The lesser apple leaf-folder is a small green “ worm” which folds the leaves of apple and plum stock in nurseries and young orchards. The leaves are folded over flat, the lower surface of the leaf outside and the fold usually along the mid-rib. The “worm” itself is green, about half an inch long, and has a pale yellow head.
The leaf-folders appear three times during the season: First, as soon as the leaves are out on the trees; second, about the middle of June; third, early in August. The folders remain on the trees from four to six weeks before they become mature.
To be effective, spraying must be done when the leaf-folders are very young, or when they are still in the egg stage. The proper times to spray, as determined by the experimental work in this state, are as follow s: First, as soon as the leaves appear; second, the first week in June; third, the first week in August. These dates are for an average season.
Webster, R. L.
"The lesser apple leaf-folder,"
Bulletin: Vol. 9
, Article 1.
Available at: https://lib.dr.iastate.edu/bulletin/vol9/iss102/1