Susceptibility of the obscure mealybug, Pseudococcus viburni (Signoret) (Pseudococcidae), to South African isolates of entomopathogenic nematodes

Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), the obscure mealybug, is a serious pest of apples and pears in South Africa. The potential use of entomopathogenic nematodes (EPNs) against P. viburni was assessed in laboratory bioassays. The results showed Heterorhabditis zealandica (J34) to be most effective, causing 80% mortality of P. viburni 48-h post inoculation at 25 oC. After 48 h, the LD50 and LD90 values were 54 and 336 nematodes, respectively. H. zealandica (J34) and Steinernema yirgalemense successfully reproduced in P. viburni, with H. zealandica (J34) attaining greater penetration ability than did the S. yirgalemense. Mealybug size affected infectivity, with the crawlers being less susceptible (22%) than were the adults and intermediates, with mortalities of 78% and 76%, respectively. H. zealandica (J34) were able to enter the apple core of infested apples, where they infected the P. viburni. This work represents the first report on using EPNs to control P. viburni.