Harnessing Semiochemicals: An Integrated and Sustainable Approach to Manage Pepper Weevil Infestations

Commodities

• Vegetables: peppers

Practices

• Pest Management: integrated pest management

The pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae) is a devastating agricultural crop pest targeting peppers. Female weevils chew into a young pepper, oviposit, and cover the hole with a plug infused with an oviposition deterrent pheromone (ODP). Once infested, fruits are terminated by the plant, decreasing yield. Fruits that survive infestations or extensive feeding are often misshapen, further decreasing total crop yield. Current strategies focus on adult A. eugneii management using contact-based chemical insecticides and sanitization of crop debris with limited management of immature stages protected by the pepper fruit. Chemical insecticides are economically expensive for growers with harmful effects on the environment and human health. Sanitation of fields can be difficult as adult A. eugenii can survive off debris from pepper plants and many native Solanaceae present near the field leading to re-infestation in the following season. Therefore, research into deterring initial oviposition is critically needed for future sustainable pest management strategies. Research suggests that the use of kaolin clay reduces oviposition and adult feeding on peppers. Similarly, young peppers treated with the ODP had 75% less oviposition compared to control peppers. Kaolin has adsorption capabilities for different type of volatile and could allow a slow release of the pheromone. These strategies in combination have not been assessed therefore, we hypothesize using kaolin clay mixed with the ODP to coat growing pepper leading to decreased oviposition, decreased adult sightings, and increased total yield while reducing the dependence on harsh chemical sprays.

1. Evaluation of different oviposition deterrent pheromone blends in greenhouse conditions

The oviposition deterrent pheromone (ODP) of A. eugenii was recently discovered and behavioral assays indicated A. eugenii females preferred clean peppers (without applied ODP) to peppers coated with ODP (Addesso et al., 2021). The study also found different ratios in the blend of semiochemicals comprising the ODP elicited similar responses when compared to clean, uninfested peppers but did not compare the different ratio blends to one another.

This experiment is designed to compare the different ratio blends of the ODP: 1) 1 mL linoleic acid with 1 µL acetophenone; 2) 6:3:1 (oleic, linoleic, and linolenic acid) with 10% acetophenone; 3) 6:3:1 (oleic, linoleic, and linolenic acid) with 10% acetophenone and 20% stearic acid; 4) Pentane solvent control. Stearic acid creates a “semi-solid” solution to mimic an oviposition plug. If behavioral responses to the blends are not different the simplest blend will be utilized for Objectives 2 and 3.

2. Evaluate the response of female eugenii with previous experience with the oviposition deterrent pheromone

A single, female A. eugenii from a mixed colony to ensure she has been mated will be placed inside a 5 cm tall glass sample vial with 0.5 mL of the ODP found to be the most deterrent (Objective 1). Female A. eugenii will be exposed to the ODP or solvent control for 24 h, 48 h or 72 h. The vials with the ODP and weevil will be placed on an automatic slow-roller to evenly spread the solution. The female will then be placed into a plastic container with 5 ODP treated peppers 24 h. After this time has passed, the number of oviposition sites will be counted.

This experiment is designed to evaluate the response of female A. eugenii with different levels of experience to the ODP. The response in this experiment will be the number of oviposition sites found on the peppers of the females from different exposure times.

3. Field evaluation of ODP combined with kaolin clay to prevent eugenii infestation.

The ODP blend that reduces oviposition, adult feeding, and fruit drop the most will be used in the field evaluation with kaolin clay. Treatments to be evaluated will be 1) ODP singularly; 2) Kaolin singularly; 3) ODP infused into kaolin; 4) Insecticide treatment (Thiamethoxam and oxamyl rotation); and 5) Untreated control.

This experiment is designed to assess the integrated method compared to the different components (ODP and kaolin) singularly.