Seasonal Abundance of Aphids and Aphidophagous Insects in Pecan.

James Dutcher,Haider Karar,Ghulam Abbas

doi:10.3390/insects3041257

Abstract

Seasonal occurrence of aphids and aphidophagous insects was monitored for six years (2006–2011) from full leaf expansion in May to leaf fall in October in “Desirable” variety pecan trees that were not treated with insecticides. Aphid outbreaks occurred two times per season, once in the spring and again in the late summer. Yellow pecan and blackmargined aphids exceeded the recommended treatment thresholds one time and black pecan aphids exceeded the recommended treatment levels three times over the six seasons. Increases in aphidophagous insect abundance coincided with aphid outbreaks in five of the six seasons. Among aphidophagous insects Harmonia axyridis and Olla v-nigrum were frequently collected in both the tree canopy and at the ground level, whereas, Coccinella septempunctata, Hippodamia convergens were rarely found in the tree canopy and commonly found at the ground level. Green lacewing abundance was higher in the ground level than in the tree canopy. Brown lacewings were more abundant in the tree canopy than at the ground level. Dolichopodid and syrphid fly abundance, at the ground level increased during peak aphid abundance in the tree canopy. Application of an aqueous solution of fermenting molasses to the pecan foliage during an aphid outbreak significantly increased the abundance of ladybeetles and lacewings and significantly reduced the abundance of yellow pecan, blackmargined and black pecan aphids.

Highlights

IntroductionPecan has many potential insect and mite pests that detract from its value in urban plantings in the southeastern U.S Insects and/or mites feed upon and cause injury to every major system of the tree [1]
The spring outbreaks are mixed populations of yellow pecan and blackmargined aphids and periods of high abundance occur after rapid exponential increases in the two populations followed by a brief (1±2 w) period of high abundance that is followed by a rapid decline in the mid-summer
Black pecan aphids typically occur as outbreaks in the late summer and fall

Summary

Introduction

Pecan has many potential insect and mite pests that detract from its value in urban plantings in the southeastern U.S Insects and/or mites feed upon and cause injury to every major system of the tree [1]. Integration of biological and chemical controls has produced management schemes to quell insect outbreaks quickly and with high effectiveness in the commercial pecan orchards. Only the biological controls are recommended for urban pecan trees or organic pecan orchards [2]. The trees typically are large, 10±22 m in height and covering an area of 0.04 ha. The trees are difficult to treat with pesticides and homeowners rely on natural enemies for pest control [3].

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