Field investigation- and dietary metabarcoding-based screening of arthropods that prey on primary tea pests.

Predatory natural enemies play key functional roles in biological control. Abundant predatory arthropod species have been recorded in tea plantation ecosystems. However, few studies have comprehensively evaluated the control effect of predatory arthropods on tea pests in the field. We performed a 1-year field investigation and collected predatory arthropods and pests in the tea canopy. A total of 7931 predatory arthropod individuals were collected, and Coleosoma blandum (Araneae, Theridiidae) was the most abundant species in the studied tea plantation. The population dynamics between C. blandum and four main tea pest species (Aleurocanthus spiniferus, Empoasca onukii, Ectropis grisescens, and Scopula subpunctaria) were established using the individual number of predators and pests in each month. The results showed that C. blandum appeared to co-occur in the tea canopy with A. spiniferus, Em. onukii, and Ec. grisescens in a longer period. The prey spectrum of C. blandum was further analyzed using DNA metabarcoding. Among prey species, A. spiniferus, Em. onukii, and Ec. grisescens were included, and the relative abundance and positive rates of target DNA fragments of A. spiniferus were greater than that of other two pests. Combined with the high dominance index of C. blandum, co-occurrence between C. blandum and A. spiniferus in time and space and high positive rate and relative abundance of target DNA fragments of A. spiniferus, C. blandum was identified to prey on A. spiniferus, and C. blandum may be an important predator of A. spiniferus. Thus, C. blandum has potential as a biological control agent of A. spiniferus in an integrated pest management strategy.

Development of a multiprimer metabarcoding approach to understanding trophic interactions in agroecosystems.

To understand trophic interactions and the precise ecological role of each predatory species, it is important to know which arthropod and plant resources are used by generalist predators in agroecosystems. Molecular approaches, such as the use of high-throughput sequencing (HTS), play a key role in identifying these resources. This study develops a multiprimer metabarcoding approach for screening the most common trophic interactions of two predatory arthropods with contrasting morphologies, Rhagonycha fulva (Coleoptera: Cantharidae) and Anthocoris nemoralis (Hemiptera: Anthocoridae) collected from a peach crop. To reduce the time and cost of this metabarcoding approach, we first evaluated the effect of using two different predator-pools of different size (10 and 23 individuals of the same species). We also used our system to analyze the performance of one and two primer pairs in the same library. Our results show that the analysis of 23 individuals together with the use of two primer pairs in the same library optimize the HTS analysis. Using these best-performing conditions, we then analyzed the entire bodies of field-collected predators as well as the washing solutions used to clean the insect bodies. We were able to identify both gut content (i.e., diet) and external pollen load (i.e., on the insects' bodies). This study also demonstrates the importance of washing predatory insects' bodies prior to HTS analysis when the target species have a considerable size (>10 mm) and hairy structures. This metabarcoding approach has significant potential for the study of trophic links in agriculture, revealing expected and unexpected trophic relationships.

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering / Distribuição espacial e tamanho de amostra para estimar a densidade populacional de Lycosa erythrognatha (Araneae: Lycosidae) durante o inverno

Abstract Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.

Resumo Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.

Can Generalist Predators Control Bemisia tabaci?

The whitefly, Bemisia tabaci, has developed resistance to many insecticides, renewing interest in the biological control of this global pest. Generalist predators might contribute to whitefly suppression if they commonly occur in infested fields and generally complement rather than interfere with specialized natural enemies. Here, we review literature from the last 20 years, across US cropping systems, which considers the impacts of generalist predators on B. tabaci. Laboratory feeding trials and molecular gut content analysis suggest that at least 30 different generalist predator species willingly and/or regularly feed on these whiteflies. Nine of these predators appear to be particularly impactful, and a higher abundance of a few of these predator species has been shown to correlate with greater B. tabaci predation in the field. Predator species often occupy complementary feeding niches, which would be expected to strengthen biocontrol, although intraguild predation is also common and might be disruptive. Overall, our review suggests that a bio-diverse community of generalist predators commonly attacks B. tabaci, with the potential to exert substantial control in the field. The key challenge will be to develop reduced-spray plans so that generalist predators, and other more specialized natural enemies, are abundant enough that their biocontrol potential is realized.

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering

Abstract Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.

Resumo Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.