Insecticidal and nematicidal properties of microbial metabolites

Metabolites from 942 microbial isolates were screened for insecticidal and nematicidal properties. The isolates included 302 streptomycetes, 502 'novel' actinomycetes including representatives of 18 genera, 28 unidentified aerobic actinomycetes, 70 fungi and 40 bacteria other than actinomycetes. When diluted 10-fold, the metabolites from 55 isolates caused nearly 100% mortality in mosquito larvae (Aedes aegypti) within 24 h. These isolates included 27 isolates of Streptomyces, four of Actinoplanes, three isolates each of Actinomadura and Streptoverticillium, two isolates each of Micromonospora, Bacillus and Paecilomyces, and one isolate each of Micropolyspora, Nocardiopsis, Streptosporangium, Oerskovia, Thermomonospora, Chainia, Pseudomonas, Fusarium, Monilia and Syncephalestrum. Two fungal isolates could not be identified to the generie level. Extracts from the culture broth of 18 isolates caused 100% mortality in mosquito larvae within 15 min to 24 h at a concentration of 1000 ppm. The LC₅₀ of partially purified products from two isolates was 1-2.5 ppm and that of the semipurified preparations from four other isolates was ≤50 ppm. Valinomycin was identified as an active component in the culture broth from one isolate. The culture broth from 15 isolates of aerobic actinomycetes and 4 of fungi were toxic to Panagrellus redivivus (Nematoda); these included 12 isolates with selective nematicidal properties.