Fungal seed treatments of cotton affect boll weevil development

Authors: CUNHA, JANAINA - Texas A&M University; RIVERA VEGA, LOREN - Texas A&M University; TORRES, JORGE - Universidade De Pernambuco; Suh, Charles; SWORD, GREGORY - Texas A&M University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2023
Publication Date: 12/8/2023
Citation: Cunha, J.C.S., Rivera Vega, L.J., Torres, J.B., Suh, C.P.-C., Sword, G.A. 2023. Fungal seed treatments of cotton affect boll weevil development. Pest Management Science. https://doi.org/10.1002/ps.7890.
DOI: https://doi.org/10.1002/ps.7890

Interpretive Summary: Because weekly applications of insecticides are often required to manage the boll weevil in heavily infested areas, there is concern that the weevils may develop resistance to these insecticides. Thus, there is a critical need to identify or develop alternative approaches for managing this insect pest. One such approach may involve the use of facultative fungal endophytes which are unspecialized fungi that can colonize plant tissues without causing symptoms of disease. Recent studies have shown that some fungal endophytes can enhance cotton plant defense against insect pests by repelling or deterring insects from feeding on plants. We treated cotton plants with several species of fungal endophytes and examined how the fungal treatments affected boll weevil development, reproduction, and survival. Overall, the fungal treatments had an adverse effect on boll weevil development, reproduction, survival, and one fungal species appeared to deter weevils from feeding on plants. However, the magnitude of these effects were considered too low for fungal endophytes to serve as a stand alone management strategy. Nevertheless, our results suggest the use of fungal endophytes could be used in conjunction with other approaches to help manage this pest in cotton.

Technical Abstract: Non-pathogenic fungi association with plants have enhanced plant performance against stressing factors including herbivory. In this study, we assessed whether cotton plants grown from seeds treated with plant-associated fungi would affect boll weevil Anthonomus grandis grandis behavior, development, and reproduction. For the behavior assays, we conducted no-choice and choice assays with flower buds of plants grown from seeds treated with different plant-associated fungi (Chaetomium globosum TAMU520 and TAMU559, Phialemonium inflatum TAMU490, and Beauveria bassiana) versus untreated controls. In the reproduction and progeny performance assays, we infested 50–70-days old cotton plants grown from seeds treated with one of several plant-associated fungi and untreated control plants in cages under greenhouse conditions. Each cage contained one plant and one mated boll weevil female and was checked daily to collect abscised squares and for oviposition. Boll weevil’s behavior towards fungal-treated cotton squares was strain-specific, in some cases making them avoid squares from fungal-treated cotton plants. Regarding BW reproduction, fewer larvae hatched, and fewer adults emerged from fungal-treated plants. In addition, developmental time to the adult stage was delayed in fungal-treated plants. Consequently, fungal treatments could negatively affect the population size of subsequent generations in the field. These results indicate the potential for cottonseed treatment with fungi for helping boll weevil management, which are presented and discussed besides other benefits for plant performance.