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Interactions of pea leaf weevil (Coleoptera: Curculionidae) with its primary and secondary host plants in Alberta
- Author / Creator
- Wijerathna, Asha Nishadini
The pea leaf weevil, Sitona lineatus Linnaeus (Coleoptera: Curculionidae), is an invasive, oligophagous herbivore that feeds on a variety of legume (Fabales: Fabaceae) plants. Field peas (Pisum sativum) and faba bean (Vicia faba) are the primary host plants of the pea leaf weevil. Adult weevils feed on the foliage of the host plants and larvae feed on Rhizobium leguminosarum Frank (Rhizobiales: Rhizobiacea) bacteria associated with root nodules. Pea leaf weevil is a major pest of field peas and faba beans and adult and larval damage can cause significant economic losses to these crops. In this study, I investigate the effect of 1. behavioural plasticity of pea leaf weevil, 2. quality of pea leaf weevil host plants in relation to nitrogen content and legume-Rhizobium symbiosis, and 3. pea leaf weevil overwintering biology in shaping pea leaf weevil interactions with host plants and 4. applications to integrated pest management (IPM).
Pea leaf weevil adults feed on legumes during two different reproductive states in a one-year life cycle. In the spring, individuals are reproductively active, and in the fall adults are reproductively inactive and feed to prepare for overwintering. The reproductive state of pea leaf weevil can influence host choice because larvae must feed on root nodules of the primary hosts to develop. I investigated how weevil reproductive state modulates host finding behaviour in the pea leaf weevil. The pea leaf weevil preference for primary hosts, field pea and faba bean, is reproductive state-dependent. Pre-reproductive weevils exhibit a preference for faba bean over field peas, while reproductively inactive weevils show no preference between hosts and the preference for faba bean is strongly linked to larval development. My findings suggest that oligophagous insects may show phenotypic plasticity in host preference to maximize fitness benefits
Legumes exhibit species-specific symbiotic associations with Rhizobium bacteria that can affect host quality (nitrogen content and host defences), and hence the above-ground and below-ground insect-plant interactions. I investigated the influence of species-specific legume-Rhizobium symbioses on pea leaf weevil adult and larval interactions with its primary and potential secondary host plants. The legume-Rhizobium association drives pea leaf weevil larval development, but not adult host acceptance. Larvae only survive in nodules associated with Rhizobium leguminosarum in field peas and faba bean. Soybean is an occasional host to larvae. Adults feed on most of the tested legume species (field peas, faba bean, alfalfa, lupin, soybean) but not on chickpeas and little feeding occurs on lentils. Rhizobium increased nodulation and protected the yield of faba bean while nitrogen amendment did not protect yield. Taken together, these findings suggest that changes to host quality as a result of legume-Rhizobium symbioses influence weevil- host plant interactions and have the potential to protect faba bean yield from pea leaf weevil damage.
A better understanding of cold hardiness and factors influencing cold hardiness is key to predict invasive pest populations. I investigated the overwintering survival and cold hardiness of the pea leaf weevil in its expanded range and the influence of overwintering temperature and duration on pea leaf weevil post-overwintering interaction with its host plants. The overwintering survival of pea leaf weevil adults increased with soil temperature and more weevils survived when they overwintered at tree shelterbelts compared to in open alfalfa fields. The lethal temperature threshold for pea leaf weevil in Alberta is -9.38C. Warmer and longer winter periods increased post-overwintering feeding and oviposition of pea leaf weevil. My study highlights that warm winters would increase overwintering survival and post -overwintering fitness and facilitate pea leaf weevil invasion in the Prairie Provinces of Canada.
Pea leaf weevil-plant interactions vary with weevil physiological state and plant host quality, and are shaped by overwintering temperature and duration. This information on pea leaf weevil-host interactions will contribute to IPM of pea leaf weevil in Alberta. A major goal of IPM is to prevent pest species from reaching the pre-determined threshold level to minimize economic losses. I developed a data-based nominal threshold for pea leaf weevil on faba bean to contribute to the IPM of pea leaf weevil in Alberta.
- Graduation date
- Fall 2021
- Type of Item
- Doctor of Philosophy
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.