Many of these pests / diseases are making their way around again. Be sure to monitor your plants, as many of these issues are easily dealt with in the early stages.
Larvae can be effectively controlled with a neem oil product or an insecticidal soap. Spray only the leaves (both sides), in the morning as neem oil can possibility hurt pollinators (More research needs to go into that). The strategy is to find larvae while they are still small and before damage becomes severe, like our roses! There is no need for control after the larvae have finished eating and left the plants, give or take mid-July.
One last note, these are not caterpillars, they are actually primitive wasps, so Bt or Bacillus thuringiensis will not work.
Oak wilt is confused with other problems such as drought, construction stress, borers, and root problems.
- More noticeable during late summer
- Regular size leaves, little wilting
- Leaves browning evenly
- Leaves remain on the tree after discoloring
- Dying trees scattered throughout stand
- More common on stressed sites
- Signs of borers or root disease
Oak Wilt symptoms:
- More noticeable during early summer
- Small leaves, thin crown, wilting
- Edges and tips of leaves bronzing first
- Leaves drop soon after discoloring
- Dying trees found in groups (root grafts)
- Streaking and discoloration of vascular tissues
The DED fungus is spread by two insect vectors: the native elm bark beetle (Hylurgopinus rufipes) and the European elm bark beetle (Scolytus multistriatus). The fungus is transported on the beetles from infected trees to healthy trees as they feed on twigs and upper branches. The beetles lay their eggs in the bark and wood of stressed trees along with elm firewood with the bark left on. Developing larvae form channels just under the bark and the fungus grows through the galleries until it reaches the tree’s water conducting cells, or xylem. Chemicals manufactured by the tree during its effort to fight the disease plug up the xylem, causing the tree to wilt. In the Midwest, beetles typically have two generations per year.
The four-lined plant bug (Poecilocapus lineatus) removes plant’s chlorophyll via their piercing-sucking mouthparts. They also secrete a toxin in their saliva that digests the components responsible for holding the plant cells together that leaves a hole in the plant’s epidermis. This feeding produces white, dark, or translucent spots the plant’s leaves, which can run together forming large blotches. Leaves can turn brown, curl-up and ultimately fall off. If feeding occurs on new growth, wilting may result. This is a photo of a nymph. He was doing just fine in the damage department.
These guys are often confused with fall webworms, and bag worms, although all three are quite different. Tent worm nests are active early in the season while webworms are active late season. Tent worms like to make their tent nests in the forks of branches, while webworm nests are located at the tips of branches. Fall webworms also enclose foliage or leaves within these nests. Tent caterpillars do not. Bag worms are single worm homes made of the foliage from the tree it has decided to call home. They mostly evergreens like junipers or arborvitae. I like to remember the difference like this… A bag can hold one, but a tent can hold many.
© Ilex ~ Midwestern plant Girl