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Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a major pest of marigolds in Thailand. It causes severe damage to flower quantity and quality. The most common control method is synthetic insecticides, although this method struggles to control hidden larvae inside flowers or buds and underground pupae. Entomopathogenic nematodes (EPNs) are widely used as biocontrol agents against many foliage and cryptic insects. The virulence of two commercial EPNs strains, Steinernema siamkayai (Stock, Somsook and Reid) and S. carpocapsae (Weiser), isolated in Thailand, were assessed against different developmental stages of S. litura. The younger larvae of first and third instar were more susceptible to S. siamkayai with the LD50 of 15.84 and 40.34 dauer juveniles (DJs) per host, whereas S. carpocapsae caused higher mortality in older larvae. Against the fifth instar larvae and pupae, the LD50 ranged between 54.37 and 607.97 DJs/host. Field experiments compared the effect of EPNs with farmer's practice (insecticides). EPNs treatments with S. siamkayai and S. carpocapsae significantly reduced the percentage of damaged flowers to 2.53 ± 1.2% and 2.97 ± 1.5%, respectively, compared with insecticide treatment at 4.21 ± 2.1% in the first trial. In trial 2, the insecticide treatment had the highest percentage of damaged flowers of 5.02 ± 5.7%. The benefit–cost ratio (BCR) of EPNs treatments ranged from 2.42 to 2.53 in the first trial and 1.24–1.50 in the second trial and was superior to insecticide treatments with 2.21 and 1.16 in the two trials.

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Background Trichoderma asperellum (Ascomycota: Hypocreaceae) is a globally recognized soil fungus due to its broad-spectrum antimicrobial and plant growth-promoting properties. To increase the availability of local strains, soil samples from a dragon fruit farm in Villanueva (Misamis Oriental, Philippines) were collected and baited using the insect-baiting technique. Results Using the baiting technique, T. asperellum strain, RMCK01, was isolated. The strain was characterized using morphological and molecular data and its biological control potential was tested using different conidial concentrations on the last larval instar of the super worm, Zophobas morio (Fabricius, 1776) (Coleoptera: Tenebrionidae). The ITS1 sequences of T. asperellum RMCK01 were 100% identical to the sequences of other T. asperellum isolates reported from Vietnam, India, Thailand, and China. In addition, T. asperellum RMCK01 was particularly efficient against Z. morio larvae. On day 21, 88.87%, 88.07%, and 86.73% of insects died when treated with a suspension containing 6 × 108, 3 × 109, and 2.68 × 107 conidia/ml, respectively. Conclusion The study highlights the potential of this fungal isolate as a biocontrol agent against insect pests.

For transport of entomopathogenic nematodes to the user, developmentally arrested dauer juveniles (DJ) are mixed with inert carriers at high density. If quiescence is not induced, DJ will quickly lose energy reserves and die. To induce quiescence DJ can be moderately desiccated. This study investigated the desiccation tolerance by measurement of water activity (ow-value) tolerated by 50% of populations (WA50) of different Steinernema species and strains. DJ were tested with or without prior adaptation to desiccation stress. Stress conditions were produced by exposure to various concentrations of poly(ethylene glycol) 600. Significant differences in desiccation tolerance were recorded between strains and species, but, except for Steinernema abbasi, not within strains of one species. Without adaptation to stress conditions, the most tolerant species was S. carpocapsae (WA50 = 0.836) followed by S. abbasi (0.86). Adaption to stress by exposure to an Ow-value of 0.95 for 48 h increased tolerance to 0.68 and 0.66, respectively. The least tolerant species were S. kraussei, S. giaseri and S. ethiopiense. Tolerance recorded would allow storage at a water activity that would inhibit growth of bacteria but not of fungi. Analysis of water activity tolerated by only 10% of the population indicated potential for genetic improvement by selective breeding for S. carpocapsae, S. abbasi and 5. arenarium to reach water activity levels that would also inhibit fungal growth.