Major Crop Pests Research Articles

Potential of Silicon to Improve Biological Control of Fall Armyworm, Spodoptera frugiperda on Maize

Silicon (Si) accumulation in plants confers a mechanical barrier to insect herbivory and may alter plant chemistry to increase the attraction of natural enemies to host insect herbivores on Si−treated plants. The fall armyworm (FAW), Spodoptera frugiperda, is a major insect pest of grain crops, including maize (Zea mays L.). This study examined whether Si supplementation alters maize volatile compounds that mediate host location in Euthyrhynchus floridanus, a generalist predator of FAW. A four-arm olfactometer was used to test the olfactory preference of nymphs and adults of E. floridanus to the odor of maize leaf materials from plants that were; Si−treated and infested, Si−treated without infestation, Si−deprived and infested, and Si−deprived without infestation. The probabilities of individual insects choosing between the four treatments were estimated using a multinomial generalized linear mixed model. There were no statistical differences in the olfactory preference of E. floridanus between Si−treated and Si−deprived maize leaf materials. However, the median estimate showed that nymphs were almost twice likely to be attracted to Si−supplemented leaf material, indicating a potential positive effect of Si. However, a more robust follow-up study is needed to further assess the impact of Si on E. floridanus.

Field, semi‐field and greenhouse testing of HOOK SWD, a SPLAT‐based attract‐and‐kill formulation to manage spotted‐wing drosophila

AbstractNative to Southeast Asia, the spotted‐wing drosophila (Drosophila suzukii) has become a major pest of small fruit crops in the Americas and Europe because females can oviposit in ripening fruit. Currently, D. suzukii management relies heavily on chemical control; thus, more sustainable approaches like attract‐and‐kill need to be evaluated to reduce insecticide use. In previous studies, HOOK SWD, an attract‐and‐kill product that combines attractants, phagostimulants and an insecticide (spinosad), showed promise for D. suzukii control; still, little is known about its performance under field conditions and under varying pest and host‐fruit densities, as well as its residual activity. Here, we evaluated the efficacy of HOOK SWD when applied in commercial blueberry farms, when deployed in semifield cages under different D. suzukii adult and fruit densities and when aged for 30 days in the greenhouse. Results from field experiments showed that HOOK SWD could reduce fruit infestation in blueberry farms; however, its efficacy varied in space and time. Semifield cage studies revealed that relatively high densities of both D. suzukii adults and fruit can reduce the effectiveness of HOOK SWD, which might explain the variation in its efficacy in the field. Ageing HOOK SWD in a greenhouse for at least 30 days yielded no significant decrease in insecticidal activity. Altogether, these studies show that HOOK SWD can potentially suppress D. suzukii populations in the field, but it should be used as part of an integrated pest management program instead of a stand‐alone control tool, especially under high pest and fruit densities.

Evaluation of chemical and microbial control options for Pangaeus bilineatus (Say) (Hemiptera: Cydnidae) infesting peanut crop.

The peanut burrower bug, Pangaeus bilineatus is a major crop pest of peanuts in the southern United States. Peanuts infested by P.bilineatus exhibit weight and quality losses and could be discounted by ≤50% of the prevailing market price. Control of this pest is difficult because it attacks peanut pods underground, thus rendering foliar pesticide applications ineffective. Integration of entomopathogenic fungi and nematodes (EPF/EPNs) with chemical insecticides in the management of P.bilineatus was investigated as a potential integrated pest management containment tool. The nymphs were less susceptible than adults of P.bilineatus to EPNs. Comparison of six strains of both Heterorhabditis spp. and Steinernema spp. demonstrated that Steinernema carpocapsae (All) was the most virulent EPN, causing 75.54% mortality of P.bilineatus adults after 7 days postinoculation (dpi), whereas the mortality generated by the application of the rest of the nematodes ranged between 17.03% (H.bacteriophora - Lewis) and 50% (H.bacteriophora VS). Application of imidacloprid by itself at ½FR (field rate) did not result in any significant mortality of P.bilineatus adults but application of chlorpyrifos at 1/8FR caused significant mortality (27.41-61.35%) at 7-14 dpi. However, combined applications of S.carpocapsae and imidacloprid resulted in significant mortality starting at 3dpi. The interactions between S.carpocapsae and imidacloprid were synergistic at 3-5dpi, but became additive at 7-14 dpi. Both chlorpyrifos and imidacloprid did not negatively impact the reproduction of S.carpocapsae. The compatibility between S.carpocapsae and imidacloprid makes a case for the combination to be used for the management of P.bilineatus. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Effects of Ultraviolet B on The Efficacy of Bacillus thuringiensis var. kurstaki Formulations Against Tobacco Armyworm, Spodoptera litura (Lepidoptera: Noctuidae)

Tobacco armyworm (Spodoptera litura Fab.) is one of the major insect pests of crops in Indonesia. The management of this pest still depends on the use of chemical insecticides. The use of bio-insecticides, such as Bacillus thuringiensis (Bt.), are known to be alternatives, but it easily degraded by sunlight. This research aimed to study the effects of UV B on Bt. pathogenicity and to explore plant-based additives as UV B protectants for Bt. against armyworm. Thirteen plant extracts were screened based on their UV spectra absorbencies using UV spectrophotometry. The extracts, namely cloves, Jicama, Celebes pepper, turmeric, and Moringa, then used for the formulations of Bt. and exposed under UV B lights for 0, 72, and 144 h. After exposure to UV B, Bt. formulations were tested for bioassay against one- day-old 1st and one day old 2nd larval instars of tobacco armyworm. The result indicated that at 72 and 144 h of UV B exposures, the Bt. added formulations were signifcantly different compared to Bt. alone. At 72 h exposure against the 2nd larval instar, the larval mortality of tobacco armyworm on the second day of observation on Bt. formulated with Celebes pepper and turmeric was 97.3 and 80%, respectively, whereas, at 144 h exposure, the mortality was 96 and 89.3%, respectively. This study concluded that Celebes pepper and turmeric extracts were the potential to be used as the Bt. protectants against UV B.

A Chromosome-Scale Genome Assembly of a Helicoverpa zea Strain Resistant to Bacillus thuringiensis Cry1Ac Insecticidal Protein.

Helicoverpa zea (Lepidoptera: Noctuidae) is an insect pest of major cultivated crops in North and South America. The species has adapted to different host plants and developed resistance to several insecticidal agents, including Bacillus thuringiensis (Bt) insecticidal proteins in transgenic cotton and maize. Helicoverpa zea populations persist year-round in tropical and subtropical regions, but seasonal migrations into temperate zones increase the geographic range of associated crop damage. To better understand the genetic basis of these physiological and ecological characteristics, we generated a high-quality chromosome-level assembly for a single H. zea male from Bt-resistant strain, HzStark_Cry1AcR. Hi-C data were used to scaffold an initial 375.2 Mb contig assembly into 30 autosomes and the Z sex chromosome (scaffold N50 = 12.8 Mb and L50 = 14). The scaffolded assembly was error-corrected with a novel pipeline, polishCLR. The mitochondrial genome was assembled through an improved pipeline and annotated. Assessment of this genome assembly indicated 98.8% of the Lepidopteran Benchmark Universal Single-Copy Ortholog set were complete (98.5% as complete single copy). Repetitive elements comprised approximately 29.5% of the assembly with the plurality (11.2%) classified as retroelements. This chromosome-scale reference assembly for H. zea, ilHelZeax1.1, will facilitate future research to evaluate and enhance sustainable crop production practices.

Effective dominance and redundant killing of single- and dual-gene resistant populations of Helicoverpa zea on pyramided Bt corn and cotton.

Pyramided Bacillus thuringiensis (Bt) crops producing multiple Bt proteins with different modes of action are widely planted in the United States. Helicoverpa zea is a major target pest of pyramided Bt crops and has evolved practical resistance to both Cry1 and Cry2 proteins in some regions of U.S. However, little information is available regarding redundant killing and the dominance of resistance for insects possessing multiple resistance on pyramided Bt crops. In this study, we evaluated redundant killing and the dominance of resistance for H.zea strains resistant to Cry1 or Cry1 + Cry2 on pyramided Bt corn and cotton. We found that the Cry1-resistant H.zea was incompletely dominant on Cry1Ac + Cry1F cotton. Pyramided crops producing Cry2 and/or Vip3Aa proteins showed a complete redundant killing against the Cry1-resistant H.zea. The Cry1 + Cry2-resistant H.zea displayed incompletely recessive to completely dominant resistance on pyramided Bt crops containing Cry1 and/or Cry2 proteins. The redundant killing was complete for the Cry1 + Cry2-resistant H.zea on pyramided Bt crops producing Vip3Aa protein. The dominant resistance of Cry1 and Cry2 in H.zea on pyramided Bt crops deviates from the assumption of functionally recessive resistance underlying the high-dose refuge strategy. However, the assumptions of complete redundant killing are achieved for both Cry1- and Cry1 + Cry2-resistant H.zea on pyramided Bt crops. These results suggest that the pyramided strategy could be valuable for increasing the durability of Bt technology for managing H.zea, a pest with inherently low susceptibility against Cry proteins. © 2022 Society of Chemical Industry.

Host plants and insecticides shape the evolution of genetic and clonal diversity in a major aphid crop pest.

Understanding the spatiotemporal dynamics of pesticide resistance at the landscape scale is essential to anticipate the evolution and spread of new resistance phenotypes. In crop mosaics, host plant specialization in pest populations is likely to dampen the spread of pesticide resistance between different crops even in mobile pests such as aphids. Here, we assessed the contribution of host-based genetic differentiation to the dynamics of resistance alleles in Myzuspersicae, a major aphid pest which displays several insecticide resistance mechanisms. We obtained a representative sample of aphids from a crop mosaic through a suction trap for 7years and from various crops as a reference collection. We genotyped these aphids at 14microsatellite markers and four insecticide-resistant loci, analyzed the genetic structure, and assigned host-based genetic groups from field-collected aphids. Four well-defined genetic clusters were found in aerial samples, three of which with strong association with host-plants. The fourth group was exclusive to aerial samples and highly divergent from the others, suggesting mixture with a closely related taxon of M.persicae associated with unsampled plants. We found a sharp differentiation between individuals from peach and herbaceous plants. Individuals from herbaceous hosts were separated into two genetic clusters, one more strongly associated with tobacco. The 4-loci resistance genotypes showed a strong association with the four genetic clusters, indicative of barriers to the spread of resistance. However, we found a small number of clones with resistant alleles on multiple host-plant species, which may spread insecticide resistance between crops. The 7-year survey revealed a rapid turn-over of aphid genotypes as well as the emergence, frequency increase and persistence of clones with resistance to several families of insecticides. This study highlights the importance of considering landscape-scale population structure to identify the risk of emergence and spread of insecticide resistance for a particular crop.

Lethal and sublethal effects of chlorantraniliprole on the migratory moths Agrotis ipsilon and A. segetum: New perspectives for pest management strategies.

Agrotis ipsilon and A. segetum are major migratory pests of many crops in China, and frequent regional outbreaks cause severe yield losses. Use of food attractants is one of the most promising control methods against adult lepidoptera, notably through the attract-and-kill strategy. Chlorantraniliprole's acute toxicity and sublethal effects on both moths were evaluated. Chlorantraniliprole showed high activity against both adults of both species, with LC20 and LC50 values of 0.08 and 0.21 mg L-1 (A. ipsilon), and 0.14 and 0.51 mg L-1 (A. segetum). The fecundity, effective oviposition rate, and egg hatching rate of both species in dual-sex exposure treatments were all significantly reduced compared with the control, and the population growth coefficients in the LC50 ♀ × LC50 ♂ treatments were only 0.32% (A. ipsilon) and 3.35% (A. segetum) that of the control. Furthermore, the flight distance was significantly suppressed from 6.67 km (control) to 0.01 km (LC50 ) for A. ipsilon, and from 7.39 km (control) to 0.78 km (LC50 ) for A. segetum. The proportions of robust- and medium-flight individuals of A. ipsilon and A. segetum in exposure treatments were greatly reduced. Low lethal concentration exposures to chlorantraniliprole can drastically reduce the reproduction and flight performance of A. ipsilon and A. segetum, while inhibiting the production of offspring, suggesting chlorantraniliprole would be an excellent compound for use in combination with food attractants. Chlorantraniliprole has good potential for management of the two long-range migratory pests tested using an attract-and-kill strategy. © 2022 Society of Chemical Industry.

A novel theta-class glutathione S-transferase gene in Rhopalosiphum padi (L.) (Hemiptera: Aphididae): Identification, recombinant protein expression and function analyses of RpGSTT1

Glutathione S-transferases (GSTs) play a major role in the detoxification of insecticides and the protection against oxidative damage caused by ROS (reactive oxygen species). The bird cherry-oat aphid, Rhopalosiphum padi (L.), is a major crop pest worldwide. Chemical insecticides are currently used to control aphids, but insecticide resistance is an evolutionary issue for aphid control. In this research, we identified and cloned the full-length cDNA of a theta-class GST gene (RpGSTT1) from R. padi, which contains 702 bp open reading frame encoding 233 amino acids. RpGSTT1 was clustered together with theta classe of insect GSTs in the phylogenetic tree. Effect of insecticide exposure on the GST enzyme activity was investigated in vivo. After affinity purification, the recombinant RpGSTT1 protein was able to catalyze the conjugation of 1-chloro-2, 4-dinitrobenzene (CDNB). A disc diffusion assay showed that the RpGSTT1 can increase resistance to cumene hydroperoxide-induced oxidative stress. In addition, the purified recombinant RpGSTT1 protected super-coiled DNA from oxidative damage. By quantitative PCR, The relative expression level of RpGSTT1 in the aphid was highly up-regulated after 12 h exposure to β-cypermethrin, isoprocarb, malathion and sulfoxaflor, respectively. To our knowledge, RpGSTT1 is the first theta class of GST gene reported in bird cherry-oat aphid. Our findings indicate that RpGSTT1 may be involved in insecticide detoxification in R. padi.

Know Your Pests When Trapping Soybean Looper in the Florida Panhandle

Pheromone trapping is a common scouting method used in collaboration with integrated pest management. A major crop pest of many plant species, including Panhandle crops like peanut and cotton, is the soybean looper. A soybean looper pheromone-trapping study performed in Panhandle commercial peanut and cotton fields also attracted other species with similar appearances, sometimes in high numbers. Misidentification would result in overestimation of soybean looper populations and likely unnecessary insecticide applications. The sharp stigma looper, due to its high seasonal abundance and flight pattern similar to that of the soybean looper, was most concerning. This insect is not a pest and can be discerned from the soybean looper easily through its wing markings, if someone knows what to look for, but if these harmless moths were unwittingly thought of as soybean loopers, it could greatly skew population numbers and prompt improper applications of pesticides.

Interspecific interaction between Anagyrus fusciventris and Tetracnemoidea brevicornis for controlling Pseudococcus calceolariae

ABSTRACT Anagyrus fusciventris and Tetracnemoidea brevicornis (Hymenoptera: Encyrtidae) are solitary endoparasitoids of Pseudococcus calceolariae and P. longispinus (Hemiptera: Pseudococcidae), major pests of many horticultural crops. The interspecific interaction relate to host-parasitoid association between these two parasitoid species was tested in the laboratory. To test the hypothesis that both species prefer the same life stages of P. calceolariae, first instar to adult mealybugs were exposed to female parasitoids of both species for either 24 h or 10 days. The parasitism by each parasitoid species of eggs and newly emerged or late first instar P. calceolariae was individually tested. A sequential test was also carried out, where mealybugs were exposed to either of the two parasitoid species with 24-h intervals between the exposure to the first and second parasitoid species. Regardless of the time or order of exposure, T. brevicornis females produced a larger proportion of parasitoid progeny within their short adult lifespan (< 10 days). The maximum daily reproductive output of T. brevicornis (32) was higher than A. fusciventris (8). Egg to adult development period of A. fusciventris was shorter (20 ± 1.6 (SD) days) than T. brevicornis (36.6 ± 4.6 (SD) days). A complementary effect of the two species on mealybug suppression was highlighted in our findings, due to their species-specific host stage preference, A. fusciventris prefer older life stages while T. brevicornis prefer younger life stages. Therefore both species together could provide stable control of the pest population more effectively than one species alone.

Natural biological control of Bagrada hilaris by egg predators and parasitoids in north-central California

Bagrada bug, Bagrada hilaris Burmeister (Hemiptera: Pentatomidae), is an invasive stink bug from Asia that has become a major pest of cruciferous crops (Brassicaceae) in California. Conventional insecticides are currently the most effective means for controlling this pest. In organic production, options are limited and generally ineffective. As part of an effort to develop a biological control program for bagrada bug, we documented attack rates by resident parasitoids and predators on sentinel bagrada bug eggs throughout north-central California, including the Salinas Valley, which is the largest cruciferous crop growing region in the US. A total of 51 sites were sampled over three years. Sentinel eggs were placed on the ground, where bagrada bug lays most of its eggs, and in foliage, where all other known stinkbug species deposit their eggs and resident egg parasitoids are most likely to search. Predation rates exceeded 20% per day on some sample dates (averaging 7.2, 7.4 and 6.3% per day in 2017, 2018 and 2019, respectively) and were generally higher on the ground than in the foliage, although temporal patterns were inconsistent and predation levels varied among the sampled regions. Burying eggs in sand did not consistently reduce predation rates, indicating that bagrada bug’s habit of burying its eggs provides only partial protection from predators. Of the 25,387 eggs deployed over the three years of this study that were not predated or missing (out of the 35,673 total eggs that were deployed), only 47 (0.19%) were parasitized. Gryon aetherium Talamas (Scelionidae), a biological control agent for bagrada bug that is currently undergoing testing, was found at one site. Only five of the parasitized sentinel eggs were on the ground, suggesting that few resident parasitoids in north-central California attack bagrada bug eggs, particularly on the ground. These results show that a parasitoid that co-evolved with bagrada bug in its native range is necessary to provide successful biological control of bagrada bug in California.

Forest Proximity Positively Affects Natural Enemy Mediated Control of Fall Armyworm in Southern Africa

The fall armyworm (FAW, Spodoptera frugiperda) is a major crop pest in southern Africa. It threatens the livelihoods and food security of smallholder farmers in the region by negatively impacting maize yield. Although scientific evidence suggests that natural enemy-mediated predation can potentially reduce FAW infestation, the effectiveness of natural enemies such as birds, bats, parasitoids, and generalist predators on FAW is poorly understood. This study reviews existing literature to assess how birds, bats, parasitoids, and generalist predators’ control FAW infestation, as well as the role of forest or tree cover in natural enemy mediated pest control of FAW in maize in southern Africa. We then present a case study to examine the role of forest proximity in reducing FAW infestation in maize in Zimbabwe. We conclude that birds, bats, parasitoids, and generalist predators are likely drivers of the reduced success of FAW near forests in southern Africa. While predators influence FAW survival and development, their role is largely undermined by parasitoids, which are more efficient in affecting FAW populations. Birds, bats, parasitoids, and generalist predators play an important role in controlling FAW on farms in heterogenous landscapes with diverse vegetation and near-forest proximity. The findings of our case study from Zimbabwe suggest that the distance to forest had a much higher impact on FAW incidence than maize variety, planting date, or the rate of nitrogen applied. Lack of enough case studies from maize in southern Africa makes it challenging to assess the mechanism and the effectiveness of bird predation on FAW. For this reason, further research is necessary to examine how predation by birds, bats and arthropods and parasitism impacts maize yield. We discuss research barriers, recommend appropriate methods for experimental studies, and suggest possible management options to control FAW in southern Africa.

Development of Temporal Model for Forecasting of Helicoverpa armigera (Noctuidae: Lepidopetra) Using Arima and Artificial Neural Networks.

Helicoverpa armigera (Hübner) (Noctuidae: Lepidopetra) is a polyphagous pest of major crops grown in India. To prevent the damage caused by H. armigera farmers rely heavily on insecticides of diverse groups on a regular basis which is not a benign practice, environmentally and economically. To provide more efficient and accurate information on timely application of insecticides, this research was aimed to develop a forecast model to predict population dynamics of pod borer using Autoregressive Integrated Moving Average (ARIMA) and Artificial Neural Networks (ANN). The data used in this study were collected from the randomly installed sex pheromone traps at International Crops Research Institute for the Semi-arid Tropics (ICRISAT), Patancheru, Hyderabad. Several ARIMA (p, d, q) (P, D, Q) and ANN models were developed using the historical trap catch data. ARIMA model (1,0,1), (1,0,2) with minimal BIC, RMSE, MAPE, MAE, and MASE values and higher R2 value (0.53) was selected as the best ARIMA fit model, and neural network (7-30-1) was found to be the best fit to predict the catches of male moths of pod borer from September 2021 to August 2023. A comparative analysis performed between the ARIMA and ANN, shows that the ANN based on feed forward neural networks is best suited for effective pest prediction. With the developed ARIMA model, it would be easier to predict H. armigera adult population dynamics round the year and timely intervention of control measures can be followed by appropriate decision-making schedule for insecticide application.

Trapping of Crucifer-Feeding Flea Beetles (Phyllotreta spp.) (Coleoptera: Chrysomelidae) With Pheromones and Plant Kairomones.

Flea beetles (Coleoptera: Chrysomelidae) of the genus Phyllotreta are major pests of cole crops, canola, and related crops in the mustard family (Brassicaceae). Adults may damage seedlings or larger crop plants, impairing crop growth, rendering crops unmarketable, or killing seedlings outright. The two major North American crucifer pest species, Phyllotreta striolata (F.) and Phyllotreta cruciferae (Goeze), have male-produced pheromones attractive to both female and male adults. We tested the racemic synthetic pheromones, himachaladiene and hydroxyhimachalanone, as well as the host-plant-produced allyl isothiocyanate, alone and in combination, with experimental trapping in Maryland, Virginia, and North Dakota, using clear and yellow sticky traps and the ground-based 'rocket' trap (modified from boll weevil trap). Phyllotreta striolata was consistently attracted to the hydroxyketone, and captures were often enhanced by allyl isothiocyanate (AITC), but its response to pheromones, AITC, and trap color were variable from state to state. Phyllotreta cruciferae was strongly attracted to AITC, but its response to pheromone components varied by state, and this species was found rarely at the Maryland site. Phyllotreta bipustulata (F.) was attracted to the diene component, a new finding for this species. Several other genera of flea beetles were captured, some showing response to the semiochemicals and/or color. Results will be helpful in monitoring and possibly population suppression; however, further research is necessary to develop more efficient syntheses, optimal lure loadings, combinations, and controlled release methods.

Planted-green cover crops in maize/soybean rotations confer stronger bottom-up than top-down control of slugs

No-till farming is a conservation agriculture practice employed on over 100 million acres of farmland in the United States. This practice provides benefits ranging from erosion control to pest suppression but can also facilitate outbreaks of novel pests. In the Mid-Atlantic, USA, where no-till production is widely adopted to help maintain the health of the Chesapeake Bay watershed, slugs have become a major pest of no-till row crops. Tillage buries slug eggs and kills all life stages; thus, slugs thrive without this interference in no-till systems. Effective slug control options are lacking, but integrating cover crops into crop rotations, especially when delaying termination until after cash crop planting (planting green), could be an ecologically based, cost effective method to control slugs. Cover crops may offer a dual-pronged approach to slug management, conferring top-down control by creating habitat for predators and bottom-up control by acting as a dietary distraction. The goal of the experiment presented here was to understand how delaying cover-crop termination until after cash-crop planting affects top-down and bottom-up control of slugs. Additionally, we assessed the effect of neonicotinoid-coated seeds on top down-control because insecticides can harm predators. Across three commercial, row-crop farms in Pennsylvania, USA, we found that slug activity-density and damage to cash crops was lowest in planting green treatments due to higher residue coverage and that planted-green maize plots without seed coatings had the lowest slug pressure. Planting-green produced lower yields that, given the conservation benefits, may be acceptable to some farmers, and yields were not enhanced by insecticidal seed coating. Collectively, our results indicate that planting-green can act as a novel, bottom-up management strategy for slugs that functions independently of top-down control.

Molecular and morphological identification of the alfalfa weevil larval parasitoids Bathyplectes anura and Bathyplectes curculionis to estimate the rate of parasitism

The alfalfa weevil (Hypera postica Gyllenhal, Coleoptera: Curculionidae) is a major pest of alfalfa crops. Chemical control measures are inefficient, but the larvae are often infested by parasitoid wasps of the genus Bathyplectes Förster (Hymenoptera: Ichneumonidae), which offer a potential biological control strategy. The development of effective biological control requires the identification of parasitoid species, but conventional methods involve the rearing of parasitoids to the puparium stage for morphological confirmation. Here we designed a PCR method in which two pairs of primers are used to detect and identify Bathyplectes curculionis Thomson and Bathyplectes anura Thomson larvae in a faster way. We compared conventional rearing to the new method as a means to determine the parasitism rates caused by each species in Spain during the 2019 and 2020 seasons. In 2019, the PCR method detected five times as many B. curculionis events and twice as many B. anura events. Similarly, in 2020, the PCR method detected seven times as many B. curculionis events and twice as many B. anura events. High mortality of H. postica larvae was recorded in 2020 due to an epizootic attack by the fungus Zoophthora phytonomi Arthur (Zygomycetes: Entomophthorales), explaining the lower overall rate of parasitism and the widespread death of the larvae. Statistical analysis confirmed that the PCR method is more sensitive than conventional rearing for the detection of target parasitoids. However, only rearing can confirm the effective parasitism or the presence of unexpected species. We therefore recommend the use of both methods in parallel when evaluating host–parasitoid systems.

Fumigation of three major soil pests (Agriotes lineatus, Diabrotica virgifera virgifera, Phyllopertha horticola) with 3-octanone and 1-octen-3-ol enantiomers

ABSTRACT New pest management solutions are needed to control soil invertebrates (insects, nematodes, mollusks) in order to implement the goals of the European Green Deal. Natural volatile organic compounds (VOCs) such as 1-octen-3-ol and 3-octanone, emitted by the entomopathogenic fungus Metarhizium brunneum could be part of the solution. Three major crop pests, Agriotes lineatus (wireworm), Diabrotica virgifera virgifera (corn rootworm) and Phyllopertha horticola (garden chafer), were susceptible to fumigation with 1-octen-3-ol and 3-octanone. The toxicity of the VOCs was tested in soil-free arenas and in soils which differed in moisture content and porosity. The mortality rates were dependent on the interaction between the VOC treatment, dose and pest species. The insects differed in their sensitivity to these VOCs. A dose of 1.25 µl of 1-octen-3-ol applied in a closed glass tube was sufficient to kill D. v. virgifera and P. horticola in soil trials whereas 5 µl was needed to kill A. lineatus. The highest dose (20 µl) was highly toxic to all insects. Soil moisture content slightly influenced mortality rates whereas porosity had no obvious impact. The mode of action of the VOCs is unknown but the compounds are likely to cause tissue damage and loss of body fluids. This may explain the shrivelled appearance of corn rootworm and garden chafer and melanisation in wireworm. Both 1-octen-3-ol and 3-octanone show promise as biofumigants.

Copy number variation of two begomovirus acquired and inoculated by different cryptic species of whitefly, Bemisia tabaci in Okra.

The whitefly, B.tabaci is a major pest of agricultural crops which transmits begomovirus in a species-specific manner. Yellow vein mosaic disease (YVMD) and okra leaf curl disease (OLCD) caused by distinct begomovirus are a major limitation to production of okra in India. In this framework the present investigation reports, for the first time, comparative study of begomovirus species viz. yellow vein mosaic virus (YVMV) and okra enation leaf curl virus (OELCuV) ingested and egested by two cryptic species (Asia I and Asia II 5) of B.tabaci at different time interval using detached leaf assay. A gradual increase of both virus copies were observed with increased feeding exposure in Asia I and Asia II 5. Both the genetic groups of whitefly could acquire the viruses within just 5 minutes of active feeding however, a significant amount of variation was noted in virus uptake by the both. At 24 hours of active feeding Asia II 5 acquired more of YVMV whereas, Asia I ingested more OELCuV. Similarly, the genetic group acquiring higher titre of virus egested higher amount during inoculation period. On the whole, it can be presumed that Asia I is a more effective transmitter of OELCuV whereas, Asia II 5 of YVMV further suggesting increased risk of virus pandemics (both YVMV and OELCuV) in regions where Asia I and Asia II 5 is dominant.

Likelihood of Extreme Early Flight of Myzus persicae (Hemiptera: Aphididae) Across the UK.

Myzus persicae (Sulzer, Hemiptera: Aphididae) is a major global crop pest; it is the primary aphid vector for many damaging viruses and has developed resistance to most insecticides. In temperate regions, the risk of widespread crop infection and yield loss is heightened following warm winters, which encourage rapid population growth and early flight. Estimates of the frequency and magnitude of warm winters are, therefore, helpful for understanding and managing this risk. However, it is difficult to quantify the statistical distribution of climate events, particularly extremes, because climate observations represent just a small sample of the possible climate variations in a region. The purpose of this study was to establish a large-scale relationship between temperature and M. persicae observations across the UK and apply this to a very large ensemble of climate model simulations, which better sample the variability in climate, to quantify the current likelihood of extreme early M. persicae flight across the UK. The timing of M. persicae flight was shown to be significantly related to January-February mean temperature, where a 1°C warmer/cooler temperature relates to about 12 d earlier/later flight. Climate model simulations predict 40% likelihood of experiencing a year with unprecedented early M. persicae flight during the next decade in the UK. Results from this method can help crop managers assess the long-term viability of crops and management practices across the UK and provide early warning information for targeting pest surveillance activities on the locations and timings at highest risk of early M. persicae flight.