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Sequential Sampling for Barley Thrips Economic Thresholds
Barley thrips are small dark brown to black insects that can cause economic yield losses in barley. Occasionally there are reports of thrips in durum. Thrips emerge from overwintering sites in late May and early June. Early seeded barley is the preferred host for thrips.
Sequential Sampling
Scouting for thrips should begin prior to heading. The field should be divided into nine equal sections and one stem sampled from each section. The total number of adult thrips from the top two leaf sheaths of each of the nine stems should be recorded. If the total number of thrips is very high or very low, a decision regarding insecticide application can be made. This sampling system is based upon "stop lines" which are the numbers of thrips that indicate whether an application is definitely needed, definitely not needed or questionable. Stop lines reflect the price of barley, cost of control and the amount of crop loss due to thrips. Do not confine counts to field margins where thrips populations are likely to be highest. To examine a plant, carefully peel down the upper leaf sheath, and count the number of dark colored thrips (about the size of a dotted i) under the leaf, and on the stem and developing head. For further information on sampling for barley thrips, see the extension publication entitled, "Biology and Management of Barley Thrips." Once the crop heads the insect's damage is done and no treatment is advised. Registered insecticides for barley thrips control are ethyl or methyl parathion at 4-6 oz. of active ingredient per acre.
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