BIOLOGICAL ASPECTS AND THERMAL REQUIREMENTS OF THE BIRD CHERRY-OAT APHID, Rhopalosiphum padi (LINNAEUS), REARED ON WHEAT SEEDLINGS

The bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus) was studied at 15, 20 and 25^oC constant temperatures. Wheat seedlings were offered for feeding and maintaining the aphid, R. padi using the Punctured Ependorf Tube Technique. R. padi showed the longest life cycle duration at 15^oC as 12.77±1.71days. This duration decreased to 8.36±0.79 and 6.74±0.56 at 20 and 25^oC, respectively. The fecundity rate was the lowest (35.41 progenies/female) at 25^oC. It was higher at both 15 and 20^oC as 50.2 and 53.429 progenies/female, respectively. The longest life span was recorded at 15^oC as 49.47±16.43days. This duration decreased to 34.05±6.22 and 19.47±4.16 days at 20^oC and 25oC, respectively. The lower developmental threshold (t0) for the R. padi nymphal instars; first, second, third and fourth were 2.216, 6.958, 3.432 and 0.164^oC, respectively. The estimated t0 values for the life-cycle and generation time were 3.537 and 3.976^oC, respectively. The thermal requirements (K) for each nymphal instar; first, second, third and fourth were, life-cycle and generation time were 45.97, 23.43, 30.97, 47.14, 142.56 and 154.15 dgree-days units, respectively.