EVALUATION OF POTENCY OF SOME MICROBIAL ISOLATES AS ABIOCONTROL AGENT AGAINST POTATO TUBER MOTH DISEASE IN EGYPT

Abstract

This study was carried out at Giza and Gharbia Governorates during two successive seasons 2001 and 2002 to clarity the strategy of using microbial treatments in controlling Potato Tuber Moth (PTM) under the Egyptian conditions. Isolation and identification of certain local microbial isolates (9 bacteria and 5 fungi) were tested on the infestation level of PTM. Some of these isolates such as B. thuringiensis. S. marcescens., Bea. bassiana and M anisopliae. were highly effective in controlling PTM, it caused high mortality which reached 86.97 %, 93.3 %, 86,67% and 100 %, respectively. Dox medium was more suitable medium for fungal isolates, where it gave the highest growth diameter 4.62 and 4.48 cm for Bea. bassiana and M anisopliae, respectively. The optimum temperature for B. thuringiensis. Bea. bassiana M anisopliae was 27 •c, but for S. marcescens was 30 •c . While optimum pH was 7.2 for B. thuringiensis and S. marcescens, whereas the optimum pH was 5.5 and 6 for Bea. bassiana and M anisopliae. Glucose and yeast extract were more suitable carbon source for B. thuringiensis., S. marcescens., while sucrose was the best carbon source for Bea. bassiana and M anisopliae. Peptone proved to be the best nitrogen source for B. thuringiensis and S. marcescens, while sodium nitrate was favorable for Bea. bassiana and M anisopliae The optimum RH was 95 %for fungal isolates at 14 days from incubation period. The mixtures of bacteria and fungi with the rate of 1 bacteria : 3 fungi were more effective on PTM stages which recorded the lowest pupation percent, adult emergence, adult longevity and hatchability, and highest larval mortality and pupal duration . Draga variety was more susceptible than Cara variety under lab and field conditions. The results recorded that the highest infestation level in summer plantation ranged from 64.0- 96.8 % and 52.0 - 78.0 %during two seasons at Giza and Gharbia Governorates, while winter plantation recorded the lowest infestation level ranged to 13- 39 % and 14 - 42 % on two potato varieties during two seasons at both Governorates. Evaluation of microbial treatments for biocontrol of PTM individually or in double combination revealed that the infestation level reduced by increasing the number of sprays. While, yield of potato production increased by increasing the number of sprays under greenhouse and field conditions. Combined application of two bioagents resulted in better suppression of PTM than single treatment, the most effective mixture was 1 S. marcescens: 3M. anisopliae.