Fall Armyworm Feeding Research Articles

Comprehensive Transcriptomic Analysis Reveals Defense-Related Genes and Pathways of Rice Plants in Response to Fall Armyworm (Spodoptera frugiperda) Infestation.

Rice (Oryza sativa L.) serves as a substitute for bread and is a staple food for half of the world's population, but it is heavily affected by insect pests. The fall armyworm (Spodoptera frugiperda) is a highly destructive pest, threatening rice and other crops in tropical regions. Despite its significance, little is known about the molecular mechanisms underlying rice's response to fall armyworm infestation. In this study, we used transcriptome analysis to explore the global changes in gene expression in rice leaves during a 1 h and 12 h fall armyworm feeding. The results reveal 2695 and 6264 differentially expressed genes (DEGs) at 1 and 12 h post-infestation, respectively. Gene Ontology (GO) and KEGG enrichment analyses provide insights into biological processes and pathways affected by fall armyworm feeding. Key genes associated with hormone regulation, defense metabolic pathways, and antioxidant and detoxification processes were upregulated, suggesting the involvement of jasmonic acid (JA) signaling, salicylic acid biosynthesis pathways, auxin response, and heat shock proteins in defense during 1 h and 12 h after fall armyworm infestation. Similarly, key genes involved in transcriptional regulation and defense mechanisms reveal the activation of calmodulins, transcription factors (TFs), and genes related to secondary metabolite biosynthesis. Additionally, MYB, WRKY, and ethylene-responsive factors (ERFs) are identified as crucial TF families in rice's defense response. This study provides a comprehensive understanding of the molecular dynamics in rice responding to fall armyworm infestation, offering valuable insights for developing pest-resistant rice varieties and enhancing global food security. The identified genes and pathways provide an extensive array of genomic resources that can be used for further genetic investigation into rice herbivore resistance. This also suggests that rice plants may have evolved strategies against herbivorous insects. It also lays the groundwork for novel pest-resistance techniques for rice.

Transcriptomic and biochemical insights into fall armyworm (Spodoptera frugiperda) responses on silicon-treated maize.

The fall armyworm, Spodoptera frugiperda, is an agricultural pest of significant economic concern globally, known for its adaptability, pesticide resistance, and damage to key crops such as maize. Conventional chemical pesticides pose challenges, including the development of resistance and environmental pollution. The study aims to investigate an alternative solution: the application of soluble silicon (Si) sources to enhance plant resistance against the fall armyworm. Silicon dioxide (SiO2) and potassium silicate (K2SiO3) were applied to maize plants via foliar spray. Transcriptomic and biochemical analyses were performed to study the gene expression changes in the fall armyworm feeding on Si-treated maize. Results indicated a significant impact on gene expression, with a large number of differentially expressed genes (DEGs) identified in both SiO2 and K2SiO3 treatments. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified critical DEGs involved in specific pathways, including amino acid, carbohydrate, lipid, energy, xenobiotics metabolisms, signal transduction, and posttranslational modification, significantly altered at both Si sources. Biochemical analyses further revealed that Si treatments inhibited several enzyme activities (glutamate dehydrogenase, trehalase, glucose-6-phosphate dehydrogenase, chitinase, juvenile hormone esterase, and cyclooxygenase while simultaneously inducing others (total protein, lipopolysaccharide, fatty acid synthase, ATPase, and cytochrome P450), thus suggesting a toxic effect on the fall armyworm. In conclusion, Si applications on maize influence the gene expression and biochemical activities of the fall armyworm, potentially offering a sustainable pest management strategy.

Dynamic regulation of phenylpropanoid pathway metabolites in modulating sorghum defense against fall armyworm.

Plants undergo dynamic metabolic changes at the cellular level upon insect infestation to better defend themselves. Phenylpropanoids, a hub of secondary plant metabolites, encompass a wide range of compounds that can contribute to insect resistance. Here, the role of sorghum (Sorghum bicolor) phenylpropanoids in providing defense against the chewing herbivore, fall armyworm (FAW), Spodoptera frugiperda, was explored. We screened a panel of nested association mapping (NAM) founder lines against FAW and identified SC1345 and Ajabsido as most resistant and susceptible lines to FAW, respectively, compared to reference parent, RTx430. Gene expression and metabolomic studies suggested that FAW feeding suppressed the expression level of genes involved in monolignol biosynthetic pathway and their associated phenolic intermediates at 10 days post infestation. Further, SC1345 genotype displayed elevated levels of flavonoid compounds after FAW feeding for 10 days, suggesting a diversion of precursors from lignin biosynthesis to the flavonoid pathway. Additionally, bioassays with sorghum lines having altered levels of flavonoids provided genetic evidence that flavonoids are crucial in providing resistance against FAW. Finally, the application of FAW regurgitant elevated the expression of genes associated with the flavonoid pathway in the FAW-resistant SC1345 genotype. Overall, our study indicates that a dynamic regulation of the phenylpropanoid pathway in sorghum plants imparts resistance against FAW.

Effects of Nano-Graphene Oxide on the Growth and Reproductive Dynamics of Spodoptera frugiperda Based on an Age-Stage, Two-Sex Life Table.

Simple SummaryFall armyworm (FAW), Spodoptera frugiperda, is an important pest in a variety of different crops. Graphene oxide (GO) is a promising candidate used in a biological context because of its versatility. In agriculture, GO could be potentially used as a pesticide additive to improve the efficacy of insecticides. In this study, the effects of GO on the development and reproduction of FAWs were determined based on life table analysis. The results showed that GO could prolong the duration of the egg stage and instar larval stages, but shorten lifespan of male and female adults, and this effect was enhanced with increasing GO concentrations. GO also reduced the number of eggs laid by female moths. In addition, the expression of genes related to reproduction have also been affected by GO. In conclusion, GO prolonged the developmental period of FAWs, decreased fecundity, and may decline the population size. The study provides a basis for the rational use of GO as a pesticide synergist for FAW control.The development and reproduction of the fall armyworm (FAW), Spodoptera frugiperda, which were reared on artificial diets containing nano-graphene oxide (GO), were determined based on age-stage, two-sex life table analysis. The results showed that GO had adverse effects on FAWs. Compared with the control, the duration of the egg stage and first, second, and sixth instar larval stages increased with increasing GO concentrations; however, the lifespan of male and female adults decreased with increasing GO concentrations. Weights of FAW pupae that were supplied with GO-amended diets increased by 0.17–15.20% compared to the control. Intrinsic growth, limited growth, and net reproductive rates of FAWs feeding on GO supplemented diets were significantly lower than the control, while mean generational periods (0.5 mg/g: 38.47; 1 mg/g: 40.38; 2 mg/g: 38.42) were significantly longer than the control. The expression of genes encoding vitellogenin (Vg) and vitellogenin receptor (VgR) expression was abnormal in female FAW adults feeding on GO-amended diets; the number of eggs laid decreased relative to the control, but Vg expression increased. In conclusion, GO prolonged the developmental period of FAWs, decreased fecundity, and led to a decline in the population size. The study provides a basis for the rational use of GO as a pesticide synergist for FAW control.

Seedling growth and fall armyworm feeding preference influenced by dhurrin production in sorghum

Cyanogenic glucosides (CGs) play a key role in host-plant defense to insect feeding; however, the metabolic tradeoffs between synthesis of CGs and plant growth are not well understood. In this study, genetic mutants coupled with nondestructive phenotyping techniques were used to study the impact of the CG dhurrin on fall armyworm [Spodoptera frugiperda (J.E. Smith)] (FAW) feeding and plant growth in sorghum [Sorghum bicolor (L.) Moench]. A genetic mutation in CYP79A1 gene that disrupts dhurrin biosynthesis was used to develop sets of near-isogenic lines (NILs) with contrasting dhurrin contents in the Tx623 bmr6 genetic background. The NILs were evaluated for differences in plant growth and FAW feeding damage in replicated greenhouse and field trials. Greenhouse studies showed that dhurrin-free Tx623 bmr6 cyp79a1 plants grew more quickly than wild-type plants but were more susceptible to insect feeding based on changes in green plant area (GPA), total leaf area, and total dry weight over time. The NILs exhibited similar patterns of growth in field trials with significant differences in leaf area and dry weight of dhurrin-free plants between the infested and non-infested treatments. Taken together, these studies reveal a significant metabolic tradeoff between CG biosynthesis and plant growth in sorghum seedlings. Disruption of dhurrin biosynthesis produces plants with higher growth rates than wild-type plants but these plants have greater susceptibility to FAW feeding.

Response of Spodoptera frugiperda (Lepidoptera: Noctuidae) to salt‐stressed maize plants

AbstractSalt‐stressed maize is an economically important crop in many arid and semi‐arid regions of the world where soil salinization is most common, and the invasive fall armyworm (FAW) Spodoptera frugiperda threatens global maize production. It thus poses a puzzle of whether FAW populations feeding on salt‐stressed maize plants are becoming more or less invasive. Here, we evaluated the FAW response to salt‐stressed maize plants by examining effects of salt‐stressed maize plants on FAW survival, development and fecundity. We found a longer larval development time (salt‐stressed, 12.9 ± 0.8 d; non‐stressed, 11.3 ± 0.4 d), but unaffected survival rate and pupal mass accumulation in FAW feeding on salt‐stressed maize plants. Moreover, the lifetime egg production of FAW females feeding on salt‐stressed maize plants (633.5 ± 62.7 eggs) was reduced by nearly half compared with those feeding on non‐stressed maize plants (1255.9 ± 70.3 eggs). Overall, FAW showed a negative response to salt‐stressed maize plants. Due to limited population increase potential, FAW populations feeding on salt‐stressed maize plants should pose less of a problem than ones feeding on non‐stressed maize plants do. In practice, salt‐stressed maize plants are quite common in arid and semi‐arid regions where the relatively high‐salinity groundwater is often used to irrigate maize plants, potentially limiting FAW population size. Thus, salt‐stressed maize plants would contribute to practical applications of integrated pest management (IPM) strategies in controlling FAW.

Evaluation of African Maize Cultivars for Resistance to Fall Armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) Larvae.

The fall armyworm (FAW) has recently invaded and become an important pest of maize in Africa causing yield losses reaching up to a third of maize annual production. The present study evaluated different aspects of resistance of six maize cultivars, cropped by farmers in Kenya, to FAW larvae feeding under laboratory and field conditions. We assessed the arrestment and feeding of FAW neonate larvae in no-choice and choice experiments, development of larvae-pupae, food assimilation under laboratory conditions and plant damage in a field experiment. We did not find complete resistance to FAW feeding in the evaluated maize cultivars, but we detected differences in acceptance and preference when FAW larvae were given a choice between certain cultivars. Moreover, the smallest pupal weight and the lowest growth index were found on ’SC Duma 43′ leaves, which suggests an effect of antibiosis of this maize hybrid against FAW larvae. In contrast, the highest growth index was recorded on ‘Rachar’ and the greatest pupal weight was found on ‘Nyamula’ and ‘Rachar’. The density of trichomes on the leaves of these maize cultivars seems not to be directly related to the preference of neonates for feeding. Plant damage scores were not statistically different between cultivars in the field neither under natural nor artificial infestation. However, plant damage scores in ‘Nyamula’ and ‘Jowi’ tended to be lower in the two last samplings of the season compared to the two initial samplings under artificial infestation. Our study provides insight into FAW larval preferences and performance on some African maize cultivars, showing that there are differences between cultivars in these variables; but high levels of resistance to larvae feeding were not found.

Evaluation of Maize Germplasm from Saint Croix for Resistance to Leaf Feeding by Fall Armyworm1

Maize (Zea mays L.) is a preferred host of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera:Noctuidae), with larvae primarily feeding on developing leaves and ear tissue. The fall armyworm is resistant to several classes of insecticide and Bt-maize grown in certain areas. Native sources of plant resistance to the pest are available for public use, but new sources of resistance need to be discovered and developed. The objective for this study was to test maize germplasm collected from Saint Croix, U.S. Virgin Islands, for resistance to leaf feeding by fall armyworm. Plants were grown in the field and artificially infested at a high level. Scores of damage by fall armyworm feeding on leaves at 7 and 14 days differed significantly for the 13 maize genotypes tested. Scores at 14 days for Saint Croix Group 1 (5.8), Saint Croix Group 3 (5.6), Saint Croix 2 (5.6), and Saint Croix 7 (6.0) were moderately resistant and not significantly different from one another. Individual plants in the populations were variable for resistance to leaf feeding, and scored between 4 and 7. It should be possible to select within the populations for greater resistance to damage by fall armyworms feeding on leaves.

Diallel analysis for aflatoxin accumulation and fall armyworm leaf-feeding damage in maize

ABSTRACTTwo major impediments to profitable maize, Zea mays L., production in the southern United States are from feeding by fall armyworm, Spodoptera frugiperda (J.E. Smith), and losses from the production and accumulation of aflatoxin in maize grain. A diallel cross was produced by making all possible crosses among five germplasm lines developed as sources of resistance to fall armyworm leaf feeding and five lines developed as sources of resistance to aflatoxin accumulation. For resistance to both leaf feeding and aflatoxin accumulation, general combining ability (GCA) was a significant source of variation. Specific combining ability (SCA) was significant for fall armyworm feeding only. Estimates of GCA effects for reduced aflatoxin accumulation were significant for Mp715 and Mp719, two lines selected for resistance to aflatoxin accumulation. The GCA effects for reduced fall armyworm damage were significant for all five lines selected for fall armyworm resistance: Mp707, Mp708, Mp713, Mp714, and Mp716.

Use of Benzimidazole Agar Plates to Assess Fall Armyworm (Lepidoptera: Noctuidae) Feeding on Excised Maize and Sorghum Leaves

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is an economically significant pest of sorghum and maize. Laboratory bioassays are often conducted for convenience and for fall armyworm confinement but as the number of entries and replications increase, the replenishing of fresh tissue daily and the cleaning of insect diet cups or petri dishes becomes laborious. The current study was conducted to determine if agar plates, used to retain leaf moisture, supplemented with benzimidazole, a fungicide that delays leaf senescence and retards fungicide growth, can be used to assess fall armyworm feeding on fresh maize and sorghum leaf tissue with minimal labor. We conducted 2 trials consisting of 3 cultivars of maize with known resistance or susceptibility to fall armyworm feeding, and 4 cultivars of sorghum that are parents of existing mapping populations. The top 2 (whorl) leaves were removed from 36–37-day old plants, 7.6 cm long pieces of leaf were excised, and each piece was placed on a benzimidazole agar plate. One larva per plate was placed on the leaf tissue; the plate was sealed with Parafilm and placed in an incubator for 7 days. Average larval weights for Trial 1 were significantly different than Trial 2 after 7 days, and thus each trial was analyzed separately. For both trials, the larvae that were fed susceptible maize line ‘AB24E’ had weights that were significantly greater than larvae fed resistant maize lines ‘Mp708’ and ‘FAW1430’. No significant differences in weight were observed for fall armyworm larvae fed on the 4 sorghum lines except for those larvae fed ‘Collier’ in Trial 2, which had weights significantly greater than larvae fed the other 3 sorghum cultivars (Entry 22, ‘Honey Drip’, ‘AN109’). Thus, the benzimidazole agar plate method is an easy and effective method for assessing fall armyworm feeding on maize and sorghum, and thus can be used to identify maize and sorghum germplasm lines with resistance to fall armyworm.

Evaluation of Whorl Damage by Fall Armyworm (Lepidoptera: Noctuidae) on Field- and Greenhouse-Grown Sweet Sorghum Plants

Abstract The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an economically important pest of sorghum, Sorghum bicolor (L.) Moench. However, resistance to fall armyworm in sweet sorghum has not been extensively studied. A collection of primarily sweet sorghum accessions were evaluated in the field for natural fall armyworm infestation. Fall armyworm damage ratings ranged from 1.88 ± 0.35 to 4.75 ± 0.37, suggesting that a range of response to fall armyworm feeding exists in this collection. Based on the results of field data from two planting dates, accessions with the highest and lowest fall armyworm damage ratings were selected for greenhouse evaluations. At 7 d after infestation, the sorghum accessions, excluding BTx623 and Plant Introduction (PI) 147573, had significantly higher fall armyworm damage than resistant control MP708. Furthermore, at 7 d after the infestation, genotype PI 147573 was the most resistant; whereas, genotypes 13, 22, ‘GT-IR8′, and ‘GT-IR6′ were th...

A Comparison of Bt Transgene, Hybrid Background, Water Stress, and Insect Stress Effects on Corn Leaf and Ear Injury and Subsequent Yield

Experimentally manipulated water and insect stresses were applied to field-grown corn with different Bacillus thuringiensis (Bt) transgenes and no Bt transgenes, and different nontransgenic hybrid backgrounds (2011 and 2012, Corpus Christi, TX). Differences in leaf injury, ear injury, and yield were detected among experimental factors and their interactions. Under high and low water stress, injury from noctuid larvae (Lepidoptera: Noctuidae) on leaves during vegetative growth (primarily from fall armyworm, Spodoptera frugiperda J.E. Smith) and on developing ears (primarily from corn earworm, Helicoverpa zea [Boddie]) was lowest on more recent releases of Bt hybrids (newer Bt hybrids) expressing Cry1A.105+Cry2Ab2 and Cry 3Bb1, compared with earlier Bt hybrids (older Bt hybrids) expressing Cry1Ab and Cry3Bb1 and non-Bt hybrids. High water stress led to increased leaf injury under substantial fall armyworm feeding pressure in 2011 (as high as 8.7 on a 1-9 scale of increasing injury). In contrast, ear injury by corn earworm (as high as 20 cm(2) of surface area of injury) was greater in low water stress conditions. Six hybrid backgrounds did not influence leaf injury, while ear injury differences across hybrid backgrounds were detected for non-Bt and older Bt hybrid versions. While newer Bt hybrids expressing Cry1A.105+Cry2Ab2 and Cry 3Bb1 had consistent low leaf injury and high yield and low but less consistent ear injury across six hybrid backgrounds, water stress was a key factor that influenced yield. Bt transgenes played a more variable and lesser role when interacting with water stress to affect yield. These results exemplify the interplay of water and insect stress with plant injury and yield, their interactions with Bt transgenes, and the importance of these interactions in considering strategies for Bt transgene use where water stress is common.

Warmer temperatures increase disease transmission and outbreak intensity in a host–pathogen system

While rising global temperatures are increasingly affecting both species and their biotic interactions, the debate about whether global warming will increase or decrease disease transmission between individuals remains far from resolved. This may stem from the lack of empirical data. Using a tractable and easily manipulated insect host-pathogen system, we conducted a series of field and laboratory experiments to examine how increased temperatures affect disease transmission using the crop-defoliating pest, the fall armyworm (Spodoptera frugiperda) and its species-specific baculovirus, which causes a fatal infection. To examine the effects of temperature on disease transmission in the field, we manipulated baculovirus density and temperature. As infection occurs when a host consumes leaf tissue on which the pathogen resides, baculovirus density was controlled by placing varying numbers of infected neonate larvae on experimental plants. Temperature was manipulated by using open-top chambers (OTCs). The laboratory experiments examined how increased temperatures affect fall armyworm feeding and development rates, which provide insight into how host feeding behaviour and physiology may affect transmission. Disease transmission and outbreak intensity, measured as the cumulative fraction infected during an epizootic, increased at higher temperatures. However, there was no appreciable change in the mean transmission rate of the disease, which is often the focus of empirical and theoretical research. Instead, the coefficient of variation (CV) associated with the transmission rate shrunk. As the CV decreased, heterogeneity in disease risk across individuals declined, which resulted in an increase in outbreak intensity. In the laboratory, increased temperatures increased feeding rates and decreased developmental times. As the host consumes the virus along with the leaf tissue on which it resides, increased feeding rate is likely to increase the probability of an individual consuming virus-infected leaf tissue. On the other hand, decreased developmental time increases the sloughing of midgut cells, which is predicted to hinder viral infection. Increases in outbreak intensity or epizootic severity, as the climate warms, may lead to changes in the long-term dynamics of pests whose populations are strongly affected by host-pathogen interactions. Overall, this work demonstrates that the usual assumptions governing these effects, via changes in the mean transmission rate alone, may not be correct.

Foliar herbivory triggers local and long distance defense responses in maize

Many studies have documented the induction of belowground defenses in plants in response to aboveground herbivory and vice versa, but the genes and signaling molecules mediating systemic induction are not well understood. We performed comparative microarray analysis on maize whorl and root tissues from the insect resistant inbred Mp708 in response to foliar feeding by fall armyworm (Spodoptera frugiperda) caterpillars. Although Mp708 has elevated jasmonic acid (JA) levels prior to herbivory, genes involved in JA biosynthesis were up-regulated in whorls in response to fall armyworm feeding. Alternatively, genes possibly involved in regulating ethylene (ET) perception and signaling were up-regulated in roots following foliar herbivory. Transcript levels of genes encoding proteins involved in direct defenses against herbivores were enhanced both in roots and leaves, but transcriptional factors and genes involved in various biosynthetic pathways were selectively down-regulated in the whorl. The results indicate that foliar herbivory by fall armyworm changes root gene expression pathways suggesting profound long distance signaling. Tissue specific induction and suppression of JA and ET signaling pathway genes provides a clue to their possible roles in signaling between the two distant tissue types that eventually triggers defense responses in the roots in response to foliar herbivory.

Insect resistance of a full sib family of tetraploid switchgrass Panicum virgatum L. with varying lignin levels

Little information is available on insect resistance mechanisms and inheritance in biomass grasses. Although reduction of lignin in biomass grasses in order to increase the efficiency of fermentation may result in increased susceptibility to insect feeding, other resistance mechanisms may be more important. Field grown leaves of two tetraploid parent (Kanlow N1, Summer) and 14 progeny switchgrass (Panicum virgatum L.) plant clones selected for a diversity of plant form and ranges in lignin levels were tested for leaf resistance to feeding by the fall armyworm (Spodoptera frugiperda J. E. Smith), a grass feeding insect pest. Although lignin generally appeared important as a resistance mechanism only at early season stages, replicate clones of two low lignin progeny plants generally remained resistant to fall armyworm feeding. Mechanical damaging increased resistance to fall armyworm feeding in several of these plants. Degrees of resistance were sometimes associated with leaf form of progeny. These results indicate there are likely multiple insect resistance mechanisms operating at different stages in switchgrass, and that segregation of some mechanisms appears related to growth form of the plants.

Efeito da aplicação de silício em plantas de milho no desenvolvimento biológico da lagarta-do-cartucho Spodoptera frugiperda (J.E.Smith) (Lepidoptera: Noctuidae)

Este trabalho, objetivou avaliar o efeito da aplicação de silício em plantas de milho no desenvolvimento da lagarta-do-cartucho Spodoptera frugiperda (J.E. Smith). O tratamento com silício consistiu na aplicação de 3,2 ml de solução de silicato de sódio [25-28% (p/v) de SiO2], mais 96,8 ml de água, via solo aos cinco dias, 10, 15, 20 e 25 dias após a emergência de plantas de milho mantidas em vasos. Outro grupo de plantas foi cultivado sem aplicação de silício. Avaliou-se o desenvolvimento de lagartas alimentadas com folhas de milho retiradas de plantas tratadas com silício, em comparação com lagartas alimentadas com folhas de milho não tratadas, registrando-se a mortalidade ao final do 2º ínstar larval, a duração do período larval e pupal, a mortalidade larval e pupal e o peso de pupa. Não se observou efeito do silício na duração da fase larval e pupal, peso de pupa e na mortalidade de pupas. Entretanto, verificou-se maior mortalidade e aumento de canibalismo em grupos de lagartas ao final do 2º ínstar, e maior mortalidade de lagartas individualizadas no 2º e 6º ínstares, quando foram alimentadas com folhas de plantas de milho tratadas com silício, em comparação com a testemunha. Observou-se que as mandíbulas das lagartas, nos seis ínstares, apresentaram desgaste acentuado na região incisora quando em contato com folhas com maior teor de silício. A aplicação de silício pode dificultar a alimentação de lagartas, causando aumento de mortalidade e canibalismo e, portanto, tornando as plantas de milho mais resistentes à lagarta-do-cartucho.

Hazard for Fall Armyworm (Lepidoptera: Noctuidae) Infestation of Maize in Double-Cropping Systems Using Sustainable Agricultural Practices

Field tests demonstrated that selected sustainable agricultural practices influence intensity of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), infestations of late planted maize, Zea mays, in double cropping systems. Reduced FAW infestations of seedling maize were associated with no-tillage as compared with plow-tillage practice. Maize in no-tillage plots required one less chlorpyrifos [0.56 kg (AI/ha] spray than in plow-tillage based on a 50% action threshold. Surface debris of winter cover crops influenced lags of FAW infestation on no-tillage maize. Surface residues from previous cover crops may account for the reduced infestations in no-tillage areas. Infestations among plots became similar as plants grew from within the mulch cover. Use of poultry manure as a soil amendment had no effect on FAW damage, but a tendency for increased yields was observed in poultry manure plots. Chlorpyrifos significantly reduced FAW feeding resulting in increased whole plant dry weight yield in treated plots.

Sweet Corn Response to Fall Armyworm (Lepidoptera: Noctuidae) Damage During Vegetative Growth

Response by sweet corn, Zea mays , to fall armyworm feeding during three vegetative periods was studied three times during the 1988-1989 growing season near Belle Glade, Fla. Feeding damage by fall armyworm during the early and midwhorl stages (V1-V9) Significantly reduced plant height, stalk diameter, leaf area, and fresh and dry weight of aboveground portions of sweet corn plants. Protecting plants from fall armyworm damage during the late whorl stage (V9-Rl) resulted in higher yields and reduced percentages of ears damaged by insects. Protecting the plants from fall armyworm damage during the midwhorl stage (V6-V9) was not as important as during the late whorl stage but was more important than during early whorl stage (V1-V6). Fall armyworm densities as low as 0.2-0.8 larvae per plant during the late whorl stage may be sufficient to reduce yields of U.S. No.1 ears by 5-20%.

Effect on Cotesia marginiventris (Hymenoptera: Braconidae) when Rearing Host Fall Armyworm (Lepidoptera: Noctuidae) on Meridic Diet Containing Foliage from Resistant or Susceptible Com Genotypes

Larval weights for fall armyworm, Spodoptera frugiperda (J.E. Smith), were not significantly affected at two constant temperature regimes (24 and 27%C) when larvae parasitized by Cotesia marginiventris (Cresson) were reared on resistant versus susceptible corn genotypes. Results indicated that the third trophic level was not adversely affected by fall armyworm feeding on pinto bean diet containing resistant versus susceptible corn genotypes. Developmental times for C. marginiventris were shorter when the parasitoids were maintained at the higher temperature. Time from egg to cocoon formation at 24%C was Significantly less when hosts were fed diet containing foliage from the susceptible genotype ‘Cacahuacintle X’. Parasitoid longevity was increased at the higher temperature regime and was not affected by the corn genotype.

Adverse effects on fall armyworm feeding on fungus-free leaves of fungus-infected plants

Adverse effects on fall armyworm feeding on fungus-free leaves of fungus-infected plants