Agrotis Ipsilon Research Articles

Olfactory receptor neuron coding in the turbulent realm

Insects are able to find their mates from the sparse pheromone patches transported by turbulent air streams. This source-finding ability is remarkable because the pheromone patches don’t point towards the source and because the temporal and concentration statistics encountered during the search are highly irregular. The knowledge of the coding dynamics at the single ORN level is presently incomplete and it seems mandatory to decipher these dynamics before further investigating the integration of the signal at higher levels of the olfactory system. A receptor that would attempt to infer the distance of a source from the detection dynamics of the pheromone patches would obviously benefit from the complete evolution of the pheromone concentration with time. Yet, it is possible to build a Bayesian model based on the known dynamics of the plume propagation [1] and to infer the distance from the temporal dynamics only. Hence, an interesting question is how much of the temporal dynamics of the patches can be encoded in the ORN signals? For example, the uncorrelated statistics of patch duration is sufficient for inferring the distance, yet including the correlations between the durations of detections and non-detections will greatly improve the decoding rate [2]. As a simplified framework, we investigated the dynamical olfactory coding of ORNs of a moth, Agrotis ipsilon, stimulated by puffs of pheromone (cis-7-dodecenyl acetate) of variable duration delivered at constant concentration. The spiking responses of ORNs to single puffs varying over four decades of durations (1ms-10s) were recorded and decoded. In the absence of precise knowledge on the decoding mechanism inside the antennal lobe and in higher neural structures of the insect brain, 3 decoding schemes were utilized, based on logistic regression, support vector machine and signal dependent Poisson firing model designed to include bursting dynamics. With this protocol the relative selectivity of ORNs coding with the variation of puff duration and thus the relative information transfer could be analyzed. Then, in order to investigate the possible coding dependency of the currently detected pheromone patch on previous patch detections, double puffs coding were investigated, similarly over four decades of durations. The evolution of the ORN coding showed that the detection of previous puffs influenced the coding of the current puff and hence that instantaneous decoding could bring information on the previous puff duration and timing. Furthermore, we quantified the relative (conditional) sensitivity of the instantaneous coding with respect to the duration and spacing of the previous puff. Interestingly, we also show that the “random spiking” dynamics bears a non-negligible amount of information on the past patch dynamics detection. The coding and decoding procedures were then evaluated on signals mimicking the temporal dynamics of patches in a turbulent stream. We found that training based on one patch and two patches allowed efficient and reliable decoding of patch dynamics in turbulent air streams. Finally, we quantified the amount of information encoded by ORNs about the duration, timing, and most importantly waiting time between consecutive pheromone puffs.

EFFECT OF SOME PLANT EXTRACTS ON BLACK CUT WORM AGROTIS EPSILON (HUFN). UNDER LABORATORY CONDITIONS

The effect of different concentrations for both of water flae-bane leaves and mango seed plant extracts were studied especially their biological and biochemical effects on the 4th larval instar of Agrotis ipsilon using toxic baits. The results clearly demonstrated that the tested extracts achieved significant increase in the pupal longevity and significant reduction in the larval longevity and pupal weight besides the percentage of pupation. Also, on the adult longevity for either male or female. There was remarkable significant increase in the percentage of malformation for both pupae and adults. The best treatment among all the tested extracts was water mango seed extract at 5% concentration followed by water flae-bane leaves at the same concentration. The biochemical studies proved that water mango seed extract caused increase in the secretion of both of glucsidase and Trehalse enzymes, and decrease in the secretion of acetyl choline esterase. While, water flae-bane leaves extract caused increase in the secretion of acetyl choline esterase. From this point of view, may be the extracts had an effect on the rate of glucose absorption in the blood.

Entomologic and Agronomic Evaluations of 18 Sweet Sorghum Cultivars for Biofuel in Florida

ABSTRACT Sweet sorghum [(Sorghum bicolor L. Moench); Cyperales: Poaceae] is a summer annual crop suitable for use as a biofuel feedstock. The juice from harvested sweet sorghum stalks can be readily converted into ethanol. The purpose of this study was to identify potential arthropod pests of promising sweet sorghum cultivars grown for biofuel on Histosols (muck soil) in southern Florida. This field study was conducted at the Everglades Research and Education Center at Belle Glade, Florida in 2010. Eighteen sweet sorghum cultivars planted at 3 dates were evaluated for insect feeding. Foliar damage was measured during the whorl stage and boring within stalks was measured at harvest. Seedling damage caused by Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae) and black cutworm Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) reduced the stand of most of the cultivars tested. Foliar feeding by Spodoptera frugiperda L. (Lepidoptera: Noctuidae) larvae was significantly affected by cultivar and plantin...

Canadian entomopathogenic nematode isolates: virulence against black cutworm (Lepidoptera: Noctuidae)

The virulence of ten indigenous and two commercial isolates of entomopathogenic nematodes against the black cutworm, Agrotis ipsilon, was assessed under laboratory conditions. When comparing commercial isolates, Steinernema carpocapsae exhibited higher virulence than S. feltiae. One indigenous isolate of S. carpocapsae (6Sc) provided similar or higher virulence than the commercial isolate against black cutworm larvae. An indigenous strain of S. kraussei demonstrated low virulence in our study.

Is the rapid post-mating inhibition of pheromone response triggered by ecdysteroids or other factors from the sex accessory glands in the male moth Agrotis ipsilon?

In many animals, male copulation is dependent on the detection and processing of female-produced sex pheromones, which is generally followed by a sexual refractory post-ejaculatory interval (PEI). In the male moth, Agrotis ipsilon, this PEI is characterized by a transient post-mating inhibition of behavioral and central nervous responses to sex pheromone, which prevents males from re-mating until they have refilled their reproductive tracts for a potential new ejaculate. However, the timing and possible factors inducing this rapid olfactory switch-off are still unknown. Here, we determined the initial time delay and duration of the PEI. Moreover, we tested the hypothesis that the brain, the testis and/or the sex accessory glands (SAGs) could produce a factor inducing the PEI. Lastly, we investigated the possible involvement of ecdysteroids, hormones essential for development and reproduction in insects, in this olfactory plasticity. Using brain and SAG cross-injections in virgin and newly-mated males, surgical treatments, wind tunnel behavioral experiments and EIA quantifications of ecdysteroids, we show that the PEI starts very shortly after the onset of copulation, and that SAGs contain a factor, which is produced/accumulated after copulation to induce the PEI. Moreover, SAGs were found to be the main source of ecdysteroids, whose concentration decreased after mating, whereas it increased in the haemolymph. 20-Hydroxyecdysone (20E) was identified as the major ecdysteroid in SAGs of A. ipsilon males. Finally, 20E injections did not reduce the behavioral pheromone response of virgin males. Altogether our data indicate that 20E is probably not involved in the PEI.

Expression of Cry1Ac in transgenicBtsoybean lines and their efficiency in controlling lepidopteran pests

Two transgenic lines of the soybean Glycine max, MON87701 expressing the Cry1Ac protein and MON87701RR2Y expressing Cry1Ac + EPSPS proteins, were evaluated for their resistance to four lepidopteran pests in the laboratory using detached-leaf bioassays throughout the soybean growth seasons (before anthesis, during anthesis and after anthesis) in China. Enzyme-linked immunosorbent assays (ELISAs) were used to monitor the Cry1Ac expression in soybean leaves. The bioassay results revealed that both transgenic soybean lines exhibited significantly high resistance against Helicoverpa armigera (Hübner) throughout the soybean growing seasons. The survival rates of H. armigera larvae ranged from 5.4 to 24.4% when feeding on the transgenic soybean leaves, significantly lower than the survival rates when feeding on control leaves (71.1-94.9%). Limited resistance was found for both transgenic soybean lines against Spodoptera litura (Fabricius), although the survival rates and weight of S. litura larvae as well as female fecundity were significantly decreased when feeding on Bt soybean leaves compared with feeding on control leaves. In contrast, both transgenic soybean lines provided almost no resistance to Spodoptera exigua (Hübner) and Agrotis ypsilon (Rottemberg). Cry1Ac expression in the leaves of both transgenic soybean lines was relatively stable throughout the soybean growing season, with a peak occurring at V6 -8 and V11 -12 before anthesis. The ELISA results were positively correlated with the results from the insect bioassays. The results show that, while Cry1Ac-expressing Bt soybeans may provide good protection against H. armigera, alternative control measures are required to manage S. exigua, S. litura and A. ypsilon.

식물정유와 파라핀오일이 검거세미나방에 미치는 영향

검거세미나방(Agrotis ipsilon)은 다양한 작물에 피해를 주며 특히 골프장 잔디에 심각한 피해를 주는 해충이다. 식물정유는 해충방제를 위한 대체방제제의 하나이다. 본 연구는 16종의 식물정유(anise, camphor, cinnamon, citronella, clove, fennel, geranium, lavender, lemongrass, linseed, neem, peppermint, pine, thyme, turpentine and tea saponin)와 파라핀오일의 검거세미나방에 대한 방제효과를 실내와 온실, 야외에서 검정하였다. 온실의 퍼레니얼라이그라스 pot에 각각의 정유를 처리한 결과 anis, cinnamon, neem, paraffin, turpentine 처리에서 잔디피해가 적었으며 neem oil (4,000, 2,000, 1,000 ppm) 처리시 검거세미나방 치사율은 각각 100, 100, 64%였다. 2,000 ppm neem oil처리 퍼레니얼라이그라스 잎을 섭식한 검거세미나방 유충의 체중은 무처리에 비해 5배정도 낮았다. 2~3령충 검거세미나방에 대하여 pot와 야외에서 고농도 neem oil 처리 후 관수가(20,000 ppm 0.1 L 처리 후 물 0.9 L <TEX>$m^2$</TEX> 살포) 저농도의 다량살포 (2,000 ppm 1 L <TEX>$m^2$</TEX>)에 비하여 효과가 높았으나 4령충에 대해서는 효과가 없었다. The black cutworm, Agrotis ipsilon (Hufnagel), damages various cultivated crops and it can also be a serious pest of turfgrass, especially on golf courses. Essential oils have potential as alternative control agents for insect pests. Sixteen essential oils (anise, camphor, cinnamon, citronella, clove, fennel, geranium, lavender, lemongrass, linseed, neem, peppermint, pine, thyme, turpentine and tea saponin) and paraffin oil were assessed in the laboratory, the green house and field trials for their efficacy against black cutworms in turf. Treatment of potted cores of perennial ryegrass turf with anise, cinnamon, neem, paraffin or turpentine reduced black cutworm damage in a greenhouse trial, and in a similar trial, applying neem oil at 4000, 2000 and 1000 ppm resulted in 100, 100 and 64% mortality, respectively, of black cutworms. Weight of survivors at the 1000 ppm rate was 5- fold less than weight of comparably-aged controls. Neem oil (2000 ppm) reduced growth of black cutworms feeding on treated clippings. A high rate of neem oil followed by irrigation (0.1 L of 20000 ppm neem oil with 0.9 L watering/<TEX>$m^2$</TEX>) was more effective than a lower concentration (1 L of 2000 ppm neem oil/<TEX>$m^2$</TEX>) against <TEX>$2^{nd}$</TEX> and <TEX>$3^{rd}$</TEX> instars in potted turf cores and field plots, respectively. However, not even the aforementioned higher rate effectively controlled <TEX>$4^{th}$</TEX> instars in the field.

Steroid hormone signaling is involved in the age-dependent behavioral response to sex pheromone in the adult male moth Agrotis ipsilon

In most animals, including insects, male reproduction depends on the detection and processing of female-produced sex pheromones. In the male moth, Agrotis ipsilon, both behavioral response and neuronal sensitivity in the primary olfactory center, the antennal lobe (AL), to female sex pheromone are age- and hormone-dependent. In many animal species, steroids are known to act at the brain level to modulate the responsiveness to sexually relevant chemical cues. We aimed to address the hypothesis that the steroidal system and in particular 20-hydroxyecdysone (20E), the main insect steroid hormone, might also be involved in this olfactory plasticity. Therefore, we first cloned the nuclear ecdysteroid receptor EcR (AipsEcR) and its partner Ultraspiracle (AipsUSP) of A. ipsilon, the expression of which increased concomitantly with age in ALs. Injection of 20E into young sexually immature males led to an increase in both responsiveness to sex pheromone and amount of AipsEcR and AipsUSP in their ALs. Conversely, the behavioral response decreased in older, sexually mature males after injection of cucurbitacin B (CurB), an antagonist of the 20E/EcR/USP complex. Also, the amount of AipsEcR and AipsUSP significantly declined after treatment with CurB. These results suggest that 20E is involved in the expression of sexual behavior via the EcR/USP signaling pathway, probably acting on central pheromone processing in A. ipsilon.

Impact of Spodoptera littoralis (Boisd.) and Agrotis ipsilon (Hufn.) larval frass on oviposition of conspecific insects

Ethanolic extracts of larval frass of the cotton leaf worm and the black cutworm were prepared and tested to deter the eggs lay of the adults of the same insects. Two different types of food were used for larval feeding. Extracts fractions were identified using gas chromatography–mass spectrometry analysis. High concentrations were more deterrent to oviposition than low. Extracted frass of fed larvae on semi-artificial diet was more effective than others fed on natural host. Sensitivity of the black cutworm adult females to the cotton leaf worm frass extract was clearly observed at high tested concentration of L1–3 and L4 frass extracts which resulted completely oviposition deterrent. Several fatty acids were identified qualitatively and quantitatively in frass extracts of different larval instars of both target insects. Type and quantity of fatty acid depends mainly on larval food source and larval instar, except palmitic acid which recorded at all larval instars and food sources. Oleic acid and ethyl 9-hexadecaenoic acid were found when semi-artificial diet used as a food source while myrisitic acid was observed only in extracted frass of fed larvae on castor oil leaves.

Insecticidal and Feeding Deterrent Effects of Fraxinellone from Dictamnus dasycarpus against Four Major Pests

Fraxinellone, a well-known and significant naturally occurring compound isolated from Meliaceae and Rutaceae spp. has been widely used as a drug for the treatment of tumors. On the other hand, fraxinellone exhibited a variety of insecticidal activities including feeding-deterrent activity, inhibition of growth, and larvicidal activity. The present study focused on the antifeedant and larvicidal activities of fraxinellone against the larvae of Lepidoptera, including Mythimna separata, Agrotis ypsilon, Plutella xylostella, and one kind of sanitary pest, Culux pipiens pallens. Meanwhile, the ovicidal activities and the effects of fraxinellone on the larval development of M. separata were also observed. The LC50 values of fraxinellone against 3rd instar larvae of M. separata, 2nd instar larvae of P. xylostella and 4th instar larvae of C. pipiens pallens were 15.95/6.43/3.60 × 10−2 mg mL−1, and its AFC50 values against 5th instar larvae of M. separata, 2nd instar larvae of P. xylostella and 2nd instar larvae of A. ypsilon were 10.73/7.93/12.58 mg mL−1, respectively. Compared with the control group, fraxinellone obviously inhibited the pupation rate and the growth of M. separata. Once M. separata was treated with fraxinellone at concentrations of 5.0, 10.0, and 20.0 mg mL−1, respectively, the stages from the larvae to adulthood and the egg hatching duration were prolonged to 1/2/3, and 4/3/4 days, respectively. Additionally, fraxinellone strongly inhibited the development rate and the egg hatch proportion of M. separata.

Pest protection conferred by a Beta vulgaris serine proteinase inhibitor gene.

Proteinase inhibitors provide a means of engineering plant resistance to insect pests. A Beta vulgaris serine proteinase inhibitor gene (BvSTI) was fused to the constitutive CaMV35S promoter for over-expression in Nicotiana benthamiana plants to study its effect on lepidopteran insect pests. Independently derived BvSTI transgenic tobacco T2 homozygous progeny were shown to have relatively high BvSTI gene transcript levels. BvSTI-specific polyclonal antibodies cross-reacted with the expected 30 kDA recombinant BvSTI protein on Western blots. In gel trypsin inhibitor activity assays revealed a major clear zone that corresponded to the BvSTI proteinase inhibitor that was not detected in the untransformed control plants. BvSTI-transgenic plants were bioassayed for resistance to five lepidopteran insect pests. Spodoptera frugiperda, S. exigua and Manduca sexta larvae fed BvSTI leaves had significant reductions in larval weights as compared to larvae fed on untransformed leaves. In contrast, larval weights increased relative to the controls when Heliothis virescens and Agrotis ipsilon larvae were fed on BvSTI leaves. As the larvae entered the pupal stage, pupal sizes reflected the overall larval weights. Some developmental abnormalities of the pupae and emerging moths were noted. These findings suggest that the sugar beet BvSTI gene may prove useful for effective control of several different lepidopteran insect pests in genetically modified tobacco and other plants. The sugar beet serine proteinase inhibitor may be more effective for insect control because sugar beet is cropped in restricted geographical areas thus limiting the exposure of the insects to sugar beet proteinase inhibitors and build up of non-sensitive midgut proteases.

Molecular identification and differential expression of sensory neuron membrane proteins in the antennae of the black cutworm moth Agrotis ipsilon

The insect sensory neuron membrane proteins (SNMPs) SNMP1 and SNMP2 are transmembrane domain-containing proteins and are homologs of the vertebrate CD36 transmembrane proteins. It has been suggested that SNMPs play a significant role in insect chemoreception. Previous studies have demonstrated that SNMP1 is expressed in the pheromone-sensitive olfactory receptor neurons (ORNs), whereas SNMP2 is expressed in the supporting cells. In this study, we identified two full-length SNMP transcripts, AipsSNMP1 and AipsSNMP2, in the black cutworm moth Agrotis ipsilon (Hufnagel). The qRT-PCR results indicated that the AipsSNMP1 and AipsSNMP2 transcripts were expressed significantly higher in the antennae than in other tissues of both sexes. The expression of AipsSNMP1 and AipsSNMP2 in the antennae from different development stages of both sexes was investigated and was shown to begin to express in the pupae stage from 3days before emergence and then increased dramatically at the day of the emergence, and the high expression levels were maintained during the following 4days after the emergence in both sexes. The mating status had no effect on the expression levels of the AipsSNMP1 and AipsSNMP2 transcripts. Consistent with previous in situ hybridization studies in other Lepidoptera insects, our immunolocalization results at protein level demonstrated that both AipsSNMP1 and AipsSNMP2 were expressed in pheromone-sensitive sensilla trichodea but with a completely different expression profile. AipsSNMP1 is more uniformed and highly expressed along the membrane of the ORN dendrites, whereas AipsSNMP2 is widely distributed at the bottom of the sensilla trichodea and highly localized in the sensillum lymph. Our studies provide further detailed evidence for the involvement and general functional role of insect SNMPs in the detection of sex pheromones and general odorant molecules.

Insecticidal activity of Vip3Aa, Vip3Ad, Vip3Ae, and Vip3Af from Bacillus thuringiensis against lepidopteran corn pests

Vip3Aa, Vip3Ad, Vip3Ae, and Vip3Af proteins from Bacillus thuringiensis were tested for their toxicity against Spodoptera frugiperda and Agrotis ipsilon. Vip3Ad was non-toxic to the two species. Vip3Ae and Vip3Af were significantly more toxic than Vip3Aa against S. frugiperda, both as protoxins and as toxins. Against A. ipsilon, Vip3Ae protoxin was more toxic than Vip3Aa and Vip3Af protoxins. Purification by metal-chelate affinity chromatography significantly affected Vip3Ae toxicity against the two insect species.

Sex pheromone recognition and immunolocalization of three pheromone binding proteins in the black cutworm moth Agrotis ipsilon

Insect pheromone binding proteins (PBPs) are believed to solubilize and transport hydrophobic sex pheromones across sensillum lymph to membrane-associated pheromone receptors. To address the molecular mechanisms of PBPs in insect pheromone perception, we undertook a systemic study on the PBPs of the black cutworm Agrotis ipsilon at transcript as well as protein level from tissue distribution and cellular localization to pheromone binding affinity. We cloned three full-length PBP genes AipsPBP1-3 from A. ipsilon antennae, and demonstrated that AipsPBP1–3 transcripts were highly expressed in male antennae. The electron microscopic examinations revealed at least six types of olfactory sensilla on male and female antenna: trichodea, chaetica, basiconica, coeloconica, squamiformia and Böhm bristles. The immunocytochemistry results demonstrated that AipsPBP1-3 proteins were strongly expressed in the sensillum lymph of the trichoid sensilla of male moth. The binding assays showed that AipsPBP1 had high binding affinities with the major sex pheromone components Z7-12:Ac and Z9-14:Ac among five related chemicals and was clustered together with the long trichoid sensilla-expressing LdisPBPs of Lymantria dispar. AipsPBP2 showed high binding affinities also with Z11-16:Ac. AipsPBP3 displayed a high affinity only with Z11-16:Ac. Our studies provide further detail evidences for the involvement of moth PBPs in pheromone discrimination and selective recognition of specific components of the female sex pheromone blends.

EFFICIENCY OF TWO FORMULATIONS OF THE PATHOGENIC FUNGI, BIOSECT (Beauveria bassiana) AND BIORANZA (Metarhizium anisopliae) AGAINST LARVAE OF Spodoptera littoralis (BOISD.) AND Agrotis ipsilon (HFN.) (LEPIDOPTERA: NOCTIDAE)

Laboratory tests and a semi-field trial were carried out to determine the efficiency of two commercial preparations of the entomopathogenic fungi,Beauveriabassiana and Metarhiziumanisopliae namely; Biosect w.p., and Bioranza10 % w.p., against the first instar larvae of the cotton leaf worm, Spodoptera littoralis(Boisd.) and, Agrotis ipsilon(Hfn.)(Lepedoptera : Noctuidae). Newly hatched, one- day and two- day old larvae of the two insects were allowed to feed on castor oil leaves (100 gram / replicate) treated with different concentrations of the two entomopathogenic fungi for 48hrs at three different temperatures, 20, 25 and 305C. Mortality rate increased by increasing the concentration, or post treatment period and temperature. Newly hatched larvae were the most sensitive to the toxic effect especially at highest concentration and temperature(305C), while the two- day old larvae were the most tolerant and the one-day old larvae expressed a moderate tolerance. S. littoralis was more sensitive than A. ipsilon. Calculated LC50s values for initial mortality of the newly hatched larvae were (0.458, 0.309 and 0.279 mg/ml. when treated with Biosect and (0.676, 0.352 and 0.317 when treated with Bioranza) at 20, 25 and 25 5C, respectively. Consumed castor oil leaves were decreased by increasing the concentration and temperature but were lower than the control.

Bioenergetics growth model for the effect of gamma irradiation and plant extract (Barnoof) on the progeny of Black cutworm, Agrotis ipsilon (Hufnagel)

This study investigated the effects of two substerilizing doses of gamma radiation, 100 and 150Gray (Gy), and/or the plant extract Conyza dioscorides (Barnoof) in two solvents on certain biological aspects and the energy budget of the Black cutworm, Agrotis ipsilon (Hufnagel).Data revealed that the treatment combination of gamma radiation with the plant extract significantly increased reproduction compared with the control at all treatment levels (doses and concentrations).Most of the treatments increased the values of developmental/day and larval duration in the F1 progeny compared with the progeny from the control treatment, although the percentage survival was decreased in all treatments. These values were more obvious in the combination treatments compared with either gamma radiation or plant extract treatments alone.The coefficient of metabolizable energy (C.M.E.) was not affected by any treatments. No consistent effect on the efficiency of storage of ingested energy [E.S.I.(E.)] and the efficiency of storage of metabolizable energy [E.S.M.(E.)] when the F1 progeny were treated with plant extract alone or with the plant extract combined with the 100Gy dose of radiation was noted, while they were both significantly increased at all treatment levels when the 150Gy dose of radiation was combined with the plant extract. The results obtained are discussed in terms of their implications for the best substerilizing dose of radiation on parental male pupae of A. ipsilon.

Concentration- and time-response characteristics of plaque isolates of Agrotis ipsilon multiple nucleopolyhedrovirus derived from a field isolate

Plaque isolates derived from the Illinois field isolate of Agrotis ipsilon multiple nucleopolyhedrovirus are distinguished by the presence or absence of a small deletion in the baculovirus egt (ecdysteroid UDP-glucosyltransferase) coding sequence. In concentration–response and time-response bioassays with both plaque and field isolates, plaque isolates with a mutated egt gene were less pathogenic against A. ipsilon larvae than other isolates, but killed larvae faster. Mixed infections with isolates representing the two different egt genotypes caused the same level of mortality as the field isolate and a plaque isolate with a wild-type egt gene.

Leaf biomechanical properties as mechanisms of resistance to black cutworm (Agrotis ipsilon) amongPoaspecies

Biomechanical properties can be important parameters in resistance of plants to herbivorous insects. As plants age, however, there can be dramatic changes in physical defenses that can then influence their susceptibility to insect herbivores. We measured changes in leaf biomechanical properties during ontogeny of Poa species and the relationship of these changes to the development of a generalist herbivore, the black cutworm, Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae), was investigated. Larvae were reared on two representative age classes, i.e., young ( 1 year after planting), of foliage in laboratory assays. Foliage generally reaches a peak fracture force between 80 and 109 days after planting depending on grass type. Foliage from old plants was significantly tougher than that of young plants, and black cutworm larvae reared on foliage from young plants gained significantly (ca. four times) more weight than those fed on foliage from old Poa plants. In addition, fracture force has a negative relationship with black cutworm development. Plant fiber, particularly neutral detergent fiber accounted for 65 and 46% of the variation in fracture force and larval development, respectively. These results provide additional insight into how plant ontogeny influences physical defenses to an insect herbivore in a grass system. Likewise, this is seemingly the first study to suggest a mechanism for host plant resistance to black cutworm. Plant fiber may be a useful trait to explore in plant improvement programs in which black cutworm is a primary pest (e.g., managed turfgrass).

COMPARATIVE STUDIES FOR USING CERTAIN BAITS AS NATURAL CONTROL AGENT AGAINST AGROTIS YPSILON, (LEPIDOPTERA) UNDER LABORATORY AND FIELD CONDITIONS

Quick lime and two other biological control agents: Bacillus thuringiensis, Metarhisium anisopliae and hostathion [triazophos] were used as poisonous pelleted semi-hard cake baits formulations contains of insecticide, sugar cane molasses and wheat brain (2: 1: 4) against the fourth instar larvae of Agrotis ypsilon. in the laboratory and the field. Quick lime was used at 1, 1.2and 1.3 kg, B. thuringiensis at 1x103, 1.5x103 and 1.75x103 spores/ ml and Metarhisium anisopliae at 1x107, 1.5x107 and 1.75x107 spores/ ml and hostathion insecticide at1, 1.5and1.75L. Double concentrations of one of the tested materials, the quick lime, bacterium, fungus and hostathion were used under field conditions. Fourth instar larvae of cut worm insect were allowed to feed on the plants treated with mixture of one of each of quick lime, microbium fungus, and hesitation and in the freely consumption (persistency) with Lc50 of one of each material without plants in the laboratory in the field for 2, 4 and 6 days. Lower amout of hostathion and quick lime semi-hard cake were consumed compared with the other biological control agents and achieved higher mortality. B. thuringiensis and M. anisopliae semi-hard cake achieved moderate mortality within plants or in the freely consumptions.

Temperature effects during development on a polyembryonic parasitoid and its host

Ambient temperature can influence development through effects on metabolic rate and by inducing physiological stress. In this study, we assessed temperature effects on a host–parasitoid interaction and on the body size and brood size of emerging wasps. By examining the development at two different temperatures of the koinobiont parasitoid, Copidosoma bakeri, and its host, Agrotis ipsilon, we asked: (1) Does the growth response to temperature by A. ipsilon depend on whether the moth caterpillar is parasitized? (2) Does the allocation pattern of body size and brood size in C. bakeri change with temperature? To answer these questions, we exposed A. ipsilon larvae parasitized by C. bakeri to high or low non-lethal temperatures when A. ipsilon was in early or late larval stages and measured their development time and body mass for all four treatment combinations. We also examined the brood size and body mass of emerging wasps. Whether parasitized or not, A. ipsilon larvae decreased development time, but generally did not decrease final body mass, at the higher temperature. When parasitized A. ipsilon was exposed to the higher temperature only late in their development, enlargement of the host by the parasitoid was reduced. C. bakeri brood size significantly increased when the higher temperature was applied early in host development. We did not detect a shift with temperature in the allocation pattern of the size–number trade-off for wasp offspring, suggesting that this trade-off relationship may be under selection strong enough to yield insensitivity to temperature.