1. Spatial synchrony, the tendency for temporal population fluctuations to be correlated across multiple locations at regional scales, is common and contributes to the severity of outbreaks and ...epidemics, but is little studied in agricultural pests.
2. This study analysed spatial synchrony from 1974 to 2008 in 16 lepidopteran agricultural pests in Maryland, U.S.A., and investigated whether pest synchrony is driven by interannual variability in seasonal weather and the areas planted in different crop types.
3. Lepidopteran pests exhibited high degrees of spatial synchrony, which was driven by environmental variation, a phenomenon known as the Moran effect. Region‐wide variation in the areas planted in major crops drove spatially synchronous abundance fluctuations in more than half of studied species. The combination of weather and crop composition explained large fractions of synchrony in black cutworm, corn earworm, European corn borer, and spotted cutworm populations. Other pests, including forage looper and variegated cutworm, displayed a high degree of spatial synchrony, but without dependence on the tested drivers.
4. The study finding that synchronous variation in the area planted in different crop types contributed to synchronous pest abundance fluctuations suggests that strategies to reduce synchrony in changes in crop type across a region could reduce the severity of pest outbreaks and enhance the stability of agricultural systems.
Abundances of 16 lepidopteran agricultural pests in Maryland, U.S.A., exhibited pronounced spatially synchronous fluctuations during 1974–2008.
A combination of weather and synchronous temporal variation in the area planted in major crops drove crop pest spatial synchrony.
Strategies to reduce spatial synchrony in crop type changes could reduce the severity of pest outbreaks and enhance the stability of agricultural systems.
Many cereals accumulate hydroxamic acids derived from 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one. These benzoxazinoid hydroxamic acids are involved in defense of maize against various lepidopteran pests, ...most notably the European corn borer, in defense of cereals against various aphid species, and in allelopathy affecting the growth of weeds associated with rye and wheat crops. The role of benzoxazinoid hydroxamic acids in defense against fungal infection is less clear and seems to depend on the nature of the interactions at the plant−fungus interface. Efficient use of benzoxazinoid hydroxamic acids as resistance factors has been limited by the inability to selectively increase their levels at the plant growth stage and the plant tissues where they are mostly needed for a given pest. Although the biosynthesis of benzoxazinoid hydroxamic acids has been elucidated, the genes and mechanisms controlling their differential expression in different plant tissues and along plant ontogeny remain to be unraveled.
Lepidopteran insects use sex pheromones for sexual communication. Pheromone receptors expressed on peripheral olfactory receptor neurons (ORNs) are critical part to detect the sex pheromones. In ...genus
, several pheromone receptors were functional analyzed in
and
but the knowledge in
was rare. In this study, seven pheromone receptors were deorphanized by heterologous expression system of
oocytes. Functional types of
were classified by single sensillum recordings to interpret the response pattern of olfactory sensory neurons to
pheromone components. OfurOR4 and OfurOR6 responded to the major sex pheromone Z/E12-14:OAc. OfurOR4 is the main receptor for both Z/E12-14:OAc and OfurOR6 mainly responded to E12-14:OAc. Functional differentiation of gene duplication were found between OfurOR5a and OfurOR5b. OfurOR5b showed a broad response to most of the pheromone components in
, whereas OfurOR5a was found without ligands. OfurOR7 showed a specific response to Z9-14:OAc and OfurOR8 mainly responded to Z11-14:OAc and E11-14:OAc. OfurOR3 did not respond to any pheromone components. Our results improved the current knowledge of pheromone reception in
species which may contribute to speciation.
SUMMARY
In maize (Zea mays ssp. mays), agriculturally damaging herbivores include lepidopteran insects, such as the European corn borer (Ostrinia nubilalis), and distantly related arthropods, like ...the two‐spotted spider mite (Tetranychus urticae). A small number of maize lines, including B96 and B75, are highly resistant to both herbivores, and B96 is also resistant to thrips. Using T. urticae as a representative pest that causes significant leaf tissue damage, we examined the gene expression responses of these lines to herbivory in comparison with each other and with the susceptible line B73. Upon herbivory, the most resistant line, B96, showed the strongest gene expression response, with a dramatic upregulation of genes associated with jasmonic acid biosynthesis and signaling, as well as the biosynthesis of specialized herbivore deterrent compounds, such as death acids and benzoxazinoids. Extending this work with allele‐specific expression analyses in F1 hybrids, we inferred that the concerted upregulation of many defense genes, including the majority of benzoxazinoid biosynthetic genes in B96, as compared with B73, for the herbivore treatment, resulted from an assemblage of trans control and multiple cis effects acting with similar directionality on gene expression. Further, at the level of individual and potentially rate limiting genes in several major defense pathways, cis and trans effects acted in a reinforcing manner to result in exceptionally high expression in B96. Our study provides a comprehensive resource of cis elements for maize lines important in breeding efforts for herbivore resistance, and reveals potential genetic underpinnings of the origins of multi‐herbivore resistance in plant populations.
Significance Statement
Upon herbivory by a generalist spider mite, transcriptome reprogramming varied among maize lines, with differences in the expression of genes involved in jasmonic acid synthesis and signaling and specialized compound production. As assessed using allelic expression, cis + trans reinforcing regulation led to the very high expression of key defense genes in the most herbivore‐resistant line.
•Pest damage in maize plants can cause electromagnetic material changes in stalks.•Electrical measurement instrument was developed to quantify pest damage in maize.•Link between pest damage and ...electromagnetic changes statistically shown in maize.
The European Corn Borer (ECB), Ostrinia nubilalis, is an agricultural pest which bores small holes in the rind of maize stalks and then proceeds to consume the pith. Because most of the damage to the stalk is internal, it is difficult to quantify the damage to an individual stalk without time-consuming, manual examination. This work focused on determining the feasibility of detecting internal damage using non-destructive, electrical measurements. Laboratory experiments and numerical simulation studies predicted changes in capacitance of stalks due to hollow core ECB damage. A guarded probe device to measure electrical impedance from 500 Hz to 100 kHz was designed and constructed for data collection. A field test with the measurement device was conducted and frequency-swept impedance measurements were taken on field-grown plants with and without ECB damage. Field measurements demonstrated that statistically significant capacitance changes associated with ECB damage could be detected in agreement with numerical simulations of stalk damage. Numerical, laboratory, and field test results all supported the hypothesis that electrical impedance measurements, in particular, capacitance, provide a promising new avenue for ECB damage evaluation. While further research will be needed to further refine this concept, this measurement approach is non-destructive, thus allowing measurements to be performed without sacrificing the infested plants.
Citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), and European corn borer (ECB), Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), are two key pests of young ...citrus and maize plants in Iran, respectively. In this study, the effects of sub‐sterilizing doses of gamma radiation (100–250 Gy for CLM, 90–180 Gy for ECB) on the biological and reproductive parameters of F1 progeny from irradiated males were determined. The results indicated that males irradiated at doses of ≥200 and ≥150 Gy produced highly sterile F1 descents for CLM and ECB, respectively. No adverse effects of radiation doses applied to males were observed on the F1 pupal emergence for both species, nor on the adult longevity of male and female ECB moths. However, the life span of CLM F1 male and female adults decreased with increasing doses. The sex ratio of emerged adults of F1 progeny from irradiated males was skewed towards males with increasing doses; the proportion of males to all emerged adults reached 0.52 and 0.54 at doses of 250 and 150 Gy for CLM and ECB, compared to 0.44 and 0.49 in the controls, respectively. The competitiveness index of irradiated and F1 males of both species fluctuated in acceptable ranges and in general F1 males were stronger competitors than their irradiated male parents. The results of the field cage experiments showed that the larval infestation in all cages including the released irradiated CLM and ECB moths decreased compared to the control treatment – the percentage of damaged leaves and stems in the cages with ratios of 20:1 and 7:1 irradiated‐to‐normal insects (highest ratios assayed) reached half and one‐third of the control for CLM and ECB, respectively.
The effects of sub‐sterilizing doses of gamma radiation on the biological and reproductive parameters of F1 progeny from irradiated male parents were determined for citrus leafminer (Lepidoptera: Gracillariidae) and European corn borer (Lepidoptera: Crambidae). Males irradiated at doses of ≥200 Gy (CLM) and ≥150 Gy (ECB) produced highly sterile F1 descents for both species. The competitiveness index of irradiated/F1 males fluctuated in acceptable ranges. The larval infestation in all field cages with sterile irradiated moths released decreased compared to control.
Female parasitic wasps seek hosts for their offspring often in a dynamic environment. Foraging egg parasitoids rely on a variety of chemical cues originating from the adult host, host products, or ...the host plant rather than from the attacked host stage—the insect egg itself. Besides pupae, insect eggs are the most inconspicuous host stage attacked by parasitic wasps. To overcome the problem of low detectability of host eggs, egg parasitoids have evolved several strategies such as exploiting long-range kairomones of the adult hosts, for example, host aggregation and sex pheromones, plant synomones induced by egg deposition or host feeding, or short-range contact cues derived from the adult host or the host plant. Moreover, egg parasitoids have evolved the ability to use chemical espionage in combination with hitchhiking on the adult host (phoresy) to compensate their limited flight capability and to gain access to freshly laid host eggs. Here, we provide a comprehensive overview on the variety of host-foraging strategies of egg parasitoids exploiting chemical signals. Furthermore, the use of such infochemicals is discussed with respect to the wasps’ dietary breadth and their ability to learn.
Genome-Wide Association Studies (GWAS) are used to identify genes and alleles that contribute to quantitative traits in large and genetically diverse populations. However, traits with complex genetic ...architectures create an enormous computational load for discovery of candidate genes with acceptable statistical certainty. We developed a streamlined computational pipeline for GWAS (COMPILE) to accelerate identification and annotation of candidate maize genes associated with a quantitative trait, and then matches maize genes to their closest rice and Arabidopsis homologs by sequence similarity. COMPILE executed GWAS using a Mixed Linear Model that incorporated, without compression, recent advancements in population structure control, then linked significant Quantitative Trait Loci (QTL) to candidate genes and RNA regulatory elements contained in any genome. COMPILE was validated using published data to identify QTL associated with the traits of alpha-tocopherol biosynthesis and flowering time, and identified published candidate genes as well as additional genes and non-coding RNAs. We then applied COMPILE to 274 genotypes of the maize Goodman Association Panel to identify candidate loci contributing to resistance of maize stems to penetration by larvae of the European Corn Borer (Ostrinia nubilalis). Candidate genes included those that encode a gene of unknown function, WRKY and MYB-like transcriptional factors, receptor-kinase signaling, riboflavin synthesis, nucleotide-sugar interconversion, and prolyl hydroxylation. Expression of the gene of unknown function has been associated with pathogen stress in maize and in rice homologs closest in sequence identity. The relative speed of data analysis using COMPILE allowed comparison of population size and compression. Limitations in population size and diversity are major constraints for a trait and are not overcome by increasing marker density. COMPILE is customizable and is readily adaptable for application to species with robust genomic and proteome databases.
The processing snap bean industry views European corn borer, Ostrinia nubilalis (Hübner), larvae as contaminates in beans and has established a near zero tolerance. Currently, growers in New York ...(USA) apply 1–2 pyrethroid insecticide treatments for O. nubilalis control in snap bean. The objective of this study was to compare the residual efficacy of diamide and traditional pyrethroid insecticides at various foliar application timings against O. nubilalis. Insecticides were tested at four different timings (1, 7, 10, and 14 days before snap bean pod formation) in field trials performed in western New York in 2015 and 2016. Treatments were evaluated for O. nubilalis plant and pod damage and yield. Bioassays using snap bean leaves collected from the treated field plots were used to assess larval mortality. All materials exhibited excellent control of O. nubilalis when applied 1 day before pod formation, reducing pod and plant damage to ∼0%. However, for applications 14 days before pod formation, chlorantraniliprole and chlorantraniliprole + lambda-cyhalothrin consistently had lower pod and plant damage and higher larval mortality compared with the other materials. Chlorantraniliprole applied at 7, 10, and 14 days before pod formation also resulted in higher yields than the untreated control in 2015. Our results indicate that chlorantraniliprole-containing insecticides could be applied only once per season, eliminating the need for multiple applications, and could also be co-applied with fungicides or herbicides, which are applied earlier than standard pyrethroid insecticides. These results indicate that the anthranilic diamides, especially chlorantraniliprole, exhibit longer-term efficacy than pyrethroids, increasing the flexibility of spray timing by growers.
•All materials tested reduced O. nubilalis pod damage to ∼0% when applied at pod stage.•Chlorantraniliprole-containing products had the longest-lasting residues.•Chlorantraniliprole foliar applications would be effective pyrethroid replacements.•Diamides have higher application flexibility due to earlier potential timing.•However, diamides are currently cost-prohibitive in this system.
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