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Conventional resistance of experimental maize lines to corn earworm (Lepidoptera: Noctuidae), fall armyworm (Lepidoptera: Noctuidae), southwestern corn borer (Lepidoptera: Crambidae), and sugarcane borer (Lepidoptera: Crambidae).

Plant resistance is a useful component of integrated pest management for several insects that are economically damaging to maize, Zea mays L. In this study, 15 experimental lines of maize derived from a backcross breeding program were evaluated for resistance to corn earworm, Helicoverpa zea (Boddie); fall armyworm, Spodoptera frugiperda (J. E. Smith); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.). Experimental line 100-R-3 was resistant in the field to leaf feeding by fall armyworm and line 116-B-10 was resistant in the field to leaf feeding by fall armyworm and leaf and stalk feeding by southwestern corn borer. When corn earworm larvae were fed field harvested silks from experimental line 81-9-B in the laboratory, their pupal weights were significantly lower than the pupal weights of larvae that were fed silks from the resistant control, Zapalote Chico. Maysin levels lower than those commonly associated with corn earworm resistance were present in the resistant experimental line, 107-8-7, indicating a new basis confers resistance to corn earworm in this line. These resistant experimental lines will provide plant breeders with new sources of resistance to lepidopterous insects for the development of improved maize breeding populations.

Animals↗

Presence of IL-1- and TNF-like molecules in Galleria mellonella (Lepidoptera) haemocytes and in an insect cell line Fromestigmene acraea (Lepidoptera).

In this study the authors give immunocytochemical evidence for the presence of interleukin (IL)-1alpha- and tumour necrosis factor (TNF) alpha-like molecules in the haemocytes of last instar larvae from the greater wax moth Galleria mellonella. Similar results are demonstrated in a continuous haemocyte line (BTI-EA-1174-A) from the salt marsh caterpillar Estigmene acraea. In Galleria mellonella larvae granular cells show a strong positive reaction with both primary antibodies, whereas plasmatocytes are stained to a lesser extent. Cell line haemocytes also react positively with both antibodies. After activating the cells with lipopolysaccharide (LPS) staining of Estigmene acraea cells is decreased, whereas Galleria mellonella haemocytes show no visible reaction in comparison to non-activated cells.

Animals↗

Efficacy of a dehydrated steinernematid nematode against black cutworm (Lepidoptera: Noctuidae) and diamondback moth (Lepidoptera: Plutellidae).

We compared the ability of in vitro-produced, commercially formulated with in vivo-produced, nonformulated Steinernema carpocapsae (Weiser) Poinar. All strain to infect and kill larvae of black cutworm, Agrotis ipsilon (Hufnagel), and diamondback moth, Plutella xylostella (L.). In vitro-produced nematodes formulated in wettable dispersible granules, which were stored dry, were rehydrated in water for 0-72 h before application. Against black cutworms, the efficacy of nematodes was (from most to least effective): in vivo > in vitro rehydrated for 72 h > in vitro rehydrated for 48 h > in vitro rehydrated for 24 h > dehydrated (0 h). Nematodes rehydrated for 72 h in water or moist soil were equally effective against black cutworm larvae, and both were significantly more effective than nematodes without rehydration. These results indicated that nematodes in the wettable dispersible granule formulation required time to rehydrate in the soil before infecting black cutworm larvae. Nematode treatments described above were applied to radish plants held at 100 or 75% RH and tested against diamondback moth larvae. At 100% RH, nematode efficacy was (from most to least effective): in vitro rehydrated for 72 h > in vivo > in vitro rehydrated 48 h > in vitro rehydrated 24 h > dehydrated (0 h). The efficacy of all treatments was lower at 75% than at 100% RH, and the ranking of in vivo and in vitro nematodes rehydrated for 72 h was reversed. The nematodes in the wettable dispersible granule formulation were effective for foliar treatments when humidity was high and nematodes were rehydrated for at least 48 h before application. The data show that nematode infectivity was reduced unless nematodes were rehydrated.

Animals↗

Comparative susceptibilities of diamondback moth (Lepidoptera: Plutellidae) and cabbage looper (Lepidoptera: Noctuidae) from Minnesota and south Texas to lambda-cyhalothrin and indoxacarb.

The susceptibility of early instars of diamondback moth, Plutella xylostella (L.), and early (first and second) and late instars (third and fourth) of cabbage looper, Trichoplusia ni (Hübner), from Minnesota and south Texas, to indoxacarb and lambda-cyhalothrin was determined in the laboratory. Susceptibilities of the two species from the two geographical locations to indoxacarb and lambda-cyhalothrin varied greatly. P. xylostella from Minnesota was as susceptible to indoxacarb as those from south Texas, whereas both early and late instar T. ni from south Texas were significantly more tolerant to indoxacarb than those from Minnesota. The LC50 values of indoxacarb for early and later instar T. ni at 48 h from south Texas were 4.3- and 34.0-fold greater than those from Minnesota, respectively. Similarly, early instar P. xylostella and late instar T. ni from south Texas were significantly less susceptible to lambda-cyhalothrin than those from Minnesota. Percentage mortality of the two insect species caused by the two insecticides varied with time of exposure and generally exhibited similar patterns of responses to different concentrations for each insecticide.

Animals↗

Mean generation analysis of the damage caused by Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae) in sweet corn ears.

Sesamia nonagrioides (Lefebvre) and Ostrinia nubilalis (Hübner) are the main maize (Zea mays L.) pests in Mediterranean countries. To develop insect-resistant cultivars, it is helpful to know the genetic control of the resistance. Our objective was to determine the genetic control of the resistance to both borers. For each of two crosses (EP59 x P51 and 15125 x EP61), six generations were evaluated (P1, P2, F1, F2, BC1, and BC2). Genetic effects x environment interactions were not significant. For the O. nubilalis resistance traits; both crosses fitted an additive-dominance model. EP59 x P51 had important dominance and additive effects, whereas for 15125 x EP61 we did not detect significant genetic effects, but significant year effects were detected. For S. nonagrioides infestation, both crosses fitted to an additive-dominance model. There were additive effects for most traits in EP59 x P51. The cross I5125 x EP61 showed significant dominance effects for several traits. Resistance to both corn borers fit an additive-dominance model, but genetic effects depend on the cross evaluated. In the resistance to S. nonagrioides, additive effects were important for shank resistance, which is a useful trait for avoiding S. nonagrioides damage on the ear. Early sowings are recommended to make good use of the resistance to both corn borers. In the late sowings, damage is so high that resistant plants are not able to control the pest.

Animals↗

Evaluation of the European Union Maize Landrace Core Collection for resistance to Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae).

Two corn borer species are the principal maize insect pests in Europe, the European corn borer, Ostrinia nubilalis (Hübner), and the pink stem borer, Sesamia nonagrioides (Lefebvre). Hence, it would be advisable to evaluate the European maize germplasm for corn borer resistance to generate European varieties resistant to corn borer attack. The creation of the European Union Maize Landrace Core Collection (EUMLCC) allowed the screening of most of the variability for European corn borer resistance present among European maize local populations from France, Germany, Greece, Italy, Portugal, and Spain, testing a representative sample. The objective of this study was the evaluation of stem and ear resistance of the EUMLCC to European corn borer and pink stem borer attack. Trials were made at two Spanish locations that represent two very different maize-growing areas. Populations that performed relatively well under corn borer infestation for stem and ear damage were 'PRT0010008' and'GRC0010085', among very early landraces; 'PRT00100120' and 'PRT00100186', among early landraces; 'GRC0010174', among midseason landraces; and 'ESP0070441', among late landraces. Either the selection that could have happen under high insect pressure or the singular origin of determined maize populations would be possible explanations for the higher corn borer resistance of some landraces. Landraces 'PRT0010008', 'FRA0410090', 'PRT00100186', and 'ESP0090214' would be selected to constitute a composite population resistant to corn borers and adapted to short season, whereas populations 'ESP0090033', 'PRT00100530', 'GRC0010174', and 'ITA0370005' would be used to make a resistant composite adapted to longer season.

Animals↗

Relative concentration of Cry1A in maize leaves and cotton bolls with diverse chlorophyll content and corresponding larval development of fall armyworm (Lepidoptera: Noctuidae) and southwestern corn borer (Lepidoptera: Crambidae) on maize whorl leaf profiles.

To manage insect resistance to transgenic crops that express insecticidal proteins from Bacillus thuringiensis (Bt) Berliner, the U.S. Environmental Protection Agency recommends a refuge-based insect resistance management strategy where a percentage of non-Bt (refuge) crop is grown in proximity to a Bt-expressing crop. An important requirement for this strategy is that the toxin exists at a high effective dose for control of the target pest(s), so that heterozygous individuals in the population do not reach adulthood. Factors that cause reduced levels of toxin in the plant are a threat to this strategy. We quantified Cry1Ab from different areas of the maize, Zea mays L., leaf. In general, the distal tip of the V7 maize leaf had a higher concentration of Cry1Ab compared with the middle section of the V7 leaf, and the middle section of the developing V9 leaf had the lowest concentration of Cry1Ab. When these sections of maize tissue were fed to fall armyworm, Spodoptera frugiperda (J.E. Smith), and southwestern corn borer, Diatraea grandiosella Dyar, there was not a reduction in development or an increase in mortality with tissue that had higher concentrations of toxin. Another study tested the relative concentration of Cry1Ab between the white-yellow, yellow-green, and green portions of the developing ninth leaf within the maize whorl. There were differences in Cry1Ab concentration among these leaf areas. The green tissue had the highest concentration of toxin followed by the yellow-green and white-yellow tissues. Correlations between concentration of Cry1Ab and 5-d fall armyworm larval weights among the three leaf color profiles were all significant and negative, i.e., decreased concentration of Cry1Ab in the leaf tissue resulted in increased 5-d larval weights. There was 100% mortality to the southwestern corn borer larvae fed Cry1Ab maize leaf tissue. Differences in the amount of Cry1Ab in the developing V9 leaf profiles did not alter the absolute susceptibility of the southwestern corn borer to the toxin. In cotton, Gossypium hirsutum L., the amount of Cry1Ac was significantly lower in boll tips where flowers had remained attached compared with normal boll tips. Boll tips where the flowers remained attached are often the site where corn earworms, Helicoverpa zea (Boddie), penetrate Bt cotton bolls. This study demonstrated that, in two diverse plant species, tissue that has low chlorophyll content does not fully express Cry1A. Photosynthesis regulating factors related to mRNA transcription and translation should be studied for their effect on Cry1A production and insect control.

Animals↗

Dermatitis causada por Hylesia metabus (Lepidoptera: Hemileucidae) en la región costera del Estado del Delta del Amacuro, Venezuela [Dermatitis caused by Hylesia metabus (Lepidoptera: Hemileucidae) in the costal region of the state of Delta Amacuro, Venezuela].

2 cases of acute dermatitis caused by butterfly Hylesia metabus in an area that so far has not been considered as endemic for this species were presented. The dermatitis observed in these individuals may be described as very circumscribed, pruriginous, erythematous generalized protruding papules that may be compared with urticaria, and with a variable degree oedema. Monomorphic eruption consisting in small hard papules crowned by a little vesicle was also present. The lesions of these 2 patients evolved with intensely pruriginous papules for a week and after that they healed without dermatological sequelae.

Adult↗

[The sex-trapping of Sterrha biselata (Hufn.) (Lepidoptera Geometridae, Sterrhinae) by acetoxy-1 dodecadiens-7 E, 9Z, the sex pheromone of Lobesia botrana (Schiff.) (Lepidoptera Tortricidae, Olethreutinae)].

7E, 9Z dodecadienyl acetate, a sex-heromone for Lobesia botrana, is selectively attractive, in vineyards, for males of this species. By testing this compound in woods and orchards, we have found that it was also selectively attractive for males of a geometrid moth; Sterrha biselata. This is one of the first examples where a definite chemical substance is active for a geometrid species.

Animals↗

In vitro metabolism of aflatoxin B1 by larvae of navel orangeworm, Amyelois transitella (Walker) (Insecta, Lepidoptera, Pyralidae) and codling moth, Cydia pomonella (L.) (Insecta, Lepidoptera, Tortricidae).

Larvae of the navel orangeworm (NOW), Amyelois transitella (Walker), a major pest of almonds and pistachios, and the codling moth (CM), Cydia pomonella (L.), the principal pest of walnuts and pome fruits, are commonly found in tree nut kernels that can be contaminated with aflatoxin, a potent carcinogen. The ability of larvae of these insects to metabolize aflatoxin B1 (AFB1) was examined. A field strain of NOW produced three AFB1 biotransformation products, chiefly aflatoxicol (AFL), and minor amounts of aflatoxin B2a (AFB2a) and aflatoxin M1 (AFM1). With AFL as a substrate, NOW larvae produced AFB1 and aflatoxicol M1 (AFLM1). A lab strain of CM larvae produced no detectable levels of AFB1 biotransformation products in comparison to a field strain which produced trace amounts of only AFL. Neither NOW nor CM produced AFB1-8,9-epoxide (AFBO), the principal carcinogenic metabolite of AFB1. In comparison, metabolism of AFB1 by chicken liver yielded mainly AFL, whereas mouse liver produced mostly AFM1 at a rate eightfold greater than AFL. Mouse liver also produced AFBO. The relatively high production of AFL by NOW compared to CM may reflect an adaptation to detoxify AFB1. NOW larvae frequently inhabit environments highly contaminated with fungi and, hence, aflatoxin. Only low amounts, if any, of this mycotoxin occur in the chief CM hosts, walnuts, and pome fruits. Characterizations of enzymes and co-factors involved in biotransformation of AFB1 are discussed.

Aflatoxin B1↗

Lack of cross-resistance to indoxacarb in insecticide-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) and Plutella xylostella (Lepidoptera: Yponomeutidae).

Two field strains of the fall armyworm, Spodoptera frugiperda (JE Smith), collected from corn in north Florida showed high resistance to carbaryl (626- and 1159-fold) and moderate resistance to parathion-methyl (30- and 39-fold) as compared with a laboratory susceptible strain. A field strain of the diamondback moth, Plutella xylostella (L.) collected from cabbage in north Florida and selected for 20 generations with permethrin showed high resistance to permethrin (987-fold) as compared with a susceptible strain. However, in all instances, no cross-resistance to indoxacarb, a novel oxidiazine insecticide, was observed in these two species. Biochemical studies revealed that, in S. frugiperda, activities of detoxification enzymes (microsomal oxidase, glutathione S-transferase and general esterase) were significantly higher in the field strains than in the susceptible strain, indicating that these detoxification enzymes were not actively involved in the resistance to indoxacarb. The lack of cross-resistance between indoxacarb and permethrin in P. xylostella further supports the notion that the mode of action of these insecticides on the insect sodium channel is different.

Animals↗

Host Specificity of Microsporidia (Protista: Microspora) from European Populations of Lymantria dispar (Lepidoptera: Lymantriidae) to Indigenous North American Lepidoptera

Results of traditional laboratory bioassays may not accurately represent ecological (field) host specificity of entomopathogens but, if carefully interpreted, may be used to predict the ecological host specificity of pathogens being considered for release as classical biological control agents. We conducted laboratory studies designed to evaluate the physiological host specificity of microsporidia, which are common protozoan pathogens of insects. In these studies, 49 nontarget lepidopteran species indigenous to North America were fed five biotypes of microsporidia that occur in European populations of Lymantria dispar but are not found in North American populations of L. dispar. These microsporidia, Microsporidium sp. from Portugal, Microsporidium sp. from Romania, Microsporidium sp. from Slovakia, Nosema lymantriae, and Endoreticulatus sp. from Portugal, are candidates for release as classical biological control agents into L. dispar populations in the United States. The microsporidia produced a variety of responses in the nontarget hosts and, based on these responses, the nontarget hosts were placed in the following categories: (1) no infection (refractory), (2) atypical infections, and (3) heavy infections. Endoreticulatus sp. produced patent, host-like infections in nearly two-thirds of the nontarget hosts to which it was fed. Such generalist species should not be recommended for release. Infections comparable to those produced in L. dispar were produced in 2% of the nontarget hosts fed Microsporidium sp. from Portugal, 19% of nontarget hosts fed Microsporidium sp. from Romania, 13% fed spores of Microsporidium sp. from Slovakia, and 11% of nontarget species fed N. lymantriae. The remaining nontarget species developed infections that, despite production of mature spores, were not typical of infection in L. dispar. We believe it is very unlikely that these atypical infections would be horizontally transmitted within nontarget insect populations in the United States.

Journal Article↗

The Effects of Ingested 20-Hydroxyecdysone on the Larvae of Aglais urticae, Inachis io, Cynthia cardui (Lepidoptera: Nymphalidae) and Tyria jacobaeae (Lepidoptera: Arctiidae).

A comparative survey was carried out to investigate the effects, distribution and metabolism of ingested 20-hydroxyecdysone in four species of lepidopteran larvae in relation to the phytoecdysteroid content of the insect's host plants. Analysis of the leaves of the host plants of each of the species revealed a strong relationship between the levels of phytoecdysteroids and the relative tolerance of the larvae to ingested 20-hydroxyecdysone. Monophagous or oligophagous species (Aglais urticae, Inachis io) feeding on ecdysteroid-negative host plants were either deterred from feeding or showed marked abnormalities in growth and development after incorporation of 20-hydroxyecdysone in their diets. Oligophagous or polyphagous species (Tyria jacobaeae, Cynthia cardui) which feed on host plants from families which are known to contain phytoecdysteroid-positive species, were able to tolerate low levels of 20-hydroxyecdysone in their diets, but exhibited developmental defects at high concentrations. These species were termed semi-tolerant. In each of the species, ingested [3H]20-hydroxyecdysone appeared to follow the same fate as injected [3H]20-hydroxyecdysone. The data are compared to those obtained in previous studies, where truly polyphagous species were shown to tolerate very high concentrations of 20-hydroxyecdysone in their diets by the production of ecdysteroid 22-fatty acyl esters. Copyright 1997 Elsevier Science Ltd. All rights reserved

Journal Article↗

Binomial sequential sampling plans for late instars of European corn borer (Lepidoptera: Crambidae), corn earworm (Lepidoptera: Noctuidae), and damaged kernels in sweet corn ears.

Late-season infestations of European corn borer, Ostrinia nubilalis (Hübner), and corn earworm, Helicoverpa zea (Boddie), were sampled to develop binomial sequential sampling plans for larval infestations and damaged kernels in sweet corn, Zea mays L., ears, near harvest. Fields were sampled to obtain a range of larval densities likely to be encountered over a range of infestation levels and field conditions. Binomial sampling plans were developed for O. nubilalis larvae, H. zea larvae, O. nubilalis, and H. zea larvae combined, and for damaged sweet corn kernels. Observed densities ranged from 0.01 to 4.40 larvae per ear for O. nubilalis, 0.005-1.62 larvae per ear for H. zea, and 0.004-36.12 damaged kernels per ear. Results of resampling analyses, based on the proportion of ears infested with one or more larvae, or damaged kernels, indicated an average sample size of 34-37 ears was necessary to classify whether larval infestations, or the incidence of damaged kernels, exceeded 5%. Two operating characteristic curves are presented for each of the four sampling plans. Initial results, with upper bounds of 0.10, and alpha (type I) and beta (type II) error rates at 0.10 and 0.05, respectively, resulted in a 90% probability of making the correct management decision at infestation levels >10%. To improve performance of the sampling plans, we modified the binomial plans by reducing the upper bound to 0.075, while maintaining the same error rates. This plan resulted in a higher probability (>95%) of making the correct management decision to reject a sweet corn load when infestation levels are >10%.

Animals↗

Toxicity and residual activity of methoxyfenozide and tebufenozide to codling moth (Lepidoptera: Tortricidae) and oriental fruit moth (Lepidoptera: Tortricidae).

A series of studies were conducted to examine the residual activity and toxicity of the ecdysone agonists tebufenozide and methoxyfenozide to codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), in North Carolina apple systems. Methoxyfenozide exhibited greater activity than tebufenozide against codling moth eggs in dose-response bioassays, with a 4.5- and 5.3-fold lower LC50 value to eggs laid on fruit treated before or after oviposition, respectively. Oriental fruit moth eggs were 57- and 12-fold less sensitive to methoxyfenozide than were codling moth eggs on fruit treated before and after oviposition, respectively. Methoxyfenozide was effective in reducing larval entries of both codling moth and oriental fruit moth in field residual activity bioassays, exhibiting activity for at least 28 d after application. Residue breakdown on fruit was approximately 80% at 28 d after treatment for both methoxyfenozide and tebufenozide, with the most rapid residue decline (60%) occurring during the first 14 d after application. Two applications of methoxyfenozide applied at 14-d intervals provided better canopy coverage and higher residue levels than one application. Spray volume (683 versus 2,057 liters/ha) did not affect the efficacy of methoxyfenozide. Leaf and fruit expansion during the season was measured to determine potential plant-growth dilution effects on residual activity. There was very little increase in leaf area after mid May, but increase in fruit surface area over the season was described by a second order polynomial regression. Implications for codling moth and oriental fruit moth management programs are discussed.

Animals↗

Susceptibility of Spanish populations of the corn borers Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae) to a Bacillus thuringiensis endotoxin.

Baseline susceptibility to the Cry1Ab delta-endotoxin from Bacillus thuringiensis (Berliner) was determined for four populations of Sesamia nonagrioides (Lefebvre) and two populations of Ostrinia nubilalis (Hübner) from Spain. This study shows that S. nonagrioides is at least as susceptible as O. nubilalis to B. thuringiensis Cry1Ab protein. We found small differences in susceptibility among the Spanish populations of S. nonagrioides that can be attributed to natural variation, because there are no records of B. thuringiensis products being used on corn crops in Spain. There were no differences in susceptibility to Cry1Ab toxin between the two populations of O. nubilalis.

Animals↗