The effects of insectary plants on natural enemy and pest abundance, and pest dispersal within cabbage agroecosystems in Hawaiʻi

Armstrong, Kevin Matthew

The effects of insectary plants on natural enemy and pest abundance, and pest dispersal within cabbage agroecosystems in Hawaiʻi

Files

Armstrong_hawii_0085O_11998.pdf (1.34 MB)

Date

2023

Authors

Armstrong, Kevin Matthew

Advisor

Shikano, Ikkei

Department

Entomology

Abstract

Habitat manipulation is the foundation of agricultural systems. Fields are cleared and leveled, waterways are diverted, soils are amended, and crops are cultivated. Often a single field corresponds to a single crop, regardless of size. This concentration of resources often leads to pest outbreaks. The massive increase in the use of conventional pesticides in the 1960-1980s, along with habitat destruction to expand farming areas, has decimated insect populations worldwide. It has also raised environmental and human health concerns. Growing demand for sustainable alternatives has led to the development of organic pesticides and support for research into biological control. While organic pesticides remain an extremely useful tool, insecticide resistance amongst certain species has become a problem. Biological control can be an environmentally sound and effective means of reducing or mitigating pest outbreaks. Natural enemies can be augmented to agricultural systems or conserved by increasing plant diversity in agroecosystems. The implementation of conservation biological control aims to mitigate the consequences of habitat loss, ecosystem simplification, and disturbance and often involves adding insectary plants to farm production areas. Insectary plants provide habitat and nutritional resources for natural enemies (predators and parasitoids). Increasing the populations of natural enemies has been shown to increase top-down control of pest populations. Non-consumptive effects, the non-lethal effects of natural enemies, have also been shown to induce fitness costs on pest populations and have become a focus area within entomological research. In Hawaiʻi, Plutella xylostella, the diamondback moth (DBM) is the major pest of concern for Brassica producers. The dominant DBM parasitoid found throughout the island chain, Cotesia vestalis, fails to control DBM below economic thresholds, causing growers to rely on a rotation of insecticides for effective control. The research described in this thesis focuses on using insectary plants to maximize the impact of parasitoids on the top-down control of cabbage pests while also exploring the nuanced relationship between C. vestalis and DBM. In the lab, I evaluated the influence of C. vestalis on the movement of DBM. In the field, I compared the impacts of natural enemies in organic and conventional (with regards to pest management) cabbage production systems when prey access was manipulated to test the sensitivity of DBM to its predators and to further investigate how DBM movement was influenced by natural enemies.

Keywords

Entomology, Diamondback moth, intercropping, natural enemies, pest dispersal

URI

https://hdl.handle.net/10125/107924

Extent

73 pages

Rights

All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.

Collections

M.S. - Entomology

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