by Nanette Londeree, Master Rosarian
SIGNS
Flat egg masses on small stems or branches
A green larva (or caterpillar) ¾ to one inch long with a black head (when young), turning to brown that wriggle vigorously when disturbed and drop to the ground on a silken thread, March through mid-May
A pupa just under 1/2 inch long, light to dark brown, and is usually formed within the rolled leaf; silk webbing lines the area around the pupa
SYMPTOMS
Tender new leaves with a ragged appearance
Leaves that are rolled and tied together with silken threads
Defoliated grass or other plants beneath the plant
CAUSE
Larvae of the fruit-tree leafroller, Archips argyrospila or A. rosanus
OPTIMAL CONDITIONS
Fruit or shade trees in the area
March through May when larvae hatch
Abundant tender new leaves and bud
TREATMENT
Prevention:
Maintain good garden sanitation
Encourage beneficial insects and birds including certain tachinid flies and ichneumonid wasps (main parasites), lacewing and certain beetles, insect eating birds (common predators)
Elimination:
Inspect new foliage and look for feeding injury and the small larvae (caterpillars); trim off and destroy
Spray with Bacillus thuringiensis; thorough spray coverage is required for control and it’s only effective on fruittree leafroller larvae when they are small (less than 1/2 inch long); it usually requires more than one application
Apply sprays only when there is evidence of a damaging leafroller population, such as large numbers of larvae early in the spring or large numbers of egg masses
GOOD GUY / BAD GUY?
A bad guy that can make a mess of your roses, though doesn’t do significant lasting damage
Photos courtesy of Baldo Villegas; from top: fruittree larvae, adult, damage to rose and nest.