Diabrotica Research Articles

Synthesis of Southern Corn Rootworm Pheromone from S-Citronellol and Its Field Evaluation

Southern rootworm (Diabrotica undecimpunctata howardi) affects several plants such as soybean, sorghum, wheat, cucumber, alfalfa, cucurbits and it is most damaging to corn and peanuts. The pheromone based “attract and kill” strategy is one of the powerful ways to control pest population. To address our key objective of the practical utility of the synthetic pheromone, we have developed a simple synthetic strategy to produce gram scale southern corn rootworm pheromone in nine simple steps starting from S-Citronellol. The present strategy takes advantage of the existing chiral center of commercially available S-Citronellol. To get the basic carbon skeleton of the pheromone, the main step in the synthetic strategy is coupling of aliphatic units through Wittig reaction. The phosphonium salt from a non-functionalized aliphatic bromide followed by Wittig reaction improved the overall yield in the multistep synthesis of this pheromone. The large-scale production of pheromone enabled us to test it in the field.

At-Plant Application of Registered Insecticidal Materials for Managing Rootworm Larvae in Corn and Its Impact on Yield, 2015: Table 1

Corn rootworm (NCR/WCR) management efficacy trials were conducted to evaluate transgenic insect-resistant hybrids, liquids, and granular insecticide combination treatments near Bryant, Cavour, and Colman in South Dakota. The experimental plots were arranged in an RCBD with four ∼50-foot-long replications. Four row treatments were established using rows that were spaced 30 inches apart at planting-time. Granular insecticides were applied with Noble metering units or the SmartBox delivery system. At-planting liquid insecticides …

Evaluation of Corn Hybrids for Rootworm Management With Insecticides and Without, 2014: Table 1

Northern and western corn rootworm (NCR/WCR) management efficacy trials were conducted to evaluate transgenic insect-resistant hybrids and granular insecticide combination treatments near Bryant, Cavour, and Colman in South Dakota. Granular insecticides were applied in-furrow to four row (∼50 ft long; spaced 30 inches apart) treatment plots at planting time. Experimental plots were arranged in an RCBD with four replications. Granular insecticides were applied with Noble metering units or SmartBox delivery system. All metering units …

V�vin kukuriciara korenov�ho Diabrotica virgifera virgifera v p�de

Monitoring of developmental stages of the Western corn rootworm (WCR) (Diabrotica virgifera virgifera) is an important aspect of its control. In the experiment there were analysed randomly selected plants of maize on six localities in western Slovakia, in the years 2008-2010 a 2014-2015. The aim of the study was to identify exact time of the emergence of the WCR adults in the consequence of different years and different localities and to find the best date for their eradication. The most of the WCR individuals at the northern locality were observed on 29 June and the first adults were found on 07 June, during colder year 2006. The development started about nine days earlier in the next year in southern Slovakia, because of extremely hot weather. The population of pest increased slower in 2008 than in previous years, and the highest appearance was monitored up-to 02 July. The first adults were monitored on 27 June in the years 2009-2010 as well as 2014-2015. Generally, the highest numbers of the first instar larvae were observed on 22 June at the locality Ciližska Radvaň. The second instar larvae and the most of adults was found on 20 June in Sokolce. On 29 June it was monitored the largest amount of the third instar larvae at the locality Ciližska Radvaň. The differences in the time of the emergence of adults depended on the year. Based on the monitoring in Slovakia, it can be expected the third instar larvae from second decade of June and the first adults in the last decade of June and in the first decade of July.

Using Agrisure Corn Hybrids in Combination with Insecticides for Rootworm Larval Suppression, 2015: Table 1

Corn rootworm management efficacy trials were conducted to evaluate transgenic insect-resistant hybrids and granular insecticide combination treatments near Bryant and Cavour in South Dakota. The study was arranged in an RCBD with four ∼50 foot long replications. Four row treatments were established using rows that were spaced 30 inches apart at planting-time. In-furrow liquid insecticide treatments were placed directly into the …

Influence of Cultural and Pest Management Practices on Performance of Runner, Spanish, and Virginia Market Types in North Carolina

Virginia market type peanut (Arachis hypogaeaL.) cultivars are grown primarily in North Carolina, South Carolina, and Virginia in the US, although growers in these states often plant other market types if marketing opportunities are available. Information on yield potential and management strategies comparing these market types is limited in North Carolina. In separate experiments, research was conducted to determine response of runner, Spanish, and Virginia market types to calcium sulfate and inoculation withBradyrhizobiumat planting, planting and digging dates, planting patterns, and seeding rates. In other experiments, control of thrips (Frankliniellaspp.) using aldicarb, southern corn rootworm (Diabrotica undecimpunctataHowardi) using chlorpyrifos, eclipta (Eclipta prostrataL.) using threshold-based postemergence herbicides, and leaf spot disease (caused by the fungiCercospora arachidicolaandCercosporidium personatum) fungicide programs was compared in these market types. Results showed that management practice and market types interacted for peanut pod yield in only the planting date experiment. Yield of runner and Virginia market types was similar and exceeded yield of the Spanish market type in most experiments.

Managing Rootworm Larvae With Insecticidal Treatments, 2015:

Corn rootworm (NCR/WCR) management efficacy trials were conducted to evaluate transgenic insect–resistant hybrids, liquids, and granular insecticide combination treatments near Brookings, Bryant, Cavour, and Colman in South Dakota. The experimental plot was arranged in an RCBD with four ∼50-ft. long replications. Four row treatments were established using rows that were spaced 30 in. apart at planting-time. Granular insecticides were applied with Noble metering units or the SmartBox delivery system. Planting-time liquid insecticides were applied using CO2-powered …

Control of Corn Rootworm Larvae with Soil-Applied Insecticides and Bt Hybrids, 2014

We established one trial at the Northwestern Illinois Agricultural Research and Development Center near Monmouth, IL, to evaluate the efficacy of soil-applied insecticides and Bt hybrids to control corn rootworm (CRW) larvae. The experimental design was a RCB with four replications. The plot size for each treatment was 10 ft (four rows) × 40 ft. The previous crop was a trap-crop (late-planted corn and pumpkins). Corn was planted on 7 May using a four-row, vacuum-style planter (SRES, South Hutchinson, KS) at a rate of 36,600 seeds/acre in 30-inch rows at an approximate depth of 1.75 inches. Hybrid information is provided in Table 1. Granular insecticides were applied through modified Noble metering units or through modified SmartBox metering …

Evaluation of SmartStax-Traited and Refuge Corn Hybrids in Combination with Soil Insecticides at Planting for Larval Corn Rootworm Control, 2014: Table 1

SmartStax traited and refuge corn hybrids in combination with soil insecticides were evaluated for effectiveness for larval corn rootworm (CRW) control near Clay Center, NE during 2015. The trial site was late-planted corn and pumpkins (insecticide free) during 2014. Experimental design was a RCB with four replicates. Plot size was 4 rows × ∼150 ft length with 30-inch row spacing. Soil type was a Crete silt loam. ‘DeKalb DKC62-77 RIB’ (contains GENSSRIB [SmartStax] insect and herbicide traits) and ‘DeKalb DKC62-98RIB’ (contains GENVT2PRIB [refuge] insect and herbicide traits) corn hybrids were planted on 30 Apr with a two-row JD 7100 Maximerge planter with finger pickup seed units. A …

Evaluation of Stacked and Single Rootworm-Traited and Refuge Corn Hybrids in Combination With Soil Insecticides at Planting for Larval Corn Rootworm Control, 2014: Table 1

Corn hybrid family isolines possessing stacked rootworm traits, a single rootworm trait, or refuge traits, in combination with soil insecticides, were evaluated for effectiveness of larval CRW control near Clay Center, NE, during 2014. Trial site was in late-planted corn and pumpkins (insecticide free) during 2013. Experimental design was an RCB with three replicates. Plot size was 4 rows by 75 ft in length with 30-inch row spacing. Soil type was a Crete silt loam. ‘Golden Harvest G11U58-3122’ (3122, contains Agrisure RW and Herculex RW rootworm traits), ‘Golden Harvest G11U58-3111’ (3111, contains Agrisure RW rootworm trait), and ‘Golden Harvest G11U58-GT’ (GT, contains no rootworm …

Tolerance of eCry3.1Ab in Reciprocal Cross Offspring of eCry3.1Ab-Selected and Control Colonies of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae).

Two new insect colonies were created by separating virgin western corn rootworm, Diabrotica virgifera virgifera LeConte, males and females from both a selected laboratory colony that was being reared on eCry3.1Ab-expressing corn (Zea mays L.) and a control colony reared on its near-isoline corn. Females from the selected colony were paired with males of the control colony and vice versa to create both a selected female by control male colony (Sel♀) and control female by selected male colony (Con♀). Both colonies along with their parental colonies (eCry3.1Ab-selected and control) were evaluated on eCry3.1Ab-expressing corn and its near-isoline in seedling assays. Larvae from each colony were also used in diet toxicity experiments in order to determine the LC50 and EC50 values for the eCry3.1Ab toxin for each. Statistical analysis of seedling assay experiments did not indicate any significant colony×corn interaction but did show a significant main effect of corn type for both larval recovery and larval head capsule widths. Results from the diet toxicity assays showed the control colony to have a significantly lower LC50 value than the selected and cross colonies and a significantly lower EC50 than the selected and Con♀ colonies. Calculations of dominance values (h) of eCry3.1Ab resistance traits from seedling assays indicated that the two reciprocal cross colonies have a dominance value (h) of ∼1, suggesting dominance of the eCry3.1Ab resistance trait.

Feeding behaviour of Diabrotica virgifera virgifera adults on corn crops

Diabrotica virgifera virgifera Le Conte (Coleoptera:Chrysomelidae), is an invasive pest in corn crops, known as western corn rootworm. For this, serious measures were taken to limit the spread; however it continued to expand and adapt to new areas. One of the causes responsible for invading is capacity of adapting to abiotic and biotic factors in the new habitat. Having in mind the orientation for adults and especially for flowering plants pollen we wanted to see if behavior of Diabrotica from a corn crop, at a time, is influenced by the presence and diversity of weeds. Observations were made during year of 2014, in July and August, in a place in western Romania. It was chased feeding behavior toward both corn plant and weed and the other hand, the level of population was observed. In our study we found that adults are attracted to flowers weeds; they found on much greater numbers in corn plot with weed abundant comparative the plot without weeds. Females predominated in corn crop with different weed species present.

Estimation of efficacy functions for products used to manage corn rootworm larval injury

AbstractMaize, Zea mays L., is an economically important crop grown throughout the world. Corn rootworm, Diabrotica spp. (Coleoptera: Chrysomelidae), larvae constitute a significant economic threat to maize production in the United States, where yield losses and management costs associated with corn rootworm species exceed $1 billion annually. Furthermore, the introduction of the western corn rootworm, D. virgifera virgifera LeConte, into maize‐producing regions of Europe has made managing corn rootworm larval injury an international concern. Larvae injure maize plants by feeding on root tissue and are the primary target of management activities. Products commonly used to protect root systems from injury include chemical insecticides (seed or soil applied) and genetically modified maize hybrids expressing toxins derived from Bacillus thuringiensis Berliner (Bt). The confirmation of field‐evolved resistance to various Bt toxins in populations of the western corn rootworm presents a significant management challenge. We performed a meta‐analysis to provide a broad understanding of the relative efficacy of the primary products currently being used to manage corn rootworm larval injury, including insecticidal seed treatments, soil insecticides and Bt hybrids (with and without the addition of soil insecticide). Our analysis is unique in the breadth of locations and years included – we analysed 135 individual trials conducted from 2003 through 2014 at multiple sites in both Illinois and Nebraska. Panel data were produced by pairing the mean node‐injury rating for each treatment of a given trial with the mean node‐injury rating for untreated maize. Linear regression models were developed to estimate the relationship between the potential for corn rootworm larval injury and product performance. For a given level of injury potential, the parameters estimated reveal differences in the degree of root protection offered by the various product categories analysed. Implications for developing long‐term, integrated, and sustainable practices for managing this important pest of maize are discussed.

Quantitative trait locus mapping and functional genomics of an organophosphate resistance trait in the western corn rootworm, Diabrotica virgifera virgifera.

The western corn rootworm, Diabrotica virgifera virgifera, is an insect pest of corn and population suppression with chemical insecticides is an important management tool. Traits conferring organophosphate insecticide resistance have increased in frequency amongst D. v. virgifera populations, resulting in the reduced efficacy in many corn-growing regions of the USA. We used comparative functional genomic and quantitative trait locus (QTL) mapping approaches to investigate the genetic basis of D. v. virgifera resistance to the organophosphate methyl-parathion. RNA from adult methyl-parathion resistant and susceptible adults was hybridized to 8331 microarray probes. The results predicted that 11 transcripts were significantly up-regulated in resistant phenotypes, with the most significant (fold increases ≥ 2.43) being an α-esterase-like transcript. Differential expression was validated only for the α-esterase (ST020027A20C03), with 11- to 13-fold greater expression in methyl-parathion resistant adults (P < 0.05). Progeny with a segregating methyl-parathion resistance trait were obtained from a reciprocal backcross design. QTL analyses of high-throughput single nucleotide polymorphism genotype data predicted involvement of a single genome interval. These data suggest that a specific carboyxesterase may function in field-evolved corn rootworm resistance to organophosphates, even though direct linkage between the QTL and this locus could not be established.

Evidence of Field-Evolved Resistance to Bifenthrin in Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) Populations in Western Nebraska and Kansas.

Pyrethroid insecticides have been used to control larvae or adults of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, a key pest of field corn in the United States. In response to reports of reduced efficacy of pyrethroids in WCR management programs in southwestern areas of Nebraska and Kansas the present research was designed to establish a baseline of susceptibility to the pyrethroid insecticide, bifenthrin, using susceptible laboratory populations and to compare this baseline with susceptibility of field populations. Concentration-response bioassays were performed to estimate the baseline susceptibility. From the baseline data, a diagnostic concentration (LC99) was determined and used to test adults of both laboratory and field populations. Larval susceptibility was also tested using both laboratory and field populations. Significant differences were recorded in adult and larval susceptibility among WCR field and laboratory populations. The highest LC50 for WCR adults was observed in populations from Keith 2 and Chase Counties, NE, with LC50s of 2.2 and 1.38 μg/vial, respectively, and Finney County 1, KS, with 1.43 μg/vial, as compared to a laboratory non-diapause population (0.24 μg/vial). For larvae, significant differences between WCR field and laboratory populations were also recorded. Significant differences in mortalities at the diagnostic bifenthrin concentration (LC99) were observed among WCR adult populations with western Corn Belt populations exhibiting lower susceptibility to bifenthrin, especially in southwestern Nebraska and southwestern Kansas. This study provides evidence that resistance to bifenthrin is evolving in field populations that have been exposed for multiple years to pyrethroid insecticides. Implications to sustainable rootworm management are discussed.

Mating Success, Longevity, and Fertility of Diabrotica virgifera virgifera LeConte (Chrysomelidae: Coleoptera) in Relation to Body Size and Cry3Bb1-Resistant and Cry3Bb1-Susceptible Genotypes.

Insect resistance to population control methodologies is a widespread problem. The development of effective resistance management programs is often dependent on detailed knowledge regarding the biology of individual species and changes in that biology associated with resistance evolution. This study examined the reproductive behavior and biology of western corn rootworm beetles of known body size from lines resistant and susceptible to the Cry3Bb1 protein toxin expressed in transgenic Bacillus thuringiensis maize. In crosses between, and within, the resistant and susceptible genotypes, no differences occurred in mating frequency, copulation duration, courtship duration, or fertility; however, females mated with resistant males showed reduced longevity. Body size did not vary with genotype. Larger males and females were not more likely to mate than smaller males and females, but larger females laid more eggs. Moderately strong, positive correlation occurred between the body sizes of successfully mated males and females; however, weak correlation also existed for pairs that did not mate. Our study provided only limited evidence for fitness costs associated with the Cry3Bb1-resistant genotype that might reduce the persistence in populations of the resistant genotype but provided additional evidence for size-based, assortative mating, which could favor the persistence of resistant genotypes affecting body size.

No impact of DvSnf7 RNA on honey bee (Apis mellifera L.) adults and larvae in dietary feeding tests.

The honey bee (Apis mellifera L.) is the most important managed pollinator species worldwide and plays a critical role in the pollination of a diverse range of economically important crops. This species is important to agriculture and historically has been used as a surrogate species for pollinators to evaluate the potential adverse effects for conventional, biological, and microbial pesticides, as well as for genetically engineered plants that produce pesticidal products. As part of the ecological risk assessment of MON 87411 maize, which expresses a double‐stranded RNA targeting the Snf7 ortholog (DvSnf7) in western corn rootworm (Diabrotica virgifera virgifera), dietary feeding studies with honey bee larvae and adults were conducted. Based on the mode of action of the DvSnf7 RNA in western corn rootworm, the present studies were designed to be of sufficient duration to evaluate the potential for adverse effects on larval survival and development through emergence and adult survival to a significant portion of the adult stage. Testing was conducted at concentrations of DvSnf7 RNA that greatly exceeded environmentally relevant exposure levels based on expression levels in maize pollen. No adverse effects were observed in either larval or adult honey bees at these high exposure levels, providing a large margin of safety between environmental exposure levels and no‐observed–adverse‐effect levels. Environ Toxicol Chem 2016;35:287–294. © 2015 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

The Temporal and Spatial Invasion Genetics of the Western Corn Rootworm (Coleoptera: Chrysomelidae) in Southern Europe.

This study describes the genetics of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte in southern Europe during the introduction (1996–2001) and establishment/spread (2002–2011) phases of its invasion. The Diabrotica microsatellite core-set was used to perform traditional population genetics analyses. Our results indicated that during the introduction phase genetic diversity and population genetic structure were lower overall as compared to the establishment/spread phase. Unusually high genetic differentiation was found between the Italy and southern Europe comparisons, including high differentiation between Italian populations separated by a short distance during the establishment/spread phase. STRUCTURE analysis revealed two genetic clusters during the introduction phase and two genetic clusters during the establishment/spread phase. However, bottlenecked populations were only detected during the invasion phase. A small but significant isolation by distance effect was noted in both phases. Serbia was the geographic source of WCR to Croatia and Hungary in the introduction phase, while the United States of America was the possible source of WCR to Italy in 2001. These introductory populations were the subsequent source of individuals sampled during the establishment/spread phase. Repeated introductions and admixture events in southern Europe may have resulted in genetically diverse WCR populations that have attained 83% of all known alleles worldwide.

Susceptibility of northern corn rootworm Diabrotica barberi (Coleoptera: Chrysomelidae) to mCry3A and eCry3.1Ab Bacillus thuringiensis proteins.

The susceptibility of the northern corn rootworm Diabrotica barberi (Smith & Lawrence) to mCry3A and eCry3.1Ab proteins derived from Bacillus thuringiensis (Bt) was determined using a diet bioassay. Northern corn rootworm neonates were exposed to different concentrations of mCry3A and eCry3.1Ab, incorporated into artificial diet. Larval mortality was evaluated after 7 d. The mCry3A and eCry3.1Ab proteins were found to be toxic to the northern corn rootworm larvae. The LC50 and LC99 values for mCry3A were 5.13 and 2482.31 μg/mL, respectively. For eCry3.1Ab, the LC50 and LC99 values were 0.49 and 213.01 μg/mL. Based on the estimated lethal concentrations, eCry3.1Ab protein was more efficacious to northern corn rootworm larvae than mCry3A. These lethal concentration values will be used as diagnostic doses for routine annual monitoring for change in susceptibility of field collected northern corn rootworm to mCry3A, and eCry3.1Ab toxins.

Early Detection and Mitigation of Resistance to Bt Maize by Western Corn Rootworm (Coleoptera: Chrysomelidae).

Transgenic Bt maize that produces less than a high-dose has been widely adopted and presents considerable insect resistance management (IRM) challenges. Western corn rootworm, Diabrotica virgifera virgifera LeConte, has rapidly evolved resistance to Bt maize in the field, leading to local loss of efficacy for some corn rootworm Bt maize events. Documenting and responding to this resistance has been complicated by a lack of rapid diagnostic bioassays and by regulatory triggers that hinder timely and effective management responses. These failures are of great concern to the scientific and agricultural community. Specific challenges posed by western corn rootworm resistance to Bt maize, and more general concerns around Bt crops that produce less than a high-dose of Bt toxin, have caused uncertainty around current IRM protocols. More than 15 years of experience with IRM has shown that high-dose and refuge-based IRM is not applicable to Bt crops that produce less than a high-dose. Adaptive IRM approaches and pro-active, integrated IRM-pest management strategies are needed and should be in place before release of new technologies that produce less than a high-dose. We suggest changes in IRM strategies to preserve the utility of corn rootworm Bt maize by 1) targeting local resistance management earlier in the sequence of responses to resistance and 2) developing area-wide criteria to address widespread economic losses. We also favor consideration of policies and programs to counteract economic forces that are contributing to rapid resistance evolution.