Apple, Integrated Mite Control Test, 1979

Abstract

Abstract Twenty insecticide and fungicide programs were tested for their compatibility with the biological control of T. urticae by T. occldentalis. A basic spray program was constructed which was varied by the addition, deletion or substitution of a single chemical for each test program. The basic program represented a typical grower spray program, and all chemicals were applied at the times and frequencies at which they are normally used. The whole block received cover sprays of Dodlne A 50W (Sep 26, Oct 11, Nov 8, 23) and Cothion 50W (Oct 26, Nov 10, 20, Dec 11, Jan 4, 31, Feb 21, Mar 22) applied by an M.B.P. Airmist drivepast sprayer at 1250 liters/ha. Treatments, replicated 4 times, were applied to single tree plots in a randomized, complete block design. Sprays were applied by handgun to run-off at lx concentration using a Bean sprayer with a 160-Iiter/min pump. About 16 liter/tree was used. Buffer trees surrounded each study tree and, except for the cover sprays, were not sprayed during the trial. The basic spray program consisted of Nimrod 25W (Sep 25, Oct 9, 23, Nov 8), Captan A 83W (Nov 28, Dec 12, 27, Jan 16, Feb 6) and Thiodan 35W (Oct 4, 12) in addition to the cover sprays. In 5 programs Benlate 50W, Sulfaloid 80W, Morocide 50W, Morestan 25W and a no-spray treatment were substituted for the mMdewicide Nimrod 25W and were applied on the same dates as Nimrod. Similarly, Dodine A 50W, Dithane M45 80W, and Zitox 80W were substituted for Captan A 83W. There was also a no-spray control for Thiodan 35W. Single greentip sprays (Sep 12) of Cuprox 50W + superior winter oil and lime sulphur + superior winter oil were added in 2 programs. Three programs compared additions of single sprays of Kilval 40W applied in spring (Nov 13) and summer (Jan 24) and Pirimor 50W (Jan 24). In 3 other programs, heavy (19.0 liter/tree) and light (7.3 liter/tree, no run-off) applications of Bugmaster Dimoth 80W were compared with NAA (Shellestone 2% w/v) + Kemotan T20 as thinning applications (Oct 24). A full program of chemicals thought to be least toxic to T. occidentalis was made by adding Cuprox 50W (Sep 12), NAA + Tween 20 (Oct 24) and Pirimor 50W (Feb 2) to the basic program. Control trees received no sprays apart from the cover sprays. The effects of the spray programs were assessed by taking samples of 25 leaves from the inner sections of each study tree below a height of 1.5 m at two-wk intervals throuqhtout the season. An extra sample of only 10 leaves/study tree was taken on Feb 6 when predator numbers peaked. The numbers of active stages of T. urticae and T. occidentalis were counted on each leaf using a dissecting stereomicroscope.