Submitted to: Society of Invertebrate Pathology
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 1997
Publication Date: N/A
Heliothis armigera GV (HaGV) capsular proteins have been shown previously to enhance H. armigera NPV (HaNPV) infection of H. armigera larvae. In the current study, 100 ul of HaGV [stock = 4-fold dilution series (1:20 to 1:81,920) of 10 g infected Lymantria dispar cadavers per 100 ml water] was applied to the diet of Helicoverpa zea first instar larvae during (0 days), and at one-day intervals before (-2 and -1 days) and after (+1, +2, and +3 days) being fed 100 ul HzSNPV (stock = 2 x 10e2 to 2 x 10e7 H. zea-produced OB/ml). HaGV, at all tested dilutions, increased the LT50 of HzSNPV when applied at 10e3 OB/ml; 1:1280 diluted HaGV increased the LT50 of 10e7 OB/ml HzSNPV treated larvae. HaGV applied at -2 to +1 days (the data suggests greater than +1 days) within application of HzSNPV interfered with HzSNPV infection; e.g., 1:320 diluted HaGV interfered with HzSNPV applied at 10e6 OB/ml. Interference was concentration dependent. Based on symptomatology,larvae that escaped early lethal infection by HzSNPV died later of HaGV infection. HaGV can therefore interfere with the progress of HzSNPV caused mortality, even after HzSNPV has had one (or more) day(s) to infect and become established in midgut cells. These results suggest that, in contrast to enhancement effects (which have been postulated by others to be mediated through enhancin action on the peritrophic membrane or midgut epithelium), HaGV interference is mediated by a different mechanism.