Andersen, Astrid H.

Beers, Elizabeth H.

Undetermined

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II. Pome Fruitsd. Chemical control1. Twospotted spider mite (Tetranychus urticae) and apple.Astrid H. Andersen and Elizabeth H. BeersTree Fruit Research and Extension CenterWashington State University1100 N. Western Ave.Wenatchee, WA 9880153The Translaminar Activity of Agri-Mek in Apple Foliage as Determined by Twospotted SpiderMite Mortality.Site and method description.This study was conducted in a mature 'Delicious' orchard at the Tree Fruit Research and Extension Centerin Wenatchee, Washington. The experimental design was a 2 x 2 x 2 factorial, with 2 leaf surfacessprayed, 2 leaf surfaces assayed, at 2 different leaf ages. An unsprayed check was used to correct fornatural mortality using Abbott's formula. One leaf from the basal part of several shoots were tagged on12 trees. Some of the tagged leaves were sprayed on the upper leaf surface, some were sprayed on thebottom leaf surface and some were left as checks. The pesticide treatment were Agri-Mek 0.15EC 11 gai/acre plus 0.25% Volck SupremeOil applied with an atomizer to the point of drip 2 July and 13 August.The residues were bioassayed weekly or biweekly 4-6 weeks post-treatment starting 1 weekafter treatment. Ten tagged leaves were collected from each treatment on each bioassay date. A 2-cmleaf disk was cut from each leaf and floated in a jelly cup with distilled water and cotton with theappropriate leaf surface uppermost. Ten adult female TSM were transferred to each leaf disk andevaluated for mortality after 72 h at 24°C. Dead and moribund mites were classed as dead, and mites thatwere not found on the leaf disk were not included in the analyses. Replicates with less than five mitesfound on the disk at time of evaluation were also excluded from the analyses. Treatment mortality datawere corrected for check mortality with Abbott's formula.Translaminar activity of Agri-Mek.The residual activity pattern for the application timings were analyzed separately. For bothapplication timings there is a prominent significant effect of leaf surface sprayed and leaf surfacebioassayed. Only where TSM was exposed to Agri-Mek sprayed on the bottom leaf surface was thereany significant residual activity. This study indicates that Agri-Mek is mainly absorbed through thebottom side of apple leaves' and that residues of Agri-Mek on apple leaves are primarily effective to mitesand insects feeding on the bottom leaf surface.The reasons for what is apparently better absorption through the lower surface is not yet clear.Some factors that may influence rate or total amount of absorption include: 1) greater pubescence on thelower leaf surface,which increases the effective amountof surfacearea to which the materialmay adhere;2) slower evaporation and/or photodegradation of the material due to sheltering from sun and wind; and3) greater amount of stomates through which there may be preferential penetration of material.54g 100(0oc0)o0)Q."Oa>"5fcoOCO*3O.a<1993 Agri-Mek Translaminar StudyApplication Date: 2 July14 21 28Residue Age (days)Fig. 1 The translaminaractivity ofAgri-Mek inapple foliageas determined byTwospotted spider mitemortality.*£> Residue on bottom.Mites on bottomo Residue on bottom.Mites on top-&- Residue on top.Mites on bottom-s- Residue on top.Mites on top1993 Agri-Mek Translaminar StudyApplication Date: 13 August14 21Residue Age (days)Fig. 2 The translaminar activity ofAgri-Mek inapple foliageas determined byTwospotted spider mitemortality.-O- Residue on bottom.Mites on bottom—O- Residue on bottom.Mites on top—£r- Residue on top.Mites on bottom-B- Residue on top.Mites on top

The translaminar activity of Agri-Mek in apple foliage as determined by twospotted spider mite mortality

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The translaminar activity of Agri-Mek in apple foliage as determined by twospotted spider mite mortality

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