Natural Enemies of Certain Insect Pests Attacking Sugar Beet Plants at Kafr El-Sheikh Governorate

For two successive seasons; 2015/16 and 2016/17, the current study was undertaken at Sidi Salem District, Kafr El-Sheikh Governorate to monitor population fluctuation of the most important insect pests attacking the early (August) plantation of sugar beet and their associated predators. Also, the parasitoids of major sugar beet insects were investigated in the late (October) plantation. In 2015/16 season, the population density of Spodoptera littoralis was relatively high, especially during September and October, the average number in September was 12.4 larvae/25 sugar beet plants, that increased to 15.5 larvae in October. As for aphids, the highest monthly average occurred  in October with 18.5 nymphs and adults/25 sugar beet plants, followed by 11.0 individuals in November. Regarding to Empoasca lybica, the insect pest was found all the season round, with the highest occurrence in November. Seasonal means  of S. littoralis, Aphis spp. and E. lybica were 5.28 + 2.79 & 7.47+ 5.40,  9.02 + 2.43 & 26.55 + 6.17 and 18.07 + 4.42 & 20.05+ 3.45 individuals/25 sugar beet plants in the first and second seasons, respetively The most occurring predators were coccinellids, Paederus alfierii and Chrysoperla carnea. Their seasonal means were 5.20 + 1.33 & 14.82+ 5.13,  1.17 + 0.40 & 1.60 + 0.56 and 2.45 + 0.50 & 4.58+ 1.00 in the first and second seasons, respectively. Three parasitoids were recorded attacking major sugar beet insects. Cassida vittata eggs were parasitized by Monorthocheata  nigra (Trichgrammatidae) and larvae-pupae were parastized by Aprostocetus sp (Eulophidae). Pegomyia mixta larvae were parasitized by Opius nitidulator (Braconidae), and larvae of Scrobipalpa ocellatella were parasitized by Diadegma sp (Ichneumonidae). Seasonal means were 6.97 + 2.80 & 8.46 + 3.35 for Monorthocheata  nigra,  5.69 + 1.94 & 6.61 + 2.17 for Aprostocetus sp, 8.87 + 3.17 & 7.76+ 1.94 for  Opius nitidulator and 9.37 + 3.52 & 11.15+ 3.68 for Diadegma sp in the first and second seasons, respectively.