Combined effect of entomopathogens against thrips tabaci lindeman (thysanoptera: thripidae) under laboratory, greenhouse and field conditions

Authors: GULZAR, SEHRISH - Agricultural University Of Pakistan; WAKIL, WAQAS - Agricultural University Of Pakistan; Shapiro Ilan, David

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2021
Publication Date: 5/15/2021
Citation: Gulzar, S., Wakil, W., Shapiro Ilan, D.I. 2021. Combined effect of entomopathogens against thrips tabaci lindeman (thysanoptera: thripidae) under laboratory, greenhouse and field conditions. Insects. 12/456. https://doi.org/10.3390/insects12050456.
DOI: https://doi.org/10.3390/insects12050456

Interpretive Summary: Onion thrips are major pests of various crops. Chemical insecticides are commonly used to control this pest. However, due to environmental and regulatory concerns, alternative methods of pest management are being sought. Entomopathogenic nematodes, also known as beneficial nematodes, are small round worms that kill insects. These nematodes occur naturally and are used as environmentally-friendly bio-pesticides. Entomopathogenic (insect-killing) fungi are also used as natural bio-pesticides. Sometimes combining two biological control agents works better than just using one agent; interactions between the two agents can be synergisitc (greater than the sum of the parts). In this study we investigated the effects of applying entomopathogenic nematodes and fungi as single or combined treatments for control of onion thrips. We tested two species of nematodes and two species of fungi. All of the treatments caused mortality in the thrips pest. However, the most promising treatment , and the only one that exhibited synergy, was a combination of nematode + fungus; the species combined were called Heterorhabditis bacteriophora and Beauveria bassiana. This combination of treatments shows potential to be used as a safe and sustainable method of controlling onion thrips. Additional field testing is needed to confirm our results.

Technical Abstract: Onion thrips Thrips tabaci Lindeman (Thysanoptera: Thripidae) is one of the most damaging insect pests of onions, Allium cepa L., which is an economically important agricultural crop cultivated worldwide. In this study we evaluated combined applications of entomopathogenic nematodes with entomopathogenic fungi against different soil dwelling stages of T. tabaci. The nematodes included Heterorhabditis bacteriophora (VS strain) and Steinernema feltiae (SN strain) and fungi included Beauveria bassiana (WG-11) and Metarhizium anisopliae (WG-02); all four paired combinations (nematode+fungus) were included. In a small cup bioassay, only the combined application of H. bacteriophora and B. bassiana (WG-11) caused a synergistic interaction against pre-pupae while all other combinations were compatible in an additive manner against pupae and late second instars. In a larger arena, a potted soil bioassay, again combined application of both pathogens produced greater mortality as compared to single applications of each pathogen; all the combinations exhibited additive interactions with the highest mortality was observed in pre-pupae, followed by pupae and late second instar larvae using H. bacteriophora and B. bassiana (WG-11). Additionally, in the potted plant bioassay, lower adult emergence was observed from treated groups compared to control groups. Under field conditions, lower numbers of adults and larvae were found in treated groups relative to controls. Overall the pre-pupal stage was more susceptible to the pathogen treatments followed by pupae and late second instar larvae, and also combined applications of both pathogens suppress the adult population. Combined application of entomopathogenic nematodes and fungi could be used for integrated pest management (IPM) of T. tabaci in onion production systems.