Sugarbeet Root Aphid Control in Southern Minnesota, 1991

Abstract

Abstract Performance of granular insecticides and granular plus liquid insecticide combinations applied before and after artificial infestation of SRA were evaluated in small plot trials at Rosemount, MN. 'Betaseed 2249' sugarbeets were planted on 21 May. Each treatment consisted of 4 50-ft rows on 22-inch centers; plants were not thinned. Treatments were arranged in a randomized complete block design with 4 replications; 1 untreated row bordered treatments on either side. Pre-infestation treatments were applied on 17 Jul. Granular insecticides were applied using a Noble applicator in a 7-inch band at the base of both sides of the plants. Liquid insecticides were applied in a directed spray at the base of plants using a CO2 backpack sprayer delivering 27 gal/acre. Plots were infested on 18 Jul by randomly planting 3, 4-wk-old SRA infested sugarbeet seedlings (x = 127.2 aphids/plant) in the center 2 rows of each treatment, as well as distributing about 200 nymphal and adult SRA by hand at the bases of plants in the same rows. Post-infestation insecticides were applied on 24 Jul with follow-up liquid insecticide applications on 14 Aug and 10 Sep. Both granular and liquid insecticides were applied in the same manner as pre-infestation treatments. All rows were cultivated about 4 d following the first post-infestation treatments. Four, 5-row-ft samples were taken from each replication (16/treatment) on 15 Oct. Percentage of beets infested was recorded and each beet was rated for level of infestation on a scale from 0 to 5: 0°uninfested beet; 1°colony diam <1 inch; 2°1 or more colonies diam < 1 inch; 3°colonies diam >1 inch covering <50% of the root surface; 4°colonies covering 50-90% of the root surface; 5°colonies covering 90-100% of the root surface. For any 5-row-ft sample with infested beets, 29 fl oz soil samples were also taken at random within the sample area to compare aphid densities.