Un Taek Lim

The spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) is a major pest across East and Southeast Asia, damaging more than a hundred plant species (Takafuji et al. 2005). This spider mi...

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a major soybean pest controlled mostly with synthetic insecticides, but environmentally friendly alternatives are needed. To develop a better microbial control option using the entomopathogenic fungus Beauveria bassiana ARP14 (ARP14), we evaluated whether azadirachtin (AZA) enhances its effectiveness in topical bioassays on eggs and second‑instar nymphs. At 10 d, the hatching rates for the AZA and the AZA + ARP14 mixture were all lower (33%) than those for the synthetic insecticide λ‑cyhalothrin (83%), ARP14 (73%) or no treatment control (100%). Similarly, in the assay of second instars in the absence of food sources, the ST50 values for AZA and the AZA + ARP14 mixture were almost 1.8 times lower than that for singly applied ARP14. Also, in the presence of food sources, earlier mortality of the 2nd and 3rd instars was observed in the treatment of the AZA + ARP14 mixture compared to agents applied singly from daily observation after treatment. Mycosis was up to 3.5 times higher at 10 d when the AZA + ARP14 mixture was applied to second‑instar nymphs compared to a single application of ARP14. Nevertheless, the developmental time became shorter only in the single treatment of ARP14 than in the control, whether applied to eggs or to second-instar nymphs. These results suggest that the combined application of AZA and ARP14 provides improved efficacy compared to single treatments against second instars of R. pedestris. Thus, the AZA + ARP14 mixture can be a potential control agent to replace synthetic chemical insecticides used against R. pedestris.

In South and East Asian countries, Riptortus pedestris (F.) (Hemiptera: Alydidae) is a major pest of soybean that causes significant yield losses. Chemical control remains the primary management strategy, but concerns over pesticide resistance and environmental impact underscore the need for sustainable alternatives. Companion planting has shown potential for pest suppression by modifying vegetation structure, influencing insect populations through top‐down and/or bottom‐up effects. This study investigated whether maize planted at soybean field edges could reduce major pest populations, including R. pedestris , and enhance biodiversity. Field experiments were conducted in seven small soybean fields, comparing monoculture soybean plots (four replicates) with those bordered by maize (three replicates). Arthropod densities were monitored from July to November 2022. The densities of R. pedestris nymphs and adults were significantly lower in maize treatment plots (peak: 0.37 per planting hole on 5 and 16 September, and 0.60 per planting hole on 7 October, respectively), than in control plots (peak: 0.74 and 1.13 per planting hole on 18 August, respectively). Furthermore, densities of whitefly (Hemiptera: Aleyrodidae) were also lower in maize treatment plots. However, the densities of other organisms, including herbivores and natural enemies, and their biodiversity or evenness indices did not significantly differ between treatments. These results suggest that maize may act as a physical or chemical barrier, limiting pest movement and reducing R. pedestris and whitefly densities through bottom‐up effects in soybean fields. Maize appears to be a promising companion plant for pest management in soybean cultivation.

Beauveria bassiana AAD16, isolated from Allomyrina dichotoma, shows promise as a mycoinsecticide against various coleopterans. However, assessing non-target impacts on beneficial beetles like ladybirds is crucial before commercialization. Here we assessed the compatibility between ladybird beetles and B. bassiana AAD16. The virulence of the AAD16 strain was compared with that of an available commercial strain, B. bassiana GHA, for two developmental stages (adults and 3^rd instar larvae) of two coccinellids, Harmonia axyridis Pallas and Chilocorus spp. Say using the topical (1μl) application method. The ST₅₀ for the two life stages of the two ladybird beetles were not different between the two tested fungal strains. Mycosis rates recorded from the dead bodies were also not significant except in the 3^rd instar which showed 36 and 63% from AAD16 and GHA strains in H. axyridis, while those of Chilocorus spp. were 40 and 63%, respectively. In adult stage, the mycosis rates of H. axyridis (males and females tested separately) were (20–23) % and (26–30) % from the AAD16 and GHA strains, while those of Chilocorus spp. (unsexed) were 23 and 30%, respectively. AAD16 caused similar rates of mortality in the adult stages of both species. Therefore, we conclude that B. bassiana AAD16 would not increase risk to these beneficial insects compared to a similar pathogen commercialized.

A strain (AAD16) of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin was isolated from field-collected Japanese rhinoceros beetle, Allomyrina dichotoma (L.) (Coleoptera: Scarabaeidae). Its virulence was compared with another strain (ARP14) recovered from a cadaver of Riptortus pedestris (F.) (Hemiptera: Alydidae) focusing on its effect on three coleopteran, i.e., Tenebrio molitor L., A. dichotoma, and Monochamus alternatus Hope. The LT₅₀ value of T. molitor for two larval sizes, i.e., 16–18 and 22–24 mm, was 15.3 and 19.4% lower for strain AAD16 compared to strain ARP14, respectively. Furthermore, after 8 and 10 days of exposure, the mycosis rate of strain AAD16 was 1.3 and 1.2 times higher than that of strain ARP14 in the 16–18 and 22–24 mm larval sizes, respectively. The LT₅₀ for M. alternatus larvae was 23.2% lower on strain AAD16 than on strain ARP14. In addition, the LT₅₀ for M. alternatus adults was 47.1% lower for strain AAD16 compared to control. The mycosis rate of strain AAD16 on M. alternatus larvae was 1.8 higher than that of strain ARP14 after 120 hours of exposure. The strain AAD16 also showed higher larval mortality (90%) for A. dichotoma compared to strain ARP14 (45.0%) at 28 days after exposure. These results suggest that B. bassiana AAD16 can be a potential biological control agent against coleopteran pests.

Trialeurodes vaporarium (Westwood) is one of the important pests of ornamental, greenhouse, field, and vegetable plants worldwide. Because of the acute effects of chemical pesticides, it is necessary to investigate low-risk alternatives for the control of this pest. In this study, the insecticidal, repellent, and oviposition-inhibiting effects of ethanolic extracts of Nicotiana tabacum, Nicotiana rustica, and Nepeta cataria on adult Trialeurodes vaporarium were calculated at three concentrations

Nabis stenoferus is a zoophytophagous predator that lives in grasslands around agricultural fields. It is a candidate biological control agent for use via augmentation or conservation. To find a suitable food source for mass-rearing and to better understand this predator’s biology, we compared the life history characteristics of N. stenoferus under the three different diets: aphids only (Myzus persicae), moth eggs only (Ephestia kuehniella), or a mixed diet of aphids and moth eggs. Interestingly, when only aphids were supplied, N. stenoferus developed to the adult stage but lacked normal levels of fecundity. There was a significant synergism of the mixed diet on N. stenoferus fitness in both the immature and adult stages, i.e., a 13% reduction in the nymphal developmental period and an 87.3-fold increase in fecundity, compared to aphid-only diet. Furthermore, the intrinsic rate of increase was significantly higher for the mixed diet (0.139) than either aphids only (0.022) or moth eggs only (0.097). These results show that M. persicae alone is not a complete diet for the mass-rearing of N. stenoferus, whereas this aphid can be a supplementary food when combined with E. kuehniella eggs. Implications and applications of these findings for biological control are discussed.

Grapholita molesta (Busck) is a major pest in orchards of apple, peach, and plum. For better rearing in the laboratory, we compared the life history characteristics of G. molesta by providing larvae with either punctured or unpunctured apple fruits. The development time of immatures and the fecundity of adult females were similar between punctured and unpunctured apples. However, the overall survival rate of G. molesta (larvae to adult emergence) was 1.7 times higher on punctured apples than unpunctured ones, resulting in a higher intrinsic rate of population increase. Therefore, punctured apples would be a better food source for rearing of G. molesta.