The effect of cultivating cotton surrounded by maize plants (A), successive applications of 10% sucrose solution (B), the recommended insecticides (C) and cotton only (0) (under two nitrogen fertility levels, 200 and 100 kg ammonium nitrate/fed.) were investigated during 1998 cotton season. The numbers of insect predators and rates of infestation caused by thrips, aphids, cotton leafworm and bollworms were estimated weekly in treatments A. B, C, D. and cotton only without N-fertilization. Cotton yield was also weighed.
Fifteen predacious species were recorded. of which Rodalia cardinalis (Muls.) was found in Moshtohor cotton fields, which could be considered the first record in cotton fields in Egypt.
Cotton-maize plants harboured significantly highest numbers of insect predators (total 4-l6 & 434 individuals/IS plants, under 200 & 100 kg Nzfed, respectively) followed by cotton that received sprays of sucrose solution (370 & 356), cotton only (0) (298 & 264), cotton only (unfertilized) (257 individuals) and lastly cotton treated with the recommended insecticides (total 256 & 242 per IS plants). Insecticidal treatment. clearly, caused drastic effect on predators numbers. while cotton surrounded by maize or cotton treated with 10% sucrose solution attracted. significantly higher numbers of predators compared to the other treatments.
The least numbers of cotton thrips and aphids occurred on cotton plants treated with the insecticide" Azodrin", while higher numbers occurred in cotton areas of the other treatments. Pests increase in numbers may be attributed to the inactive role of predators on cotton plants at that time.
The reduction in the cotton leafworm and bollworms infestations and increase in the obtained cotton yield occurred in cotton plantations surrounded by maize plants, treated with sucrose solution and those received the chemical insecticides, while the highest rate of infestation that decreased yield occurred in
|
