STUDIES ON THE BIOLOGY AND LIFE TABLE OF THE SOFT SCALE INSECT; PULVINARIA TENUIVALVATA ATTACKING SUGAR CANE IN EGYPT (HEMIPTERA: HOMOPTERA: COCCIDAE)

Biology and life table studies were conducted for sugar cane soft scale insect. Pulvinaria tenuivalvata (Newstead) (Hemiptera:Homoptera: Coccidae) reared on sugar cane, Saccharum officinarum L. under labora­tory conditions of 20. 24, 28 and 32 °C and relative humidity of 72±5%. P. tenuivalvata reproduces parthenogenetically due to absence of males in the field and in the laboratory. Duration of different stages de­creased as the temperature increased. Life cycle was recorded as 60 ± 2.11. 42 ± 1.29, 34 ± 1.68 and 30 t 1.82 days at 20, 24.28 and 32 °C. respectively. The highest reproductive rate (1%) occurred at 28°C as 200.64 expected females /female. Intrinsic and finite rates of increase (I:, and exp r_m) were greater as temperature increased, while mean gen­eration time decreased as temperature increased. It was 83.5. 61.0, 51.0 and 45.5 days at 20, 24, 28 and 32 °C. respectively. The popula­tion had a capacity to multiply (Dubling time) every 11.95 days at 20°C and every 6.19 days at 32°C. Zero of development for the different stages was calculated as 4.59 °C for egg, 6.45²C for l^it nymphal instar 9.87 ²C for 2^nd instar and 5.22 ²C for 3^rd instar. The calculated required thermal units were 112.75, 129.73, 212.90 and 280.16 degree-days (DD) for egg, 1^s1, 2^nd and 3'^d nymphal instars, respectively, with 1010.95 units for the whole generation.