Abstract
The present work was conducted to study the relationship between developmental stages of the spiny bollworm, Earias insulana (Boisd.) and required thermal units at constant temperatures, 20, 25 and 30°C ± 1°C in Sharkia and Kafr El-Sheikh Governorates, in Delta, Egypt. Results showed that there was variation in developmental periods of the spiny bollworm in different stages at the two Governorates. Increasing in the temperature led to an increase in the developmental rate and reduce the development periods of the different stages. The generation period of the spiny bollworm collected from Sharkia was shorter than that collected from Kafr El-Sheikh. The lower thermal threshold differed from Governorate to another for the different development stages of the spiny bollworm. The averages of generation period of the spiny bollworm collected from the two Governorates were 35.46 and 36.68 days, respectively. In Sharkia and Kafr El-Sheikh Governorates, the lower developmental temperatures were 12.26 and 11.82 °C for the generation and the thermal units required were 402.94 and 434.73 units, respectively. This means that the difference in developmental periods of generation between the two Governorates must be taken into consideration during application of control measures against this pest.
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