E-548 gTATE PLANT BO september 1941
PHTHALONITRILE AS AN INSECTICIDE
By M C. Swingle. J. B. Gahan, and A. M. hill ips.
Division of Control Investigations
For several years the Division of Control In investigations of the
Bureau of Entomology and Plant Quarantine has maintained a laboratory at Sanford, Fla.. for studying the insecticidal action of synthetic organic compounds and other samples supplied chiefly by the Division of Insecticide Investigations of this Bureau The purpose of these i nvestigations is the development of new insecticidal materials which may be em her nore economical or more effective than present commercial insecticide which o, re limited in number and effectiveness. Although the results of laoratory tests should not be used as a basis of practical control recommerdatie until tests have been made in the field, they give some indication of results that may
be expected in the field. The results obtained < p.mising compounds will be published from time to time to invite fue testing by those engaged in specific field problems.
One of the most promising of the organic compo 1n ste :t was phthalonitrile, and it was later patented by M. S. Schechter and H. L. J. Haller, of the Division of Insecticide Investigations (3). Phlihalcnitrile. or orthodicyanobenzene (CcH4(CN)2), is an organic compound tsed coimercially in the preparation of a new class of blue and green pigmenls, .re phthalocyanines
(1). It is a colorless. crystalline solid, insoluble in ater but soluble in most organic solvents.
Testing of the compound followed a definite sysi~... recently described by the authors (5). These tests were designed to give preliminary evidence of toxicity, and then to show in more detail the mode of toxic action, the amount of dust or concentration of spray required -or satisfactory control
of various insects, and the utility of the compound as a spray on tender foliage.
>~arvfull gro- axewr generally used in the tetbecause
__ ~e z~eresstal +. oSet~-es therefore gave a better index
to h- 2Xi ?vlue. All iar e wee rE,ee in the laboratory by m-ethods p;iua~ sl :soibed (4) Lh e--arious speciens used and Th plants on1 which
i.e ;ere tested are as f ol Iows,
Cccho 0 otato beetle -Lnictracecemlineata (Say)) Potato
Do~m~uciIao mot (Put-l mui ni (Cu r t. Collards
G er e P- ~~Abalis (G uen.) Do.
Ha~~~n~~~ n-- 1ee wbrmHmn'.aiis (Crami). Swiss hrda,d beet
Tmoehc~)aewom i~i xneL. ) Collad
So>: c~wehwori,~cv~oahiuoai F) Swiss dad n be
Yc:; wolybear (Darii vffinjoa (F.) Collards
2 relioninary Petri-Dish Tests
~> relir~rar ~s a~er x~deby f eeding insects foIa tbat had
rae t> ~ av yC~ ~e Kb to i.re compound. The du ,s s applied in oriuerprm~~sl (ecil~e 5). The insects wrcniedwith :aoi olag i Ptr :s~whchwere held at roo emeatr for
A'~ > ::~ hen etn.>
ms~tai it result rm 2:in contact, or feeding.
7: ll~tn thse s:- vc~tests of the standard isccdeused for
~on~rcilnS eac se cios
~ l.~irilewoe.~.~c' -:vey toxic to all nine species of insects
I. i. is resei e jult or better than the standard insecti0>2 x~ '~itls -~~c tadpsit of 40 icrograms per square centimete: ably gP---)~r onrl of'ms species und:er th-e condi+s e~.7 rsne for th e Colorado poaobeetle. the
A~m:7 >o>">t th o~~ m 1e .-ter, and. the yellowwoll bearare
'>~e.try bcame sm~a~mr nt ear ed over a period suffi -cient for ~f hO es ~ dpostswere effective ont.e Haw1%aiian
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Although no odor could be detected from the compound, f on
tests were made to check the possibility of fumigation having oc in
the Petri-dish tests. Unmeasured quantities of the dust were plae The
lids of Petri dishes in such a way that only the vapor could pi:ea the dish and come in contact with the larvae, which were confined with u rated foliage. The dishes were held for 48 hours at room temperatur. the
previous tests. As no significant mortality occurred in tests with larvae of the melonworm, the southern beet webworm, and the Hawaiian be;t e 0:orm, it was concluded that no fumigating action occurred in the tests reported in table 1, but that the mortality was due to contact or sT, ~.on
With the toxicity of phthalonitrile established by the pi.e i ininary tests, a study was made of the effectiveness of spray deposit. o-t pted
plants in cylindrical screen cages. For this purpose the ccmpounA ade
up as a spray at concentrations of 8, 4, 2, and 1 pound per 100 plions of water and each spray applied to two plants with a compresse pray
gun. When the plants were dry, 15 larvae were confined on each p :n by a
cylindrical screen cage. The cages were examined at 2-day inte vais or larval mortality and the feeding on the plants.
The method by which a spray suspension is made may determine i s effectiveness as an insecticide. A spray suspension that can be appie: with little run-off is essential for comparing various concentrations of spray.
Obviously, if run-off is not prevented, an 8-100 spray may be no r fore offective than a 2-100 spray properly made and applied. Suitable .itads of preparation will vary with the insecticidal compound, the water ,:e, and the foliage on which the spray is to be applied. Since some o' the first sprays made up gave low toxicity as compared with the preliminary ests, several dispersing and wetting agents were tried to increase the effectiveness of the phthalonitrile.
Of the various wetting agents tried, the most satisfcc .ry was found to be saponin. The weighed portion of phthalonitrile was dissolved in 5 cc. of acetone and slowly poured, with agitation, into 95 cc. uo acer containing 0.12 percent (by 'weight) of saponin (equivalent to I/ pce of saponin per 100 gallons of water). The phthalonitrile was recrys llied in the form of fine white needles, which remained well in suspe sion. This spray could be applied heavily to collards without run-off, but it was not ideal for pumpkin and squash, which wet more readily.
A satisfactory spray was also made with bentonite, although with more difficulty owing to its sticky nature when wet. Best results were obtained by first wetting the bentonite with alcohol or acetone : then diluting gradually with the full amount of water. With the beItn: ite in suspension, an acetone solution of phthalonitrile was added wiith constant
STATE PLANT BOAR
agitation. The bentonite was always used at a 1-percent concentration in ra-.er This spray was rot always satisfactory on collards, but it worked well on pumpkin foliage.
Fairly good results were also obtained with calcium caseinate, sodu.n monosulfonate of monobutyldiphenyl, and saponin alone without acetore Each was ground to a thin paste with the insecticide and a little war and then gradually diluted with ,,ater to the desired concentration. ish-oil soap and sodium oleyl sulfate made inferior suspensions, and some other wetting agents were entirely unsatisfactory.
Spray suspensions were tested against five species of insects (table S P:hthalonitrile was effective c all species at a concentration as low a s unds per 100 gallons. The melonworm was most susceptible, complete c' 1r :esulting from a 2-100 sp ,y. Fair results were obtained with this
e- w souhern and Havii 'n beet webworms, but not on the imported cabbae worm or the southern armyworm.
in general. phthalonitrile does not appear to be so effective as he standard insecticides when ated as a spray deposit. Actually the material is as effective at the higher concentrations, but it appears to beccn less effective with dilutio: Since the compound is slowly volatile, it apareotly cannot long maintrii a lethal deposit when applied in such low concentrations.
Early in this work an experiment was conducted to determine the tolerance of tender truck-crop plants to spray deposits of phthalonitrile. The spray was made at a concentration of 8 pounds of phthalonitrile and 8 pounds of bentonite per 100 cillons of water, as described under the a ,en rests Small field plots containing from 4 to 20 plants each were pr~p ed with a hand sprayer and examined at intervals for symptoms of .ujur;. The plants included beai, collards, squash, potato, tomato, beet, an ::sss chard. weatherr conditions during the period were fair with no rainfall.
For 12 days after the spray was applied the treated plants appeared to e11 affected. A second application was then made, and the plots were se0vd over an additional 12-day period. Since no visible differences cau'I be :ound between the sprayed and unsprayed check plots, it was con.lu ihat, under certain conditions at least, phthalonitrile may be safely applied to foliage.
The effectt of exposure or weathering on spray deposits of phthaloIe 11as then studied by means of tests combining field and laboratory rhi
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melonworm. Other plots were sprayed with lead arse.ate ur 2'> plus
bentonite, and others with bentonite alone. When thoroughly dry plants
in each plot were infested with nearly full grown larvae (10 p pla L),
which were confined by screen cages. At the same time samples ; f aves
were taken at random from tho ile:aining plan s in each plot to e d to larvae (5 per leaf) in PetLri dishes in the laboratory. 1il Mples
of leaves were taken from the plants at 2-day intervals theae: i( 10
days ard fed to larvae in the laboratory. Observations for isco rility
were made 2 and 4 days after the leaf samples were infested, and t snount of feeding was observed after 4 days (table 3).
In the field-cage tests against the melonworm phthalo:it ile was more effective than derris, the results being almost identical ;h those for the same spray in table 2, except that the derris was slig ly less effective. Against the southern armyworm phthalonitrile was only slightly less effective than lead alsenate, the mortality being in genera] slightly lower than in table 2. Although these tests ate similar to t- l':ratory screen-cage tests, the plants were more exposed to heavy de, a7 1 hi:e,
two important factors in weathering.
The field-laboratory tests of leaf samples revealed a c1iircteristic of phthalonitrile that was not apparent in any of the other tests. In the tests on the southern armyworm 48 hours of weathering greatly i educed the toxicity of the deposit, and after 96 hours it was practically nontoxic. Against the melonworm the deposit was effective about /3 hours longer than against the southern armyworm. The results indict e that
deposits of phthalonitrile may remain toxic only 3 to 5 days after Aplication. Derris and lead arsenate deposits remained effective fo: 10 days. The increased mortality with lead arsenate after 8 and 10 days i iot considered significant. A greater number of samples might show less t nationn.
Volatility appeared to be a likely cause of the loss in o ^cotiveness of the phthalonitrile, because no extreme change in temperature ur rainfall had occurred during the test period. To check on this possibility, glass slides were coated with the spray and exposed to the air in the laboratory. Examination under the microscope at daily intervals showed that the deposit
gradually decreased, until on the fourth or fifth day it had disappeared. The period of volatilization would undoubtedly vary with the v:eight of the deposit and possibly with the wetting and emulsifying agents used.
Tests on Termites
Phthalonitrile was also tested as a soil treatment for the control of termites (Reticulitermes sp.). The method described by Hockenys (2) was used. A weighed quantity of the insecticide, according to the concentration desired, and 40 grams of sarc'y soil were ground in a m 1or until thoroughly mixed and then poured into a 150-cc. beaker containing about 12 cc. of water and a little tissue paper. After the dry soil had n1sorbed
the wa:er, 30 adults or large nymphs of the worker caste were place. in the beaker, which was held for 3 days in a cabine at approximately 80c F
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All concentrations down to 1 part in 3,000 parts bf soil by weight killed all the termites within 24 to 48 hours. They were not repelled by the insecticide, for they penetrated the soil to the usual depth. At concentrations of 1-4,000 and 1-5,000 approximately 93 percent of the termites were killed in 3 days; at 1-10,000 only 12 percent were killed in 5 days. Orthodichlorobenzene, a material often used in the control of terites, at a concentration of 1-1,000 repelled them, preventing penetration of the soil, but caused no mortality within 4 days.
Phthalonitrile, or orthodicyanobenzene, was tested on nin.e species of leaf-eating insects in comparison with standard insecticides against the respective species. Whon used in preliminary tests as a dust on foliage, this material was in general superior to the standard insecticide w1 which it was compared. Fumigation tests with phthalonitrile in cloPed tetri dishes gave no mortality, showing the compound to be either a stomach or a contact poison.
Sprays made up with various wetting and dispersing agents showed considerable variation in effectiveness. The most satisfactory sprayy used on cruciferous plants was made by dissolving the phthalonitrile in ace-Lone and adding the solution to water containing saponin.
In cage tests with various concentrations of spray, phthalonitrile was effective when used at 2 pounds per 100 gallons. At very dilute concentrations phthalonitrile was not so effective as the standard insecticides.
Small field plots of collard and pumpkin plants were sprayed with an 8-8-100 concentration of phthalonitrile with bentonite, and leaf samples taken from the plots every 2 days were fed to insects in the laboratory. The leaves were toxic to larvae for the first 96 hours after spraying, but were almost nontoxic thereafter.
An 8-100 concentration of spray applied to several varieties of truck-crop plants caused no injury within a 24-day period of observation.
Phthalonitrile was effective against termites when applied as a soil treatment at a concentration of 1-3,000.
(1) Dahlen, Miles A.
1939. The phthalocyanines. A new class of synthetic pigments and dyes. Indus, and Engin. Chem. 31: 839-847, illus.
(2) Hockenyos, C. L.
1939. Laboratory evaluation of soil poisons used in termite control. Jour. Econ. Ent. 32: 147-149.
12 UNIVERSITY OF FLORIDA
3 1262 09230 4020
(3) Schechter, M. S., and Hailer, H. L. J.
1940. Phthalonitrile a new insecticide. U.S. Patent 2,200,564, issued May 14.
(4) Swingle, M. C., Gahan, J. B., and Phillips, A. M.
1941. Laboratory rearing of certain leaf-eating insects. Jour.
Econ. Ent. 34: 90-95, illus.
(5) Phillips, A. M., and Gahan, J. B.
1941. Laboratory testing of natural and synthetic organic substances as insecticides. Jour. Econ. Ent. 34: 95-99, illus.