A nutrient-based feeding stimulant and a diaminostilbene disulfonic acid-derived enhancer (fluorescent brightener, Blankophor BBH^®; Burlington Chemical, Burlington, NC) were evaluated as adjuvants for the nuclear polyhedrosis virus of the celery looper, Anagrapha falcifera (Kirby) (AfMNPV), against the beet armyworm, Spodoptera exigua (Hübner), on collard, Brassica oleracea L. (Acephala group), cv. ‘Vates’. Tests included holding larvae on sprayed potted plants in the laboratory and bioassays of foliage collected from sprayed plants in the field. The feeding stimulant increased virus-caused mortality in all tests. The enhancer increased virus-caused mortality in the bioassays of field-collected foliage but not in the test of potted plants. Treatments with both materials maintained the greatest levels of activity over time in the field. At the concentration tested on potted plants (up to 0.5% of the spray), the enhancer may have acted as a feeding deterrent. Therefore, on the whole plants, where the larvae were free to move around, effects on feeding behavior may have reduced the effectiveness of the enhancer. In the bioassay of field-collected foliage, larvae were confined on small pieces of foliage and, thus, did not have the option of moving away from the enhancer. Because the enhancer and the feeding stimulant have both been previously reported to also protect viruses from degradation by ultraviolet light, exposure to sunlight in the field could also have contributed to differences in larval mortality.

The nuclear polyhedrosis virus (NPV) from Spodoptera frugiperda (J. E. Smith) (SfMNPV) was the most active virus tested against fall armyworm, larvae (LC₅₀ = 8.1 PIB per mm²). No LC ₅₀s could be obtained for the alfalfa looper, Autographa californica (Speyer), NPV (AcMNPV), the celery looper, Anagrapha falcifera (Kirby), NPV (AfMNPV), the wax moth, Galleria mellonella (L.), NPV (GmMNPV), or the bollworm, Helicoverpa armigera (Hübner), NPV (HaMNPV). The addition of an optical brightener, Tinopal LPW® (1%), (Sigma Co., St. Louis, MO) significantly enhanced the activities of all NPVs. The most activie NPV/Tinopal LPW combination was SfMNPV, followed by AcMNPVm HaMNPV, AfMNPV, and GmMNPV. In terms of speed of kill, SfMNPV was the most active virus tested. When Tinopal LPW was added, the LT₅₀ was reduced by more than 35%. The addition of Tinopal LPW to the heterologous NPVs resulted in LC₅₀ and LT₅₀ values that were comparable to SfMNPV alone. Five of eight brighteners acted as activity enhancers for SfMNPV (i.e., Blankophor BBH, Blankophor HRS, Blankophor P167, Blankophor RKH, and Tinopal LPW), whereas Blankophor BSU, Blankophor DML, and Blankophor LPG did not enhance virus activity.

We examined aspects of the gypsy moth, Lymantria dispar (L.)/nuclear polyhedrosis virus relationship, and the effects of Blankophor BBH on that relationship, that might impact the timing of virus kill in a cohort of treated larvae. We studied this relationship both for virus and enhancer applied together and separately. We found that a portion of larvae ingesting virus polyhedral inclusion bodies die later (more than 4 wk after infection) in the season, and that this can be affected by the presence of Blankophor BBH if the virus dose is above a certain level (in this study, 10⁷ polyhedral inclusion bodies per 378 liters). Furthermore, the pattern of mortality resulting from virus ingestion was elucidated. This pattern was affected by Blankophor BBH, but only when the virus dose was above a certain higher level (in this study, 10¹¹ inclusion bodies per 378 liters). We also found that Blankophor BBH alone had no obvious effect on the course of the disease in gypsy moth larvae that had previously ingested virus; it caused neither an increase in mortality, a decrease in time to kill, nor any obvious effect on the pattern of kill. Most larvae died between 18 and 29 d. Few larvae ingesting virus died earlier (13 to 17 d); however, about 5% of the larvae died later than 30 d after infection, which may be late enough to contribute to the second wave of mortality. A combination of Blankophor BBH at 0.5% and virus at 10¹¹ inclusion bodies resulted in an increase in mortality and a decrease in time of kill compared with that seen for that level of virus without the enhancer, while eliminating the “tail” of mortality occurring 30 d after infection. However, a combination of Blankophor BBH at 0.5% and virus at 10⁹ inclusion bodies still give higher mortality than expected with the virus alone, but did not decrease the time of kill or eliminate the “tail.”

Gypsy moth, Lymantria dispar (L.), populations in three Maryland plots and three West Virginia plots were treated aerially with the gypsy moth multienveloped nuclear polyhedrosis virus product, Gypchek^® (U.S. Forest Service, USDA, Washington, DC). The study was a pilot test to demonstrate the efficacy of a single application of Gypchek suspended in the commercially-produced Carrier 038^® (Abbott Laboratories, N. Chicago, IL) at 9.5 liters and 1 × 10¹² polyhedral inclusion bodies per ha. This treatment resulted in virus levels that were significantly higher in the treated woodlots (58.7%) than in paired control woodlots (10.5%), with treatment effects highly significant. Results from treated plots in West Virginia (67.7% posttreatment virus infection) were clearly superior to results from Maryland (49.7% post-treatment virus infection) probably due to more favorable conditions during application in West Virginia. Defoliation averaged 15% in the treated woodlots and 32% in the control woodlots; however, a high degree of variability in the control woodlots, perhaps due to compensatory mortality, probably caused by a late-season epizootic of the fungus Entomophaga maimaiga Humber, Shimazu & Soper, accounted for the treatment effects being statistically non-significant at P = 0.05. Significantly higher levels of virus were found in treated woodlots than in control woodlots in an early-season larval collection made the year following treatment (1997) with virus levels averaging 11.7% in treated plots vs 5.0% in control plots. The second-year effects were particularly striking in the West Virginia plots (12.7% in treated plots vs 3.0% in control plots) suggesting that Gypchek applications may be particularly desirable in situations where natural virus is low or absent. The results of the pilot test now give forest managers the option of using one application (full dose) or two applications (split dose) of Gypchek against the gypsy moth.

A laboratory bioassay was used to evaluate Bt transgenic sweet corn hybrids for resistance against the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J. E. Smith). Whorl leaves, silks, and kernels, either fresh or oven-dried and ground with a mill, were incorporated into a dilute pinto bean diet and bioassayed against neonate, 3-, or 6-day-old larvae. Regardless of age of the larvae, results with the diet bioassay using fresh silks, oven-dried silks or fresh kernels were highly correlated with those for the fresh silk bioassay. Differences in susceptibility between insect species to the CrylA(b) toxin produced in the transgenic plants were also readily discernable using the diet bioassay. Based on results of the bioassays, Novartis sweet corn hybrids containing a crylA(b) gene gene for δ-endotoxin production were very highly resistant to leaf, silk and kernel feeding by the corn earworm and highly resistant to leaf and silk feeding by the fall armyworm.

One-d-old Heliothis virescens (F.) larvae were placed on Bacillus thuringiensis var. kurstaki Berliner-treated cotton leaves and terminals in the laboratory. Larval movement, food consumption and mortality were examined at 3, 6, 12, 24 and 48 h. Untreated leaves had a greater percentage of larvae on their under side than on their upper side; this location was not influenced by treatment with B. thuringiensis. When B. thuringiensis was applied to cotton terminals, first instars moved from B. thuringiensis-treated meristems; this movement increased with an increase in rate. Bacillus thuringiensis treatment also resulted in increased movement of larvae from the leaves and terminals onto the inner cup surface, although this movement was significantly greater than the untreated control only during the first 12 h after treatment. The leaf area consumed decreased with an increase in B. thuringiensis rate, but was not significantly correlated with larval mortality.

Extract of the venom glands of the adult female ectoparasitic wasp Microbracon hebetor (Say) (Hymenoptera: Braconidae) inhibited larval growth in the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae). The inhibition was dose dependent and at 5 d after injection larval growth was reduced 50% by 2 × 10⁻³ μg venom gland protein per mg larval weight. Doses greater than 2.5 × 10⁻² μg per mg larval weight prevented growth completely and accelerated larval death. Size-exclusion fractions of gland extract, which eluted between 35 kD and 66 kD molecular weight markers, inhibited growth and caused delayed pupation. At 5 d after injection of active chromatographic fractions, larval growth was reduced 50% by 2 × 10⁻⁴ μg fraction protein per mg larval weight. Doses greater than 1 × 10⁻³ μg fraction protein per mg larval weight stopped growth completely. Both crude extract and active column fractions caused their effects without evidence of extended paralysis.

Ovipositional preferences of Sitotroga cerealella (Olivier) were measured in the laboratory to characterize the stimuli eliciting oviposition in this widespread pest of stored grains. Substrates used for oviposition included grains presenting both physical and chemical stimuli as well as surrogates presenting only physical stimuli. Chemical factors associated with grains stimulated oviposition, but physical stimuli, primarily the presence of crevices, were of much greater importance. Moths reared for approximately 15 generations in the laboratory were less sensitive to grain factors than were moths more recently collected from the field. Experiments with surrogrates presenting a precisely defined range of crevice sizes confirmed that ovipositional response increased as crevice size narrowed. The results suggest that factors influencing habitat selection are probably very important in this insect because of indiscriminate oviposition on substrates that present appropriate physical stimuli but are entirely unsuitable for larval consumption.

Regulations of atmospheric emissions of phosphine have been enacted by a number of states in the U.S. The maximum concentration allowed at the property of fumigated sites addresses not environmental contamination, but rather the health and safety of citizens in the proximity of warehouse fumigations. In a warehouse fumigation, phosphine is most rapidly vented just after opening the warehouse for aeration. Therefore, alternative aeration techniques were tested with the objective of minimizing peak concentrations outside the warehouse through a slower and more uniform emission rate. Three types of warehouse aerations were tested: (1) a standard aeration with all doors and vents open for 3 d, (2) a modified aeration with only roof vents open for 1 d and then all doors and vents open for the following 2 d, and (3) a second modified aeration with only one large door open for 1 d and then all doors and vents open for the following 2 d. Rates of phosphine emission from the warehouses throughout aeration, gas concentrations downwind from the warehouse, and the adequacy of aeration in both the commodity and warehouse freespace were determined. Modified aerations greatly reduced phosphine peak emission rates, adequately aerated the warehouse freespace, and for most application situations, adequately aerated the tobacco. At one warehouse complex, the three types of aeration (Standard, Roof-Vent-Only and Door-Only) released 45.7, 8.5 and 9.7%, respectively, of the available gas during the first 30 min of aeration. Compared with the Standard aeration, both types of modified aeration delayed aeration of both freespace and tobacco by less than 24 h. Outside downwind concentrations of phosphine were greatly reduced by the modified aerations, especially the Roof-Vent-Only in which downwind concentrations were virtually undetectable.

Host-seeking activity of adult Diachlorus ferrugatus (F.) was studied in northwest Florida during its peak abundance period in June 1993 and 1994. Primary peak activity occurred at sunset (1945h Central Standard Time) with a minor secondary peak at 1145h. Temperature explained the major portion of variation in host-seeking behavior with relative humidity and light intensity as statistically non-significant factors. No host-seeking activity was observed at darkness. Mark-recapture studies indicated that the majority of individuals did not remain in the area after initial capture but were transitory. Anthrone assays from D. ferrugatus collected adjacent to the immediate study area revealed that about 72% had fed on fructose, while parity assays indicated 96.9% of host-seeking adults were nulliparous.

Slug problems have increased in frequency as conservation tillage has become a more widely adapted practice for production of corn, Zea mays (L.), and soybean, Glycine max (L.) Merrill, in the Midwest. Because of the increasing concern about slug damage to these crops, we initiated studies to aid growers in management of this serious pest. Slug populations were sampled in conservation-tillage fields in seven counties in Ohio from 1994–1996 to determine the species that were present in field crops and to gain insights into their life histories and damage potential. Four slug species were collected in numbers sufficient to be considered of potential economic importance. The predominant species in population size and geographic range were Deroceras reticulatum (Müller), followed closely by D. leave (Müller). Both species were common in most fields. The third most numerous slug species was Arion subfuscus (Drapamaud). Although this species was found in fewer fields, it was often collected in very large numbers. The fourth slug. A. fasciatus (Nilsson), was found only in two counties. We observed juvenile D. reticulatum causing the most damage by their feeding in late-May and in June. Damage caused by the other species was not as evident, with the possible exception of A. subfuscus causing stand loss in soybeans.