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Copyright 2005, Board of Trustees, University
S-AGRICULTURAL RESEARCH & EDUCATION CENTER QT- PI 0 1C
IFAS, University of Florida
POPULATIONS OF INSECT AND MITE PESTS ON COMMODITIES IN
PENINSULAR FLORIDA, 1975
David J. Schuster
Bradenton AREC Research Report GC1976-5 March, 1976
The abundance of damaging, as well as beneficial, insects and mites on plants
varies from year to year depending upon many factors. In some cases, weather
fluctuations and natural enemies are responsible for population surges or
declines. However, other factors such as cropping history and pesticide usage
may also play a role. A knowledge of the population fluctuation over a period
of years may aid in determining which factors are most significant in holding
specific insect or mite populations in check. In addition, this information
may enable the grower to predict trends in pest populations in his own crop,
thus permitting better timing of control measures.
The data reported herein were collected in 1975 from experimental plots and
commercial enterprises. In addition to specific population numbers, information
is given for the population trends, source, (Dover, Bradenton, Immokalee or
Stuart areas) season and relative economic importance (Table 1). Brief
biological observations are also included in Table 1 and are expanded for
certain pests below.
1) Spodoptera eridania (Cramer), the southern armyworm, was not abundant in
the spring but reached economic levels on untreated tomatoes in the fall both
at Immokalee and Bradenton. Parasitism appeared low in both areas.
2) Spodoptera exigua, the beet armyworm, was not as abundant in the spring and
fall season in Bradenton as anticipated. However, populations on chrysanthemums
in the Stuart area (east coast) were large and damage was extensive. Newly
hatched larvae attacked foliage and then moved to buds where they soon spun a
protective silk covering. This silk prohibited the spray penetration. Some
growers experienced egg hatch daily indicating an influx of adults from surround-
ing vegetation. No large larvae were collected. Populations peaked in April-
May and again in October-November. Little parasitism was noted. Population
decline in the winter corresponded to decreasing nightly temperatures.
3) Spodoptera frugiperda (J. E. Smith), the fall armyworm, is becoming more
important in the Bradenton area as the acreage planted to sweet corn increases.
Seedling corn may be consumed to the soil surface while on older plants the
leaves and whorls are attacked. A hundred or more larvae may hatch from a
single egg mass on a single plant, but generally only one or two remain per
plant, the rest migrating to nearby plants. Cannibalism may also occur. The
fall armyworm also attacks ears, the damage resembling that of the corn earworm.
4) Trichoplusia ni (Hubner), the cabbage looper, is the most serious pest
attacking cabbage. It occasionally attacks gladiolus and tomato. Populations
on cabbage far exceeded the proposed threshold of .1 looper/plant. Populations
on late cabbage declined due to larval viral infection following heavy rains.
Parasitism in the fall ranged from 17 to 67% on untreated plants. Looper
populations survived the winter of 1975-76 in reduced numbers on cabbage as
larvae were found in all winter months.
5) Taeniothrips simplex (Morison), the gladiolus thrips, was a concern to
gladiolus growers in the spring although the numbers collected were small.
Unemerged spikes and florets were damaged. Infested corms and volunteer plants
left in fields allowed later plantings to become infested. It is thought that
the cancellation of insecticides used as corm dips has intensified the problem.
At present no insecticides are registered for this use.
6) Diaphania hyalinata (L.), the melonworm, was extremely heavy on cucumbers
and 'Morgan' honeydew melon in the Bradenton area and killed untreated plants
through defoliation. The adult appeared to prefer the melon for oviposition
while larvae migrating from dead and dying plants demonstrated no preference.
Damage was primarily restricted to the foliage although some entered developing
7) Liriomyza sativae Blanchard, the vegetable leafminer, was again considered
a major problem on tomatoes and chrysanthemums in both seasons in the areas
sampled. Data does not indicate economic loss due to this insect on tomatoes,
as parasites will normally hold populations in check. However, intensive
spraying for other pests may upset the balance in favor of the leafminer. Some
old tomato varieties such as 'Pearson' indicate intermediate to low levels of
Leafminer damage to ornamental crops is more critical than on vegetable crops
because aesthetic qualities of the plants must be considered. Many registered
insecticides are reported by growers to be losing their effectiveness. The
development and registration of replacement materials has not kept pace.
Fall populations were apparently held in check by late summer and early fall
rains. However, populations increased in late fall and inflicted extensive
heavy damage in the Stuart area on chrysanthemums.
8) Keiferia lycopersicella (Walshingham), the tomato pinworm, continues to be
the number one insect concern of many tomato producers. Control on seedlings
for transplant has improved but many infested plants are still being transported
to the fields. Since the host range of the insect is very narrow, planting
insect-free transplants and destroying volunteer plants, especially in abandoned
fields, can aid in reducing populations. Larvae may also emerge from fruit and
pupate in tomato containers.
Spring populations were large while fall populations were apparently held in
check by late rains. Large populations were found in December in abandoned
fields in the Bradenton area.
Although the foliage is damaged by mining and leaf rolling, the most significant
damage occurs when older larvae bore into the fruit under the calyx. Invasion
of secondary pathogens may intensify the damage through rot.
9) Tetranychus urticae Koch, the two-spotted spider mite, has generally been a
major concern on strawberries and ornamental plants. This problem was intensi-
fied as mites developed resistance to many acaricides. However, the registration
of miticides in new chemical classes has eased the situation. On strawberries
Omite (a sulfite) and Plictran (an organotin) have permitted the production of
a crop with less concern for mites. However, there is much that needs to be
learned of this pest. Some strawberry varieties.appear resistant in some growth
stages and less so in others. The influence of flowering and fruiting in
stimulating mite populations is well known but little understood. Sources of '
plants have been demonstrated to effect mites as well.
On ornamentals mites still pose an immediate threat since many available miti-
cides are phytotoxic to blossoms. Some promising new pesticides offer safety
and should soon be registered.
Table 1. Economic insect pests of crops of peninsular Florida during 1975
Spodoptera eridania (Cram.) B,I Tomato S Light 0-1/10 plants Damaged fruit.
Southern armyworm- B,I Tomato F Heavy 0-15/10 plants Damaged foliage & fruit. Many
plants with hatching egg masses
with more than 50 larvae.
B Cabbage F Light 3-1/10 plants Feeding in head.
Spodoptera exigua (Hub.) B Gladiolus S Light 3-3/10 plants
Beet armyworm S Chrysanth. F Heavy 0-6/10 plants Population heaviest late Oct.
to mid Nov. at time of count.
B Cabbage S,F Moderate 0-7/10 plants Feeding on leaves.
(J. E. Smith)
Fall armyworm .B Gladiolus S Light 0-3/10 plants Usually located in stem or sheath
B Corn F Heavy 2-30/10 plants Skeletonizing leaves and damagin!
Trichoplusia ni (Hub.)
Cabbage looper B Cabbage S,F Heavy 2-.20/10 heads In untreated plants, up to 100%
of the heads were unmarketable.
B Tomato F Light 0-1/10 plants
B Gladiolus S Light 0-1/10 spikes Late season on spikes.
Gladiolus thrips B Gladiolus S Light 0-L2/spike Populations were sparsely
separated and damage was restric-
ted to flowers.
Table 1. (continued)
Species Sourcel Crop Season2 Population Abindance Comments
Diaphania hyalinata L. B Morgan F Heavy 10-/plant Untreated plants defoliated
melon and killed.
Melonworm B Cucumber F Heavy 10+/plant Plants defoliated, and fruit
Liriomyza spp. I Tomato S Mod. 0-15/leaflet Population declined late spring
as parasites increased.
Vegetable leafminer I Tomato F Light 10-50 mines/lft Late fall population buildup.
B Tomato F Mod. 1-10/leaflet
B Chrysanth. F Light 0-25 mines/plant
B Squash S Heavy 30-100 mines/leaf
B Morgan melon F Light 0-5 mines/plant
B Cucumber F Light 0-20 mines/plant
Keiferia lycopersicella (Walst.)
Tomato pinworm I Tomato S Mod. 5-20% damaged
B Tomato F Heavy 50Z or more Larvae transported to field.
B Tomato F Light 0-3/10 Seedlings infestations did
trifoliates not survive, apparently due
to unusually wet fall.
Tetranychus urticae Koch
2-spotted spider mite D Strawberries F Light 0-3/leaf Cool weather held populations
B Chrysanth. F Light 0-4/5 blossoms No buildup of mites noted
in untreated mum foliage.
Table 1. (continued)
Species Sourcel Crop Season2 Population Abundance Comments
Heliothis zea (Boddie) B Gladiolus S Light 0-1/10 plants Feeding on spikes.
Corn earworm B Tomato F Light 0-1/10 plants In fruit.
Erinnyis ello (L.)
Ello sphinx B Poinsettia F Moderate 0-2/5 plants Mature larvae defoliateplant.
Nezara viridula (L.) B Tomato F Moderate 5-10/10 plants
Southern green stink bug B Cabbage F Moderate 2-20/10 head Heavy on cabbage adjacent to
Feltia subterranea (Fab.) B Gladiolus S Light 0-1/10 plants
Granulate cutworm B Cabbage .. S Light 0-1/10 heads Feed in head.
Hellula undalis Fab. B Cabbage S Moderate 0-5/10 plants Bore into buds on young lants,
Cabbage Webworm and into heads and midris on
Diaphania nitidalis Stoll. B Squash S Moderate 1-5/10 fruit Primarily a problem on frit.
Frankliniella spp. B Chrysanth. F Heavy 1-140/5 Foliar damage apparent though
thrips blossoms season. Blossom fleck at arves
Population on foliage declined
due to cool weather and paiisit-
ism. Populations later increase
B = Bradenton; I = Immokalee; S = Stuart (east coast); D = Dover
2S = Spring; F = Fall.