Laboratory and Greenhouse Evaluation of a Granular Formulation of Beauveria bassiana for Control of Western Flower Thrips, Frankliniella occidentalis.

Xingrui Zhang,Zhongren Lei,Shengyong Wu,Yulin Gao,Stuart Reitz

doi:10.3390/insects10020058

Abstract

Western flower thrips (WFT) is one of the most important pests of horticultural crops worldwide because it can damage many different crops and transmit various plant viruses. Given these significant impacts on plant production, novel methodologies are required to maximize regulation of WFT to minimize crop losses. One particular approach is to develop control strategies for the non-feeding, soil-dwelling stages of WFT. Control of these stages could be enhanced through the use of granules impregnated with entomopathogenic fungi mixed in the soil. The use of soil-applied fungi contrasts with existing approaches in which entomopathogenic fungi are formulated as oil-based suspensions or water-based wettable powders for foliar applications against the feeding stages of WFT. To examine the efficacy of this approach, we evaluated the effects of a granular formulation of Beauveria bassiana on the soil-dwelling, pupal phases of Frankliniella occidentalis in laboratory bioassays and greenhouse experiments. Based on micromorphological observations of fungal conidia during the infection process after treatment of WFT with a B. bassiana suspension, fungal conidia complete the process of surface attachment, germination, and penetration of the body wall of the WFT pupa and enter the host within 60 h of treatment. Given these results, we undertook a controlled greenhouse experiment and applied B. bassiana granules to soil used to cultivate eggplants. Populations of F. occidentalis on eggplants grown in treated soil were 70% lower than those on plants grown in the untreated soil after 8 weeks. Furthermore, when measuring the survival and growth of B. bassiana on granules under different soil moisture conditions, survival was greatest when the soil moisture content was kept at 20%. These results indicate that the application of B. bassiana-impregnated granules could prove to be an effective biological control strategy for use against F. occidentalis under greenhouse conditions.

Highlights

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is one of the most important pests of horticultural crops worldwide [1,2,3]
The use of chemical insecticides remains commonplace for managing WFT, with intensive use and application occurring in high-value crops such as pepper, tomato and eggplant [13]
Mortality of F. occidentalis increased with increasing concentrations of B. bassiana (Figure 1)

Summary

Introduction

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is one of the most important pests of horticultural crops worldwide [1,2,3]. WFT serves as an important vector of several species of damaging plant viruses in the genus Tospovirus (Bunyaviridae) [5], including tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV), which may cause over 90% yield loss in some instances [6,7,8]. The life cycle of WFT contains the foliar-feeding (adult, first and second larval instars) and soil-dwelling developmental stages (late second larval instars, pre-pupae, and pupae). The majority of current pest management strategies focus on control of adults and larvae with a substantial portion of the soil-dwelling stages being neglected [11,12]. The use of chemical insecticides remains commonplace for managing WFT, with intensive use and application occurring in high-value crops such as pepper, tomato and eggplant [13]. Frequent applications of chemicals may leave excessive pesticide residues on the plant, result in high levels of insecticide resistance, and are expensive [3,14,15,16,17]

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Results

Discussion

Conclusion