small black caterpillar with yellow stripes curled in leaf

The final generation of the season overwinters in the ground in the form of pupae, becoming adult sawflies in the early to late spring, depending on the species, and starting a new generation. In mild climates, there is sometimes even a third generation in the fall, but so insignificant it usually goes unnoticed. pusilla) follows this with a second one in summer, although only the spring infestation is very visible. Most species have one generation per year, but the birch leafminer ( F.

The larvae drop to the ground after a few weeks of feeding and become pupae. In extreme cases, the entire tree seems to turn an unhealthy bronze color. There may have more than one larva per leaf, in which case it may turn completely brown. Photo: Later, after the larva has left the leaf, the patches turn brown and then become much more visible. Only in severe cases does the tree turn entirely brown. If you hold the leaf up in front of a light at this point, you can see the larva, like a small white or translucent caterpillar, inside the leaf along with numerous black spots (its excrements). Photo: At first, the damage is barely noticeable, at least from a distance, as the leaf remains green, but up close you can see small pale green or gray patches. If you peel open the leave, you can see the larvae and their frass (excrements) inside the leaf. The adult lays eggs under or inside the leaf and the larvae penetrate it, feeding on tissue from the inside of the leaf. All the adults are female, as the birch leafminers are parthenogenic (reproduce without fecundation). But they’re not really flies either, but rather hymenoptera, four-winged insects, therefore closer relatives of bees and ants than to flies which, being diptera, have only two wings.Īlthough their timing varies, the different leafminer species follow the same pattern.

They’re not real caterpillars (which are the larvae of moths and butterflies), but rather the young of sawflies, very small, inconspicuous and rarely noticed black flylike insects. There are several species that affect birches, the most common of which are the birch leafminer ( Fenusa pusilla) and the amber-marked birch leafminer ( Profenusa thomsoni), both of European origin, but now well established in North America as pests. What can I to do to prevent them?Īnswer: The larvae you see are leafminers.

Photo: Question: My birch tree is being attacked by tiny caterpillars that live inside the leaf.

Small black caterpillar with yellow stripes curled in leaf