Effect of storage of host egg on parasitism of Trichogramma spp.

Abstract

Trichogramma spp. is one of the most common natural enemies used in the world against many lepidopterous pests. Improving storage of host egg technique for parasitoid production is important for biological control program to supply sufficient parasitoid at the time of release. The objective of this research is to evaluate the suitable storage conditions of rice moth eggs, Corcyra cephalonica (Stainton) for the following 4 packaging treatments: (T1) eggs wrapped under 2 layers of tissue paper, placed in a plastic box with cover, then put in a zipper storage bag, (T2) eggs wrapped under 2 layers of tissue paper then put in a zipper bag, (T3) eggs wrapped under 2 layers of aluminum foils, placed in a plastic box with cover, then put in a zipper bag; and (T4) eggs wrapped under 2 layers of aluminum foils then put in a zipper bag, stored at temperatures: 3±1^oC, 8±1^oC and 12±1^oC for durations of 1 - 9 weeks. The results showed that the temperature and the storage packaging methods affected the reduction of the eggs’ weight since the first week of the storage. The most egg weight reduction in all treatments were found in 8±1^oC and 12±1oC with statistical different to 3±1^oC. The least reduction at 3±1oC was found in T4 (with 1.90 mg.) followed by T3 (3.48 mg.), T2 (4 mg.) and T1 (7.50 mg), respectively. The egg weight deceased further more as the storage period increased. The parasitoid parasitized more than 80% of eggs stored for 1 week from 4 treatments at temperature 8±1oC and 12±1^oC, of which both T1 and T2 showed the same result for 2 week storage. The least parasitism percentage was from the eggs stored at temperature 3±1^oC. The adult emergence was more than 80% for the storage at temperature 12±1^oC for 1-6 weeks.