Persistence of a nucleopolyhedrovirus on plant surfaces

A critical factor in the effectiveness of insect viruses as microbial control agents is their short persistence on leaf surfaces. The reduction of infective virus on a leaf surface is largely due to virus inactivation. The purpose of this study was to assess the effect of host plant on the persistence of the Helicoverpa zea single-nucleocapsid nucleopolyhedrovirus (SNPV). Small field tests were conducted on six host plants. Virus was applied at application rates of 1.2 X 10¹¹, 2.4 X 10¹¹, and 8.1 X 10¹¹ occlusion bodies (OB's) /acre with each of the virus treatments and the untreated control replicated four times. Virus activity was measured using six d old H. virescens larvae at 0, 1, 3, 5, and 7 d post application. All virus treatments were equally effective at the 0 d sampling date. Virus persistence varied depending on the host plant. Virus inactivation was rapid on cotton, whereas inactivation of H. zea SNPV on the remaining host plants was not as rapid.