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

Commodities

Practices

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.