The flies stay around longer than those of the boxwood miner.
They feed for about 10 days, puncturing new leaves, and then lay eggs
for another 10 days. The American holly leaf miner (P. ilicicola) is sometimes present, making narrow, yellow sinuate mines up and down the
leaf. The mines are on the upper leaf surface, but the flies of this species
emerge from the lower side.
Control. DDT is effective, at the same strength as used for the box-
wood miner, applied when new leaves are 3/4 inch long or black flies
first appear. A second application 10 days after the first is advisable.
Because DDT increases southern red mite on holly, Aramite, Ovotran,
or other miticide should be added to the spray. Dieldrin (1 to 2 teaspoons
15% emulsion) is also effective applied in late May.
LOCUST LEAF MINER (Chalepus dorsalis).
Common through eastern states
to Virginia this species often destroys all the foliage of black locust,
turning it an ugly brown, and feeds sometimes on other trees. The female
adult, a small beetle with a black stripe inside its orange wing covers,
lays her eggs in a pile on the leaf, and the little grubs, yellowish with
black heads, burrow from the bottom of the mass into the leaf.
Control. Lead arsenate has given fair control of locust miners in the
past, but lindane or chlordane is now suggested, as for the birch miner.
SPINACH LEAF MINER (Pegomya hyoscyami).
Spinach, beet leaves, and
Swiss chard are often rendered unfit to eat by the conspicuous
blotched mines. Gray, black-haired flies lay eggs on leaves in April and
May. The maggots feed first in a slender winding mine but this is soon
joined to others to form a large blotch. The maggots migrate from leaf to
leaf, and there may be 3 or 4 generations a season.
Control. This is rather difficult because of the danger of poisonous
residue. Destroy lamb's quarter and other weed hosts around the garden.
Plant spinach very early in spring or late in fall. Remove and destroy
mined leaves from beets or chard as soon as noticed.
Many other leaf miners cause prominent injury in the garden. The
lilac leaf miner, like the azalea species, first mines and then rolls leaves.
Chrysanthemum leaf miners bother marguerite and Shasta daisy as
well. The larkspur leaf miner forms tan blotches on delphinium, lark-
spur, and monkshood. Blotch mines are almost always in verbena leaves.