Specialized Pheromones Can Boost the Ability of Beneficial Nematodes to Control Pecan Weevil and Other Pests

Authors: Shapiro Ilan, David; Hofman, Camila; KAPLAN, FATMA - Pheronym, Inc

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 9/24/2020
Publication Date: 10/1/2020
Citation: Shapiro Ilan, D.I., Hofman, C.O., Kaplan, F. 2020. Specialized Pheromones Can Boost the Ability of Beneficial Nematodes to Control Pecan Weevil and Other Pests. Pecan Grower. 23(5): 25-33.

Interpretive Summary: Beneficial nematodes (also known as entomopathogenic nematodes) are safe environmentally friendly biopesticides. These nematodes have been shown to be highly effective at killing the soil-dwelling stages of pecan weevil, a major insect pest of pecans. Mechanisms to enhance the activity of the beneficial nematodes could increase their efficacy in controlling pecan weevil and may reduce costs. Recently, specialized pheromones called ascarosides were identified in beneficial nematodes. We discovered that these pheromones can increase beneficial nematode dispersal in soil and increase infectivity (the number of nematodes that invade the insect). Therefore, we then hypothesized that pheromone extracts added to mixtures containing beneficial nematodes would result in increased pecan weevil control. We tested the hypothesis in a greenhouse experiment. Two species of beneficial nematodes (S. carpocapsae and S. feltiae) were tested and compared to a non-treated control. Nematode treatments applied with or without pheromones caused higher pecan weevil mortality than the control (water only). However, beneficial nematodes performed better in killing pecan weevil when applied with pheromones compared with the treatments without pheromones. This study demonstrates that pheromone extracts can improve beneficial nematode’s ability to control insect pests such as pecan weevil. Field tests using this pheromone-nematode approach will be implemented.

Technical Abstract: Entomopathogenic nematodes are safe environmentally friendly biopesticides. These nematodes have been shown to be highly effective at killing the soil-dwelling stages of pecan weevil, Curculio caryae. However, the cost of entomopathogenic nematodes can be high relative to alternative tactics such as canopy application of chemical insecticides. Thus, mechanisms to enhance the activity of the nematodes could increase their efficacy in controlling pecan weevil and may reduce costs. We discovered that these ascarosides-based pheromones can increase entomopathogenic nematode dispersal in soil and increase infectivity. Therefore, we then hypothesized that pheromone extracts added to mixtures containing beneficial nematodes would result in increased pecan weevil control. We tested the hypothesis in a greenhouse experiment. Two species of nematodes (S. carpocapsae and S. feltiae) were tested and compared to a non-treated control. Nematode treatments applied with or without pheromones caused higher C. caryae mortality than the control (water only). However, entomopathogenic nematodes performed better in killing C. caryae when applied with pheromones compared with the treatments without pheromones. In the case of S. carpocapsae, the number of surviving C. caryae was more than twice as low when pheromones were added compared to the treatment without pheromones. This study demonstrates that pheromone extracts can improve beneficial nematode’s ability to control insect pests such as C. caryae. Field tests using this pheromone-nematode approach will be implemented.