Potential of Nuclear Polyhedrosis Virus (NPV) and Bacillus thuringiensis (Bt) for Spodoptera Control in Yellow Granex Onions (Microbial Control of Spodoptera in Onions)
Penn State University
AVRDC, UPLB, PhilRice
Field trials in Bongabon, Nueva Ecija have shown that NPV, Bt, and NPV+Bt are more effective against Spodoptera larvae, than Karate insecticide application. Larval counts were significantly lower in the microbial treatments than the control or Karate treatment later in the season. Onion yields in the Bt+NPV- treated and the Karate-treated plots were significantly higher than in the control (no insecticide) plots, although the differences between them were not significant. The lowest yields were observed in control plots. These results show that microbials, alone or in combination, are effective alternatives to insecticide application, confirming their positive potential for Spodoptera management.
Onion yields among the treatments in San Jose, Nueva Ecija also had the same trend. Onion yields were significantly higher in NPV+Bt-treated plots than in NPV- and Karate treated plots, respectively. However, the cutworm larval densities were too low to demonstrate the effects of the treatments on them and on onion yields.
The degree of onion leaf damage caused by larvae was relatively higher in the Demonstration farm in Bongabon than in the farmer’s field in Palestina, San Jose, Nueva Ecija, which could be attributed to late planting. Onion yields from both sites differed considerably owing to rice hull burning, which could have reduced soil-borne diseases and nematodes, the timing of planting, the planting density, and the soil type.