Citricola scale causes loss of tree vigor, yield reduction anddowngrading of fruit in the packing house due to sooty mold growthon honeydew deposited by the insect. A field trial was conducted in a28-yr-old ‘Cutter’ Valencia orange orchard at the Lindcove Researchand Extension Center, Exeter, California to compare various rates ofinsecticides for efficacy against citricola scale. Insecticides were appliedusing 200 PSI and 500 gpa to 10 trees per treatment using a 100gal high-pressure D30 diaphragm pump sprayer with mechanical agitation.Treatments were assigned to trees on 25 Apr 2019 in an RCBdesign based on pretreatment counts of mature female scale foundon five twigs (approximately 40 cm in length) randomly selectedfrom the northeast corner of the tree. All insecticide treatments wereapplied with 0.5% Omni 6E oil on 31 Jul or 1 Aug, when the populationconsisted of first-instar nymphs infesting leaves. Posttreatmentsampling consisted of counts of first-instar nymphs infesting fiveleaves collected from the NE corner of each sample tree during Sepand Oct 2019. An additional sample of mature females on five twigsper tree was collected on 5 May 2020. Data were analyzed usingone-way ANOVA after testing for NS block effect. Differences inthe mean numbers of nymphs per leaf or adult female scale per twigwere determined using Fisher’s Protected Least Significant DifferenceTest (P 0.05) after log10(x+1) transformation of numbers.
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