It's always a learning experience for me to hear what's going on in Washington area landscapes. I again share some of your e-mails, so you might also benefit from one another's queries.
Q. I transplanted Pink Evening Primrose (Oenothera speciosa) this spring. They did great until midsummer and then stopped flowering, so I cut them to the ground. When they started to flower again, I noticed small iridescent black beetles, about three-eighths inch long, on the flowers. I drenched the plants with Safers Insecticidal Soap twice. Within two weeks the majority of primrose were dead. I cut them again on Sept. 11 and drenched the area with Sevin, as I had little larvae crawling everywhere (gray, about three-eighths to one-quarter-inch long). What are they? How do I control them?--Nadene L. Neel
A. This sounds like flea beetles. If so, Sevin is probably the least effective control. Adults feed on leaves, and larvae eat roots and sometimes the underside of the leaves. Some larvae go to the roots of other plants. They generally eat weeds and are more of a pest to agricultural crops, such as potatoes.
According to Stanton Gill, a University of Maryland Cooperative Extension principal regional specialist, concentrations of flea beetles have been tearing up perennials this year. The drought seems conducive to their life cycle, and controls seem to work only for larvae. Insecticidal soap helps. But allowing the population to decline naturally without insecticides allows beneficial insects, such as the assassin bug, to control the beetle. One very specific bacterium that doesn't harm beneficial insects and controls these larvae, is Bt (Bacillus thuringiensis)/San Diego strain, available through garden centers.
Q. Cherokee Chief dogwoods that I planted last spring get a good amount of sunlight. However, during late August the leaves started turning reddish-brown on the edges, and this color is now creeping over the entire leaf, pretty much over the entire tree. What's happening?--Mike Ahern
A. The stress could be from sun and a record drought this summer. Native dogwoods, from which your Cherokee Chiefs are hybridized, prefer protection from full sun and often decline in this situation. A soil rich in leaf compost will help. If your tree is not mulched with a partially decomposed material, lay compost two inches thick over the roots--not against the trunk--and see how they do in spring. If they brown again early next year, transplant them to a shadier site in fall.
Q. We have had a severe infestation of inchworms, especially on our maple trees the past few springs. An article in The Post on May 21 said wingless moths climb up the trees in late fall to lay their eggs and that homeowners could use "sticky burlap" to prevent their climb and break the infestation cycle. Please give me specifics on this method. We and our neighbors will be extremely grateful to find a way to deal with this problem.--Robert Veltkamp
A. Inchworms, also known as measuring worms or cankerworms, are caterpillars and will eat the leaves of your maples. Their feeding is specific to trees, not shrubs. There are spring and fall generations.
There are several things that will intercept the wingless females as they ascend the trees: sticky tar paper; burlap tied around and flapped over a piece of twine; fine-mesh screening tied as a funnel with the wide end toward the ground; or a commercial sticky product sold at garden centers. Place them about three to four feet above ground or, if using a commercial product, according to directions.
Because of the worms' movement from one tree canopy to another and because of spreading by wind, this kind of banding is considered 10 percent effective. Bt, a bacteria considered safe for people, is more effective against the caterpillar. There is certainly no harm in using banding in conjunction with Bt.
Q. I have seen English ivy used as groundcover and always admired it. But this ivy of mine is huge--monstrous. It is now at least 18 inches high. I have never seen ivy grow like this. Do my plants suffer from gigantism? Short of ripping it out, is there any way of taming this mess?--Toni Vogel
A. For your "ivy on steroids," set a rotary power mower on its highest setting and cut it next March before growth begins. If it's beyond mowing size because of its thick woody stems, try a hedge trimmer. Cut it to 4 inches in height. Rake off debris. It'll fill in at a much more reasonable size by June or July. Repeat as required.
Q. Our lawn has never been dethatched. Do you recommend a dethatcher? Additionally, should I use a power slicer/verticut?--Phil Coghlan
A. Thatch is a buildup of root mass from turfgrass. If you aerate and sprinkle compost, you also spread the organisms that break down thatch. But if thatch buildup is so thick that you can put your finger into a tight mass of dead roots and have to tear them up to make contact with the soil, then it may help to dethatch. Do it before aerating.
A power slicer or machine that cuts vertically and places grass seed directly into the soil is another useful tool for getting good contact with the soil and keeping the seed exactly where you put it. It isn't necessary for seeding your lawn, but if you want to use one, get it at a tool or equipment rental company.
Q. I have had a problem with moles for the last three to five years. I've tried everything from putting grub control down, chewing gum, mole poison, etc., but nothing works. What do you suggest?--Steve Urman
A. Moles eat insects, not grass seed or plants. Other than the channels they cut through your lawn in search of insects, they do no damage.
There are innocuous, but effective, castor-oil-based substances, such as Mole-Med and Mole Away, that you can spray on your lawn to make their food taste bad. The aim is to have the moles leave to search out food in a more hospitable environment. It's not foolproof, but it's your best bet. Moles could be considered beneficial animals because of their appetite for insects.
Write on! And keep reading "Green Scene."
Lerner is president of Environmental Design in Capitol View Park, Md. His e-mail address is email@example.com