studies on the effect of some plant extracts mixed with detergent against cotton whitefly, bemisia tabaci gennadius (homoptera: aleyrodidae)

abstract in recent decades the use of environmentally friendly biological and non-chemical materials for the control of plant pests has found good position. due to this reason the effect of some plant extracts (kernel extract of azadirachta indica with 1:12.5, fruit extract of chinaberry, fruit extract of iranian lilac and leaf extract of chinaberry with 1:3 with water), cotton seed oil and neem oil at the rate of 3.4 and 2.7 li/ha, respectively, and half a kg/ha detergent, amitraz20% ec, 2li/ha and control, were evaluated against bemisia tabaci, in a r.b.d. with four replications. observations on pest population were done 3, 5, 7, 10 and 15 days after spraying. from each plot (central row) 10 leaves were selected randomly. population of nymph was then counted in laboratory. the result showed that there were significant differences among treatments. in 3, 5, 7, 10 and 15 days after spraying the best result (excluding amitraz) was obtained by riped fruit of chinaberry with 74.62%, neem oil with 77.50 & 80.97%, cotton seed oil with 76.47 & 66.65% reduction of pest population, respectively. the second year results showed that in 3 and 5 days after spraying, the best result (81.93 & 82.47% reduction) was obtained by using amitraz, respectively. next to amitraz, fruit extract of chinaberry with 67.15 and 70.00% reduction, respectively was placed in second position. in 7 & 10 days after spraying excluding amitraz, cotton seed oil with 77.85 and 71.87% reduction was placed in first position and fruit extract of chinberry with 76.27 and 70.80% reduction was placed in second position. in 15 days after spraying, amitraz with 71.27% achieved highest performance and fruit extract of chinaberry with 69.97% reduction was placed in second position. the comparison of two year results showed that, in second year the percent reduction was somewhat lower than the first year, which may be due to effect of certain ecological factors.