ASKtheexpert

Ask the Expert

By Debra Ricigliano Brown Spots on Leaves

Q: I am seeing damaged leaves on some of the plants in my flower and herb gardens. The leaves have round, brown-to-black indented spots about 1/16th of an inch in diameter on them. I have checked the plants over carefully, but don’t see anything there. A: This sounds like the four-lined plant bug, a short-lived early-summer insect. By the end of June, they have already come and gone. This plant bug has a large range of host plants. The damage can look very dramatic, but it is cosmetic. Their sucking mouthpart is inserted into a leaf like a straw, fluid is removed, and then the process is repeated multiple times on the same leaf. This results in clusters of spots (known as stipples) and eventually holes as the damaged tissue drops out. No treatment is necessary. Simply remove the damaged leaves or wait for new growth to mask the damage.

Tomato Foliage Woes

Q: Every year, our tomatoes get spotty leaves. The problem seems to start at the bottom. Then the leaves turn yellow and die. It progresses and works its way to the top of the plant. Help! This is very frustrating. Is there anything I can do? A: This sounds like the work of one or both of the very common fungal leaf spot diseases of tomato: early blight (Alternaria linariae) and Septoria leaf spot (Septoria lycopersici). Infections can result in defoliation and reduced yields. If there is room in your garden, plant them in an area where you have not grown tomatoes for at least two years. The fungal spores overwinter in the soil and on any partially decomposed plants not removed from the garden in the fall. The following strategies can also help. Space plants farther apart to improve air circulation. After planting, cover the soil around the plants with three to four layers of newspaper or heavy-weight brown paper covered with an organic mulch. The idea is to reduce spores from the soil splashing onto leaves. Support tomatoes off the ground using

Four-lined plant bug damage and nymph. Photo by Matthew Borden, Bartlett Tree Experts, Bugwood.org.

stakes or cages. Remove the lowest three to five side branches back to the stem as soon as the plant is large enough to sustain the loss of leaves. Avoid overhead watering and monitor your tomatoes frequently. Remove badly infected lower leaves. If necessary, start to spray with an organic fungicide (fixed copper) according to label directions as soon as symptoms appear early in the season to slow down the disease progression.

Is Damage to Trees and Shrubs from Cicadas?

Q: Is it possible that some of my trees and shrubs are still suffering damage from last year’s cicada invasion? My oak tree has branches ranging from 6 inches to about a foot that are drooping now that they have new leaves. I have some inkberry shrubs (Ilex glabra) that have some dead branches and when I examine them, I see slits in the bark. What can this be? A: Yes, It certainly sounds like the aftereffects of the 17-year cicada female egg-laying process, as you suggested. What you are seeing now should be the end of the damage. The good news is that this will not severely damage your plants. Consider tip pruning on your oak and some thinning of your inkberries. The new growth will continue to mask the damage. Native plants like your oak and inkberries support our native insects like the 17-cicada and a multitude of others. This is just one positive reason of the many to add native plants to your landscape.

A Note to Readers

The time has come to pass the honor of writing the “Ask the Expert” column to my co-worker, Miri Talabac. Her name is most likely already familiar to many plant-loving readers who may know her from her many years at Behnke Nurseries. It has been my pleasure to write the column for the Washington Gardener Magazine over many years, but I am ready to be off for some new gardening adventures. Happy gardening! o

Debra Ricigliano is a Certified Professional Horticulturist who has worked as a horticulture consultant for the University of Maryland Extension Home and Garden Information Center since 1997. She is a graduate of the Institute of Applied Agriculture at UMCP. To ask a gardening question, go to http://extension. umd.edu/hgic.