تعيين بهترين زمان مبارزه با پوره هاي ملخ كوهان دار تاغ DERICORYS ALBIDULA با استفاده از تركيبهاي هورموني IGRS( )

Optimal timing for IGRs application against Dericorys albidula nymphs.

Dericorys albidula is one of the most important pests of saxaul trees (Haloxylon spp.) in major saxaul plantation areas of Iran, in particular Isfahan, Semnan, Tehran and Khorasan provinces. Because of regular outbreak of this pest, control measures are carried out annually using phosphorus insecticides, specially fenitrothion. In order to optimize timing of chemical applications, a field test was conducted in 1996 to 1997 in a randomized complete block designs with 3 treatments and 3 replications in saxaul plantations of Ardestan. Treatments include 2 formulations of diflubenzuron 45% (oil based and wettable powder) and nomolt (2.5 1/ha as ULV) and water as control. As nymphs were mobile and move around activity, experiment was performed in. 2x2x2 m cages with an screen iron over saxaul plants treated with chemicals. Twenty five nymphs were released in each cage. The experiment was carried out in two stages: on 2nd and 3rd nymphal stages as first group and 4th and 5th nymphal stages as the second group. Criteria for appraising chemicals include the effect of compounds on nymphal mortality rate for each treatment. Samplings were at 5, 10 and 15 days intervals following treatment application and the number of dead nymphs was recorded. Duncan test was conducted to compare average values. Based on the results, mortality rate in the first group for treatments of Oil-Dimilin, Nomolt and Powder-Dimilin at 15 days after operation were 73, 61 and 23 percent respectively. The mortality for the second group were 56, 44 and 23 percent respectively. There was significant differences (1%) between treatments and Oil-Dimilin which caused the highest mortality. Powder Dimilin showed the least mortality on 2 and 3 as well as 4 and 5 instars nymphs.