Host effects on the development and fecundity of gypsy moth, Lymantria dispar L., reared under field conditions

Abstract

We reared gypsy moth larvae outdoors under natural temperature and photoperiod regimes on red oak (Quercus rubra L.) and sugar maple (Acer saccharum Marsh). Initiation of the experiment coincident with the peak hatch of the local gypsy moth population assured normal synchrony between foliage quality and larval development. Compared with larvae reared on oak foliage, the mortality of maple-fed larvae is greatest and development slowest in the first instar. Overall, the larvae reared on sugar maple have higher mortality, extended development time, lower pupal weights, and lower fecundity relative to larvae reared on red oak. The mean diameter of individual eggs did not differ between oak- and maple-fed larvae, nor was the rate of increase in egg mass weight with female pupal weight host dependent. The egg masses from oak-fed moths hatched more completely than did those from moths reared on maple. In the interaction between these two abundant potential hosts and gypsy moths, the interspecific differences between the hosts are more important than any effects of seasonal asynchrony between larvae and foliar development. Gypsy moth larval success is much greater on red oak, and survival and reproduction on sugar maple under field conditions are likely to be marginal at best.