Biodiversity of lepidopteran pests and their parasitoids in organic and conventional cranberry crop
2019
Drolet, Isabelle | Guay, Jean-Frédéric | Fournier, Valérie | Cloutier, Conrad
A 2-year study was conducted in the main cranberry (Vaccinium macrocarpon Aiton) growing region of Québec to determine the biodiversity of lepidopteran pests and their parasitoids, which may differ in organic and conventional integrated pest management (IPM) systems. We also aimed to compare densities and parasitism on five caterpillar pest species of primary economic importance: Macaria sulphurea (Packard), Macaria brunneata (Thunberg), Xylena nupera (Lintner), Rhopobota naevana (Hübner) and Sparganothis sulfureana (Clemens), which accounted for more than 80% of the pest community each year. The lepidopteran pest communities clearly varied between the two pest management systems, suggesting efficacy differences among them. Rhopobota naevana was dominant on organic farms, whereas conventional farms had greater pest richness and evenness, with M. sulphurea, M. brunneata and X. nupera being the most abundant. Based on laboratory rearing of field collected caterpillars, the parasitoid community was composed of 25 species or taxa (22 from primary pests) and communities were not significantly different between the two farming regimes. The most common species belonged to the braconid genera Aleiodes, Meteorus, Microplitis, Oncophanes; ichneumonids Hyposoter, Exetastes, Phytodietus; and tachinids Campylocheta, Nemorilla. Of the five primary pests, X. nupera was the most parasitized, while no parasitoids were reared from M. brunneata. Annual parasitism rate of the primary pests ranged 20–40% and data showed that it was explainable by host availability rather than farming system.
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