Biology of the Swaine Jack-Pine Sawfly in Wisconsin

Abstract

The Swaine jack-pine sawfly, Neodiprion swainei Midd., is a serious defoliator of jack pine in Canada, and has been reported widely in the Lake States. The largest populations in Wisconsin were on plantations and windbreaks. It is host specific and feeds primarily on old foliage. Damage to new foliage is sporadic, usually being heaviest late in the season. When forced to feed on red, eastern white, or Scotch pines the sawfly develops abnormally. It is not a serious threat to these species. In southern Wisconsin, adults emerge during June; eggs are present from mid-June to mid- July; larvae feed during July and August; heaviest feeding damage occurs in late July and early August; late larval populations feed throughout September. Fecundity was 116 ± 17 eggs. Eggs are placed in new needles, and "paired eggs" are characteristic. The distribution pattern of eggs within a single cluster is characterized for long and for short shoots of new growth. Female larvae require five or six feeding instars, males five. Phenological observations are correlated with sawfly development.