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Life history and population dynamics of western flower thrips, Frankliniella Occidentalis (Pergande) (Thysanoptera:Thripidae) in Nectarine Orchards in the Dry Central Interior, British Columbia

University of British Columbia

Nectarine production in the Dry Central Interior, British Columbia, has recently grown in status from a minor specialty crop to a regular commodity. However, this developing industry is threatened by the damage done by the western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), an insect showing high levels of insecticide resistance and apparently without effective natural enemies in this crop. This three-year study involved an examination of WFT biology, habitat, dispersal, and behaviour in nectarine orchards in the Okanagan and Similkameen valleys. The aim was to identify stages in the life cycle where a control effort could be focused and to aid in creating an appropriate pest management program for thrips. Emergence and immigration into orchards were gradual and widespread processes. Egg-laying also occurred over an extended period of time, but with the bulk of eggs laid early in the development of nectarine buds, which is much earlier than prior studies had suggested. The lack of peak periods for these activities hinders control. Feeding by first generation larvae was identified as the primary cause of russetting damage to nectarine fruit. Direct bud sampling was found to more efficient than using sticky cards to trap adult WFT. However, neither adult counts from sticky cards nor buds allowed me to predict either future larval or damage levels which makes it difficult to produce damage thresholds for this insect on this crop. WFT tended to move into orchards from the direction of patches of wild land, but moved out of orchards in accordance with the dominant wind patterns. Immigration occurred mainly at ground level in the early spring. Flower preference studies suggested that exploitation of this flight behaviour by using a trap crop that blooms in the early spring is unlikely to succeed. Orchards located adjacent to tracts of wild land appeared to be most at risk for immigration of WFT in early spring, and showed higher incidence of damaged fruit than orchards that are surrounded, and thus protected, by other orchards. Careful choice of planting sites appears to be one of the only control options available at present.

Thesis/Dissertation

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2009-06-02

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http://hdl.handle.net/2429/8593

Plant Science

University of British Columbia

UBCV

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