Prodiplosis morrisi

Prodiplosis morrisi Gagne

A little known leaf roll midge, Prodiplosis morrisi Gagne, is an important pest of Populus species in North America, especially in hybrid poplar plantations and nurseries in southern Canada and in P deltoides in the southern United States. Its larvae feed in the tightly rolled blade tissues of leaves newly emerged from terminal tips of young trees.  The leaf veins and tissues are damaged and the leaf does not unroll and develop normally. Lightly damaged leaves are stunted and have crinkled, distorted margins. With heavy damage, they turn black and drop off the tree. Each midge generation affects 4 or 5 leaves and 5 generations can occur in southern Ontario between June and September. 

Subsequent studies showed the margins of new emerging leaves are naturally rolled laterally and inward to the mid-rib on their upper surface. A viscuous yellowish "balsam" fluid surrounding the terminal bud and new tiny leaves is naturally present in Populus sp. This material fills the leaf tissue rolls and the feeding larvae are surrounded by it. Rather than causing the leaves to roll, the midge larvae prevent the normal unrolling of the leaf blade and its growth into a flat leaf. 

The first larval collections of P morrisi were made near Beaumont, Texas in May 1965 and Stoneville MS in June 1965. The author found typical foliar damage near DC in July 1965. Prior to 1977, the midge was found at Phillipsburg, PA in 1973 and it was reported in southern Ontario in 1973-6. 

A survey of hybrid poplar plantings in June, August, and September, 1977 verified the presence of P morrisi throughout southern Ontario. It was found near Wichita KS in P deltoides in 1977 and in NY in 1979. It was found in hybrid poplars in northern MI in August 1979 and it probably occurs throughout the range of P deltoides. It, or a similar species, was found in P tremuloides in eastern Ontario in 1978-9. More study is needed to determine the complete range of this native insect of poplars. It has not been found in P balsamifera, or in P alba, or P alba x hybrids in Ontario. 

[Morris provides detailed information about methods in rearing experiments and other life history details] 

Prodiplosis Morrisi Gagne, a New Pest of Poplars (Diptera: Cecidomyiidae)