Implications For Pest Management Research Articles

Expansion of the geographic range of the eucalypt pest Paropsisterna cloelia (Stål) (Coleoptera: Chrysomelidae) through synonymy and invasion

AbstractThe accidental introduction of the eucalypt‐feeding paropsine beetle Paropsisterna cloelia (Paropsisterna variicollis) into New Zealand (NZ) in 2016 prompted investigation of the species complex to which the invasive species belongs. Two mitochondrial gene regions, Cytochrome c oxidase subunit 1 and Cytochrome b, were sequenced from field‐collected specimens superficially resembling P. cloelia collected in Queensland, the Australian Capital Territory, New South Wales, Victoria, South Australia, Tasmania, Western Australia (WA) and NZ. Four distinct Paropsisterna species groups were found, and representatives from each clade were identified with named species using morphology. P. cloelia was confirmed via sequencing and morphology to occur in all sampled geographic regions. The WA and NZ populations showed no diversity at the gene regions studied and hence represent invasive populations. The invasive WA haplotype was shared with both Tasmania and Victoria, whereas the NZ haplotype was unique, but most similar to one shared between WA, Tasmania and Victoria. The melanistic colour variant of P. cloelia was only found in eastern mainland Australian populations and was absent from Tasmania and invasive populations. Implications for pest management, including biological control, are discussed.

Tamarixia triozae, an important parasitoid of Bactericera cockerelli: circadian rhythms and their implications in pest management

Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) is an important primary parasitoid of Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). This study aimed to unveil the parasitoid’s circadian rhythms and provide information for enhancement of its biological control. Most emergence occurred in the morning and most mating took place early next morning. Oviposition only occurred during the daytime, peaking between mid-morning and mid-afternoon while host feeding had three peaks in the early morning, late afternoon and dawn, respectively. We demonstrate that circadian activity peaks for different life functions did not overlap, suggesting that T. triozae have developed strategies for maximal fitness gain. These findings have implications in pest management, which can be tested under field conditions. For example, release of sexually mature and host-fed adults in the early morning may help achieve better control. Moreover, insecticide sprays, when necessary, may be applied as late in the evening as possible to reduce side effects on this parasitoid.

Bt-toxin susceptibility and hormesis-like response in the invasive southern armyworm (Spodoptera eridania)

Bacillus thuringiensis (Bt) varieties of soybean and cotton have been widely adopted in South America, but defoliation by the southern armyworm Spodoptera eridania (Lepidoptera: Noctuidae) has increased in these crops. This issue may be linked to the low inherent susceptibility of the larvae to some Bt toxins. However, this hypothesis was not yet tested, nor was the potential sublethal effects of the toxins on larval development of southern armyworm. Here we determined the response of southern armyworm larvae exposed to Bt toxins representative of those used in soybean and cotton cultivars. In concentration-response bioassays, whereas a low median lethal concentration (LC50) value was found for Cry2Aa (11 ng/cm2), higher LC50 values were found for Cry1F (>3000 ng/cm2) and Cry1Ac (>10000 ng/cm2). Larval growth of the southern armyworm showed a hormesis-like response when the larvae were reared on artificial diet containing increasing Cry1Ac concentrations. Such enhanced larval growth was also observed when fresh foliage of Cry1Ac soybean or its lyophilized tissue in an artificial diet were fed to the larvae. Although the foliage of the dual-toxin Bt cotton producing Cry1Ac + Cry2Ab killed all larvae, its lyophilized leaf tissue caused no significant larval mortality when diluted 25 times. These results indicate that southern armyworm larvae have low inherent susceptibility to Cry1Ac and Cry1F toxins, while the Cry1Ac Bt toxin can enhance its larval growth. In addition, Cry1Ac + Cry2Ab Bt cotton may not meet the high-dose condition for the southern armyworm. These findings have important implications for pest management of the southern armyworm, which is discussed.

Sexual communication of Spodoptera frugiperda from West Africa: Adaptation of an invasive species and implications for pest management

The pest species Spodoptera frugiperda, which is native to North and South America, has invaded Africa in 2016. The species consists of two strains, the corn-strain and rice-strain, which differ in their sexual communication. When we investigated populations from Benin and Nigeria, consisting of corn-strain and rice-corn-hybrid descendants, we found no strain-specific sexual communication differences. Both genotypes exhibited the same pheromone composition, consisting of around 97% (Z)-9-tetradecenyl acetate (Z9–14:Ac), 2% (Z)-7-dodecenyl acetate (Z7–12:Ac), and 1% (Z)-9-dodecenyl acetate (Z9–12:Ac), they had similar electrophysiological responses, and all mated around three hours into scotophase. However, we found geographic variation between African and American populations. The sex pheromone of African corn-strain and hybrid descendant females was similar to American rice-strain females and showed higher percentages of the male-attracting minor component Z7–12:Ac. In addition, African males exhibited the highest antennal sensitivity towards Z7–12:Ac, while American males showed highest sensitivity towards the major pheromone component Z9–14:Ac. Increasing the production of and response to the critical minor component Z7–12:Ac may reduce communication interference with other African Spodoptera species that share the same major pheromone component. The implications of our results on pheromone-based pest management strategies are discussed.

Invasion origin, rapid population expansion, and the lack of genetic structure of cotton bollworm (Helicoverpa armigera) in the Americas.

In 2013, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) was officially declared as present in Brazil and, after two years, the species was detected in the Caribbean and North America. Information on genetic features and accurate distribution of pests is the basis for agricultural protection policies. Furthermore, such knowledge is imperative to develop control strategies, understand the geographical range, and genetic patterns of this species in the Americas. Here, we carried out the widest sampling of H. armigera in the South American continent and Puerto Rico, after we estimated the diversity, demographic parameters, and genetic structure. The Internal Transcribed Spacer 1 (ITS1) nuclear marker was used to investigate the presence of putative hybrids between H. armigera and H. zea, and they were observed at a frequency of 1.5%. An ABC analysis, based in COI gene fragment, suggested Europe as the origin of South America specimens of H. armigeraand following a movement northward through the Caribbean. Three mtDNA genes and three nDNA markers revealed high genetic diversity distributed without the defined population structure of H. armigera in South America. Most of the genetic variation is within populations with a multidirectional expansion of H. armigera among morphoclimatic regions. High genetic diversity, rapid population expansion, and hybridization have implications for pest management since they suggest that adaptive alleles are spread through wide areas in South America that favor rapid local adaptation of H. armigera to new and disturbed environments (e.g., in agricultural areas).

Agricultural insect hybridization and implications for pest management.

Biological invasions, the expansion of agricultural frontiers, and climate change favor encounters of divergent lineages of animals and plants, increasing the likelihood of hybridization. However, hybridization of insect species and its consequences for agroecosystems have not received sufficient attention. Gene exchange between distinct and distant genetic pools can improve the survival and reproduction of insect pests, and threaten beneficial insects in disturbed agricultural environments. Hybridization may be the underlying explanation for the recurrent pest outbreaks and control failures in putative hybrid zones, as suspected for bollworm, corn borer, whiteflies, and stink bugs. Reliable predictions of the types of changes that can be expected in pest insect genomes and fitness, and of their impacts on the fate of species and populations remain elusive. Typical steps in pest management, such as insect identification, pest monitoring, and control are likely affected by gene flow and adaptive introgression mediated by hybridization, and we do not have ways to respond to or mitigate the problem. To address the adverse effects of farming intensification and global trade, we must ensure that current integrated pest management programs incorporate up-to-date monitoring and diagnostic tools. The rapid identification of hybrids, quantification of levels of introgression, and in-depth knowledge of what genes have been transferred may help to explain and predict insect population outbreaks and control failures in the future. © 2019 Society of Chemical Industry.

Stored product insects at a rice mill: Temporal and spatial patterns and implications for pest management: Presentation

Monitoring is fundamental to integrated pest management programs since it provides feedback on effectiveness of prevention programs and helps with targeting interventions as needed and evaluating their effectiveness. Rice mills are spatially complex facilities that have a combination of rough rice storage bins, buildings where rice is milled and processed, and warehouses and bulk storage bins where finished product is held before shipment. Each of these structures can have its own suite of insect species, different levels of risk, as well as different suites of management tools available. At a large rice mill in Brazil, stored product insect activity was monitored using food bait traps placed around rough rice receiving areas and storage bins; inside building containing white rice mill, rice flour mill, and packaging; and inside building for processing parboiled rice. The facility was monitored from 2010 to 2018 with 100 traps. Major pest species recovered at the facility included Sitophilus oryzae, Sitophilus zeamais, Rhyzopertha dominica, Tribolium castaneum, Cryptolestes ferrugineus, Ahasverus advena, Oryzaephilus surinamensis, Typhaea stercorea, Anthicus floralis, and Nitidulidae species. Temporal and spatial patterns in abundance were evaluated for each of the major species and for major functional groups (primary feeders, secondary feeders, and fungal feeders). Monitoring data generated was used to guide pest management programs and also provided the information needed to develop management thresholds.

Spillover of Drosophila suzukii between noncrop and crop areas: implications for pest management

Abstract Semi‐natural areas may promote Drosophila suzukii population dynamics by providing alternative host resources, overwintering habitats and refuge areas during cold, warm or dry periods, or when crops are sprayed with insecticides. In the present study, we investigated the spillover of D. suzukii between noncrop and crop areas using sweet cherry as a model crop. We sampled the pest at different heights and at different distances from the forest, from the the winter dormancy stage to the post‐harvest period. Drosophila suzukii activity‐density in the orchards declined strongly with increasing distance from the forest margin and with increasing height above the ground. The observed patterns varied over the crop phenological development stages, indicating that the pest used multiple habitats throughout the year. When the host plant was not suitable for reproduction, D. suzukii preferred to fly closer to the forest margin and at lower heights. When the host plant was suitable (i.e. ripe cherries), D. suzukii further colonized the orchards both horizontally and vertically, exploring the canopy volume more in depth. The results of the present study will contribute to the development of more effective and practical approaches for protecting fruit crops from D. suzukii and improving chemical, physical or mechanical control measures.

Substrate-borne vibrations disrupt the mating behaviors of the neotropical brown stink bug, Euschistus heros: implications for pest management

Stink bugs are key pests around the world. The principal method for managing these pests is the use of broad-spectrum insecticides. However, disrupting sexual communication could also be a biorational alternative for pest management. In this study, pure tone vibrations, mechanically transmitted to plants, were tested for their potential to disrupt the reproductive behavior of the neotropical brown stink bug, Euschistus heros. This species is one of the main pests in soybean production in Brazil. Three experimental procedures were developed using artificial pure tone vibrations (20–200 Hz), which were played back and mechanically transmitted to plants as background noise. In Test 1, the impact of pure tones on the emission of male and female vibratory signals was analyzed. In Test 2, reproductive behavior was monitored in the presence of background noise, and in Test 3, long-term effects (24 h) of noise on reproductive success were evaluated. Results showed that pure tone vibrations of 75–200 Hz increased the proportion of females that spontaneously emitted signal while inhibiting the signaling and searching of males for females. It reduced copulation of 94.2–100% compared to control pairs. In long-term experiments, background noise delayed and slightly reduced mating frequency by 24.7%. Females exposed to background noise had reduced fecundity and fertility. This study demonstrates the potential of mechanical vibrations as a mating-disrupting tactic for stink bug management.

Ongoing changes in migration phenology and winter residency at Bracken Bat Cave.

Bats play an important role in agroecology and are effective bioindicators of environmental conditions, but little is known about their fundamental migration ecology, much less how these systems are responding to global change. Some of the world's largest bat populations occur during the summer in the south-central United States, when millions of pregnant females migrate from lower latitudes to give birth in communal maternity colonies. Despite a relatively large volume of research into these colonies, many fundamental questions regarding their abundance-including their intra- and interseasonal variability-remain unanswered, and even estimating the size of individual populations has been a long-running challenge. Overall, monitoring these bat populations at high temporal resolution (e.g., nightly) and across long time spans (e.g., decades) has been impossible. Here, we show 22 continuous years of nightly population counts at Bracken Cave, a large bat colony in south-central Texas, enabling the first climate-scale phenological analysis. Using quantitative radar monitoring, we found that spring migration and the summer reproductive cycle have advanced by approximately 2weeks over the study period. Furthermore, we quantify the ongoing growth of a newly-established overwintering population that indicates a system-wide response to changing environmental conditions. Our observations reveal behavioral plasticity in bats' ability to adapt to changing resource availability, and provide the first long-term quantification of their response to a changing climate. As aerial insectivores, these changes in bat phenology and propensity for overwintering indicate probable shifts in prey availability, with clear implications for pest management across wider regional agrisystems.

Nerolidol production in agroinfiltrated tobacco: Impact of protein stability and membrane targeting of strawberry (Fragraria ananassa) NEROLIDOL SYNTHASE1

The sesquiterpene alcohol nerolidol, synthesized from farnesyl diphosphate (FDP), mediates plant-insect interactions across multiple trophic levels with major implications for pest management in agriculture. We compared nerolidol engineering strategies in tobacco using agroinfiltration to transiently express strawberry (Fragraria ananassa) linalool/nerolidol synthase (FaNES1) either at the endoplasmic reticulum (ER) or in the cytosol as a soluble protein. Using solid phase microextraction and gas chromatography–mass spectrometry (SPME-GCMS), we have determined that FaNES1 directed to the ER via fusion to the transmembrane domain of squalene synthase or hydroxymethylglutaryl – CoA reductase displayed significant improvements in terms of transcript levels, protein accumulation, and volatile production when compared to its cytosolic form. However, the highest levels of nerolidol production were observed when FaNES1 was fused to GFP and expressed in the cytosol. This SPME-GCMS method afforded a limit of detection and quantification of 1.54 and 5.13 pg, respectively. Nerolidol production levels, which ranged from 0.5 to 3.0 μg/g F.W., correlated more strongly to the accumulation of recombinant protein than transcript level, the former being highest in FaNES-GFP transfected plants. These results indicate that while the ER may represent an enriched source of FDP that can be exploited in metabolic engineering, protein accumulation is a better predictor of sesquiterpene production.

Genetic characterization of Bactrocera fruit flies (Diptera: Tephritidae) from Northeastern India based on DNA barcodes

The Northeastern region of India, one of the mega biodiversity hot spots has enormous potential for the production of fruits and vegetables. Fruit flies of the genus Bactrocera Macquart are important pests of fruits and vegetables, and one of the limiting factors in successful production of these commodities. The relationship among some of the species is unclear due to their high molecular and morphological similarities. Moreover, due to the significant morphological resemblance between fruit fly species, reliable identification is very difficult task. We genetically characterized 10 fruit fly species of the genus Bactrocera by using standard DNA barcoding region of COI gene. The characterization and identification of eight species were straight forward. This study was unable to establish the molecular identity of Bactrocera sp. 2. Within the 547 bp region of partial COI gene, there were 157 variable sites of which 110 sites were parsimony informative, 153 were synonymous substitutions and 4 were non-synonymous substitutions. The estimate of genetic divergence among the ten species was in the range of 0–21.9% and the pairwise genetic distance of Bactrocera. (Bactrocera) dorsalis (Hendel) with B. (B.) carambolae was only 0.7%. Phylogenetic analysis formed separate clades for fruit and vegetable infesting fruit flies. B. (B.) aethriobasis Hardy, B. (B.) thailandica and B. (B.) tuberculata (Bezzi) have been reported for the first time from the Northeastern India. The information generated from this study would certainly have implications for pest management, taxonomy, quarantine and trade.

Ecological and pest-management implications of sex differences in scarab landing patterns on grape vines.

BackgroundMelolonthinae beetles, comprising different white grub species, are a globally-distributed pest group. Their larvae feed on roots of several crop and forestry species, and adults can cause severe defoliation. In New Zealand, the endemic scarab pest Costelytra zealandica (White) causes severe defoliation on different horticultural crops, including grape vines (Vitis vinifera). Understanding flight and landing behaviours of this pest can help inform pest management decisions.MethodsAdult beetles were counted and then removed from 96 grape vine plants from 21:30 until 23:00 h, every day from October 26 until December 2, during 2014 and 2015. Also, adults were removed from the grape vine foliage at dusk 5, 10, 15, 20 and 25 min after flight started on 2015. Statistical analyses were performed using generalised linear models with a beta-binomial distribution to analyse proportions and with a negative binomial distribution for beetle abundance.ResultsBy analysing C. zealandica sex ratios during its entire flight season, it is clear that the proportion of males is higher at the beginning of the season, gradually declining towards its end. When adults were successively removed from the grape vines at 5-min intervals after flight activity begun, the mean proportion of males ranged from 6–28%. The male proportion suggests males were attracted to females that had already landed on grape vines, probably through pheromone release.DiscussionThe seasonal and daily changes in adult C. zealandica sex ratio throughout its flight season are presented for the first time. Although seasonal changes in sex ratio have been reported for other melolonthines, changes during their daily flight activity have not been analysed so far. Sex-ratio changes can have important consequences for the management of this pest species, and possibly for other melolonthines, as it has been previously suggested that C. zealandica females land on plants that produce a silhouette against the sky. Therefore, long-term management might evaluate the effect of different plant heights and architecture on female melolonthine landing patterns, with consequences for male distribution, and subsequently overall damage within horticultural areas.

Using bioassays with the green peach aphid (Myzus persicae) to determine residual activity of two systemically soil-applied neonicotinoid insecticides in field-grown tobacco

ABSTRACTDuration of systemic pesticide activity under field conditions has wide implications for pest management. Our aim was to determine the duration of activity of systemic insecticides commonly used in cultivated tobacco (Nicotiana tabacum) by measuring the levels of insect infestations on field plots and effects on reproduction and survival of the green peach aphid (Myzus persicae) in controlled bioassays using field grown leaves. Plants were treated with different concentrations of two systemic neonicotinoid pesticides, imidacloprid and thiamethoxam, and grown in small field plots. Our results show that these materials are effective under field conditions against aphids for at least 13 weeks after transplant. Pesticides also affected aphid reproduction and nymph survival in bioassays, although some aphids survived on pesticide-treated leaves. We also observed that leaf age affected aphid survival. We showed that neonicotinoids were very effective against M. persicae, aphids are a useful organism to assess pesticide efficacy early in the growing season, but plant characteristics are more important than pesticide concentration in the second half of the growing season.

Avoidance, escape and microstructural adaptations of the tea green leafhopper to water droplets.

Rain and dew droplets can dislodge or drown small insects and may be important factors that drive adaptations for avoidance and escape. Studying the microstructure of small insects and insect behaviour can help understand these adaptations. We quantified avoidance behaviour and entrapment of nymphs and adults of the tea green leafhopper (Empoasca onukii) using simulated rainfall onto host plant foliage and made observations of pretarsi and abdomen microstructures. Adults responded rapidly to simulated rainfall and escaped by jumping whilst most young nymphs were washed from water-sprayed leaves though older nymphs tended to remain on leaves and subsequently escaped from water droplets. Adults had denser covering of water-repelling brochosomes on pretarsi and abdomen surface than nymphs, and were able to stand on water film whilst most nymphs had multiple penetrating tarsi. Removal of brochosomes from the abdomen of adults reduced hydrophobicity, demonstrating the hydrophobic significance of brochosomes in the capacity of leafhopper to escape from water droplets. Nymphs exhibited a higher pull-off force than adults. This research is one of the few studies to focus on the wettability and water avoidance of small insect pests and has implications for pest management.

Dispersal of the Invasive Pasture Pest Heteronychus arator into Areas of Low Population Density: Effects of Sex and Season, and Implications for Pest Management.

African black beetle, Heteronychus arator (Scarabaeidae), is an exotic pest of pastures in northern New Zealand. Both adults and larvae feed on pasture grasses. Adults disperse by walking (short range) or flying (long range). Dispersal flights are triggered by warm night temperatures in spring and autumn. Short range adult dispersal in search of mates, food or oviposition sites is poorly understood. This study investigated walking activity of H. arator adults over three seasons in New Zealand pastures. Adult walking activity was monitored using pitfall traps along fence lines and in pasture plots on a dairy farm in Waikato, New Zealand, in spring 2013, spring 2014, and autumn 2015. Beetle populations were reduced by application of a biopesticide bait to compare walking activity between treated and control plots for up to 26 days post-treatment. Marked beetles were released into the pasture plots to measure the distance traveled by recaptured individuals. Trap catches along the fence lines were correlated with air temperatures in 2013. Trap catches were male biased in spring 2014 compared with autumn 2015. Trap numbers in the control plots were nearly double that of treated plots in both seasons. More beetles were caught in the pitfall traps at the edges of the treated plots than in the center. Trap catches were consistent throughout the control plot in spring 2014, but in autumn 2015 more beetles were caught in the center of the control plot than at the edges. Few marked beetles were recaptured with dispersal rates estimated as <0.5 m per day. Warmer temperatures encouraged short range dispersal in H. arator. Males were more active than females during the spring mating season. Edge effects were strong and should be considered in the design of field experiments.

Green tea and its waste attract workers of formicine ants and kill their workers—implications for pest management

Daily, 3 billion cups of tea consumed worldwide and this consumption is accompanied by the discarding of huge waste amounts into the environment. Tea leaf contains a diverse array of toxic molecules. Despite evidence that its waste is almost as rich in toxicants as green leaves; no research has been done to turn this source of pollution into a benefit for ant pest management, where new chemistries are highly needed as a result on insecticide resistance. The present study was performed to explore the behavioral and lethal effects of tea and its leftovers on the black crazy ant (BCA), Paratrechina longicornis Latreille, yellow crazy ant (YCA), Anoplolepis gracilipes Smith, and weaver ant (WA), Oecophylla smaragdina Fabricius. Both fresh tea extract (FTE) and used tea extract (UTE) were detrimental to the survival of BCA, YCA, and WA. FTE was the most toxic solution and BCA was the most vulnerable species. The presence of tea extracts in meals did not prevent workers of all three species from visiting and feeding in the presence their preferred foods. The results presented here suggest that diets containing tea extracts are attractive to BCA, YCA, and WA when in competition with their preferred foods. These extracts were also insecticidal to the worker ants. These properties demonstrate the potential of tea and its waste products for developing novel environmentally friendly and low-cost ant control strategies, which could also be a practical solution to the growing environmental problem it causes.

Citrus Insect Interactions: Implications for Pest Management

Citrus Insect Interactions: Implications for Pest Management

Genetic Diversity and Structure of Brazilian Populations of Diatraea saccharalis (Lepidoptera: Crambidae): Implications for Pest Management.

The sugarcane borer, Diatraea saccharalis (F.), is the main pest of sugarcane in Brazil. Genetic variability and gene flow among 13 Brazilian populations of the species were evaluated based on mitochondrial DNA sequences to estimate the exchange of genetic information within and among populations. We found high genetic structure among sampled localities (ΦST=0.50923), and pairwise genetic distances were significantly correlated to geographic distances. Demographic analysis and genealogical network of mitochondrial sequences indicate population growth and admixture of D. saccharalis populations, events likely related to the sequential expansion of the corn and sugarcane crops in Brazil. The implications of these findings for pest management are discussed.

Effects of Abiotic Factors on HIPV-Mediated Interactions between Plants and Parasitoids.

In contrast to constitutively emitted plant volatiles (PV), herbivore-induced plant volatiles (HIPV) are specifically emitted by plants when afflicted with herbivores. HIPV can be perceived by parasitoids and predators which parasitize or prey on the respective herbivores, including parasitic hymenoptera. HIPV act as signals and facilitate host/prey detection. They comprise a blend of compounds: main constituents are terpenoids and “green leaf volatiles.” Constitutive emission of PV is well known to be influenced by abiotic factors like temperature, light intensity, water, and nutrient availability. HIPV share biosynthetic pathways with constitutively emitted PV and might therefore likewise be affected by abiotic conditions. However, the effects of abiotic factors on HIPV-mediated biotic interactions have received only limited attention to date. HIPV being influenced by the plant's growing conditions could have major implications for pest management. Quantitative and qualitative changes in HIPV blends may improve or impair biocontrol. Enhanced emission of HIPV may attract a larger number of natural enemies. Reduced emission rates or altered compositions, however, may render blends imperceptible to parasitoides and predators. Predicting the outcome of these changes is highly important for food production and for ecosystems affected by global climate change.