عنوان مقاله [English]
Background and Objectives
The two-spotted spider mite, Tetranychus urticae Koch is one of the most important pests of soybean fields. This mite is one of the most important and harmful pests of soybeans in hot and dry summers, which often begins to cause damage at the end of the growing stage and the beginning of the reproductive stage of plants. Damaged leaves turn yellow and brown and fall off prematurely. The severity of the damage of this pest is greater when the distance between the plants is short and irrigation is not enough. This mite feed on soybean leaves and cause injury by sucking contents out of leaf cells. In severe infestations, infested leaves will turn yellow to tan, or sometimes bronze-colored, and may drop off plants. Infestations can reduce yield. In most cases, the use of acaricides is the only way to control this pest. The use of new acaricides while avoiding their resistance is important for plant mites control.
Materials and Methods
The present study was conducted in soybean fields of Golestan and Ardabil provinces (Moghan) with 6 treatments and 4 replicates. Treatments were, including clorfenapyr (Payton®) 36% SC 0.5 ml/L (recommended dose), clorfenapyr (Payton®) 36% SC 0.4 ml/L, propargite (Omite®) 57% EC 1 ml/L (recommended dose), bromopropylate (Neuron®) 25% EC 1 ml/L (recommended dose), hexythiazox (Nissorun®) 10%EC 0.75 ml/L (recommended dose) and a control treatment by spraying water. Mean number of mites per leaf was counted one day before and 3, 7, 14, 21 and 28 days after spraying in three floors of plant (bottom, middle and top of plant).The percentage of efficiency was calculated by the Henderson-Tilton method. Statistical analyses were done using SAS software with randomized complete block design in multiple spaces. Data analysis and comparison of means were performed using Tukey test.
The efficacy of studied acaricides was acceptable in all three floors. In Moghan and Glostan province, before spraying on the lower, middle and upper leaves of soybean plants, the number of T. urticae mites counted per leaf in different treatments did not differ significantly. Clorfenapyr (Payton®) was effective after 3 days. The percent mortality of mites when were treated with clorfenapyr (0.5 ml/L) in the upper, lower and middle floors was 83-86% in Ardabil province, although has been reported 72-84% for Payton (0.4 ml/L). While in Golestan province, it has been 100%. The efficacy of the compound was 68-72% (0.4 ml/L) and 78-94% (0.5 ml/L) in Ardabil province (Moghan) and was 100% in Golestan province after 7 days. The knock down effect of this acaricide compared the others was significant. The efficacy of the compound was up to 99% (Ardabil province) and 96% Golestan province after 28 days that indicated the persistence of these acaricides. The results showed that two-spotted spider mite on the lower leaves in both provinces showed more infection. However when used pesticides, it did not show any significant differences. The percentage mortality of mites in Moghan were reported for Payton (0.4 ml/L) (86.32 ± 2.75%, 83.61 ±7.21%), (78.49 ± 4.01%, 82.87 ± 4.58%), (93.52 ± 1.47%, 74.80 ± 9.91%), (95.12 ± 3.90%, 80.39 ± 3.54%) and (99.33 ± 0.67%, 84.82 ± 8.29%) respectively after 3, 7, 14, 21 and 28 days in lower leaves, while the percentage mortality of the spider mites when treated with Payton (0.5 ml/L) after 3, 7, 14, 21 and 28 days were 100 ± 0%, 100 ± 0 %, 94.94 ± 5.05%, 100 ± 0% and 93.95 ± 4.72% and for Payton (0.5 ml/L) were 100 ± 0%, 100 ± 0%, 88.80 ± 8.57%, 95.02 ± 2.87% and 85.51± 4.92% in lower leaves in Glostan province.
It is recommended to use chlorfenapyr acaricide with Payton brand due to high short-term effect (three days after spraying) and duration of action up to 28 days after spraying to control two-spotted spider mite in soybean fields. These compounds showed acceptable efficacy in controlling two-spotted sider mites on soybean fields. In most cases, the application of the two concentrations of the clorfenapyr was not significantly different, but the percent mortality was more when it treated with 0.4 ml/L. The number mites in lower floors of soybean was more than the upper and middle floors, but after the application of this pesticides was not significantly different. Based on these results, we recommend the 0.4 ml/L dose of clorfenapyr (Payton®) for the control of two-spotted spider mite in soybean fields.