The present work is a trial to study the population density of Spodoptera littoralis (Boisd.) on cowpea, Vignaun guiculata (L.) Walpis plant. Also, to evaluate the effect of some insecticides against the pest under field conditions.Field experiments has been done at Zagazig District, Sharkia Governorate, during the seasons of 2015 and 2016.With the completion of the work, egg-masses and larval stages were fluctuated in the mean number. On other word, population density was higher with appreciable rate in 2015 than 2016with mean number of 10 egg-mass, 366l arva/sample and 7.75egg-mass, 279.16larva /sample in both seasons, respectively.
The population density of S. littoralis larvae on cowpea plants differed in the two seasons and appeared highly average number644 larva/sample inthe first season and536larva/sample in the second season. In conclusion, certain points can be deduced from this work. The patterns observed during and after treatment with different regimes were:
1-Two peaks in the first season,and three in the second for larval population of S. littoralis
2-Population of S. littoralis larvae differs during the growing stages of cowpeaplant.
3-The infestation percent was highly in flowering and reproductive stages(73.33%)in season2015 while it recorded 88.0% in 2016 in the vegetative stage. Regarding to the efficacy of treated insecticides on S. littoralis data revealed that Match had the potential reduction on the larvae in the two seasonsrecording 88.67% initial effect and the residual was 92.44% .Reduction values were somewhat low at the onset of treatment, but starting from 5days to rose up sequentially till the end period. The poorly effect was recorded in the case of the carbamate Methomate.
100 REHAB ABD ALLAH et al.
Fortunately, the latent effects of the tested compounds are seem to be promising in regard to the rate of reduction of S. littoralis.
Conclusively, the acquaintance of the number of generations of S. littoralis infesting cowpea plants can help in implementation of an integrated pest management program against that pest.