Black Pecan Aphid (Hemiptera: Aphididae) Management on Pecan When Gibberellic Acid Is Applied Concurrently With Broad-Spectrum Insecticides.

Abstract

Aphids (Hemiptera: Aphididae) are serious pests of pecan foliage (Carya illinoinensis [Wangenh.] K. Koch). The black pecan aphid, Melanocallis caryaefoliae (Davis) (Hemiptera: Aphididae), feeds on pecan foliage and elicits leaf chlorosis that can cause defoliation. In contrast, the blackmargined aphid, Monellia caryella (Fitch) (Hemiptera: Aphididae), and yellow pecan aphid, Monelliopsis pecanis Bissell (Hemiptera: Aphididae), feed on pecan foliage but do not elicit chlorotic feeding injury. Application of gibberellic acid (GA3) to pecan foliage reduces chlorotic foliar injury and nymphal populations of the black pecan aphid. GA3 has potential to manage black pecan aphid later in the season when broad-spectrum insecticides are used to control direct pests of pecan nuts but also inadvertently induce aphid outbreaks. Here, broad-spectrum insecticides were used with GA3 or aphicides in orchard trials for 2 yr. Populations of aphids and natural enemies along with chlorotic feeding injury on foliage were assessed. When used concurrently with GA3 or aphicides, broad-spectrum insecticides did not flare black pecan aphid populations. However, combined populations blackmargined aphids and yellow pecan aphids were higher in treatments with GA3 than with an aphicide or in the control treatment during one of two years. Application of GA3 or the aphicide often led to significantly less chlorotic injury than observed in the control. Surprisingly, natural enemies were not significantly affected by broad-spectrum insecticides when applied concurrently with GA3. These results show that GA3 can be used as part of a late-season IPM strategy to protect foliage from localized chlorotic leaf injury elicited by the black pecan aphid.