Hydroprene prolongs developmental time and increases mortality in wandering-phase Indianmeal moth (Lepidoptera: Pyralidae) larvae

Wandering phase Indianmeal moth, Plodia interpunctella (Hübner), larvae were exposed to the label rate of hydroprene (1.9 x 10(-3) mg [AI] /cm2) sprayed on concreted petri dishes. Larvae were exposed for 1, 3, 6, 12, 18, 24, and 30 h and maintained at 16, 20, 24, 28, and 32 degrees C and 57% RH until adult emergence. Larval developmental time and mortality were significantly influenced by temperature and exposure intervals. Maximum developmental time (47.2 +/- 1.3 d) occurred at 16 degrees C, and the minimum developmental time (7.0 +/- 0.5 d) occurred at 32 degrees C. Larval mortality generally increased at all of the five tested temperatures as exposure period increased. The greatest mortality (82.0 +/- 0.1%) occurred when larvae were exposed for 30 h at 28 degrees C, and minimum mortality (0.0 +/- 0.5%) occurred at 16 degrees C when larvae were exposed for 1 h. The relationships between temperature, exposure period, and developmental time were described by polynomial models, based on lack-of-fit tests. Hydroprene has potential to be an effective alternative to conventional insecticides in surface treatments for Indianmeal moth management. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.     

Evaluation of transgenic Bt corn for resistance to the Asian corn borer (Lepidoptera: Pyralidae)

The Asian corn borer, Ostrinia furnacalis (Guenée), is the most important insect pest on corn in China. Bt transgenic corn provides a new tool for Asian corn borer control. Monsanto's YieldGard Bt transgenic corn expressing Cry1Ab protein, and a non-Bt control, were evaluated in Beijing. Laboratory bioassays were carried out by exposing neonates to an agar-free diet containing Bt corn whorl leaves, tassels, and anthers, or by exposing neonates directly to fresh silk and pollen. These are the tissues initially attacked by neonates in the field. All of these tissues, with the exception of pollen, contained sufficient insecticidal protein to kill > or = 95% of larvae within 7 d. Surviving larvae had also not grown beyond first instar and weighed < or = 0.1 mg. Although larvae feeding on Bt corn pollen were significantly smaller than those on non-Bt corn pollen, there was no significant difference in mortality. Field trials were also conducted with artificial infestations of Asian corn borer at mid whorl, late whorl, and silking stages. Damage ratings and number of larvae surviving per plant indicated that Bt corn was highly resistant to Asian corn borer. Therefore, YieldGard offers the potential for season-long protection against first- and second-generation Asian corn borer.     

Biological control of Indianmeal moth (Lepidoptera: Pyralidae) on finished stored products using egg and larval parasitoids

Biological control using hymenopteran parasitoids presents an attractive alternative to insecticides for reducing infestations and damage from the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), in retail and warehouse environments. We examined the potential for using combinations of the egg parasitoid Trichogramma deion Riley (Hymenoptera: Trichogrammatidae), and the larval parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) for preventing infestations of P. interpunctella in coarse-ground cornmeal as well as the influence of packaging on parasitoid effectiveness. Treatments included one or both parasitoids and either cornmeal infested with P. interpunctella eggs or eggs deposited on the surface of plastic bags containing cornmeal. H. hebetor had a significant impact on the number of live P. interpunctella, suppressing populations by approximately 71% in both unbagged and bagged cornmeal. In contrast, T. deion did not suppress P. interpunctella in unbagged cornmeal. However, when released on bagged cornmeal, T. deion significantly increased the level of pest suppression (87%) over bagging alone (15%). When H. hebetor was added to bagged cornmeal, there was a significant reduction of live P. interpunctella compared with the control (70.6%), with a further reduction observed when T. deion was added (96.7%). These findings suggest that, in most situations, a combined release of both T. deion and H. hebetor would have the greatest impact; because even though packaging may protect most of the stored products, there are usually areas in the storage landscape where poor sanitation is present.     

Sex pheromone gland of the female European corn borer moth,Ostrinia nubilalis (Lepidoptera,Pyralidae): ultrastructural and biochemical evidences

The sex pheromone gland of the female European corn borer moth, Ostrinia nubilalis was studied using light and electron microscopy. The pheromone gland is formed by hypertrophied epidermal cells at the mid-dorsal region of the intersegmental membrane between abdominal segments 8 and 9/10. Active glandular cells contain extensive apical membrane foldings, a single nucleus, many free ribosomes, numerous mitochondria, microtubules and lipid droplets. Smooth endoplasmic reticulum is scanty. In young moths, the glandular cells are smaller in size, the microvilli at the apical membrane are poorly developed and the cytoplasm contains fewer mitochondria, microtubules, and no lipid droplets. The surrounding unmodified epidermal cells are small cuboidal or squamous cells. These cells have ill-defined apical membrane foldings and do not contain lipid droplets in the cytoplasm and the overlying cuticle. Fatty acids analyses revealed the presence of the sex pheromone components, (E)-11-tetradecenyl acetate, and their immediate precursors, methyl (E)-11- and methyl (Z)-11-tetradecenoate, only in the dorsal portion of the cylindrical intersegmental membrane. Results of the present study show that the sex pheromone gland of O. nubilalis is restricted to the dorsal aspect of the intersegmental membrane between segments 8-9/10 and is not a ring-gland.     

Hydroprene prolongs developmental time and increases mortality of Indianmeal moth (Lepidoptera: Pyralidae) eggs

Eggs of the Indianmeal moth, Plodia interpunctella (Hübner), were exposed to the labeled rate of hydroprene (1.9 x 10(-3) mg [AI]/cm2) sprayed on concreted petri dishes. These eggs were exposed for 1, 3, 6, 12, and 18 h and until hatching (continuous exposure) at temperatures of 16, 20, 24, 28, and 32 degrees C and 57% RH until the emergence of first instars. The developmental time and egg mortality were significantly influenced by temperature and exposure periods. At 16 degrees C, hydroprene did not cause differences in developmental time when eggs were exposed for different periods. At temperatures >16 degrees C, both exposure period and temperature influenced developmental time. The maximum developmental time (15.0 +/- 0.2 d) occurred at 16 degrees C, and the minimum developmental time (3.2 +/- 0.3 d) occurred at 32 degrees C. Mortality increased when eggs were exposed to hydroprene for longer periods at all of the five tested temperatures. The greatest mortality (81.6 +/- 2.1%) occurred when eggs were continuously exposed on treated surfaces at 32 degrees C. We used developmental time instead of rate (1/ developmental time) to fit simple linear or polynomial regression models to the development data. Appropriate models for developmental time and mortality were chosen based upon lack-of-fit tests. The regression models can be used in predictive simulation models for the population dynamics of Indianmeal moth to aid in optimizing use of hydroprene for insect management.     

Age- and density-related oviposition behavior of the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Age-related oviposition patterns ofOstrinia nubilalis were studied at three population densities in the laboratory by releasing newly eclosed adults in wire-screened cages and analyzing their oviposition throughout the adult stage with digital analysis. Oviposition sequences of individual females depositing egg masses were documented on the third and seventh nights after eclosion with a video camcorder. During a sequence, a female produced an egg in an average time of 15 or 26 s on the third and seventh nights, respectively, and completed depositing an egg mass the size of 20–39 eggs in an average time of 316 and 525 s, respectively. Females were not easily disturbed during egg mass deposition and pulsated their abdomen before deposition of each egg. Females produced few egg masses the first night after eclosion. Oviposition increased on nights 2 and 3 but declined steadily thereafter as females matured. Females older than 6 nights produced fewer egg masses; the proportion of egg masses with fewer than 20 eggs increased gradually. By the end of the adults' lifetime, nearly 100% of the egg masses had fewer than 20 eggs. The data are fundamental to our research to define the role of phytochemicals in modifying oviposition behavior of the European corn borer.     

Relationship between supercooling point and mortality at low temperatures in Indianmeal moth (Lepidoptera: Pyralidae)

Indianmeal moth, Plodia interpunctella (Hübner), is classified as a freeze-intolerant organism and one of the most cold-tolerant stored-product pests. The objective of this study was to determine the relationship between mortality at low temperatures after minimum exposure and the supercooling point (SCP) for laboratory-reared P. interpunctella at different stages of development. This relationship also was analyzed for field-collected, cold-acclimated fifth instars. Mean SCP of laboratory-reared larvae (i.e., feeding stage) was consistently above approximately -16 degrees C. Mean SCP of laboratory-reared pupae and adults (i.e., nonfeeding stages) and field-collected, cold-acclimated fifth instars was consistently below approximately -21 degrees CP seemed to be the boundary between survival and death for larvae. However, it seemed that a 1-min exposure was not sufficient to cause larval mortality at the SCP. Alternatively, for both pupae and adults, the SCP seemed not to play an important role in their survival at low temperatures, with significant mortality observed at temperatures higher than the mean SCP. Adults were the most susceptible to low temperatures with no survival occurring at -20 degrees C, > 3 degrees C above its mean SCP. Results of this investigation demonstrate that P. interpunctella has a different response to low temperatures depending on stage of development and cold acclimation. Classifying P. interpunctella only as a freeze-intolerant organism disregards the occurrence of prefreeze mortality in this species. Therefore, a reclassification of this species (e.g., chill tolerant or chill susceptible) based on the extent of prefreeze mortality and the temperature and time of exposure at which it occurs is suggested.     

Attractancy and toxicity of an attracticide for Indianmeal moth, Plodia interpunctella (Lepidoptera: Pyralidae)

Plodia interpunctella (Hübner) is a serious and widespread postharvest pest on cereal products, dried fruits, candy, and pet food. Due to the strong positive anemotactic flight response of P. interpunctella males to the main component of the female-produced pheromone [(Z,E)-9,12-tetradecadienyl acetate, herein referred to as ZETA], we evaluated the potential of an attracticide for this pest, in which ZETA as attractant was combined with permethrin as the killing agent. Two concentrations of ZETA [0.16 and 0.32% (wt:wt)] and five concentrations of permethrin [0, 3, 6, 12, and 18% (wt:wt)] were incorporated into Last Call gel (10 different permethrin:ZETA combinations). All attracticide gels were evaluated in a toxicity test, in which either the tip of a leg or an antenna of a virgin P. interpunctella male was touched < 3 s into a dot of attracticide gel. These males were subsequently transferred to jars with virgin females. The toxicity test showed that a brief and gentle contact of P. interpunctella males with attracticide gel containing 3-18% permethrin caused a significant reduction in mating and killed males moths within 24 h. A wind tunnel test was conducted to evaluate the flight responses of P. interpunctella males to the same 10 attracticide gels. Male moths displayed significantly higher levels of positive anemotactic flight and more males made contact with the attracticide gel when the ZETA concentration was 0.16% compared with 0.32%. P. interpunctella males showed no signs of repellency to permethrin concentrations within a range of 0-18% in the attracticide gel. Three densities of P. interpunctella pairs were released into small warehouse rooms, and we found that the attracticide gel suppressed oviposition when the moth density was at a low level, but it was ineffective when the moth density exceeded one male-female pair per 11.3 m3.     

Mortality of Indianmeal moth (Lepidoptera: Pyralidae) populations under fluctuating low temperatures: model development and validation

A model for predicting mortality of Indianmeal moth larvae [Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)] under fluctuating low-temperature conditions was developed. The time and temperature combinations required to achieve 100% mortality of field-collected, cold-acclimated P. interpunctella larvae obtained from laboratory mortality experiments were used to develop the mortality model. Accumulation of mortality rate over time was called the cumulative lethality index (CLI). Complete mortality of insect populations would occur when CLI equals 1. Observed mortality of field-collected, cold-acclimated P. interpunctella larvae in five 76.2-T (3,000-bu) shelled corn bins located in Rosemount, MN, during the winters of 2003-2004 and 2004-2005 were used to validate the CLI model (i.e., mortality model). Excellent agreement between predicted and measured time to 100% larval mortality was observed. The CLI model would be useful for developing low-temperature aeration management strategies for controlling overwintering P. interpunctella in grain bins. In addition, this model will be useful when determining if additional control measures will be required as a result of above-seasonal ambient temperatures.     

Artificial carbon dioxide source to attract lesser cornstalk borer (Lepidoptera: Pyralidae) larvae

Different combinations of urea, urease (in jack bean meal, Canavalia DC.), and water were tested as carbon dioxide sources to attract larvae of lesser cornstalk borer, Elasmopalus lignosellus (Zeller), by using olfactory bioassays with an olfactometer and infrared gas analysis. A combination of urea, jack bean meal, and water was necessary to release a high level of carbon dioxide to attract the larvae. Different proportions of the three ingredients had different carbon dioxide release rates and exhibited different levels of attraction to the larvae. When carbon dioxide concentration was too high, attractiveness declined. Combinations with different amounts of water remained attractive for a period of up to 3 d, depending on the moisture of the samples. When Zonolite was used to simulate the soil conditions in the olfactometer, significantly more larvae located the area near the artificial carbon dioxide sources compared with the control. When combined with the artificial carbon dioxide sources, three insecticides (Lorsban, Temik, and Force) did not obviously affect the release rates of carbon dioxide, and more larvae were attracted to samples with the carbon dioxide source than to the samples without carbon dioxide.     

Seed inoculation with beneficial rhizobacteria affects European corn borer (Lepidoptera: Pyralidae) oviposition on maize plants

Larvae of Ostrinia nubilalis (Hübner) cause significant damage to maize ears and reduce market value of fresh sweet corn. Females rely on volatile cues to locate and oviposit preferentially on maize plants. In addition, oviposition behavior of females is influenced by soil management practices as they usually lay more eggs on maize plants grown on conventional soil than on organic soils that harbor rich microbial diversity. Since some plant growth‐promoting rhizobacteria (PGPR) are known to mediate plant health via suppression of soil pathogens and enhanced uptake of nutrients; we hypothesized that inoculation of maize seeds with PGPR will alter emission of maize volatile and reduce the attractiveness of plants to ovipositing O. nubilalis. Plants treated with the single PGPR strain Bacillus pumilus INR‐7, two PGPR mixtures (Blend‐8 or Blend‐9) or untreated plants were presented to O. nubilalis females in oviposition choice bioassays. Headspace volatile organic compounds (VOCs) from the plants were analyzed by gas chromatography–mass spectrometry (GC–MS). Ostrinia nubilalis laid significantly fewer eggs on PGPR‐treated plants compared to untreated plants. In two‐choice oviposition experiments, significantly higher numbers of eggs were laid on untreated plants compared to PGPR‐treated plants. PGPR‐treated plants emitted fewer VOCs than untreated plants which, in part, explains the relatively fewer eggs on PGPR‐treated plants. These results indicate that selected PGPR treatments can alter maize plant volatiles with important ramifications for plant‐insect interactions. The implication of this finding is discussed in the context of integrated management of soil health to improve crop resistance to biotic stressors.     

Effects of height and adjacent surfaces on captures of Indianmeal moth (Lepidoptera: Pyralidae) in pheromone-baited traps

Diamond-shaped pheromone-baited traps are used widely in food storage and food processing facilities for monitoring of Plodia interpunctella (Hübner), and here we evaluated to what extent trap captures were affected by 1) vertical placement of traps, 2) deployment of a horizontal landing platform to the diamond-shaped pheromone trap, and 3) placement of traps either freely exposed or along a sidewall. In the small sheds (height 1.8 m), traps were placed in three heights and significantly highest trap captures were obtained near the ceiling. When the same experiment was conducted in a larger room (height 6 m) with traps at seven heights, highest captures were obtained at both the lowest and highest traps. In a subsequent experiment, we deployed a horizontal platform to traps at seven heights and found that the importance of vertical placement became less important. Thus, it seemed that male moths preferred to orient to a pheromone source associated with a physical surface, such as the floor, ceiling, or landing platform. In a comparison of P. interpunctella male trap captures in a completely dark room (no visual cues), traps with a landing platform caught significantly more than traps without the platform. In a final experiment, we evaluated the effect of hanging traps either freely or adjacent to sidewalls, and significantly highest trap captures were obtained along side-walls. The results presented here suggest that deployment of a horizontal platform reduces the importance of the vertical placement of traps and seems to increase the trap efficiency, and we recommend placement of traps along sidewalls and/or near the ground.     

Evaluation of oviposition deterrence in management of resistance to transgenic corn by European corn borer (Lepidoptera: Crambidae)

We modified an existing model for European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), population dynamics and genetics to evaluate the effectiveness of oviposition deterrence in transgenic fields for resistance management. We simulated two types of deterrence: one type has females reducing their oviposition because of lost opportunities to lay eggs (eggs lost), and the other type has the deterred females moving to the refuge to lay eggs. Oviposition deterrence was clearly effective in extending the time to resistance to transgenic corn (R allele) in the European corn borer, particularly when 80% or more of the eggs were deterred from being oviposited on the transgenic plants. With 90% of eggs deterred, the time required to reach 50% R-allele frequency increases 3.7- to 5.5-fold compared with the no-deterrence scenario. The time to 50% R-allele frequency was similar for the two types of simulated deterrence, but the densities of the European corn borer were 100-fold higher when the deterred females oviposited in the refuge. The Y allele for insensitivity or resistance to deterrence never reached 50% within the 50-yr time line for these simulations except when the R allele was dominant and the Y allele was not recessive. The time to 50% Y-allele frequency was 33 and 26 yr when the Y allele was additive or dominant, respectively, when 50% of the eggs were deterred, but the time decreased to 18 and 16 yr when 90% of the eggs were deterred. The effectiveness of oviposition deterrence on time to resistance to transgenic insecticidal plants was not changed much when we altered our assumptions about behavior in a sensitivity analysis.     

Dispersal behavior of neonate European corn borer (Lepidoptera: Crambidae) on Bt corn

European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), has historically been a significant economically important insect pest of corn (Zea mays L.) in the United States and Canada. The development in the 1990s of genetically modified corn expressing genes derived from Bacillus thuringiensis (Bt) that encodes insecticidal crystalline (Cry) proteins has proven to be effective in controlling this insect as well as other corn pests. The purpose of this study was to assess the movement and dispersal behavior of neonate European corn borer on Bt corn. We examined differences in neonate European corn borer dispersal behavior for the first 4 h after eclosion in the field among a stacked pyramid (Cry1F X Cry1Ab X Cry34/35Ab1) Bt corn, a Cry1F Bt corn, and a non-Bt sweet corn; and in the laboratory among a Bt corn hybrid containing Cry1F, a hybrid containing Cry1Ab, a pyramid combining these two hybrids (Cry1F X Cry1Ab), and a non-Bt near isoline corn. In field experiments, we found that dispersal was significantly higher on Bt corn compared with sweet corn. In laboratory experiments, dispersal was significantly higher on Cry1Ab Bt corn and Cry1F X Cry1Ab Bt corn than on non-Bt near isoline corn. Results indicated that neonate dispersal may be significantly greater in Bt cornfields compared with non-Bt cornfields. The findings on dispersal behavior in this study will be useful in evaluating the efficacy of a blended seed refuge system for managing European corn borer resistance in Bt corn.     

A technique using reusable components for hand-infesting cornstalks with European corn borer (Lepidoptera: Crambidae) larvae

Field trials were conducted in 2005 and 2006 to evaluate the use of reusable wire nuts and nonreusable gelatin capsules for hand-infesting cornstalks with European corn borer, Ostrinia nubilalis (Hübner), (Lepidoptera: Crambidae) larvae. The reusable technique, which consists of a modified WingGard plastic wire connector (i.e., wire nut) as a containment device for larvae, was compared over three plant growth stages to a gelatin capsule technique. In 2005 and 2006, the wire nut technique resulted in significantly higher number of wire nuts still intact (i.e., undamaged, with or without a larva) on the stalk at 72 h after infestation compared with the gelatin capsule technique. In addition, the wire nut technique resulted in significantly higher number of tunnels per stalk compared with the gelatin capsule technique at all three corn growth stages during both years. In 2005, the mean +/- SEM number of tunnels per stalk was 0.53 +/- 0.03 in the wire nut technique compared with 0.13 +/- 0.03 tunnels per stalk in the gelatin capsule technique. In 2006, the mean number of tunnels per stalk was 0.45 +/- 0.03 in the wire nut technique compared with 0.08 +/- 0.02 tunnels per stalk in the gelatin capsule technique. In addition, the relative net precision in the wire-nut technique was approximately 2 times higher compared with the gelatin capsule technique.     

Ionizing irradiation of adults of Angoumois grain moth (Lepidoptera: Gelechiidae) and Indianmeal moth (Lepidoptera: Pyralidae) to prevent reproduction, and implications for a generic irradiation treatment for insects

Ionizing irradiation is used as a phytosanitary treatment against quarantine pests. A generic treatment of 400 Gy has been approved for commodities entering the United States against all insects except pupae and adults of Lepidoptera because some literature citations indicate that a few insects, namely, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), and the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), are not completely controlled at that dose. Radiotolerance in insects increases as the insects develop, so the minimum absorbed dose to prevent F1 egg hatch for these two species when irradiated as adults was examined. Also, because hypoxia is known to increase radiotolerance in insects, Angoumois grain moth radiotolerance was tested in a hypoxic atmosphere. A dose range of 336-388 Gy prevented F1 egg hatch from a total of 22,083 adult Indianmeal moths. Dose ranges of 443-505 and 590-674 Gy, respectively, prevented F1 egg hatch from a total of 15,264 and 13,677 adult Angoumois grain moths irradiated in ambient and hypoxic atmospheres. A generic dose of 600 Gy for all insects in ambient atmospheres might be efficacious, although many fresh commodities may not tolerate it when applied on a commercial scale.     

Tolerance of Bt corn (MON 810) to maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

Transgenic corn (MON 810), expressing the Bacillus thuringiensis (Bt) protein, Cry1Ab, was evaluated under greenhouse conditions for its tolerance to the maize stem borer, Chilo partellus. Bt corn (MON 810) provided effective protection against the stem borer even under a high level of larval infestation in the greenhouse. The observed tolerance is examined and discussed in the light of the susceptibility of C. partellus to the Cry1Ab protein in laboratory bioassays. The implications of the tissue concentrations of Cry1Ab in MON 810, and baseline susceptibility recorded in the current study, for insect-resistance management are discussed.     

Age-specific dose-mortality effects of Beauveria bassiana (Deuteromycotina: Hyphomycetes) on the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Three isolates of Beauveria bassiana were evaluated under laboratory conditions for pathogenicity against the European corn borer, Ostrinia nubilalis. Dose-mortality regressions and nonparametric statistical analyses revealed significant differences in pathogenicity between isolates and across O. nubilalis instars. First instars were found to be the most susceptible of the five larval stages. Little difference was noted for instars 2, 3, and 5 within any of the three B. bassiana isolates. Fourth instar larvae were found to be the most tolerant in all cases.     

Life history attributes of Indian meal moth (Lepidoptera: Pyralidae) and Angoumois grain moth (Lepidoptera: Gelechiidae) reared on transgenic corn kernels

The Indian meal moth, Plodia interpunctella (Hübner), and Angoumois grain moth, Sitotroga cerealella (Olivier), are two globally distributed stored-grain pests. Laboratory experiments were conducted to examine the impact that corn (Zea mays L.) kernels (i.e., grain) of some Bacillus thuringiensis Berliner (Bt) corn hybrids containing CrylAb Bt delta-endotoxin have on life history attributes of Indian meal moth and Angoumois grain moth. Stored grain is at risk to damage from Indian meal moth and Angoumois grain moth; therefore, Bt corn may provide a means of protecting this commodity from damage. Thus, the objective of this research was to quantify the effects of transgenic corn seed containing CrylAb delta-endotoxin on Indian meal moth and Angoumois grain moth survival, fecundity, and duration of development. Experiments with Bt grain, non-Bt isolines, and non-Bt grain were conducted in environmental chambers at 27 +/- 1 degrees C and > or = 60% RH in continuous dark. Fifty eggs were placed in ventilated pint jars containing 170 g of cracked or whole corn for the Indian meal moth and Angoumois grain moth, respectively. Emergence and fecundity were observed for 5 wk. Emergence and fecundity of Indian meal moth and emergence of Angoumois grain moth were significantly lower for individuals reared on P33V08 and N6800Bt, MON 810 and Bt-11 transformed hybrids, respectively, than on their non-Bt transformed isolines. Longer developmental times were observed for Indian meal moth reared on P33V08 and N6800Bt than their non-Bt-transformed isolines. These results indicate that MON 810 and Bt-11 CrylAb delta-endotoxin-containing kernels reduce laboratory populations of Indian meal moth and Angoumois grain moth. Thus, storing Bt-transformed grain is a management tactic that warrants bin scale testing and may effectively reduce Indian meal moth and Angoumois grain moth populations in grain without application of synthetic chemicals or pesticides.     

Establishment of Cry9C susceptibility baselines for European corn borer and southwestern corn borer (Lepidoptera: Crambidae)

In 1997 and 1998, Cry9C susceptibility baselines were established for field-collected populations of European corn borer, Osrinia nubilalis (Hubner), and southwestern corn borer, Diatraea grandiosella Dyar. Bioassay of neonate European corn borer larvae of 16 colonies collected from the midwestern United States indicated LC50 values ranging from 13.2 to 65.1 ng of Cry9C protein per square centimeter. Neonate European corn borer LC50 values ranged from 46.5 to 214 ng/cm2. Neonate larvae of three colonies of southwestern corn borer collected from the southern and southwestern United States exhibited LC50 values from 16.9 to 39.9 ng of Cry9C protein per square centimeter. Southwestern corn borer neonate LC90 confidence limit values ranged from 40.3 to 157 ng of Cry9C protein per centimeter. The most sensitive southwestern corn borer colony was collected from the Mississippi delta exhibiting an LC50 value of 22.6 ng of Cry9C per cm2 and also displayed the widest LC0 confidence limits of 40.3-94.8 ng of Cry9C per cm2. Geographic baseline susceptibility data establishes the natural genetic variation and provides the foundation for future testing of insect populations exposed to increased use of Bacillus thuringiensis-based crops. Insect resistance management and stewardship of Cry9C will rely upon baseline data for the validation of discriminating dose assays for European corn borer and southwestern corn borer.