Andersen, Astrid H.

Beers, Elizabeth H.

Undetermined

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II. Pome Fruitsd. Chemical control1. European Red Mite (Panonychus ulmi), Twospotted spider mite (Tetranychusurticae) and apple.Astrid H. Andersen and Elizabeth H. BeersTree Fruit Research and Extension CenterWashington State University1100 N. Western Ave.Wenatchee, WA 98801Efficacy of Agri-Mek against European Red Mite and Twospotted Spider Mite on Apple inRelation to the Translaminar Activity of Agri-Mek in Apple Foliage.Site and method description.This study was conducted in a mature 'Delicious' orchard at the Tree Fruit Research andExtension Center in Wenatchee, Washington. The experimental design was a 2 x 2 factorial,with 2 mite species (ERM orTSM) and 2 leafsurfaces assayed (upper and lower). An unsprayedcheckwas used to correct for natural mortality using Abbott's formula. The pesticide treatmentwas Agri-Mek 0.15EC 11 g ai/acre plus 0.25% Volck Supreme Oil, applied 23 July with ahandgun sprayer at 300 psi to the point of drip.The residues were bioassayed weekly for 4 weeks post treatment starting 1 week aftertreatment. Ten tagged leaveswere collectedfromeach treatmenton each bioassaydate. A 2-cmleaf disk was cut fromeach leaf and floated in a jelly cup with distilledwater and cotton, with theappropriate leaf surface uppermost. Ten adult female mites (TSM from greenhouse colony onbean, ERM from local 'Delicious' orchard) were transferred to each leaf disk and evaluated formortality after 72 h at 24°C. Dead and moribund mites were classed as dead, and mites that werenot found on the leaf disk were not included in the analyses. Replicates with less than five mitesfound on the diskat timeof evaluation were also excluded from the analyses.Mite susceptibility and Agri-Mek translaminar activity.Both mite species were primarily susceptible to Agri-Mek residues exposed from thebottom side of the leaves. There were no significant differences between the two mite species insusceptibility when exposed to Agri-Mek from either side of the leaves.This study shows that Agri-Mek is mainly absorbed through the bottom side of appleleaves. Residues ofAgri-Mek on apple leaves were only effective to mites feeding on the bottomleafsurface. TSM tend to colonize on the bottom surfaces of leaves, while ERM are thought tocolonize both sides of the leaves. This study indicates that Agri-Mek's lack of performanceagainst ERM in field trials may possibly be explained by behavior rather than physiology.49501993 Agri-MekTranslaminar StudyWith European Red Mite &Twospotted SpiderMite.14 21Residue Age (days)Fig. 128-o- ERM.Bottom-0- ERM.Top•&•• TSM.Bottom-B- TSM.Top* Corrected mortality calculated from total number of individuals as opposed to within replicates, due to lownumbers of mites in most replicates.Check Mortality For 1993 Agri-Mek Translaminar StudyWith European Spider Mite &Twospotted Spider Mite.14 21Residue Age (days)Fig. 228-D- ERM.Bottom-o- ERM.TopTSM.Bottom~B- TSM.Top

Efficacy of Agri-Mek against European red mite and twospotted spider mite on apple in relation to the translaminar activity of Agri-Mek in apple foliage

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Efficacy of Agri-Mek against European red mite and twospotted spider mite on apple in relation to the translaminar activity of Agri-Mek in apple foliage

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