Lower threshold temperature and thermal unit of American bollworm, Helicoverpa Armigera (Hubner)‎ reared on pea and lettuce and its rearing on a new modified artificial diets

Abstract EN

The present work was conducted to study the relationship between developmental stages of the cotton bollworm, Helicoverpa armigera (Hübner) (ABW) reared in the laboratory on pea and lettuce and the required thermal units (DD's ) at constant temperatures, ٢٣, ٢٧ and ٣٠°C ± ١°C.

Also, to evaluate the use of two new modified artificial diets (A and B) for mass rearing of ABW and compared with natural food (lettuce).

Diets A and B contained dried active yeast, ascorbic acid, sorbic acid, methyl parahydroxy benzoate, liquid milk, vitamin mixture and formaldehyde ٣٤ - ٣٨%.

In addition to the essential ingredient, in diet A is kidney beans and wheat grated while, diet B is chickpea and wheat grated.

Results showed that there was variation in developmental periods of the ABW in different stages reared on pea and lettuce.

Temperature increasing led to an increase in the developmental rate and reduce the development periods of the different stages.

The generation period of the ABW reared on lettuce was shorter (٣٢.٢٣ days) than that reared on pea (٣٤.٧٠ days).

The lower developmental temperatures were ١١.٦٠ and ١١.٣٩ °C for the generation and the thermal units required were ٤٦٧.١٣ and ٥١١.٢٦ DD's, respectively.

On the other hand, results showed that highest larval and pupal weight, adult emergence and number of eggs/female (٥٦٠ eggs/female) and lowest larval and pupal mortality percentage of ABW were observed on diet B followed by diet A and lastly natural food (lettuce).

In conclusion, the two new modified artificial diets (A and B) developed in this study has proved to be satisfactory for mass rearing of ABW, Helicoverpa armigera (Hübner).