Evaluation of novel pheromone lures against striped flea beetle (Phyllotreta striolata Fab.) on brassicas and bean pod borer (Maruca vitrata Fab.) on yard-long bean in Southeast Asia

Striped flea beetle (Phyllotreta striolata) is an important pest of leafy brassicas in Southeast Asia. Bean pod borer (Maruca vitrata) is the most damaging pest of food legumes in tropical Asia, sub-Saharan Africa, Oceania and South America. Male-borne aggregation pheromones have been identified in P. striolata. Although six male-specific sesquiterpenoid compounds were identified, active component was identified as (+)-(6R,7S)-himachala-9,11-diene. Sex pheromone of M. vitrata consists of (E,E)-10,12-Hexadecadienal, (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal. Two types of aggregation pheromone lures were evaluated against P. striolata on leafy brassicas in Cambodia, Laos, Taiwan, Thailand, and Vietnam during 2015. In Cambodia, Himachala-9,11-diene 0.3 mg attracted significantly higher P. striolata (188 beetles trap(-1)) compared to check (52 beetles trap-1), but the yield of pak-choi (18.45-25.25 t ha(-1)) did not differ significantly. However, none of the lures were attractive for P. striolata in the other four countries. In 2016 trials, none of the lures were attractive in all the five countries. Besides Himachala-9,11-diene, a second compound, (3S,9R,9aS)-3-hydroxy-3,5,5,9-tetramethyl-5,6,7,8,9,9ahexahydro-1H-benzo[7]annulen-2(3H)-one was recently reported. Hence, future blends should contain both these components to enhance the attraction of P. striolata. Four types of blends using the three pheromone compounds were evaluated against M. vitrata on yard-long bean in 2015. None of the blends were attractive to M. vitrata male moths in Laos, Taiwan, Thailand and Vietnam. An improved blend [Z,E-10,12-hexadecadienal; (E,E)-10,12-hexadecadienol; E-10-16OH (100:10:5)+1-Octene-3-ol (50%)] was evaluated in Laos, Taiwan, Thailand and Vietnam during 2016. This pheromone lure was also unattractive to M. vitrata in all countries. Hence, pheromone lures of M. vitrata should be refined for other countries in the region.