Apple, Prebloom Evaluation of Insecticides, 1995

Abstract

Abstract Two experimental and one registered insecticide were applied prebloom to evaluate their activity on a number of early season pests and to determine if honey bee activity at bloom was adversely affected. The experimental plot design was a RCB, with 5 insecticide treatments and a control, replicated 4 times. Plots consisted of 2-tree plots, 1 tree each of the cultivars ‘Yorking’ and ‘Golden Delicious’. The trees were planted at a spacing of 20 X 20 ft and were 22 yr old. Experimental sprays were applied with a Myers Mity Mist airblast sprayer calibrated to deliver 100 gpa at 2 mph. All treatments were applied at the pink stage (26 Apr) of ‘Golden Delicious’ development. A regular fungicide schedule (Dithane 75DF, Nova 40WP and Ziram 76WP) was maintained throughout the season. Post-bloom insecticides (Guthion 50WP) were applied at 1- to 2-wk intervals beginning at petal-fall in early May. Effectiveness of the sprays for RAA control was evaluated by counting the total number of RAA-injured clusters/tree and total number of injured apples per tree (both cvs) in a 5 min sample per tree for each variable. WALH was sampled by counting the number of nymphs present on 25 injured leaves per tree (cv ‘Yorking’). Also, 200 leaves per tree (cv ‘Yorking’) were randomly sampled for evidence of stippling caused by the feeding of WALH. Effectiveness of the test chemicals on the ERM was evaluated by counting the mites on samples of 25 random leaves/tree, 100 leaves/treatment. STLM was evaluated on 6 Jun by counting the number of tissue-feeding mines per 3 minutes around the periphery of the ‘Yorking’ tree/replicate. A sample of tissue-feeding mines was collected and the percentage of parasitized STLM determined. Honey bee sampling was conducted by making a number of 1-min examinations of each replicate tree during the blossom period. The number of blossoms on 2 tagged limbs per replicate tree was counted on 28 Apr and a measurement of limb cross-section area was taken. On 3 Jul, the number of apples that set on each tagged limb was counted. All insecticide treatments effectively controlled RAA with an application at the pink stage. WALH populations were lower on trees treated with BSN-2894. The high rate of BSN-2894 was more effective on STLM than Provado or Aphistar. None of treatments adversely affected honey bee activity during bloom or subsequent fruit set. Pest pressure was moderate.