PARASI IIES
PATROG~l..S andd
PBtEBATOIIS of somen
Lepidopteros 
Pests inAlabama
Zoology-Entomology Department 
Series
Entomology No. 1
September 1966
PARASITES, PATHOGENS and PREDATORS
of some
Lepidopterous Pests in Alabama
T. F. WATSON,
1
R. T. GUDAUSKAS,
2
and T. DON CANERDAY
"3
SEVERAL LEPIDOPTEROUS pests are economically 
impor-
tant in Alabama. Some of the more important ones are
corn earworm, Heliothis zea (Boddie), also known as the
bollworm and the tomato fruitworm; tobacco budworm,
H. virescens (F.); cabbage looper, Trichoplusia ni (Hub-
ner); and false looper, Pseudoplusia includens (Wik.).
Brazzel, et al., (4) noted that the bollworm has been rec-
ognized as a pest of cotton since 1820. By 1841 the boll-
worm had become prominent as an enemy of cotton and
corn in the Southeastern United States (10). Folsom (6)
reported that in 1934 the tobacco budworm, long recog-
nized as a tobacco pest (9), occurred on cotton at Tallulah,
Louisiana, in almost as great numbers as the bollworm.
The cabbage looper is a serious pest of crucifers and many
other cultivated crops. At least one other looper species,
P. includens, attacks practically the same hosts as the cab-
bage looper, and is often found in mixed populations with
T. ni (5, 8).
Synthetic organic insecticides used during the late 1940's
temporarily provided effective controls of these pests.
However, the bollworm became difficult to control with
DDT in certain areas of Louisiana during 1956, and Graves
et al. (7) determined that the bollworm had developed re-
sistance to some of the chlorinated hydrocarbon insecti-
cides. The tobacco budworm has since developed resis-
tance to the same class of insecticides (3). Subsequent
widening of geographic areas having resistant populations-
of bollworm and tobacco budworm and difficulty encoun-
tered in controlling looper populations have caused in-
creased concern. These circumstances provided stimulus
for more research in the area of biological control, especi-
ally since many natural enemies of this group of pests
were already known.
This paper reports the parasites, pathogens, and preda-
tors found on bollworm, tobacco budworm, cabbage looper,
and false looper in Alabama during 1965.
Methods and Materials
Parasites. Egg and larval parasites of Heliothis spp.,
T. ni, and P. includens were obtained by collecting eggs
and larvae from the field and holding them in the labora-
tory until parasites emerged or until development was
completed. Eggs were collected by removing the small
section of plant tissue upon which the egg had been
placed. Larvae were collected individually by hand or
swept from the foliage with a 15-inch insect net. Eggs
were held in half-ounce coffee creamers until parasite
emergence or hatching occurred. Larvae were placed in
individual, 1-ounce, plastic containers one-third to one-
2
Department of Botany and Plant Pathology.
Department of Zoology-Entomology.
half full with artificial diets [modified from Berger (2) and
Shorey (11)].
Predators. Presence of predaceous species known to
attack Heliothis spp. was determined from whole-plant
examinations and samples taken with sweep nets or D-Vac
suction sampling machine.
Pathogens. Larvae, both dead and those suspected of
being diseased, of H. virescens, H. zea, P. includens, and
T. ni were collected from various crops. Host, date, and
location as well as any disease symptoms were recorded
for each larva collected.
Larvae were examined to determine if fungi, bacteria,
or viruses were present. Where microbial growth was ap-
parent, direct transfers to isolation media (potato dextrose
agar, Sabouraud's dextrose agar, or egg-yolk agar) in petri
dishes were made from diseased larvae. In the absence
of conspicuous microbial growth, oral and anal openings
of larvae were sealed with paraffin and larvae were rou-
tinely surface sterilized for 2 to 3 minutes in aqueous
mercuric chloride (diluted 1:1000), followed by 3 rinses
in sterile, demineralized water. Following the final rinse,
larvae were bisected with a flamed scalpel and one-half of
each larva was aseptically cut into smaller pieces, which
were then plated on isolation media. The remaining half
was aseptically macerated in sterile water, and the suspen-
sion streaked on the isolation media. A portion of the
larval suspension was retained for microscopic examination
and bioassay to determine if viruses were present. Isola-
tion plates were held at room temperature and at 300 C.,
and examined daily for microbial growth.
Pathogenicity Tests. Healthy, 5 to 7-day old larvae of
H. virescens, H. zea, P. includens, or T. ni that had been
reared in the lab were used for pathogenicity tests. Each
larva was kept in a 1-ounce plastic carton containing an
artificial diet. All larvae were held at 250 C. and 75 to 85
per cent relative humidity. Mortality counts were made
daily for 15 days. Observed mortalities were corrected ac-
cording to Abbott's formula (1).
Fungal isolates were increased on agar media in petri
dishes at room temperature. Heavily sporulating cultures
were used as inoculum sources and inoculations were made
by: (1) stroking a loopful of spores and mycelia on the
dorsum of the integument, (2) spraying the larva with a
suspension of spores in sterile, demineralized water con-
taining 0.01 per cent Triton X-100, or (3) allowing a larva
to crawl for 15 to 30 minutes over a fungal culture in an
agar plate. Control larvae were handled similarly using
a sterile loop, water alone, or fungus-free agar plates.
Numerous bacterial isolates obtained from diseased
larvae were also tested for pathogenicity. Bacterial cells
suspended in sterile saline (0.85% NaC1) were used as
inoculum. Suspensions were prepared by adding saline to
24-hour-old cultures on agar slants followed by a gentle
stroking of the slant with a rubber-tipped glass rod. Ap-
proximately 0.1 ml. of suspension was pipetted on the
diet in a carton, and inoculation was accomplished through
larval ingestion of bacterial-contaminated diet. Control
larvae ingested diet upon which only sterile saline was
pipetted.
Several isolates of a virus, apparently 
of the nuclear
polyhedrosis type, were tested 
for pathogenicity. The
integument of each larva from which these isolates 
were
obtained was dark colored and easily ruptured. The highly
liquified contents of the larvae contained numerous par-
ticles morphologically characteristic of nuclear polyhedro-
sis. A suspension of the body contents from a diseased
larva in sterile, demineralized water was used as 
inoculum.
Inoculation was accomplished by pipetting 0.1 ml. of the
inoculum onto the diet and allowing the larva to ingest the
contaminated medium. Control larva ingested diet upon
which 0.1 ml. of sterile, demineralized water was pipetted.
Results and Discussion
Parasites. Heliothis eggs collected from corn and toma-
toes were heavily parasitized with Trichogramma minutum
Riley, whereas those collected from cotton showed little
parasitism. The combined 
results from both 
1964 and
1965 collections, involving several hundred Heliothis eggs
showed 66.5, 72.7, and 5.2 per cent of the eggs from corn,
tomatoes, and cotton, respectively, were parasitized.
Larval parasites encountered in Heliothis 
spp. included
members of two families of Hymenoptera 
(Braconidae and
Ichneumonidae) and one of Diptera (Tachinidae). 
These
parasites and their Heliothis hosts were: Microplitis 
cro-
ceipes (Cress.) (both H. zea and H. virescens); 
Cardio-
chiles nigriceps Vierick (H. virescens), Apanteles margini-
ventris (Cress.) (H. zea), and Meteorus atutographae
Mues. (Heliothis spp., undetermined) of the family Bra-
conidae; Archytas marmoratus (Tns.) (H. zea and 
H.
virescens) and Lespesia sp. (H. zea) among the Diptera;
and Netelia sp. (tentative identification) (H. zea and H.
virescens) which belongs to the family Ichneumonidae.
The amount of larval parasitism 
in Heliothis spp. during
the 1965 growing season was relatively low on 
most crops
from which collections were made 
(Table 1). Parasitism
was much greater on H. virescens collected 
from beggar's
ticks, a weed of the genus Desmodium. 
The parasite in-
volved was the Ichneumonid, Netelia sp.
A certain amount of larval parasitism may 
have been
overlooked since many of the larvae died of 
diseases. This
would tend to mask the effects of the parasite.
Two parasites appeared to be more important than all
others on late season populations of Heliothis larvae. A
large fly, Archytas marmoratus, was more prevalent 
on H.
zea on grain sorghum in September and early October, and
a large Ichneumonid wasp, probably Netelia sp., was found
TABLE 1. FATE OF Heliothis LARVAE COLLECTED FROi
VARIOUS CROPS IN 1965
Host collected Pupating Parasitized Diseased
No. Pct. Pct. Pct.
Cotton ----..... 550 65.2 4.0 
39.8
Peanuts 
--------- 
150 
31.3 
1.3 
68.0
Sorghum ...------- 168 56.5 4.8 36.0
Beggar's ticks . 479 23.6 23.8 54.7
on H. virescens collected from beggar's ticks throughout
the fall months. The last collection of live larvae was
made December 3 following a period of sub-freezing tem-
perature. This parasitism undoubtedly influenced the num-
ber of Heliothis that successfully entered hibernation.
Fewer parasitic species were collected from the loop-
ers; however, less emphasis was placed on this group.
Parasites obtained from field-collected larvae included an
egg/larval parasite, Copidosoma truncatellum (Dalm.)
(family, Encyrtidae) and the tachinid fly, Eucelatoria
rubentis (Coq.). Parasites also successful against the cab-
bage looper in the laboratory were the egg parasite, Tri-
chogramma minutum, and the larval parasite, Netelia sp.
These may occur on loopers in the field.
Predators. Although the predators observed or collected
in this study were generally widespread and prevalent 
on
many crops, those reported in this publication were pri-
marily those found in cotton at some time during the grow-
ing season. These predators are listed in Table 2. Actu-
TABLE 2. PREDACEOUS ARTHROPODS KNOWN TO PREY ON
Heliothis spp. THAT WERE OBSERVED IN ALABAIA
COTTON FIELDs, 1965
Order Family Group or species
Odonata Aeshnidae Dragonflies
Neuroptera Chrysopidae Lacewings
Hemiptera Anthocoridae Flower bugs
Hemiptera Phymatidae Ambush bugs
Hemiptera Reduviidae Assassin bugs
Hemiptera Nabidae Damsel bugs
Hemiptera Lygaeidae Big-eyed bugs
Hemniptera Pentatomidae Stink bugs
Coleoptera Carabidae Ground beetles
Coleoptera Cicindelidae Tiger beetles
Coleoptera Melyridae Flower beetles
Coleoptera Coccinellidae Lady beetles
Diptera Asilidae Robber flies
Diptera Syrphidae Syrphid flies
Hymenoptera Formicidae Ants
Hymenoptera Pompilidae Spider wasps
Hymenoptera Vespidae Vespid wasps
Hymenoptera Sphecidae Sphecid wasps
Araneida -- -Spiders
ally, several species of many of the groups listed are known
to occur in cotton fields. Whitcomb and Bell (12) reported
findings of approximately 600 species of predators repre-
senting 45 families of insects, 19 families of spiders, and 4
families of mites that were associated with cotton in
Arkansas.
Pathogens. More than 500 diseased larvae were 
col-
lected during 1965. H. zea larvae comprised almost 
90
per cent of the total, with greatest numbers of this insect
being found on corn. The microorganisms associated with
diseased H. zea larvae are tabulated by crop in Table 3.
Aspergillus flavus, A. niger, Rhizopus sp., Fusidium sp.,
Penicillium sp., and Spicaria sp. were some of the fungi
commonly isolated from diseased larvae on most crops.
Isolation frequency for bacteria was about as high as that
for fungi from insects on each host. Numerous isolates
were made from larvae suspected of having viruses, but
only approximately 20 per cent contained recognizable
polyhedral bodies.
The kinds and numbers of microorganisms isolated from
diseased H. virescens larvae collected on various crops
were: A. flavus 2 (cotton), 7 (rearing room); Penicillium
TABLE 3. MICROORGAIS SAssoCIrED XITH DISEASED
Heliothis zea COLLECTED FROM VAuous CROPS
DUIUNG 1965
Number isolates by crop
Microorganism Cot- 
- Pea- Sor- Toma
Corn toncsov nuts ghum toes None'
t clover
Alternaria sp.-----. 0 0 0 1 0 0 0
Aspergillus
flavu- - 28 17 22 7 0 1 3
A niger-_ 10 7 6 4 5 0 6
Cephalosporium
sp.2 0 0 1 1 0 0
Cladosporium sp. 0 0 0 1 0 0 4
Fusarium spp..-- 3 3 0 5 0 5 1
Fusidium sp.----- 17 1 0 1 0 0 1
Monilia sp... ---- 1 0 0 0 0 0 0
Penicillium spp.--. 8 7 1 3 0 0 4
Rhizopus sp.,-------15 6 0 0 0 0 0
Spicariasp.----- 1 6 0 11 2 0 0
Unknown
(fungi)--- 6 2 0 5 4 1 2
Bacteria__ J_____127 38 0 12 4 2 27
Viruses ------ 107(19) 20(0) 0 2(0) 5(1) 0 32(16)
None .12 23 0 5 0 0 3
1
Rearing room.
2 Suspected virus; 
number of larvae 
containing polyhedra 
in-
dicated in parentheses.
sp. 1 (crimson clover), 3 (cotton); Rhizopus sp. 3 (cot-
ton); Spicaria sp. 1 (cotton); bacteria 4 (cotton); suspect
virus 2 (cotton), no polyhedra found; and no microorgan-
isms were isolated from 16 other larvae collected or cotton.
The fungus Spicaria 
rileyi was isolated from 
Pseudo-
plusia includens larvae Collected on cotton, peanuts, and
soybeans. A bacteriwn, Sre ptucoccus sp., was isolated
from diseased P. includens and another looper, Rachiplusia
att (Gn.), reared in the laboratory. One isolate of S. riley-i
was obtained from a T. ni larva on cotton.
Numerous isolates of a nuclear. polyhedrosis virus were
obtained from T. ni larvae throughout the season. Epi-
zootics of this virus among T. ni larvae have frequently
been observed in Alabama fields.
Eighteen fungal, 71 bacterial, and 118 suspect-viral iso-
lates were tested for pathogenicity.. Numerous isolates in
each group were found to cause some mortality among
test larvae.. Those microorganisms that induced highest
and most rapid mortalities and thereby considered the
most promising as control agents are listed in Table 4.
Pathogenicity tests revealed many potential control
agents for H. virescens, H. zea, P. includens, and 
T. nz.
Several factors influencing the activity of the pathogens
and 0 disease 1 developmentL must beLI- nvestigated before--3 1
TABLE 4. MICROORGANISMS PATHOGENIC TO'CERTAIN
LEPiDOPTEROUS INSECTS
Insect Pathogen
Fungi
Heliotzis zea ------------- Alternaria sp.
H. ciresceis, H. zee--------- Aspergillus flavur
H. zea------------------- Cladosporium sp.
H. zeaspp.
H.zea Fusidiumsp.
H. ea__ M on lia sp.
H. zea ____Penicillium spp.
Pseudoplusia includens,
Trichoplusia ni- - Spicaria rileyi
Bacteria
H. zea____ -------___Achrombacter sp.
H. sp.ea -A b r
H. zea---Pseudamonassp.
H. za- ertasp.
P. includens, Rachiplusia a Streptococcus sp.
Viruses
H. virescens, H. zea, T. ni--.Nuclear polyhedrosis virus
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(12)~ ~~~~~~~1 71TOB-V .,ADBL .PedcosIscs