Study the Biology and Thermal Requirements of Pectinophora gossypiella (Saunders), Infestated Cotton Bolls var Giza 90, Under Natural Conditions.

Abstract

The Egyptian cotton variety Giza 90 was planted in a wire green house (4 sides and rough of wire 0.1mm mesh) and the recommended agronomic practices were followed during 2013 and 2014 cotton seasons. The cotton bolls 20-25 days of age were tagged and artificially infected with newly hatched larvae of Pink Bollworm (PBW), Pectinophora gossypiella and followed daily during cotton season as well as during late season. The present results revealed that the PBW ability infestation% (= infestation severity) and infestation % are affected significantly by ambient temperature °C and relative humidity (R.H. %) at the first half hour of infestation at the infestation date. Also, PBW larval instars were photographed inside the cotton bolls samples as well as determination thermal requirements of all PBW stages under the natural conditions In addition, present results recorded the average of head capsule width for the four instars of larvae. It ranged between (0.17±0.002 mm) to (1.30±0.23 mm) for the first and fourth larval instars, respectively. Statistical analysis proved significant negative correlation between temperature and all instars duration (r = - 0.77576, - 0.89575, - 0.99905 and - 0.98433) .In contrary there was significant positive correlation between temperature and rate development of all instars (r = 0.96, 0.94, 0.98 and 0.94) for (the first, second, third and fourth instars, respectively). Also, PBW heat unites requirements for larval instars and total larval stage under natural fluctuated temperature was estimated according to Campbell and Mackaure (1975). The developmental zero (to) for successive instars recorded (15.17&15.12&15.11and 15.5), °C respectively. While it recorded 15.22 °C for the larval stage under field conditions. Furthermore, development rates, durations as well as thermal requirements of larvae, pupae, pre-oviposition, and incubation period under field conditions were evaluated according to (Zalom1983). DD, s values for the respective stages were (149- 153), (238.5-248.7), (44.6-56.7) and (54.6-73). The emergence of adult moths (91%) took place after 22 - 23 days from the egg hatchability, with the sex ratio (1.5♀: 1♂). The pre-oviposition period and the incubation period of eggs on cotton Varity Giza 90 recorded (3 - 4 days) & (4 - 5 days), respectively, during cotton season. General results showed that one generation of PBW recorded 30-31 days with 485-502 DD, s through period from 20th July to 3rd September 2014.