A ton of tent caterpillars just ate the leaves on my tree. The branches are too high for us to cut off. Will the tree die?
Your tree should be fine. The fall webworm, a caterpillar of our native tiger moth, has two generations a year. The spring population is largely unnoticed, but the late summer-fall one is bigger — and this year it was record-setting. Their webs differ from tent caterpillars because tent caterpillars build in tree crotches (in spring only), whereas webworms build nests at branch tips. Webworms feed inside their webs. Because they're native, more than 75 species of predators and parasites (insects and birds) normally control their population. Your simplest solution is to break up low webs with a pole and let predators feast on the caterpillars. Webs can be pruned out or removed by hand, but it's not necessary. Though webs look unsightly now, they'll disintegrate over the winter. Late season webworm feeding should have no lasting effect on your tree, because its leaves already manufactured plenty of energy reserves during the summer.
My basil is being ruined by a fuzzy coating with black spots under the leaves. First the leaves got smaller and a washed-out pale green. Now this. Can I spray something?
Your basil has downy mildew. You can't solve this with spray. Harvest the symptomless leaves, then cut the plant to the base. It may have time to regrow some clean leaves. The pathogen cannot overwinter here; it comes in on infected plants or seed. If symptoms developed only recently, you had a clean plant that was infected from other basil in the area. Purple leaved varieties are most resistant. Some green varieties are more resistant than others.
University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to the website at extension.umd.edu/hgic.
Plant of the Week
Ironweed, New York Ironweed
The rich glowing purple of ironweed pops against the warm autumn hues of goldenrod and mums. Depending upon its site, ironweed may reach 4 feet in the back of the perennial bed or soar 7 feet or more. This Maryland native is a butterfly favorite. Plant in full sun to slight shade. A perennial, it likes moisture and is a good candidate for a rain garden. Give good air circulation by not overcrowding or planting flat against a wall. The brown fluffy seed heads are small and spread by wind. Its name may refer to the strength of its stems or its general constitution. — Ellen Nibali