Sesbania exaltata(Rafinesque-Schmaltz) Cory (Fabaceae) as a Warm-Season Cover Crop in Pecan Orchards: Effects on Aphidophagous Coccinellidae and Pecan Aphids

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Abstract
The effects of warm-season cover crops on aphidophagous Coccinellidae and pecan aphids were evaluated in replicated studies at three commercial pecan orchards in southern Georgia. Each orchard featured cover-cropped plots dominated by sesbania (Sesbania exaltata [Rafinesque-Schmaltz] Cory) and control plots containing resident vegetation. Sesbania was the only understorey plant that harboured substantial densities of alternative prey, such as cowpea aphid (Aphis craccivora Koch) and bandedwinged whitefly (Trialeurodes abutilonea [Haldeman]), suitable for Coccinellidae. When densities of pecan aphids dropped during July or August, whitefly-infested understorey stands of sesbania arrested and retained high densities of convergent lady beetle (Hippodamia convergens Guerin-Meneville) and the principally-arboreal Olla v-nigrum (Mulsant). In two separate studies, highly significant differences were found for season-long mean densities of pooled adult lady beetles: densities were 125 and 48 times greater in cover-cropped understoreys than in control understoreys of resident vegetation. However, these understorey differences did not lead to significantly different coccinellid or aphid densities in the associated pecan trees.