R. E. Lynch

Interaction of larval age and antibiotic on the susceptibility of three insect species to Bacillus thuringiensis

Abstract The addition of chlortetracycline hydrochloride to bioassay diets increased the LC50S of the HD-1 isolate of Bacillus thuringiensis 2.4–67.1 times when bioassayed against 4-day-old larvae of Trichoplusia ni, Heliothis virescens, and Ostrinia nubilalis. There were no significant differences in LC50 s when bioassays were conducted with neonate larvae in the presence or absence of antibiotic, nor were there any highly significant differences between the LC50 s for HD-1 when neonate larvae were used in the presence or absence of antibiotic or when 4-day-old larvae were used in the absence of antibiotic. Viable counts of B. thuringiensis did not increase over time in any of three bioassay diets. There were no differences in activity of pure chlortetracycline hydrochloride and veterinary grade Aureomycin. There was a direct correlation between amount of antibiotic and elevation of HD-1 LC50 s when 4-day-old larvae were used. LC50 elevation in presence of antibiotic first appeared in 2-day-old larvae.

Fungi associated with eggs and first-instar larvae of the European corn borer☆☆☆

Abstract Fungi isolated from field-collected egg masses of the European corn borer, Ostrinia nubilalis , were identified as Alternaria spp., A. porri, Fusarium spp., Fusarium oxysporum, Beauveria bassiana, Mucor spp., and an unidentified yeast. Most fungi were associated with predator injury to the egg mass. Bioassay of fungi on egg masses, however, showed that Alternaria spp. and A. porri reduced the hatch of both injured and uninjured egg masses, and Mucor sp. reduced the hatch only when the egg mass was injured.

Treatment of Ostrinia nubilalis larvae with Fumidil B to control infections caused by Perezia pyraustae

Abstract Fumidil B has the potential of substantially reducing the level of Perezia pyraustae infection in laboratory colonies of the European corn borer, Ostrinia nubilalis. Drug levels of 200 to 12,000 ppm of prepared diet significantly reduced the level of P. pyraustae infection. Higher levels (e.g., 12,000 ppm) tend to increase the time to pupation and reduce the pupal weights, whereas levels up to 1500 ppm do not severely affect time to pupation, pupal weights, percentage survival, or egg production. Levels up to 12,000 ppm improved all aspects of adult fecundity. Fumidil B can be added to the diet at a diet temperature of 71°C (160°F) at levels as low as 200 ppm and still significantly reduce the level of P. pyraustae infection.

Lyophilization, vacuum drying, and subsequent storage of Nosema pyrausta spores☆☆☆

Abstract Methods of preserving Nosema pyrausta spores were developed by subjecting laboratoryreared, nondiapausing larvae of the European corn borer, Ostrinia nubilalis , infected with N. pyrausta to different techniques of lyophilization and vacuum drying. Such material was still viable when it was stored in an airtight container and held at −12°C for 12 months, or when it was stored in a vacuum desiceator and held at 22–24°C for 6 months.

Bacteria associated with eggs and first-instar larvae of the european corn borer: Isolation techniques and pathogenicity☆

Abstract Egg masses of the European corn borer, Ostrinia nubilalis, were collected from caged corn plants to study the bacterial diseases of egg masses and first-instar larvae. In 1972, a reduction in the percentage hatch, indicative of a disease epizootic, was noted among the first-generation egg masses. Bioassays of the bacteria on first-instar larvae and egg masses showed that Bacillus thuringiensis var. kurstaki was pathogenic only to larvae. Bacillus megaterium was active primarily against the egg stage.

Bacteria associated with eggs and first-instar larvae of the European corn borer: Identification and frequency of occurrence☆

Abstract Bacteria isolated from egg masses of the European corn borer, Ostrinia nubilalis, were identified by biochemical and other definitive tests as: Bacillus thuringiensis var. kurstaki, B. cereus, B. megaterium, Acinetobacter spp., Erwinia herbicola, Enterobacter cloacae, Serratia marcescens, Pseudomonas spp., and Xanthomonas sp. With the exception of S. marcescens and Pseudomonas spp., this is the first report of these bacteria from insect eggs. In addition, Enterobacter sp., Klebsiella sp., Micrococcus luteus, Streptococcus sp. and S. faecalis were isolated from first-instar larvae.

Reoccurrence of the microsporidan Perezia pyraustae in the European corn borer, Ostrinia nubilalis, reared on diet containing Fumidil B

Abstract Fumidil B suppressed the level of Perezia pyraustae infection in the larvae of the European corn borer, Ostrinia nubilalis, while they were feeding on diet containing the drug. After feeding ceased and the gut was emptied of diet containing Fumidil B, the level of infection again increased. Drug levels of 1000 and 1500 ppm in the meridic diet significantly reduced the mean level of P. pyraustae in the adult stage as compared with lower drug levels of 200 and 500 ppm. The level of infection increased throughout the pupal and adult stages, but during the pupal stage it increased much faster in the female than in the male. The rapid increase in the level of infection in the female is discussed in relation to transovariole transmission to the next generation.

Effect of Perezia pyraustae on oxygen consumption by the European corn borer, Ostrinia nubilalis

Abstract Standard Warburg manometric techniques were used to determine the oxygen consumption by European corn borers, Ostrinia nubilalis , infected with Perezia pyraustae and by borers not infected with the protozoan. The curve of oxygen consumption for disease-free corn borers resembled that reported for other Lepidoptera; diseased corn borers had a slightly higher rate of consumption throughout the life cycle.