Agrotis Ipsilon Research Articles

Application of Bioactive Coatings Based on Chitosan for Soybean Seed Protection

Soybean seeds suffer attacks of various pests that result in a decreased yield in northeastern China. Until recently, people use pesticides such as insecticides to achieve the goal of controlling pests. Chitosan extracted from deacetylation of chitin is promising candidates as a seed-coating agent to control agrotis ypsilon, soybean pod borer, and soybean aphid effectively. An experimental study on influences of chitosan with different concentrations on pest controlling and soybean growth was made in the paper. Coating based on chitosan was used as a feeding deterrent and for enhancing the germination and quality of soybean seeds. Results indicated that all chitosan coating had a significant effect on antifeeding against pests; with the increasing concentration, antifeedant rate (AR) were increased obviously, especially when in the concentration of 5%, santifeedant rate of agrotis ypsilon, soybean pod borer, and soybean aphid reached 82.89%, 87.24%, and 80.21%, respectively. Also chitosan coating increased seed germination, plant growth, and soybean yield efficiently, especially when, in the concentration of 5%, the yield was increased by about 20% compared with CK. The application of chitosan in soybean seed coated is an appropriate option to control pests replacing high-toxicity pesticides and enhance soybean yield.

Plant odour stimuli reshape pheromonal representation in neurons of the antennal lobe macroglomerular complex of a male moth

Male moths are confronted with complex odour mixtures in a natural environment when flying towards a female-emitted sex pheromone source. Whereas synergistic effects of sex pheromones and plant odours have been observed at the behavioural level, most investigations at the peripheral level have shown an inhibition of pheromone responses by plant volatiles, suggesting a potential role of the central nervous system in reshaping the peripheral information. We thus investigated the interactions between sex pheromone and a behaviourally active plant volatile, heptanal, and their effects on responses of neurons in the pheromone-processing centre of the antennal lobe, the macroglomerular complex, in the moth Agrotis ipsilon. Our results show that most of these pheromone-sensitive neurons responded to the plant odour. Most neurons responded to the pheromone with a multiphasic pattern and were anatomically identified as projection neurons. They responded either with excitation or pure inhibition to heptanal, and the response to the mixture pheromone + heptanal was generally weaker than to the pheromone alone, showing a suppressive effect of heptanal. However, these neurons responded with a better resolution to pulsed stimuli. The other neurons with either purely excitatory or inhibitory responses to all three stimuli did not exhibit significant differences in responses between stimuli. Although the suppression of the pheromone responses in AL neurons by the plant odour is counter-intuitive at first glance, the observed better resolution of pulsed stimuli is probably more important than high sensitivity to the localization of a calling female.

Effect of Bacillus thuringiensis and Farnesol on Haemocytes Response and Lysozymal Activity of the Black Cut Worm Agrotis ipsilon Larvae

Effect of Bacillus thuringiensis and Farnesol on Haemocytes Response and Lysozymal Activity of the Black Cut Worm Agrotis ipsilon Larvae

Differential Interactions of Sex Pheromone and Plant Odour in the Olfactory Pathway of a Male Moth

Most animals rely on olfaction to find sexual partners, food or a habitat. The olfactory system faces the challenge of extracting meaningful information from a noisy odorous environment. In most moth species, males respond to sex pheromone emitted by females in an environment with abundant plant volatiles. Plant odours could either facilitate the localization of females (females calling on host plants), mask the female pheromone or they could be neutral without any effect on the pheromone. Here we studied how mixtures of a behaviourally-attractive floral odour, heptanal, and the sex pheromone are encoded at different levels of the olfactory pathway in males of the noctuid moth Agrotis ipsilon. In addition, we asked how interactions between the two odorants change as a function of the males' mating status. We investigated mixture detection in both the pheromone-specific and in the general odorant pathway. We used a) recordings from individual sensilla to study responses of olfactory receptor neurons, b) in vivo calcium imaging with a bath-applied dye to characterize the global input response in the primary olfactory centre, the antennal lobe and c) intracellular recordings of antennal lobe output neurons, projection neurons, in virgin and newly-mated males. Our results show that heptanal reduces pheromone sensitivity at the peripheral and central olfactory level independently of the mating status. Contrarily, heptanal-responding olfactory receptor neurons are not influenced by pheromone in a mixture, although some post-mating modulation occurs at the input of the sexually isomorphic ordinary glomeruli, where general odours are processed within the antennal lobe. The results are discussed in the context of mate localization.

Entomopathogenic nematodes for the management of Agrotis ipsilon: effect of instar, nematode species and nematode production method

Previous laboratory studies have indicated the potential of some entomopathogenic nematode (EPN) species for the control of larvae of the black cutworm (BCW). To determine the most promising EPN species and the most susceptible BCW stages, a more in-depth evaluation of seven EPN species against different BCW instars was carried out, the efficacies of in vitro- and in vivo-produced EPNs were compared and the suitability of BCW instars for EPN reproduction was examined. Heterorhabditis megidis was the most virulent species, irrespective of larval stage in small arenas, followed most often by H. bacteriophora. In pots with grass, Steinernema carpocapsae tended to be the most virulent species, followed by H. bacteriophora, H. megidis and S. riobrave. Fourth and/or fifth instars were the most susceptible stages to most EPN species, and pupae the least susceptible. Furthermore, H. bacteriophora, H. megidis and S. carpocapsae successfully reproduced in fifth and sixth instars and pupae. In vivo-produced H. megidis and S. carpocapsae controlled fifth instars better than the corresponding in vitro-produced products; production method did not affect H. bacteriophora and S. riobrave efficacy. Several in vitro-produced commercial EPN strains were highly virulent to BCW and warrant further testing under field conditions, along with some in vivo-produced strains.

The transcription factor Krüppel homolog 1 is linked to the juvenile hormone-dependent maturation of sexual behavior in the male moth, Agrotis ipsilon

In the male moth, Agrotisipsilon, the behavioral response and neuronal sensitivity in the primary olfactory center, the antennal lobe (AL), to sex pheromone increase with age and juvenile hormone (JH) biosynthesis. Although JH has been shown to control this age-dependent plasticity, the underlying signaling pathway remains obscure. In this context, we cloned a full cDNA encoding the Krüppel homolog 1 transcription factor (AipsKr-h1) of A. ipsilon, which was found to be predominantly expressed in ALs, where its amount increased concomitantly with age and sex pheromone responses. Conversely, the expression of AipsKr-h1 protein in the antenna was age-independent. Moreover, the administration of JH in immature males or fluvastatin, an inhibitor of JH biosynthesis, in mature males induced an increase or a decline of the AipsKr-h1 protein level in ALs, respectively. This effect was suppressed with a combined injection of fluvastatin and JH. Our results showed that Aipskr-h1 is a JH-upregulated gene that might mediate JH action on central pheromone processing, modulating sexual behavior in A. ipsilon.

EFFICIENCY OF TWO NOVEL BIOCONTROL COMPOUND AT LC50Ś AGAINST THE FOURTH LARVAL INSTAR OF BLACK CUTWORM, AGROTIS IPSILON (HUFNAGEL) (LEPIDOPTERA: NOCTUIDAE)

The efficiency of two novel compounds (takumi and radiant) and conventional insecticide (methomyl) against the fourth instar larvae of Agrotis ipsilon was evaluated under laboratory conditions through determination their LC50 values. Takumi was the most toxic one against the 4th larvae treated by both feeding and dipping techniques showing LC50s of 6 and 80 ppm, respectively. While, Radiant was the second one, the LC50s were 28 and 500 ppm, respectively. Whereas, methomyl was the least one, its LC50s were 187.5 and 900ppm, respectively. All the treated larvae were biologically affected by the three tested compounds. The effects were varied according to the applied method and compound. The larval treatments via leaf dip method had the highest effect in larval and pupal duration increase.Methomyl treatment induced the longest period in this respect, followed by takumi and radiant ones. Therefore, the treated larvae by this method were resulted in pupal malformation percent increase. While, the larval treatment via dip method had the strongest effect in shifting of sex ratio of males and females percent, decrease of pupation percent, pupal weight and adult longevity and increase of adult malformation percent. Also, the larval treatment of 4th instars with takumi by both leaf and larval dip and the treatment with radiant via larval dip method had the strongest effect in adult fecundity reduction to reach zero, as compared to591.6 and 524.9 eggs/female of control of both methods, respectively.

Antifeedant, insecticidal and growth inhibitory activities of selected plant oils on black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

ObjectiveTo evaluate antifeedant, insecticidal and insect growth inhibitory activities of eucalyptus oil (Eucalyptus globules) and gaultheria oil (Gaultheria procumbens L.) against black cutworm, Agrotis ipsilon. MethodsAntifeedant, insecticidal and growth inhibitory activities of eucalyptus oil and gaultheria oil were tested against black cutworm, A. ipsilon. ResultsSignificant antifeedant activity was found in eucalyptus oil (96.24%) where as the highest insecticidal activity was noticed in gaultheria oil (86.92%). Percentages of deformities were highest on gaultheria oil treated larvae and percentage of adult emergence was deteriorated also by gaultheria oil. ConclusionsThese plants oil has potential to serve as an alternative eco-friendly control of insect pest.

Bioenergetics Growth Model for the Effect of Gamma Irradiation and/or Plant Extract Barnoof on the Progeny of Black Cutworm, <I>Agrotis ipsilon</I> (Hufngel)

In this study, we investigate the effects of two substerilizing doses 100 and 150 Gray (Gy) of gamma irradiation applied to Full grown pupae of the Black cutworm, Agrotis ipsilon (Hufngel). and/or plant extract, Conyza dioscorides (Barnoof) with two different solvents and applied to the resulting 5 th -6 th instar larvae in F 1 generation on certain biological aspects and the energy budget. Data revealed that gamma irradiation when combined with the extract in most treatments significantly higher than the control of reproduction at all treatments (doses and concentrations). Most of the treatments increased the values of developmental/day, larval duration and % survival were measured. These indices in the F 1 progeny as compare to the control treatment, except, at the % survival it was decreased at all treatments. These values were more obvious in combination treatments compared to gamma irradiation or plant extract treatments each of them alone. The coefficient of metabolizable energy (C.M.E.) not affected at all treatments. The efficiency of storage of ingested energy [E.S.I.(E)] and the efficiency of storage of metabolizable energy [E.S.M.(E)] were between increasing and decreasing when the F 1 progeny treated with plant extract alone or combined with the dose 100 Gy while it were significantly increased at all treatments when the dose 150 Gy combined with the plant extract. The results obtained were discussed in terms of their implications for the best substerilizing dose for the irradiation of parental male pupae of A. ipsilon combined with the dose 150 Gy.

Preference and Performance of Black Cutworm (Lepidoptera: Noctuidae) on Poa Species

Abstract Black cutworm (Agrotis ipsilon Hufnagel) is a destructive pest of golf course turf. Previous work suggests that Poa pratensis ‘Midnight’ is resistant to black cutworm, but it is not known if resistance also exists among other Poa species and cultivars. This study compared preference and performance of black cutworm on Poa species and cultivars to a susceptible host plant, creeping bentgrass (Agrostis stolonifera L. ‘Penncross’) in laboratory choice feeding assays and rearing experiments. Seven-and 14-day-old larvae were used in performance feeding tests. Larvae reared on all Poa spp. exhibited significantly lower developmental and survival rates than larvae fed creeping bentgrass. Young (7 days old) larvae did not survive to pupation. Although older (14 days old) larvae pupated and eclosed on Poa, larval weight gain was significantly lower than those reared on creeping bentgrass. In choice feeding bioassays, regardless of larval stage, black cutworm preferred creeping bentgrass over all Poa species and cultivars. The results of this research suggest that although Poa species are generally resistant to black cutworm, the resistance varies among cultivars and insect growth stage.

EFFECT OF EGG AGE AND FERTILITY ON SOME BIOLOGICAL ASPECTS OF THREE TRICHOGRAMMA SPECIES

Two laboratory experiments were carried out to determine the effect of egg age and its fertility on fecundity, progeny survival and sex-ratio of three trichogrammatids i.e., Trichogramma evanescens, Trichogrammatoidea bactrae and Trichogramma brassicae. In the first experiment, three different ages (one, two and three days old) of fertile eggs from three lepidopterous hosts (Pectinophora gossypiella Saund., Agrotis ipsilon Hufn. and Sitotroga cerealella Olivier) were introduced to Trichogramma females. In the second experiment, infertile eggs of P. gossypiella and A. ipsilon were introduced to Trichogramma females to test the acceptability of these eggs to be parasitized by those females. The number of parasitized eggs/ female was higher on 0-l day old eggs and decreased significantly as the host eggs became older. Higher percentages of progeny were emerged from all the tested ages of P. gossypiella and S. cerealella eggs. On the other hand, the emerged progeny of the three Trichogramma species was decreased significantly by the progress of embryo development in A. ipsilon eggs. Furthermore, infertile P. gossypiella and A. ipsilon eggs were not accepted by the three Trichogramma species.

Endophyte-mediated tritrophic interactions between a grass-feeding caterpillar and two parasitoid species with different life histories

Plant secondary chemicals can alter herbivore suitability for parasitoids by weakening or stunting the host, delaying its development, or when larval parasitoids encounter ingested phytotoxins in the body of their host. Experiments with different parasitoids that exploit the same host species feeding on the same plant may provide insight about how parasitoid life history affects the strength of such interactions. The encyrtid wasp Copidosoma bakeri, a slow-developing polyembryonic egg-larval parasitoid, and the tachinid fly Linnaemya comta, a fast-developing solitary species, both parasitize Agrotis ipsilon, a generalist noctuid. We tested the hypothesis that of the two parasitoid species, the encyrtid, because of its more prolonged developmental association with the host, would suffer greater fitness costs when A. ipsilon feeds on perennial ryegrass containing an alkaloid-producing fungal endophyte. Indeed, fewer parasitized cutworms yielded C. bakeri broods, and those host mummies were smaller, formed more slowly, and contained fewer adults when the hosts fed on endophytic as opposed to endophyte-free grass. In contrast, L. comta fitness parameters were similar regardless of the type of grass upon which their host fed. Our results highlight that the outcome of endophyte-mediated tritrophic interactions may differ for different parasitoid species. Implications for integrating the use of endophytic grasses and biological control are discussed.

Generalist Predators and Predation of Black CutwormAgrotis ipsilonLarvae in Close Mown Creeping Bentgrass

Predators play a significant role in regulating pest outbreaks in turfgrass (Potter 2001). The most common predaceous arthropods recorded from turfgrass are spiders, predatory beetles (Carabidae and Staphylinidae) (Kunkel et al. 1999; Rothwell & Smitley 1999), predatory hemipterans, and ants (Lopez & Potter 2003; Frank & Shrewsbury 2004a). Natural enemies and their effects can be monitored by pitfall traps (e.g., Kunkel et al. 1999; Frank & Shrewsbury 2004a) or by exposing prey overnight without direct observation (Kunkel et al. 1999; Lopez & Potter 2000; Frank & Shrewsbury 2004a). Furthermore, most studies are conducted in roughs or fairways, which have more biodiversity (Lopez & Potter 2000), greater mowing height, and are less intensely managed than greens. Predation and predator abundance can be significantly different based on mowing heights (Rothwell & Smitley 1999). A better understanding of ecosystem services in putting greens may provide insights into reducing pesticide inputs. The objectives of this study were to determine the types of nocturnal predators in putting greens and determine which taxa are involved in predation of black cutworm larvae (Agrotis ipsilon Hufnagel) in close-mown bentgrass. Black cutworms provide a model system to investigate predation in turfgrass. Black cutworm larvae feed nocturnally on creeping bentgrass ( Agrostis stolonifera L.) greens causing pock marks that interfere with ball roll and aesthetics (Potter 1998). Predation trials were conducted at the Turfgrass Research Unit, Auburn, Alabama and the Grand National Golf Course, Opelika, Alabama. Plots or greens had not been sprayed with insecticides for at least 2 wk prior to each experiment. At the Turfgrass Research Unit, 2 plots of creeping bentgrass were used. A 706 m2 plot was used for larval predation trials, and a 929 m2 plot for predator surveys. Turfgrass in these plots was maintained at 0.33 cm with surrounding turf 2.54 cm high. Putting greens have 'Dominant' creeping bentgrass, whereas 'El Toro* zoysiagrass ( Zoysia japonica Steud), and 'Tifway' bermudagrass (Cynodon dactylon L. Pers Cynodon transvaalensis Burtt-Davy) were established in collars. Greens and collars are maintained at 0.36 and 1.27 cm, respectively. Larvae were obtained from a commercial in-

Can a chitin‐synthesis‐inhibiting turfgrass fungicide enhance black cutworm susceptibility to a baculovirus?

Developmental resistance, i.e. reduced virulence and speed of kill of late instars, is a limiting factor in the use of baculoviruses for caterpillar control. Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) is highly infective to young black cutworms, Agrotis ipsilon, but too slow-acting against late instars for effective curative control on golf courses or sports fields. Chitin-synthesis-inhibiting fungicides containing the active ingredient polyoxin-d are used to control fungal diseases in turfgrass, and similar compounds have been shown in the laboratory to synergize baculoviruses by disrupting peritrophic membrane function. This study tested whether applying the virus together with such a fungicide can synergize AgipMNPV activity against A. ipsilon in turfgrass. The addition of a chitin synthesis inhibitor failed to increase AgipMNPV infectivity to A. ipsilon in the field. Rather, delayed and slightly reduced mortality from viral infection was seen when larvae fed on fungicide/virus-treated grasses as opposed to virus-only treatments. Choice tests revealed the fungicide residues to be a mild feeding deterrent. Because polyoxin-d does not deactivate AgipMNPV, the two substances are compatible. However, combination applications of polyoxin-d and Agip MNPV on turfgrass might interfere with larval ingestion of a lethal virus dose, resulting in prolonged larval feeding in the field.

Construction of a Bacillus thuringiensis genetically-engineered strain harbouring the secreted Cry1Ia delta-endotoxin in its crystal

Unlike other Bacillus thuringiensis Cry proteins, Cry1Ia does not form a crystal since it is a secreted delta-endotoxin. We have engineered a Cry1Iac chimeric protein by substituting the C-terminal part of Cry1Ia by the corresponding Cry1Ac part. When expressed in an acrystalliferous B. thuringiensis strain, Cry1Iac did not crystallize, but when expressed in the crystalliferous strain BNS3, the chimeric protein co-crystallized with the endogenous Cry1A delta-endotoxins forming a typical bipyramidal crystal. The integration of Cry1Ia in the composition of the crystal of BNS3 led to an increase of its delta-endotoxin production (13%) and to an improvement (60%) of its toxicity against Agrotis ipsilon.

Improved insecticidal efficacy of a recombinant baculovirus expressing mutated JH esterase from Manduca sexta

Juvenile hormone esterase (JHE), a member of the carboxylesterase family (EC 3.1.1.1), metabolizes JH that is found in juvenile insects. A highly conserved amphipathic alpha helix is found on the surface of known JHEs. This helix is implicated in receptor-mediated binding and endocytosis of JHE by the pericardial cells resulting in the clearance of JHE activity from the hemolymph. In this study, Lys-204 and Arg-208 of the amphipathic alpha helix of the JHE of Manduca sexta (MsJHE) were mutated to histidine residues generating MsJHE-HH. Pharmacokinetic studies following the injection of MsJHE-HH into the hemocoel of larval M. sexta, Heliothis virescens, and Agrotis ipsilon indicated that MsJHE-HH and wild type MsJHE are cleared at similar rates. The infectivity (lethal concentration and lethal time) of a recombinant baculovirus, AcMsJHE-HH, expressing MsJHE-HH was not significantly different than that of a recombinant baculovirus, AcMsJHE, expressing MsJHE in first instars of H. virescens and A. ipsilon. However, the mass of AcMsJHE-HH-infected larvae was 40–50% lower than that of larvae infected with AcMsJHE, and 70–90% lower than that of wild type AcMNPV-infected larvae.

Endophyte-Mediated Resistance to Black Cutworm as a Function of Plant Cultivar and Endophyte Strain in Tall Fescue

To improve Neotyphodium endophyte-mediated resistance to black cutworm Agrotis ipsilon (Hufnagel) (BCW), a series of experiments was conducted by using several different cultivars of tall fescue, Schedonorus arundinaceus (Schreb.) Dumort. in combination with several different haplotypes of the endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (plant cultivar × endophyte haplotype = plant line), each producing unique alkaloid profiles. BCW settling response, survival at 5 and 10 d, and larval biomass varied significantly among plant lines. In general, greater variation BCW performance was observed within a single plant cultivar infected with different endophyte haplotypes than among different plant cultivars infected with the same endophyte haplotype, but comparisons among the former were far more numerous. Although five endophyte-mediated alkaloids representing three alkaloid classes were quantified in the plants, the pyrrolizidine alkaloid N-acetyl norloline was consistently the single best predictor of BCW performance. BCW settling response, 5-d survival, and 10-d survival decreased as levels of the alkaloid N-acetyl norloline increased. The same three response variables also decreased with increasing levels of peramine, but increased with increasing levels of ergovaline. Minor variation in endophyte infection levels occurring among infected plant lines had no significant influence on BCW performance. Results indicate a potentially important role for N-acetyl norloline and peramine in providing resistance to black cutworm whereas ergovaline appears to be much less important. Therefore, endophyte haplotypes expressing high levels of N-acetyl norloline and peramine may be of particular importance for developing 'friendly' endophyte-enhanced turf and pasture grasses that resist challenging lepidopteran pests, although remaining safe for wildlife and grazing mammals.

Efficacy and persistence of entomopathogenic nematodes for black cutworm control in turfgrass

Field experiments were conducted in turf maintained under golf course fairway conditions in May, June, and August 2009 and in August and September 2010 to evaluate the ability of entomopathogenic nematodes to control larval populations of the black cutworm, Agrotis ipsilon, on golf courses. Commercial products containing the entomopathogenic nematodes Heterorhabditis bacteriophora, Steinernema carpocapsae, S. feltiae, and S. riobrave were applied at 1.0 or 2.5×109 infective juveniles per ha against fourth-instar black cutworms. Larval mortality and turf damage were evaluated at 4 and/or 7 days after treatment (DAT). Steinernema carpocapsae was the best performing species due to a combination of high control rates (average 83%), most consistent results (70–90% range), high speed of kill (average 68% at 4 DAT), and prevention of significant turf damage despite very high larval densities at 0 DAT. Efficacy of S. feltiae and H. bacteriophora was often similar to that of S. carpocapsae but overall less consistent. Short-term persistence of the nematodes was evaluated in four turfgrass sites maintained under golf course putting green, fairway, or rough conditions in June and August 2009 by baiting soil samples at 0, 4, 7, and 14 DAT. Relative to recovery immediately after application, at least 50% of S. feltiae and 25% of S. carpocapsae consistently persisted up to 4 days in one of the greens and up to 7 days in some trials. Our finding suggests that S. carpocapsae and S. feltiae may provide adequate black cutworm control in golf course turf under moderate summer temperatures.

Mating-induced differential coding of plant odour and sex pheromone in a male moth

Innate behaviours in animals can be influenced by several factors, such as the environment, experience, or physiological status. This behavioural plasticity originates from changes in the underlying neuronal substrate. A well-described form of plasticity is induced by mating. In both vertebrates and invertebrates, males experience a post-ejaculatory refractory period, during which they avoid new females. In the male moth Agrotis ipsilon, mating induces a transient inhibition of responses to the female-produced sex pheromone. To understand the neural bases of this inhibition and its possible odour specificity, we carried out a detailed analysis of the response characteristics of the different neuron types from the periphery to the central level. We examined the response patterns of pheromone-sensitive and plant volatile-sensitive neurons in virgin and mated male moths. By using intracellular recordings, we showed that mating changes the response characteristics of pheromone-sensitive antennal lobe (AL) neurons, and thus decreases their sensitivity to sex pheromone. Individual olfactory receptor neuron (ORN) recordings and calcium imaging experiments indicated that pheromone sensory input remains constant. On the other hand, calcium responses to non-pheromonal odours (plant volatiles) increased after mating, as reflected by increased firing frequencies of plant-sensitive AL neurons, although ORN responses to heptanal remained unchanged. We suggest that differential processing of pheromone and plant odours allows mated males to transiently block their central pheromone detection system, and increase non-pheromonal odour detection in order to efficiently locate food sources.

Sublethal Effects of Cry 1F Bt Corn and Clothianidin on Black Cutworm (Lepidoptera: Noctuidae) Larval Development

Black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is an occasional pest of maize (corn), Zea mays L., that may cause severe stand losses and injury to corn seedlings. The efficacy of the neonicotinoid seed treatment clothianidin at two commercially available rates and their interaction with a transgenic corn hybrid (Bt corn), trait expressing the Bacillus thuringiensis variety aizawai insecticidal toxin Cry 1Fa2, against black cutworm larvae was investigated. Clothianidin at a rate of 25 mg kernel(-1) on Bt corn increased larval mortality and reduced larval weight gains additively. In contrast, weights of larvae fed non-Bt corn seedlings treated with clothianidin at a rate of 25 mg kernel(-1) increased significantly, suggesting either compensatory overconsumption, hormesis, or hormoligosis. Both Bt corn alone and clothianidin at a rate of 125 mg kernel(-1) applied to non-Bt corn seedlings caused increased mortality and reduced larval weight gains. In two field trials, plots planted with Bt corn hybrids consistently had the highest plant populations and yields, regardless of whether they were treated with clothianidin at the lower commercial rate of 25 mg kernel(-1) The use of Bt corn alone or in combination with the low rate of clothianidin (25 mg kernel(-1)) seems suitable as a means of suppressing black cutworm in no-tillage cornfields, although rescue treatments may still be necessary under severe infestations. Clothianidin alone at the low rate of 25 mg kernel(-1) is not recommended for black cutworm control until further studies of its effects on larval physiology and field performance have been completed.