hexane and analyzed on a Varian Model 3740 gas chromatograph equipped with a thermionic specific detector. The column used was a 6 ft X 2 mm glass column packed with 2% OV-101 on 80-100 mesh UltraBond 20M. The operating conditions were column, 185°C; injection port, 200°C; detector, 250°C; nitrogen carrier gas, 30 ml/min; air, 175 ml/min; and hydrogen, 4.5 ml/min. In experiments with malathion fortified laying mash, 100% recovery was observed. There was no loss of malathion from heating at 70°C for 24 hours. Residues were expressed as mg malathion/gm dry bait. Final results for both covered and uncovered

PAGE 31

25

PAGE 32

26 bait were expressed as a percent of control malathion using fresh bait as a standard. Extractions were replicated 3-5 times per sample and regression analysis was performed on the arcsin 100 transformation. Bioassays Weathered samples from uncovered bait were tested for efficacy by the method described in carrier efficacy trials. Bait was air dried several hours before testing and applied at 56 kg formulation/ha to four replicates of 10 crickets each. Percent mortality was transformed to arcsin V'%/100 and correlated with malathion residues, cumulative rainfall, and time by regression analysis. Bait Acceptance : To evaluate the loss of bait acceptability, an acceptance index was defined as a ratio of observed vs. predicted mortality. The equation log(% mortality) = 0.27 + 0.47 log concentration (bait concentration x 2 1000), r = 0.97, was fit to dose-mortality data for malathion bait in earlier toxicant studies. This was used to predict mortality based on malathion residues from chemical analysis. Results from weathered bait bioassays were used as observed mortality. Percent acceptance was transformed to arcsin V%/ 100 and correlated with time and cumulative rainfall by regression analysis.

PAGE 33

RESULTS Feeding Stimulants Agar Plug Assay S. vicinus. Sucrose significantly enhanced feeding response at concentrations of 5, 10, and 20%. Glucose, fructose, maltose and lactose did not stimulate feeding but melibiose did elicit a significant response at 10% (Table 1). In Tables 2-3, no fatty acids or amino acids induced feeding at concentrations tested. Bait additives, malt extract and Coax (commercial insect feeding stimulant) enhanced feeding activity at 1, 5, 10, and 20% (Table 4). Brewers concentrate (brewery by product) was effective at 5, 10, and 20%, and blackstrap molasses at 10 and 20%. Amyl acetate failed to elicit a feeding response. Crude cottonseed oil (5%) and refined soybean oil (5%) , both in combination with sucrose (10%), induced significantly more feeding than the respective oils alone but were no more effective than sucrose (10%) (Table 5). Neither crude cottonseed oil (5%) or refined soybean oil (5%) alone elicited a feeding response greater than controls. Comparisons of the more promising feeding stimulants are summarized in Table 6. Brewers concentrate (20%) was preferred over malt extract (20%), Coax (20%), sucrose (10%) and blackstrap molasses (20%). There was no significant difference among brewers concentrate (20%), refined soybean oil (5%) plus sucrose (10%), and crude cottonseed oil (5%) plus sucrose (10%). Coax (20%), sucrose (10%), and blackstrap molasses (20%) were no better than the control. 27

PAGE 34

28 o •H M O 00 S T3 (U B 3 CO C o o 60 •H (U 00 3 o 6^ O in O to o •H B cu CO • • • • 00 00 00 CO CSI • • 1—1 1— ( f— I +1 +1 +1 +1 +1 +1 * . CO vO in 00 <• CO 1— 1 •—1 r-H CO ^ o 0> Cvl CO ^ eg ^ CO +1 00 +1 1— ( +1 in CO CO +1 i — CO o vO 0^ U in CO in CO »— t 00 0) +1 +1 +1 +1 +1 +1 > 0) CM CM iH 00 CJN in m in 00 o 1—1 CN o CM 00 Cvl eg o CO o CO CO CO •H o u o o o ^1 a o 4-1 u •H a 3 3 <-i u .H 3 u rH Cfl cfl -l •H T3 CO o •H c 60 •H CO CO C CO 0) S w to +1

PAGE 35

4J > (U (d d 60 0) Ki p. S m 60 3 iH 0) u o T-l 3 iH rH 0) O u 60 (d o CO p I to g •H u > • CO 14 CD 4>l n a « Id i-H • M-l CO O T3 •H (U U CO Id C o p. .u CO (U to l-l CO fi 3 •H O •a •H (U M cd > 0) u •H U U (U e 3 CO C o o u 00 •H 0) 3 3 ca 0) o csl O u-1 o o e O n ro +1 +1 +1 I-H 1—4 r— ) « •—1 O vO CO • CM 1-H in +1 +1 +1 CM <• 00 CN CM o I-H I-H +1 + 1 + 1 ir, o 0^ CN ON CN I-H CO 00 u-i CM I-H CO CSI I-H +1 + 1 + 1 CO \o 00 I-H CNI n o O • CN I-H +1 +1 + 1 a^ a\ CO 00 00 n •3 •H II •H U CJ tC 3 T3 cd •H o O o •H w Cd •H 3 CO (U
PAGE 36

30 o •H >-i U (U e 3 CO c o u •H 00 3 H P. C 0) s in •oo o 1— 1 1— 1 00 CM in CS o 1— 1 +1 +1 +1 +1 +1 in •H •H )-4 0) •H C B c tfl rH O •H 0) PO 3 u J= iH M CO (U 0) o tfl 1 cfl •H iH CO 4-1 1 »J 1 hJ 1 4-1 1 II a s — ' w CA +1 +

PAGE 37

0) u •H U o 0 •V 0) e 3 CO c o o 00 •H 0) tlO 3 c to O CM o 6-S in 6^ 6-S f— 1 O t— 1 »— t in • • o> in IN in CO I-H +1 +1 +1 1 ^ K 00 -H O CM a vO o m • H o o I-H O 2 PQ o u PP B 4J CO (U 4-1 1 4-1 Q) H & CO o u iH > (U r-l in o o (1) 4-1 4-) CO H O 4-1 o U S o fr rH 4-1 c CO u •H i4-< •H C (JO •H CO o 1— 1 )H 0) II MH MH c •H TJ CO CO C CO +1 cu 1 X * +

PAGE 38

32 TABLE 5. Feeding response of adult female S^. vicinus to agar/ cellulose plugs impregnated with crude cottonseed oil and refined soybean oil in combinations with sucrose. Mean plug weight consumed Feeding stimulant (mg/cricket) Crude cottonseed oil (5%) + sucrose (10%) 232.7 ± 28.9 a Sucrose (10%) 194.2 ± 46.6 a Crude cottonseed oil (5%) 59.0 ± 21.3 b Control 4.6 ± 1.8 b Refined soybean oil (5%) + sucrose Sucrose (10%) Refined soybean oil (5%) Control (10%) 327.5 ± 41.7 a 281.6 ± 50.6 a 35.3 ± 10.0 b 1.0 ± 0.4 b X ± SE (n = 13). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 39

33 TABLE 6. Feeding response of late instar S^. vicinus to agar/cellulose plugs impregnated with various feeding stimulants. Feeding stimulant Mean plug weight (% concentration) consumed (mg/cricket) ijrewers concentrate V 0 n 1 Q c 1 r\ DL .0 a Refined soybean oil (5%) + sucrose (10%) 158.1 + 37.5 ab Crude cottonseed oil (5%) + sucrose (10%) .'-j 154.9 + 37.0 abc Malt extract (20%) •: 114.2 + 28.0 be Coax (20%) 78.3 + 18.1 bed Sucrose (10%) 74.7 + 21.9 bed Blackstrap molasses (20%) 72.3 + 12.1 dc Control 8.56 + 1.9 d X ± SE (n = 15). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 40

34 S. acletus . Results of feeding stimulant assays are summarized in Tables 7-10. Sucrose enhanced feeding at 5, 10, and 20%. Glucose and fructose were also stimulating at 1 and 5%, respectively (Table 7). None of the fatty acids enhanced feeding activity at concentrations tested (Table 8). Of the six refined oils tested, only wheat germ oil (15%) induced a feeding response significantly greater than controls (Table 9). Bait additives, malt extract (15%), Coax (5, 10, and 15%), brewers concentrate (1, 5, 10, and 15%), and honey (5 and 10%) all significantly enhanced feeding activity (Table 10). Blackstrap molasses and amyl acetate did not induce a significant feeding response. Comparisons of the more promising feeding stimulants are summarized in Tables 11-12. As shown in Table 11, Coax (15%) was preferred to all other materials tested. The refined soybean oil (5%) sucrose (10%) combination was significantly more stimulating than sucrose (10%), refined soybean oil (5 and 10%) and refined soybean oil (10%) plus sucrose (10%). Sucrose (10%), soybean oil (5 and 10%), and soybean oil (10%) plus sucrose (10%) were no more stimulating than the control. As shown in Table 12, brewers concentrate (10%) was preferred over all other materials tested. Refined soybean oil (5%), and crude cottonseed oil (5%), both in combination with sucrose (10%), were no better than sucrose (10%) but the crude cottonseed oil-sucrose combination was significantly more active than crude cottonseed oil alone. Coax (15%) was more effective than soybean oil (5%) plus sucrose (10%), malt extract (15%), crude cottonseed oil (5%), and blackstrap molasses (15%). Malt extract (15%) was more stimulating than crude cottonseed oil (5%) and blackstrap molasses (15%). All feeding stimulants tested elicited a feeding response significantly greater than the control.

PAGE 41

35 0) M u •H U O B e 3 CO c o o 4J 42 bO •H lU IS (30 3 C CO (U in 6^ O o o •H B 0) 00 CM 1— 1 cn in CO VO CNI rH cs r— ( CNI CN +1 + 1 + 1 + 1 + 1 * CNI O CO • • • • • O CO CN 00 (>4 m (N o O CN 00 in ro in 0) .H m o o (U ,13 4J 4-1 cd iH o u u 0 O CJ e o fr >^ .H 4-1 C CO O •H M-l •H C 60 •H CO ^ — \ o u 4-1 II >w •H s •TJ N^ CO M C CO 0) +1 1 >
PAGE 42

(U u •H M U bO S % CO o u u 00 •H & 60 I-l PL. c
PAGE 43

4J td M-l O 0) CO c o p< CO CO iH 0) •H O C (U •H C T) •H 0) "4-1 0) (U u 9) U •H U U 00 a (U a 3 CO C o u (30 •H (U 3 B CO 0) S in 6-S O 6-S o •H o cn in liS 4-1 M tfl •H >^ 4J O (U O O O CV, o C« 0) 60 to 01

PAGE 44

o •H u u e 3 CO C o o u •H (U 15 bD 3 C to 0) in o 6^ in in I— I o O c 3 o ft e o u o +1 * 00 o St CO 00 o 00 in o in 0^ CO 00 o +1 o CM +1 * in +1 00 in in 00 00 ^ 00 St CO ON 00 in +1 m ^ +1 +1 (U m o o . rH 4J c CO o •H 14H •H 00 •H / N CO o rH u 0) II MH MH c •H -o u CO w c CO +1 s 1 X * + 38

PAGE 45

39 TABLE 11. Feeding response of adult female S. acletus to agar/ cellulose plugs impregnated with various feeding stimulants, Feeding stimulant Mean plug weight consumed (% concentration) (mg/cricket) o /. c o + 21.0 a Refined soybean oil (5%) + sucrose (10%) 167.8 + 33.5 b Malt extract (15%) 126.5 + 18.7 be Sucrose (10%) 71.4 + 13.1 cd Refined soybean oil (10%) + sucrose (10%) 71.4 + 13.1 d Refined soybean oil (5%) 45.1 + 10.7 d Control 42.5 + 4.2 d Refined soybean oil (10%) 31.3 + 10.5 d X ± SE (n = 15). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 46

40 TABLE 12. Feeding response of adult female S. acletus to agar/ cellulose plugs impregnated with various feeding stimulants. Feeding stimulant Mean plug weight consumed (% concentration) (mg/cricket) 0^17 1^ Z.0 / .D JO . Z a Coax n S9''i 1 OA O or\ o IV . I b Sucrose (10%) 137.1 + 19.2 be Crude cottonseed oil (5%) + sucrose (10%) 128.9 + 12.9 bed Malt extract (15%) 123.7 + 22.0 cde Refined soybean oil (5%) + sucrose (10%) 116.5 + 15.4 cde Blackstrap molasses (15%) 81.43 + 17.6 de Crude cottonseed oil (5%) 74.8 + 17.7 e Control 19.8 + 3.5 f X ± SE (n = 15). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 47

41 Dye Impregnated Bait Assay S. vicinus . Results of feeding stimulant comparisons on corn cob grit baits are summarized in Table 13. The crude cottonseed oil (5%) sucrose (10%) combination was significantly more stimulating than all other materials tested. There was no significant difference among brewers concentrate (20%), Coax (20%), malt extract (20%), sucrose (10%), and blackstrap molasses (20%) as compared with the control. S. acletus . Results of feeding stimulant comparisons on corn cob grit baits are summarized in Table 14. Crude cottonseed oil (5%) plus sucrose (10%), refined soybean oil (5%) plus sucrose (10%), and Coax (15%) induced significantly more feeding activity compared to all other materials tested. Malt extract (15%) was significantly more stimulating than sucrose (10%), crude cottonseed oil (5%), and blackstrap molasses (15%). The latter three compounds were no more active than the control. Carriers Bait Acceptance S. vicinus . Results of carrier evaluations are summarized in Tables 15-16. Brewers concentrate (20%) significantly increased the consumption of cracked corn and wheat bran (Table 15). Based on percent acceptance (Table 16), cottonseed meal, corn cob grits, and citrus pulp were significantly more acceptable when the feeding stimulant was added. Percent acceptance of laying mash, cracked corn, and wheat bran were not enhanced by the addition of brewers concentrate (20%) . S. acletus . Results of carrier evaluations are summarized in Tables 17-18. Based on mean bait consumption, laying mash, cracked corn, corn cob grits, and peanut hulls were significantly more acceptable when impregnated with the feeding stimulant, crude cottonseed oil

PAGE 48

42 TABLE 13. Feeding response of adult female S. vicinus to corn cob grit bait impregnated with various feeding stimulants. Feeding stimulant Mean bait consumption (% concentration) (mg/cricket) Crude cottonseed oil (5%) + sucrose (10%) 38.6 + 5.5 a Brewers concentrate (20%) 20.1 + 7.4 b Coax (20%) 18.7 + 7.4 b Malt extract (20%) 18.1 + 6.9 b Sucrose (10%) 16.3 + 4.8 b Blackstrap molasses (20%) 10.1 + 3.4 b Control 6.6 + 1.4 b X ± SE (n = 10). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 49

43 TABLE 14. Feeding response of adult female S. acletus to corn cob grit bait impregnated with various feeding stimulants. Feeding stimulant Mean bait consumption (% concentration) (mg/cricket) Crude cottonseed oil (5%) + sucrose (10/) 13.3 + 1 . 1 a Loax (Lj7o) 13.2 + 2.7 a Refined soybean oil (5%) + sucrose \W7o) 12.6 + 1 . 7 a Malt extract (15%) 8.9 + 1.5 b Brewers concentrate (10%) 6.3 + 0.7 be Refined soybean oil (5%) 6.3 + 0.9 be Sucrose (10%) 4.6 + 1.1 cd Crude cottonseed oil (5%) 3.6 + 1.0 cd Blackstrap molasses (15%) 3.3 + 0.4 cd Control 2.0 + 0.3 d X ± SE (n = 4). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure.

PAGE 50

44 TABLE 15. Feeding response of adult female S^. viclnus to various bait carriers with and without feeding stimulant added. Mean bait consumption Formulation (mg/cricket) Q 7.0 a WliCd L U L dll ' r • o • 97 A Q A aD T avHno" TnaeVi + 17 Q i-idjr Xllg uLdolL ' r • O • 17 A A DC Ltdy Xllg UldbU 17 9 9 R C WVi^at" V\T"aTi rViiCClL. U L dlL + 9 Q C ordCK-cu corn 1 /i c Paa-niiiVtii1 1 c + 17 Q Q n 9 7 Ca L/OLi-onseea uiedx + r . o • o . U 9 n CCl A 1 1 7 J u 7 7 9 Q a Appxe pomace/ rxce nuxxs + r.o. T 9 1 /i a ^ ^ e ^ /I moot 9 Z.J 1 A a L-itrus pulp + r . i> . 1 Q 1 . o n 7 U . / J u Sawdust + F.S. 1.0 + 0.4 d Apple pomace/rice hulls 1.0 + 0.5 d Citrus pulp 0.6 + 0.4 d Peanut hulls 0.5 0.1 d Corn cob grits 0.3 + 0.2 d Vermiculite 0.2 + 0.1 d Sawdust 0.1 + 0.1 d X ± SE (n = 4). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. F.S. = Brewers concentrate (20%).

PAGE 51

45 TABLE 16. Feeding response of adult female S_, vicinus to various bait carriers with and without feeding stimulant added. Formulation Percent bait acceptance Wheat bran + F.S.^^ 77.1 + 15.7 a Cracked corn + F.S. 63.7 + 10.5 ab Laying mash + F.S. 60.0 + 8.9 abc Wheat bran 59.2 + 3.4 abc Cottonseed meal + F.S. 52.5 + 12.5 be Cracked corn 48.3 + 6.9 be Laying mash 39.6 + 6.3 cd Corn cob grits + F.S. 22.9 + 7.9 de Citrus pulp + F.S. 22.5 + 8.3 de Peanut hulls + F.S. 20.8 + 7.2 de Apple pomace/rice hulls + F.S. 21.3 + 14.2 de Cottonseed meal 12.5 + 12.5 ef Peanut hulls 5.0 + 5.0 ef Vermiculite + F.S. 0 + 0 f Sawdust + F.S. 0 + 0 f Vermiculite 0 + 0 f Sawdust 0 + 0 f Corn cob grits 0 + 0 f Citrus pulp 0 + 0 f Apple pomace/rice hulls 0 + 0 f X ± SE (n = 4). Means followed by the same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. F.S. = Brewers concentrate (20%).

PAGE 52

46 TABLE 17. Feeding response of adult female S_. acletus to various bait carriers with and without feeding stimulant added. Mean bait consumption Formulation (mg/cricket) ++ Laying mash + F.S. / /. 1 a Laying mash o . 5 D LracKea corn + r.o. jU . U D wneaL oran + r.o. 1 c i . J DC L.om COD grius t r,o« DCu wnear oran 0 0 0 D . 0 Dcae Cracked corn 1 fl Ci D . 0 cde reanut nuxxs + ^.o. 1 D . 0 0 Q Z . O J A f der Cottonseed meal + F.S. 1 / "7 14 . 7 + o c 2 . 5 defg LiOuconseea meax 1 J. 0 + efg Liitrus puxp ^ r.o. + o o 2 . J fgh vermicuj-ice + r.o. 8.9 + 1.9 fgh Apple pomace/rice hulls + F.S. 6.9 + 1.4 gh Citrus pulp 5.5 + 1.3 gh Peanut hulls 3.0 + 0.5 h Apple pomace/rice hulls 2.6 + 0.2 h Corn cob grits 1.5 + 0.2 h Sawdust + F.S. 0.7 + 0.3 h Sawdust 0.3 + 0.1 h Vermiculite 0.3 + 0.1 h X ± SE (n = 4). Means followed by the same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. F.S. = Crude cottonseed oil (5%) and sucrose (10%).

PAGE 53

47 TABLE 18. Feeding response of adult female S^. acletus to various bait carriers with and without feeding stimulant added. Formulation Percent bait acceptance Laying mash + F.S.^* 100.0 + 0 a Wheat bran + F.S. 100.0 + 0 a Wheat bran 95.0 + 5.0 ab Cracked corn + F.S. 95.0 + 5.0 ab Peanut hulls + F.S. 95.0 + 5.0 ab Vermiculite + F.S. 90.0 + 5.8 abc Cracked corn 83.8 + 9.9 abc Cottonseed meal + F.S. 81.7 + 6.7 be Corn cob grits + F.S. 80.0 + 8,2 be Citrus pulp 80.0 + 8.2 be Apple pomace/rice hulls + F.S. 77.5 + 10.3 e Cottonseed meal 77.5 + 10.3 c Apple pomace/rice hulls 77.5 + l.A c Laying mash 76.7 + 8.8 c Citrus pulp + F.S. 73.8 + 9.4 c Peanut hulls 23.3 + 3.3 d Sawdust + F.S. 21.3 + 8.3 d Corn cob grits 20.0 + 8.2 d Sawdust 0 + 0 e Vermiculite 0 + 0 e X ± SE (n = 4). Means followed by the same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. F.S. = Crude cottonseed oil (5%) and sucrose (10%).

PAGE 54

48 (5%) plus sucrose (10%). Wheat bran consumption was not enhanced as in S_. vlcinus . As shown in Table 18, percent acceptance of laying mash, corn cob grits, vermiculite, and sawdust was significantly enhanced by the addition of the feeding stimulant. Carrier Efficacy Trials Results for efficacy trials are shown in Table 19. Control mortalities for cracked corn, laying mash, and wheat bran were 0%, 0%, and 15%, respectively. Wheat bran bait was significantly less efficacious (14.7%) compared to cracked corn (67.5%) and laying mash (60.0%) baits. There was no significant difference between cracked corn and laying mash bait. Toxicant The log dose-probit line and regression equation for malathion bait are shown in Figure 6. Malathion bait had a LC^^ and LC^^ of 0.9% and 4.7%, respectively. The 4% bait was significantly more toxic to adult S^. acletus than the 2% bait presently used. Field Tests Field Bucket Trials Results of field bucket tests are summarized in Table 20. Mean control mortality after 72 hours was 31.3%. During the experiment, air temperatures ranged from 20-33°C with no rainfall. The data indicate no significant differences in efficacy among the 3 rates tested for malathion 4% bait. Commercially prepared Dursban 0.5% bait, Sevin 20% bait, and Dylox 5% bait were equally as effective as the malathion 4% bait applied at 0.56, 1.12, and 2.24 kg Al/ha. Malathion 4% bait was significantly more efficacious than either the grower formulated or commercial malathion 2% bait when applied at the same 2.24 kg Al/ha rate. There was no significant difference between malathion 4% bait at 0.56 and 1.12

PAGE 55

49 TABLE 19. Efficacy of malathion 2% bait formulated with various carriers on adult female S. acletus in laboratory trials. Carrier* % Mortality** Cracked corn + F.S. 67.5 ± 10.3 a Laying mash + F.S. 60.0 ± 10.8 a Wheat bran +F.S. 14. 7+2. 9b Baits applied at 2.24 kg Al/ha rate. * X ± SE (n = 4). Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. F.S. = Crude cottonseed oil (5%) and sucrose (10%).

PAGE 56

50 % MORTALITY CO 0> IT) o o o 00 rjo Lf) o o o '300 CNJ J L cn 3 4J OJ iH O cfl «:| OJ iH CO £ It 3 -a n! CO 0 I— 1 4-1 cfl •H c J-i o 4-1 H 4J rt 3 Q O" 4J 01 CO 1-1 c o 0 •H c3 M iH CO 0) C •H 4J ^ •H CO x c CO c O ai •H C x: •H u iH CO H 4-1 CO •H e. XI 0 u u •H (U cn 13 o (U •a 4J Cfl 6C (U o (-1 u 0) 3 •H

PAGE 57

51 TABLE 20. Efficacy of 4% malathion bait and several commercial bait formulations on adult female S_. acletus in field bucket trials. Bait formulation Rate (kg Al/ha) % Mortality"*" naiatnion 0 0/. Q ^ t; y J . J /i H . J a oevin ZU/o \VL) 0 0 /. Q 1 n 1 n 1 . U ab naxarnion 1 10 OO . D A . J ao Dursban 0.5% (SMCP) 0.84 86.6 + 8.6 ab Malathion 4% 0.56 82.1 + 0 abc Dylox 5% (Asgrow) 1.68 82.1 + 1.0 abc Malathion 2%"*""*" 2.24 73.1 + 5.2 be Orthene 5% (Chevron) 2.24 64.1 + 7.3 cd Baygon 2% (SAI) 4.48 46.2 + 7.3 d Malathion 2% (SMCP) 2.24 41.7 + 15.3 d X ± SE (n = 4) . Means followed by same letter do not differ significantly at the K-ratio = 100 level, Waller-Duncan K-ratio procedure. Grower formulated (see appendix).

PAGE 58

52 kg Al/ha and the grower formulated malathion 2% bait at 2.24 kg Al/ha. Commercial malathion 2% bait was significantly less effective compared to all other malathion formulations tested. Baygon 2% bait and Orthene 5% bait were no better than the commercial malathion 2%, bait but Orthene 5% bait was equally as effective as the malathion 4% bait (0.56 kg Al/ha), Dylox 5% bait, and the grower formulated malathion 2% bait. Field Tests Relative population levels of S^. vicinus before and after bait treatments are shown in Figures 7-9. The mean reduction in ^. vicinus 24 hour pitfall trap catch for all three fields is summarized in Table 21. Malathion 4% bait reduced S^. vicinus catch by 98.8% at 1.12 kg Al/ha rate and 94.0 and 97.5% for the two treatments at 0.56 kg Al/ha rate. There was no significant increase in population levels seen during the 2-3 week period following each treatment. Additionally, no mole cricket activity was observed in fields 1 and 2 for as long as two months following treatment. Field Persistence During the 8 week study (Sept. 12 Nov. 6, 1984) total rainfall was 128.3 mm. Air temperatures underneath the plastic canopy were comparable to outside temperatures but surface temperatures were as much as 3-5°C cooler on sunny days. During the final week, high winds and heavy rainfall destroyed the plastic cover and subsequently no data were collected for the covered bait. Chemical Analysis Loss of malathion from uncovered and covered bait is described in Figure 10. Malathion residues from control bait were 42.8 mg/gm dry bait (4.28%). For the uncovered bait, percent malathion was signifi-

PAGE 59

J 200r1.12 kg Al/ha 9 10 13 14 is 16 17 22 23 24 25 28 29 30 31 dslTl 8~T lb ri12 DATE: AUGUST SEPTEMBER Figure 7. Mean 24 hour pitfall trap catch of S^. vicinus in bahiagrass pasture before and after treatment with malathion 4% bait in 1984. Arrow indicates date of treatment.

PAGE 60

54 60,0.56 kg Al/ha Figure 8. Mean 24 hour pitfall trap catch of S^. vicinus in bahiagrass pasture before and after treatment with malathion 4% bait in 1984. Arrow indicates date of treatment.

PAGE 61

55 Figure 9. Mean 24 hour pitfall trap catch of S^. vlclnus in bahiagrass pasture before and after treatment with malathion 4% bait in 1984. Arrow indicates date of treatment.

PAGE 62

56 TABLE 21. Mean percent reduction of relative S^. vicinus population levels in three bahiagrass pastures treated with malathion 4% bait. Treatment (n = number of traps) % Reduction* 1.12 kg Al/ha (n = 2) 98.8 ± 0, ,9 0.56 kg Al/ha (n = 2) 94.0 ± 1. ,1 0.56 kg Al/ha (n = 3) 97.5 ± 0. ,4 + X ± SE. Based on mean 24 hr. pitfall trap catch for a 2-3 week period both before and after treatment.

PAGE 63

57 Figure 10. Effect of weathering on loss of malathion from covered and uncovered 4% bait.

PAGE 64

58 cantly related to both time (in days) and rainfall (cumulative) with a significant interaction between time and rainfall (P < 0.008): Transformed (% malathion) = 80.0 0.5 (day) 0.04 (day)^ 0.28 2 (rainfall) 0.01 (rainfall) + 0.03 (time x rainfall) (r^ = 0.99) Based on a linear relationship with time, the tj (half-life) of malathion was 29.6 days (4.23 weeks): Transformed (% malathion) = 82.6 1.27 (days) (r^ = 0.97) For the covered bait, percent malathion was significantly related to time (in days) (P < 0.001): Transformed (% malathion) = 90.77 24.35 (Log (Day + 1)) (r^ = 0.94) Based on the above equation, the tj for malathion was 74.8 days (10.7 weeks) . Bioassay Loss of bait efficacy for uncovered bait is described in Figure 11. Percent mortality was significantly related to time (in days) (P < 0.001): Transformed (% mortality) = 82.6 1.31 (days) (r^ = 0.90) There was no relationship between mortality and percent malathion or cumulative rainfall. Based on the above equation, the tj for bait efficacy was 28.7 days (4.1 weeks). Bait Acceptance Loss of bait acceptance for the uncovered bait is described in Figure 12. Percent acceptance is defined as the ratio of actual vs.

PAGE 65

59 4 ^ 1 1 1 1 1 1 \ r r 0 7 14 21 28 35 42 49 56 TIME (DAYS) Figure 11. Effect of weathering on loss of efficacy of control of adult S^. acletus for uncovered raalathion 4% bait.

PAGE 66

60 3020^ 100 T 1 1 1 1 1 1 1 10 7 14 21 28 35 42 49 56 TIME (DAYS) Figure 12. Effect of weathering on loss of acceptance to adult S. acletus for uncovered malathion 4% bait. "

PAGE 67

61 predicted mortality. Percent acceptance was significantly related to time (in days) (P < 0.001): Transformed (% acceptance) = 90.5 1.09 (days) (r^ = 0.53) There was no relationship between percent acceptance and cumulative rainfall. Based on the above equation, the for bait acceptance was 41.7 days (5.96 weeks).

PAGE 68

DISCUSSION The results of this study show that generally mole crickets appear to prefer sugars, namely sucrose, or sweet tasting compounds. Sucrose was the most stimulating sugar tested for both species. Sucrose has been shown to be an effective feeding stimulant for almost all insect species tested. Melibiose was also found stimulating to S^. vicinus and is known to elicit feeding in the Egyptian cotton leafworm, Spodoptera littoralis (Meisner et al. , 1972), and the grass grub Costelytra zealandica (Sutherland, 1971). The common sugars, glucose and maltose, stimulated feeding by S^. acletus . Maltose has been shown to enhance feeding by the Egyptian cotton leafworm, S_. littoralis (Meisner et al., 1972) and the scarabs, Sericesthis geminate (Wensler and Dudzinski, 1972) and Heteronychus arata (Sutherland and Hillier, 1976). Glucose is known to stimulate feeding in the sweet clover weevil (Akeson et al. , 1969), European corn borer, Ostrinia nubilalis (Beck, 1956), Egyptian cotton leafworm, S^. littoralis (Meisner et al. , 1972), and the locust, Locusta migratoria (Cook, 1977). Bait additives malt extract, brewers concentrate, and Coax all stimulated feeding by both species. Malt extract has been shown to elicit a feeding response by S^. acletus (Walker, 1979) and enhance the efficacy of sawdust-malathion bait in field trials (W. Stackhouse and S. Walker, personal communication). Wheat germ oil elicited a feeding response by S^. acletus . This has also been demonstrated in locusts (Thorsteinson and Nayar, 1963; Dadd, 1960). 62

PAGE 69

63 The combination of crude cottonseed oil or refined soybean oil with sucrose was found to be one of the most effective feeding stimulants for both species. Coax contains a combination of vegetable oil and sugar. The combination of cottonseed oil and sugar is also highly stimulating to pink bollworm larvae (Bell and Kanavel, 1975), tobacco budworm larvae (Bell and Kanavel, 1978), and boll weevils (McLaughlin, 1976). Combinations of several chemicals are effective feeding stimulants in other insects. Amino acids in combination with sucrose have been effective on locusts (Cook, 1977; Thorsteinson, 1960; Ma and Kubo, 1977) and the cabbage worm, Pieris brassicae (Ma, 1972). Mixtures of sugars (Cook, 1977; McMillan and Starks, 1966), amino acids (Davis, 1965), and fatty acids (Davis, 1968) have also been shown to act synergistically as feeding stimulants for various insects. Molasses and amyl acetate were not very effective as feeding stimulants for either species though molasses did enhance feeding in some agar plug assays. This may explain why molasses has not been recommended in the past. Walker (1979) did find molasses to elicit feeding in S^. acletus but this was only after A8 hours without an alternative food source. Prolonged periods of starvation are known to lower the feeding stimulant threshold in insects forcing them to feed on compounds not normally preferred (Chin, 1950). Field trials have demonstrated that corn cob grit bait impregnated with molasses was just as efficacious as laying mash-molasses bait based on surface mortality (W. Stackhouse and S. Walker, personal communication). However, surface counts do not reflect true bait efficacy and these results cannot be considered reliable. Based on the present studies, neither molasses or amyl acetate can be recommended in bait formulations.

PAGE 70

64 Results from agar plug and dye impregnated bait assays generally demonstrate similar responses to feeding stimulants but there are some differences. The activity of brewers concentrate and sucrose dropped off significantly when tested on corn cob grit carriers. This is not unusual as physical factors such as hardness, texture, water content, and shape are all known to influence the acceptability of insect diets (Singh, 1977). The feeding response of several insects to known feeding stimulants has been shown to change considerably depending on the medium offered (Niimura and Ito, 1964; Harris and Mohyuddin, 1965; Haines and Haines, 1979). These differences in response may also be due to the testing procedures themselves. Agar plug assays are conducted in empty petri plates with an artificial diet while the bait method utilizes a more natural environment of moist sand and a natural diet. A greater amount of stress may be associated with the agar plug assay which could alter feeding behavior. Additionally the length of time food is offered is different for the two as says (18 hr vs. 8 hr) • Prolonged exposure may increase the probability of feeding on less stimulating compounds thereby making it difficult to differentiate between weaker and more powerful feeding stimulants. While it is valid to accept that increased consumption reflects greater feeding stimulation, one must consider the above mentioned factors before interpreting results. The agar plug assay is useful for screening purposes but for final evaluations, the dye impregnated bait assay is most appropriate in determining effective feeding stimulants for bait formulation. There are big differences in acceptability among the various carriers tested. Generally inert compounds (eg. corn cob grits, peanut

PAGE 71

65 hulls, and vermiculite) are unpalatable when offered alone. The addition of feeding stimulants enhances consumption as much as 18X though not always significantly. Materials such as laying mash, cracked corn, and wheat bran are moderately to highly acceptable alone. This can be attributed to their inherent nutritional qualities. The addition of feeding stimulants significantly enhances consumption in most cases, but increases are not as dramatic as with inert compounds. Laying mash, cracked corn, and wheat bran were the three most acceptable carriers tested. In efficacy trials, however, wheat bran bait was significantly less effective than laying mash and cracked corn. Possibly there was some interaction between wheat bran and malathion reducing bait acceptability. Based on these results wheat bran cannot be recommended as a carrier for malathion baits. Results from field bucket trials indicate that there are significant differences in efficacy among commercial bait formulations which may explain the numerous reports of poor control with available treatments. Malathion 4% bait was highly efficacious (>80% control) at all three rates tested suggesting that substantial reductions (50-75%) in the use of malathion can be made compared to current label recommended rates (1.12-2.24 kg Al/ha).. Field trials further demonstrated the effectiveness of reduced malathion rates seen in field bucket trials. These results indicate a more judicious use of malathion is feasible, proving advantageous from both an economical and environmental standpoint. Several methods have been employed in the past to evaluate the efficacy of chemical treatments in the field with limited success. Pitfall trapping offers an effective means for monitoring mole cricket activity for an extended period of time both before and after treatment.

PAGE 72

66 After the initial set up, traps are easily maintained and monitored for any length of time. Though attractive as a sampling tool, recent studies have shown that this method is not without problems. Hudson (1985) found that trap catch does not correlate well with known changes in population levels and that mole cricket density and age greatly affect surface activity as measured by trapping. Soap flush sampling has been shown to be more sensitive to changes in population density and may offer a more accurate estimate of field populations. Though not as sensitive to population changes, pitfall trap data do reflect a significant reduction in mole cricket populations following treatment. This has been further supported by more recent observations. Winter rye planted in treated fields in late fall 1984 showed no evidence of mole cricket damage as seen in previous years (A. J. Thompson, personal communication). Additionally by July 1985, bahiagrass had begun growing back in damaged areas with still no mole cricket activity observed. These observations give further evidence to the effectiveness of reduced malathion treatments and suggest that season long control may be attained with a single application. Malathion is generally believed to have a very short residual life in the environment due mainly to rapid hydrolytic degradation (Mulla et al. , 1981). In the 4% bait formulation, malathion residues were persistent for a considerable length of time. The half life for malathion in uncovered bait (29.6 days) was comparable to the 20-31 days observed for malathion bait under dry conditions in New Zealand (Blank et al., 1984). Malathion loss was significantly correlated with time and rainfall and this is in agreement with studies by Blank et al. (1984). They found that in general increased rainfall enhanced the loss of malathion and

PAGE 73

67 shortened tj 's to as little as 7 days. Williams et al. (1982) found a malathion bait to have a of only 6 days, but weather conditions were not given. In general, malathion is unstable in wet environments, and high levels of moisture increase the degradation of malathion by hydrolysis. In addition to promoting chemical degradation, increased moisture levels also encourage fungal growth. Uncovered bait became infected and subsequently covered with a green-black mold after 2 weeks. This may be partially responsible for the loss of malathion as microorganisms are quite capable of detoxifying malathion (Mulla et al., 1981). Though residual life is significantly effected by moisture, malathion bait was able to withstand heavy rainfall. During the third week of exposure, tropical storm Isadore dropped 48 mm of rain in 24 hours. Malathion residues only decreased about 20% during that week. Similar conditions have also been shown to have little effect on malathion bait in persistence studies by Vellacott (1978). Weather conditions for September and October, 1984 were considerably drier than normal. Undoubtedly malathion residual life would be significantly shortened under increased rainfall, especially during the summer months. The half lifes for malathion in the covered bait (74.8 days) and uncovered bait (29.6 days) are markedly different. The covered bait shows a typical exponential decay curve while the malathion residues in the uncovered bait decrease much more rapidly. Both baits were exposed to similar temperatures and light. Malathion is stable to light and is only decomposed at excessively high temperatures (Anonymous, 1982). The gradual loss of malathion from the covered bait can be attributed to evaporation over time. Malathion has a moderate vapor pressure (1.25 x -4 10 mm Hg at 20°C) and increased temperatures have been shown to

PAGE 74

68 significantly enhance the loss of malathion through evaporation (Toson et al. , 1967). Vaporization may also account for a significant loss of malathion from the uncovered bait in addition to rainfall. Bait efficacy had a half life of 28.7 days and is comparable to the 28 days determined for a malathion bait in persistent studies by Vellacott (1978). Smith (1966), Williams et al. (1982), and Blank et al. (1984) have all shown that malathion baits remain effective for as long as 4-6 weeks. Bait efficacy was not correlated with malathion residues and this is in agreement with studies by Blank et al. (1984). The loss of efficacy is attributed to the loss of bait acceptability. Smith (1966) observed that the effectiveness of malathion bait was lost due to loss of attractiveness rather than loss of toxicity (malathion residues). Haines and Haines (1979) also demonstrated that the toxicity of an aldrin bait was lost at a much slower rate than bait attractiveness in studies on leaf cutting ant control. Weather conditions were not correlated with bait acceptance or efficacy. Loss of acceptance may have been due to the crude cottonseed oil becoming rancid. It has been shown that oil randicity markedly reduced the acceptability of soybean oil bait to fire ants (Lofgren et al. , 1964). Additionally, mold, rainfall, light, and temperatures all may have contributed to the loss of bait acceptability. These present studies indicate that toxic baits are a very effective means for suppressing large numbers of mole crickets. However, before chemical control can be effectively implemented, further research is required. Future studies should concentrate on a) establishing reliable economic thresholds in turf and pasturegrass , b) evaluating the effect of population density on application rates, c) evaluating the

PAGE 75

69 duration of control of chemical treatments, and d) determining optimal time for bait applications. Though toxic baits are an effective method of control, they can only offer temporary relief. Additional studies to establish resistant grass varieties and/or introduced biological control agents will be necessary before more permanent solutions to mole crickets are found.

PAGE 76

APPENDIX TABLE A-1. Percent recovery of Calco dye from various bait carriers. Carrier % Recovery'*' Apple pomace/rice hulls 108.2 + 3.0 Citrus pulp 104.2 + 1.7 Corn cob grits 96.7 + 0.4 Cottonseed meal . 95.6 + 2.4 Cracked corn 92.2 + 4.7 Laying mash 107.0 + 0.6 Peanut hulls ':'.]' , 101.8 + 0.7 Sawdust 107.2 + 1.1 Vermiculite 105.1 + 7.7 Wheat bran . . 101. A + 1.7 X ± SE (n = 3) 70

PAGE 77

71 TABLE A-2. Weather conditions monitored at the University of Florida Agronomy farm during 1984. Air temp. Rainfall Total Solar 2 Date (max-min) (mm) % RH Radiation (MJ/M ) 12 94-67 — 42 19.6 13 95-69 _ 40 19.0 14 95-66 — 45 16.3 15 95-69 — 46 17.0 16 94-69 48 14.7 17 0 c no /U 0 . H 18 81-69 0.25 66 10.0 19 82-67 1.02 66 10.3 20 87-66 _ 46 18.6 21 88-66 39 19.6 22 90-69 — 50 17.7 23 90-67 — 44 18.7 24 88-68 — 46 16.8 25 88-67 — 48 16.2 26 90-69 — 45 16.4 27 89-69 T 70 8.9 28 80-64 47.75 92 2.9 29 83-63 3.81 53 17.1 30 85-63 _ 49 13.3 1 83-58 — 40 19.0 2 76-52 37 19.1 3 79-48 48 17.9 4 82-53 _ 45 18.3 5 83-57 _ 48 14.0 6 85-59 42 15.9 7 85-64 0.25 52 13.2 8 84-67 4.57 54 15.2 9 85-64 — 51 13.1 10 84-67 _ 57 13.0 11 82-65 55 14.5 12 82-62 41 16.9 13 84-54 37 15.6 14 88-58 33 16.0 15 89-61 49 13.1 16 91-69 T 48 15.3 17 90-66 48 11.8 18 89-65 48 14.2 19 88-66 48 13.3 20 88-65 44 14.1 21 89-68 49 11.9 22 90-69 49 12.9 23 90-65 45 N/A 24 88-62 41 N/A 25 86-65 39 N/A 26 86-70 T 66 N/A

PAGE 78

72 TABLE A-2. Continued Air temp. Rainfall Total Solar ^ Date (max-min) (mm) % RH Radiation (MJ/M ) 27 90-71 2.54 53 N/A 28 89-74 14.22 54 N/A 29 90-71 20.57 54 N/A 30 87-68 2.29 56 N/A 31 84-71 1.02 60 N/A 1 83-67 T 54 N/A 2 83-65 60 N/A 3 81-64 17.53 68 N/A 4 82-64 T 59 N/A 5 80-65 12.45 69 N/A 6 74-53 27 N/A

PAGE 79

73 TABLE A-3. Grower formulated 2% malathion bait for mole cricket control (from Koehler and Short, 1976b). Material Amount Laying Mash 100 lb Crude Molasses 2 qt Water 1-5 qts Malathion SEC 52 oz (2 lb AI)

PAGE 80

REFERENCES Abbott, W. S. 1925. A method of computing the effectiveness of an insecticide. J. Econ. Entomol. 18: 265-67. Akeson, W. R. , H. J. Gorz, and F. A. Raskins. 1969. Sweet clover weevil feeding stimulants: isolation and identification of glucose, fructose and sucrose. Crop Science 9: 810-12. Annand, P. N. 1941. Mole cricket control. U.S. Dep. Agric, Bur. Entomol. Plant Quar. Annu. Rep. 1940-41: 73-74. Anonymous. 1982. Cythion: technical information sheet. American Cyanamid. 1 p. Ascher, K. R. S., and N. A. Nemny. 1981. Use of foamed polyurethane as a carrier for phagostimulant assays with Spodoptera littoralis larvae. Entomol. Exp. Appl. 25(3): 346-48. Barrett, 0. W. 1902. The changa, or mole cricket ( Scapteriscus didactylus Latr.) in Puerto Rico. P.R. Agric. Exp. Stn. Bull. 2: 19 pp. Beck, S. D. 1956. A bimodal response to dietary sugars by an insect. Biol. Bull. 3: 219-28. Beck, E. W., and J. L. Skinner. 1967. Screening of insecticides against the changa and southern mole cricket attacking seedling millet. J. Econ. Entomol. 60(6): 1517-19. Bell, M. R., and R. F. Kanavel. 1975. Potential of bait formulations to increase effectiveness of nuclear polyhedrosis virus against the pink bollworm. J. Econ. Entomol. 68(3): 389-91. Bell, M. R., and R. F. Kanavel. 1978. Tobacco budworm: development of a spray adjuvant to increase effectiveness of a nuclear polyhedrosis virus. J. Econ. Entomol. 71(2): 350-52. Blank, R. H. , R. F. Henzell, and D. R. Lauren. 1984. Longevity of maldison-treated grain bait used to control black field cricket ( Teleogryllus commodus ) . N. Z. J. Agric. Res. 27: 265-70. Brooks, T. J. 1947. Plant diseases and pests and their treatment. Fla. Bull. Dep. Agric. 3: 56-58. Callan, E. McC. 1945. Observations on mole crickets and their control in Trinidad, B.W.I. Trop. Agric. 22(8): 146-49. 74

PAGE 81

Chao, Y. 1975. Mole cricket — its behavior and control. Scienta Scinica. 18(1): 88-105. Chin, C. T. 1950. Studies on the physiological relations between the larvae of Leptinotarsa decemlineata Say and some solanaceous plants. Tydschr. Planlenziehten. 56: 1-88. Cook, A. G. 1977. Nutrient chemicals as phago stimulants for Locusta migratoria (L.). Ecol. Entomol. 2: 113-21. Dadd, R. H. 1960. Observations on the palatibility and utilization of food by locusts with particular reference to the interpretation of performances in growth trials using synthetic diets. Entomol. Exp. Appl. 3(4): 283-304. Daum, R. S., G. H. McKibben, T. B. Davich, and R. McLaughlin. 1969. Development of the bait principle for boll weevil control: Calco Oil Red N-1700 dye for measuring ingestion. J. Econ. Entomol. 62(2): 370-75. Davis, G. R. F. 1965. Phagostimulatory effects of amino acids for larvae of Ctenicera destructor (Brown) (Coleoptera: Elateridae) . Arch. Internat. Physiol. Biochem. 73(4): 610-26. Davis, G. R. F. 1968. Phagostimulation and consideration of its role in artificial diets. Bull. Entomol. Soc. Am. 14: 27-30. Gast, R. T., and M. Landin. 1966. Adult boll weevils and eggs marked with dyes fed in larval diet. J. Econ. Entomol. 59: 474-75. Graham, H. M. , and C. L. Mangum. 1971. Larval diets containing dyes for tagging pink bollworm moths internally. 64(2): 376-79. Green, M. E., E. L. Matheny, and S. J. Yu. 1984. Laboratory and field techniques for evaluating mole cricket (Orthoptera: Gryllotalpidae: Scapteriscus ) baits. J. Ga. Entomol. Soc. 19(2): 151-56. Guthrie, F. E. , R. L. Rabb, and H. E. Scott. 1958. Tobacco insect control— 1958. N. C. Pesticide Manual 1958: 63. Habeck, D. H., and L. C. Kuitert. 1964. Control of mole crickets. Sunshine State Agric. Res. Rep. 9(1): 11-12, 20. Haines, I. H. , and J. B. Haines. 1979. Toxic bait for the control of Anoplolepis longipes (Jerdon) (Hymenoptera: Formicidae) in the Seychelles. I. the basic attractant carrier, its production and weathering properties. Bull. Entomol. Res. 69: 65-75. Harris, P., and A. I. Mohyuddin. 1965. The bioassay of insect feeding tokens. Can. Entomol. 97: 830-33. Hayslip, N. C. 1943. Notes on biological studies of mole crickets at Plant City, Florida. Fla. Entomol. 26(3): 33-46.

PAGE 82

76 Hayslip, N. C. 1948. Insect pests and their control. Fla. Agric. Exp. Stn. Annu. Rep. 1948: 190-93. Hendricks, D. E. , and H. M. Graham. 1970. Oil-soluble dye in larval diet for tagging moths, eggs, and spermatophores of tobacco budworms. J. Econ. Entomol. 63(3): 1019-20. Hsiao, T. H., and G. Fraenkel. 1968. The influence of nutrient chemicals on the feeding behavior of the Colorado potato beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) . Ann. Entomol. Soc. Am. 61: 44-54. Hudson, W. G. 1985. Ecology of the tawny mole cricket, Scapteriscus vicinus (Orthoptera: Gryllotalpidae) : population estimation, spatial distribution, movement, and host relationships. Ph.D. dissertation. University of Florida, Gainesville. 77 pp. Ismalov, M. G., and M. R. Rustamova. 1981. Effectiveness of poison baits. Zashchita Rastenii 10: 32. Kassab, A. 1939. The control of mole crickets with barium f luosilicate. Dep. Agric. E,N,A,G, (France), Minist. of Agric, Egypt. Tech. and Sci. Serv. Entomol. Sect. Bull. No. 193. 13 pp. Kelsheimer, E. G. 1945. Economic control of mole crickets. Fla. Agric. Exp. Stn. Annu. Rep. 1945: 118-19. Kelsheimer, E. G. 1947. Chlordane controls mole crickets. Fla. Agric. Exp. Stn. Press Bull. 640: 6pp. Kelsheimer, E. G., and S. H. Kerr. 1957. Insects and other pests of lawns and turf. Fla. Agric. Exp. Stn. Circ. 5-96: 22 pp. Kepner, R. L. 1981. Evaluation of bait attractants for mole crickets Scapteriscus vicinus and S^. acletus (Orthoptera: Gryllotalpidae). M.S. Thesis. Univ. of Florida, Gainesville. 38 pp. Kepner, R. L. 1984. Chemical control of mole crickets. Fla. Agric. Exp. Stn. Bull. 846: 41-48. Kerr, S. H. 1966. Recommendations for commercial lawn spra}nnen. Fla. Agric. Exp. Stn. Circ. S-121C: 18 pp. Koehler, P. G., and D. E. Short. 1976a. Control of mole crickets in pasturegrass. J. Econ. Entomol. 69(2): 229-32. Koehler, P. G., and D. E. Short. 1976b. Pasture mole cricket control with an applicator-formulated bait. Fla. Entomol. 59(2): 181-82. Koehler, P. G., D. E. Short, and C. S. Barfield. 1979. Mole crickets: IFAS research project. Fla. Cattleman. 43(9): 91, 99, 101. Lawrence, K. 0. 1982. A linear pitfall trap for mole crickets and other soil arthropods. Fla. Entomol. 65(3): 376-77.

PAGE 83

77 Lofgren, C. S., F. J. Barrett, and C. E. Stringer. 1964. The acceptability of some fats and oils as food to imported fire ants. J. Econ. Entomol. 57: 601-02. Ma, W. C. 1972. Dynamics of feeding responses in Pieris brassicae Linn, as a function of chemosensory input: a behavioral, ultrastructural and electrophysical study. Meded. LandbouHoogesh. Wageningen. 72-11: 162. Ma, W. , and I. Kubo. 1977. Phagostimulants for Spodoptera exempta : identification of adenosine from Zea mays . Entomol. Exp. Appl. 22: 107-12. Madden, A. H. 1937. Notes on the changa or West Indian mole cricket, in Puerto Rico in 1935 and 1936. J. Agric. Univ. P.R. 21(2): 115-20, McLaughlin, R. E. 1976. Development of feeding formulations for boll weevil: effect of ratios of cottonseed oil to invert sugar on quantity ingested and initiation of a feeding response. J. Econ. Entomol. 69(3): 374-76. McMillan, W. W., and K. J. Starks. 1966. Feeding responses of some noctuid larvae (Lepidoptera) to plant extracts. Ann. Entomol. Soc. Am. 59(3): 516-19. Meisner, J., and K. R. S. Ascher. 1968. A method to assay the phagostimulatory effect towards insects of plant extracts applied to styropor discs. Riv. Parassit. 29: 74-77. Meisner, J., K. R. S. Ascher, and H, M. Flowers. 1972. The feeding response of the larvae of the Egyptian cotton leafworm, Spodoptera littoralis Boisd., to sugars and related compounds. 1. phagostimulatory and deterrent effects. Comp. Biochem. Physiol. 42: 899-914. More, J. D. 1924. The mole cricket ( Scapteriscus vicinus Latr.). Ga. Agric. Exp. Stn. Bull. 101: 12 pp. Morrill, A. W. 1919. The value of molasses and syrups in poisoned baits for grasshoppers and cutworms. J. Econ. Entomol. 12: 337-43. Mulla, M. S., L. S. Mian and J. A. Kawecki. 1981. Distribution, transport, and fate of the insecticides malathion and parathion in the environment. Res. Rev. 81: 1-159. Ngo, D., and H. W. Beck. 1982. Mark-release of sound attracted mole crickets: flight behavior and implications for control. Fla. Entomol. 65(4): 531-38. Niimura, M. , and T. Ito. 1964. Feeding on filter paper by larvae of the silkworm, Bombyx mori L. J. Ins. Physiol. 10: 425-30.

PAGE 84

78 Norris, D. M. and J. E. Baker. 1967. Feeding responses of the beetle Scolytus to chemical stimuli in the bark of Ulmus . J. Insect Physiol. 13: 955-62. Ray, A. A. 1982. SAS users guide: Statistics 1982 edition. SAS Institute. Gary, North Carolina. 584 pp. Reinert, J. A., and D. E. Short. 1981. Present status of mole crickets in Florida. Fla. Turf 14(3): 5, 7-9, 11. Reinert, J. A., D. E. Short and P. G. Koehler. 1981. Present status of mole crickets in Florida. Fla. Gattleman. 45(9): 36-38. Ritter, F. J. 1967. Feeding stimulants for the Colorado beetle. Meded. Fac. Landb. Wet. Rijksuniv. Gent. 32: 291-327. Schroeder, H. 0. 1941. Mole cricket control project. Plant City, Florida. Report of control activities, September 1 December 31, 1940. 75 pp. In Unpublished report, U. S. Dep. Agric, Bur. Entomol. Plant Q. (copy on file at Dlv. Plant Ind. Library, Fla. Dep. agric, Gainesville, FL) . Shargel, L. , A. Shoshana, and P. Mazel. 1972. The reduction of nitro and azo compounds by housefly microsomes. J. Agric. Food Chem. 20(1): 27-29. Short, D. E., and D. P. Driggers. 1973. Field evaluation of insecticides for controlling mole crickets in turf. Fla. Entoml. 56(1): 19-23. Short, D. E. and P. G. Koehler. 1977. Control of mole crickets in turf. Fla. Entomol. 60(2): 147-48. Singh, P. 1977. Artificial diets for insects, mites, and spiders. IFI/Plenum, New York. 594 pp. Smith, A. G. 1966. Residual effectiveness of poison-baits used for cricket control. Proc. 19th N.Z. Weed Pest Control Conf. 19: 22-25. Southern, P. S. 1983. Southeastern branch insect detection, evaluation and prediction report, 1981. Southeast. Branch, Entomol. Soc. Am. 6: 35 pp. Stacey, A. L., W. C. Yearian, and S. Y. Young III. 1977. Evaluation of Baculovirus heliothis with feeding stimulants for control of Heliothis larvae on cotton. J. Econ. Entomol. 70(6): 779-84. Sutherland, 0. R. W. 1971. Feeding behavior of the grass grub, Costelytra zealandica (White) (Coleoptera: Melolonthinae) . 1. the influence of carbohydrates. N.Z. J. Sci. 14: 18-24. Sutherland, 0. R. W. , and J. R. Hillier. 1976. The influence of maltose and other carbohydrates on the feeding behavior of Heteronychus arata (Scarabaeidae : Coleoptera). Expercentia 32: lOT.

PAGE 85

79 Tappan, W. B. 1963. Mole cricket control in shade tobacco plant beds. Fla. Entomol. 46(3): 238-41. Thomas, W. A. 1926. The control of the Puerto Rican mole cricket, or changa, on golf courses. U.S. Golf Assoc. Green Sec. Bull. 6: 197-200. Thomas, W. A. 1928. The Puerto Rican mole cricket. U.S. Dep. Agric. Farmers' Bull. 1561: 9 pp. Thorsteinson, A. J. 1960. Host selection in phytophagous insects. Ann. Rev. Entomol. 5: 193-218. Thorsteinson, A. J., and J. K. Nayar. 1963. Plant phospholipids as feeding stimulants for grasshoppers. J. Canadian Zoology. 41: 931-35. Tosen, M. A., S. B. Vinson, and J. R. Brazzel. 1967. Effect of environmental and biological factors on persistence of malathion applied as ultra-low-volume or emulsifiable concentrate on cotton plants. J. Agric. Food Chem. 15(6): 1009-13. Ulagaraj , S. M. 1974. Effects of insecticides on mole crickets (Orthoptera: Gryllotalpidae) . Fla. Entomol. 57(4): 414. Ulagaraj, S. M. and T. J. Walker. 1973. Phonotaxes of crickets in flight: attraction of male and female crickets to male calling songs. Science. 182(4118): 1278-79. Van Zwaluwenburg , R. H. 1918. The changa on West Indian mole cricket. P. R. Agric. Exp. Stn. Bull. 23: 28 pp. Vellacott, P. 1978. More about baiting of crickets. J. Agric. Victoria. 76: 22-24. Walker, S. L. 1979. Population estimation, damage evaluation and behavioral studies on mole crickets Scapteriscus vicinus and S. acletus (Orthoptera: Gryllotalpidae)"] M.S. Thesis, Univ. of ~ Florida, Gainesville. 83 pp. Walker, T. J. 1982. Sound traps for sampling mole cricket flights (Orthoptera: Gryllotalpidae: Scapteriscus ) . Fla. Entomol. 65(1): 105-10. Walker, T. J., and D. A. Nickle. 1981. Introduction and spread of pest mole crickets: Scapteriscus vicinus and ^. acletus reexamined. Ann. Entomol. Soc. Am. 74(2): 158-63. Watson, J. R. 1915. New mixture kills mole crickets. Fla. Grower. 12(32): 19. Watson, J. R. 1921. Mole crickets. Fla. Grower. 23(5): 7. Watson, J. R. 1925. Mole crickets. Fla. Agric. Exp. Stn. Press Bull. 372: 2 pp.

PAGE 86

Watson, J. R. 1934. Controlling mole crickets. Fla. Agric. Exp. Stn. Press Bull. 461: 2 pp. Watson, J. R. 1938. Control of mole crickets. Citrus Ind. 19(4): 6, 19, 22. Watson, J. R. 1938. Control of mole crickets. Citrus Ind. 16. Watson, J. R. 1939. Control of mole crickets. Citrus Ind. 20(5): 14. Watson, J. R. 1941. Entomol. Rep. Fla. Agric. Exp. Stn. 1939-1940: 72-76. Wensler, R. S., and A. E. Dudzinski. 1972. Gustation of sugars, amino acids, and lipids by larvae of the Scarabeid, Sericesthis geminata (Coleoptera) . Entomol. Exp. Appl. 15: 155-65. Williams, P., P. P. Stable, S. J. Gagen, and G. D. Murphy. 1982. Strategies for control of the black field cricket, Teleogryllus commodus (Walker). Proc. 3rd Australasian Conf. Grassl. Invert. Ecol. Adelaide, South Australia Government Printer pp. 365-369. Wisecup, C. B., and N. C. Hayslip. 1953. Control of mole crickets. U.S. Dep. Agric. Leafl. 237: 7 pp. Worsham, E. L. 1909. Insects of the year in Georgia. J. Econ. Entomol. 2: 206-10. Worsham, E. L., and W. V. Reed. 1912. The mole cricket ( Scapteriscus didactylus Latr.) . Ga. Agric. Exp. Stn. Bull. 101: 250-63.

PAGE 87

BIOGRAPHICAL SKETCH Rodney Leon Kepner was born on October 9, 1957, in Rochelle, Illinois. He is the youngest of three children of Robert and Leonce Kepner . In 1975 he graduated from Rochelle Township High School. Following graduation, he majored in biology at Rockford College in Rockford, Illinois, and graduated in May, 1979, with a Bachelor of Science degree. The following September, he began graduate studies in entomology at the University of Florida under the direction of Dr. E. L. Matheny, and received a Master of Science degree in December, 1981. In January, 1982, he began studies toward the Doctor of Philosophy degree in entomology, and has been employed as a graduate research assistant under the direction of Dr. S. S. J. Yu throughout his training. 81

PAGE 88

I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Associate Professor of Entomology and Hematology I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. S. H. Kerr Professor of Entomology and Hematology I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. M. Wilcox Professor of Agronomy This dissertation was submitted to the Graduate Faculty of the College of Agriculture and to the Graduate School, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. August 1985 Dean, C^]JLege of Agricu]^re Dean, Graduate School