The objective of this study was to compare repellency effects ofvarious materials to pear psylla (PP). Repelling adults PP from enteringpear orchards and creating a barrier against oviposition isimportant during prebloom colonization. Kaolin clay (Surround)and/or horticultural oils are most often used for this purpose, butgrowers also apply other materials for tree nutrition or diseasemanagement, and it is of interest to know if these treatments alsoinfluence PP colonization and oviposition. Experimental units inthis trial were individual potted ‘Anjou’ pear trees on Old Home× Farmingdale 87 rootstocks, ca. 76 cm tall and 1.3 cm caliper.The experiment was conducted in a large mesh cage in a greenhouseat the Washington State University’s Tree Fruit Researchand Extension Center in Wenatchee, WA. Forty-five trees wereplaced in the cage, and 14 materials and a water check allocatedin randomized complete block design (one treatment per tree). Theexperiment was conducted in two runs, each with three replicationsof each treatment. The first run was on 20 Mar and evaluatedon 27 Mar, and the second was on 29 Mar and evaluated on 4Apr. One block of replicates from the first run of the experimentwas excluded from analysis (N = 5) because adults aggregated atthe south end of the cage due to greater sunlight. This issue wascorrected in the second run by adding shade netting to that endof the greenhouse. For each run, treatments were applied using1-liter plastic hand-pump spray bottles to spray ca. 100 ml of testsolution per tree. Trees were left to dry for at least 1 h before beingplaced in the cage. The next day, 1,200 adult PP were collectedfrom the field using an aspirator and then released inside the edgesof the cage. After 6 d, in the morning when PP are less active,adult PP were counted on each tree with the unaided eye and eggswere counted under 5× magnification glasses (OptiVISOR DA-10,Donefan Optical Inc., Lenexa, KS). Response variables (numbersof PP adults and PP eggs) were pooled across runs and analyzedwith R using the ‘anova’ function for two-way ANOVA with explanatoryvariables of treatment and block, followed by mean separationwith Fisher’s least significant difference using the ‘LSD.test’ function of the ‘agricolae’ package.
展开▼
