Control of Tuliptree Aphids with a Systemic Insecticide, 1993

Abstract

Abstract Treatments were applied on 18 Mar to individual tree replicates for street trees grouped in a RCBD (5 replicates) by proximity and caliper in Claremont, CA. Leaves on the trees had just emerged and were 1 cm across at the time of application. Trees varied from 18 to 56 cm diam at breast-height (DBH). Two application methods were used, in each method 0.6 g AI was applied per cm DBH. Granules were poured into 10 cm deep holes spaced in a 1 m grid pattern under the tree’s drip line. The wettable powder was suspended in water (34 g/liter) then 30 ml injected with a Kioritz applicator into the soil per site, with 0.78 injection sites per cm DBH. Most tees were located in residential lawns and received irrigation from lawn watering; 7.7 cm of precipitation also occurred within 11 d following the application. Ten leaves were sampled from the lower canopy of each tree on 16 Aug. Aphids were counted from each sample and the leaves rated individually for honeydew and sooty mold presence. A few specks of honeydew gave a leaf a rating of 1, substantial honeydew and sooty mold gave a leaf a rating of 10. The ratings were then totalled for all leaves sampled from each tree, to give a rating with possible values on a scale from 0-100.