Insecticide Efficacy for Controlling Pecan Aphids, 2018

We evaluated the efficacy of insecticide tank mixes for yellow pecan aphid (YPA) and blackmargined aphid (BA) suppression in pecan. The trial was conducted in a 24-yr-old pecan orchard (cv. Kanza and Pawnee) at the Cimarron Valley Research Station in Perkins, OK (Payne County). Four treatments and an untreated check were organized as an RCB design with two blocks of plots containing 12 to 20 trees representing both cultivars. Aphicides were applied on 30–31 Aug 2018 as a tank mix with Silencer (λ-cyhalothrin) for pecan weevil, Curculio caryae (Horn). All treatments included the nonionic surfactant Transfix at a rate of 6 fl oz/100 gallons of water. At the time of application aphid density was very high (up to 4,000 + per compound leaf) following a weevil treatment using only a pyrethroid 2 wk earlier (Silencer, 16–17 Aug). Applications were made using a Savage PTO-driven, air-blast sprayer calibrated to deliver 100 gpa. Because of increasing winds on 30 Aug 2018, one treatment (Carbine, 2.4 oz) was delayed until the next morning.

Sampling for aphids was conducted on 27 Aug (pretreatment), then 2, 9, and 14 Sept 2018 by counting the number of aphids (YPA + BA) per compound leaf on ten randomly chosen leaves (high and low) from each of the eight center trees within each plot. During the 2 wk after application, average daily temperatures were in the mid-20s with 13.2 cm of rainfall accumulating 2–9 DAT. Data on the average number of aphids per compound leaf were analyzed by ANOVA for each cultivar with means separated by LSD (<0.05) following square root transformation.

All aphicide treatments, with the exception of Movento applied to both pecan cultivars 2 DAT and Carbine 2.4 oz applied to Kanza pecans 14 DAT, reduced aphid density compared with the Silencer alone (check) on all posttreatment evaluation dates (Tables 1 and 2). The lowest aphid densities 9 and 14 DAT in each cultivar were in plots treated with Closer. There were no significant differences in aphid density between the low and high rates of Carbine on any post-application evaluation date. Data suggest that Movento, Carbine, and Closer, each of which represents a different mode of action, can be effective tools in resistance management programs against aphids in pecan.

This research was supported in part by industry gifts of pesticides and/or research funding.