Project Overview
Commodities
- Vegetables: brassicas
Practices
- Pest Management: biological control, cultural control, integrated pest management
Abstract:
Diamondback moth (DBM), Plutella xylostella (L.), is a ubiquitous pest of Brassicaceae crops, causing a global economic burden of $4-5 billion annually. Although natural enemies can suppress DBM population through high parasitism rates (>80%), growers' reliance on insecticides reduces beneficial insects and drives DBM insecticide resistance. Therefore, a sustainable DBM management approach is needed. This project investigates the impact of sweet alyssum flowers (which attract and enhance the efficiency of natural enemies) in suppressing DBM populations. We conducted trials on small and commercial brassica farms in the southern United States to provide equal benefits to both small- and large-acreage growers. Our results suggested that alyssum could be beneficial in improving biological control in small plots, but selective insecticides (such as Bt) could be necessary if a secondary pest (such as CSCW) is present in the agricultural surroundings. Alyssum could enhance DBM biological control in commercial farms, consequently increasing marketable brassica production. A high parasitism rate (64-78%) results highlighted the crucial role of parasitoid wasps in suppressing DBM in the southern US (South Carolina). To maximize the potential and survival of natural enemies, it is vital to conserve predators and parasitoid wasps during high parasitism periods by minimizing insecticide application and providing them resources (food, shelter) such as refuge or insectary plants (such as alyssum). This project addresses environmental, economic, and health sustainability by developing a total-system approach that relies on naturally occurring resources (natural enemies) that will reduce chemical use, thus increasing profitability, yield, and land use efficiency, ultimately improving the quality of life for farms and communities.
Project objectives:
The objectives of this project are:
1. Develop a habitat management strategy that uses sweet alyssum flowers to improve biological control of DBM in the Brassica fields of the southern United States.
1a. This sub-objective tested the hypothesis that integrating interspersed sweet alyssum flowers will enhance DBM parasitism rates, decrease DBM densities, and increase marketable yields. We also expected repeated broad-spectrum insecticide applications would eliminate natural enemies and increase DBM pest pressure (for small-acreage growers).
1b. This sub-objective tested the hypothesis that incorporating Sweet alyssum flowers will increase the rates of DBM parasitism and predation on large commercial farms, but that parasitism and predation will decrease at increasing distances from alyssum strips (for commercial brassica growers).
2. This objective will test the hypothesis that the parasitism rate would be higher (>80%) during late-spring and late-fall, with Diadegma insulare being the most abundant species, and that parasitism will be directly proportional to DBM density.