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.

Exogenous plant hormones regulate the agronomic and physiological performance of plants and thus can influence the abundance of insect groups. We surveyed the arthropods on flowering plants Cnidium monnieri and found that the abundance of natural enemies Propylaea japonica and Orius minutus in the plots treated with salicylic acid (SA) and indole acetic acid (IAA) was significantly increased compared with those in the clean water (control) plots. Then, we investigated the effects of spraying SA, IAA, and clean water on the population parameters of Semiaphis heraclei reared on C. monnieri. Our results from the age-stage, two-sex life table analysis revealed a significantly shorter pre-adult duration for aphids reared on SA-treated C. monnieri compared to those reared on the other two treatments. The intrinsic rate of increase, finite rate of increase, and net reproductive rate of aphids reared on SA- and IAA-treated C. monnieri were significantly higher than those of aphids reared on clean water-treated C. monnieri. The fecundity rate was higher under the SA and IAA treatments than in the control, but the difference was not significant. This improved the ability of flowering plants to attract natural enemies by providing a larger food source.

The soil-inhabiting predatory mite Stratiolaelaps scimitus (Womersley) (Acari: Laelapidae) and the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) can both serve as effective biocontrol agents against the pest Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Assuming the fungus B. bassiana does not adversely affect S. scimitus, the combined application of these 2 agents could enhance the suppression of F. occidentalis. The age-stage, 2-sex life table was used in the present study to evaluate the effects of B. bassiana strain GZGY-1-3 on S. scimitus, mediated through F. occidentalis feeding. When S. scimitus fed on the prepupae of F. occidentalis that had been exposed to the GZGY-1-3 suspension for 24 h, the developmental times of protonymph, deutonymph, and preadult mites were significantly longer and the mites’ longevity and fecundity were significantly lower than mites fed on untreated F. occidentalis. The intrinsic rate of increase (r), finite rate of increase (λ) and net reproduction rate (R0) of the mite population were all significantly lower in the treatment where B. bassiana was applied compared to untreated populations. Specifically, the indirect effects of B. bassiana on S. scimitus was mediated through mite consumption of fungus-infected pupae of F. occidentalis. Our results showed that the combined application of B. bassiana and S. scimitus may pose potential risks for the simultaneous biocontrol of F. occidentalis.

Semiaphis heraclei Takahashi (Hemiptera: Aphididae) serves as a vital resource for natural enemies from functional plant Cnidium monnieri (L.) Cusson (Apiaceae), playing a crucial role in ecological dynamics. Endosymbionts influence the performance of their hosts. Here, we determined the communities of facultative endosymbionts in aphids from Lonicera japonica Thunb. (Caprifoliaceae), Apium graveolens L. (Apiaceae), and C. monnieri and assessed the performance of four aphid clones. The infection rates of Serratia symbiotica Moran (Gammaproteobacteria: Enterobacteriaceae) and Regiella insecticola Moran (Enterobacteriales: Enterobacteriaceae) reached 100%. Notably, the infection rates of Spiroplasma and Rickettsia varied across host plants. Fitness assessment revealed that aphids performed better on their natal hosts, exhibiting shorter nymphal development times and higher fecundity. S. symbiotica had contrasting effects on aphids based on their origin. It prolonged the development duration and decreased the intrinsic rate of increase (r_m), net reproductive rate (R₀), and finite rate of increase (λ) in aphids collected from plant A. graveolens. However, for aphids collected from plant C. monnieri, it shortened the doubling time (DT) and improved r_m, R₀, and λ, while prolonging the mean generation time. Our studies are the first to investigate the infection status and role of facultative endosymbionts in aphid S. heraclei, extending the documented effects of plant diversity to fluctuations in the infection rate, with potentially far-reaching consequences for related endosymbionts’ ecosystem processes.