SUSCEPTIBILITY OF FOUR SOYBEAN VARIETIES TO INFESTATION WITH SOME SUCKING PESTS AND COTTON LEAFWORM AND THE EFFECT OF MAIN WEATHER FACTORS ON INFESTATION

The population of six pests (cotton leaiworm Spodopiere iiiioraiis (Bosid),
whitefly Bemisia tabacr‘, cotton aphid Aphis gossypr’i, jassids Empoasca iypica and
spider mite Tetranychus urtica) infesting soybean varieties (Giza 21, G. 22, G. 35 and
G. 111) was investigated during 2003 and 2004 seasons.
The results obtained revealed the following indications.
1.There were significant differences between the four soybean varieties in case of
whitefly (adult and immature) population in two growing seasons and the highest
mean numbers of white fly were recorded with Giza 21 and Giza 111 varieties in
two seasons.
2. One peak was recorded with all soybean varieties in the two growing seasons in
case of cotton leafworm (larvae) and the highest number was recorded on Giza 22
variety.
3. There were significant differences among all soybean varieties (G. 21, G. 22, G. 35,
and G. 111) in case of Aphis gossypr'r‘ in two seasons and the highest mean number
of aphids was 341.79 insects“ 00 plant/week with Giza 35.
4. The population of jassids on soybean was considerably low during the two ses..cr.s
and the pest started to appear on soybean during June and reached its maximum
during the 1“ of September.
5. in case of Tetranychus urticae, significant differences were recorded among all
soybean varieties in the two seasons and the highest mean numbers were 305.43
pestsi400 leaves with Giza 35 in 2003 season and 485.92 with Giza 111 in 2004
season.
6. The effect of the prevailing weather factors (Max. and Min. temperatures, relative
humidity and wind speed on the infestation degree of soybean varieties with these
insects revealed that there were insignificant correlation values except some factors
on some soybean varieties.