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Q: I’m hoping you might be able to identify the problem with my tomatoes. The leaves are curling on four of my seven plants. Two are Celebrity and two are Jet Star. The other three are fine. Hopefully the picture will help you. — Mike H.

A: If a picture is worth a thousand words, your photo says it all. The curling, distorted stems and leaves are classic symptoms of exposure to herbicide. There are no other disorders or diseases that create the tell-tale symptoms of tomato foliage that has absorbed weed-killing chemicals.

There are several ways tomatoes or other garden vegetables are exposed to herbicides. Drift is the most obvious, as spray droplets of herbicide waft onto the garden from a lawn or farm field that’s being sprayed for weeds.

Becoming more common, though, is herbicide injury from residue of weed-killing chemicals present in compost, manure, straw, hay, lawn grass clippings, or other materials we add to the soil or use as mulch.

Many herbicides used on pastures, fields, or lawns persist tenaciously in the materials to which they’re applied, which can cause straw, hay and grass clippings to contain herbicide residue that can harm plants such as tomatoes when the materials are used in gardens or flowerbeds.

Manure can contain herbicide when residue on forage passes through the animal. If the manure, even if composted, is added to garden soil, it can injure tomatoes or other vegetables.

Unfortunately, once tomato plants are exposed to herbicide and have begun showing symptoms, there isn’t much that can be done to reverse the situation.

Q: I am so sad. I have a beautiful ninebark, but it stopped growing taller and only grew wider. I looked in the middle, and it is dead, in the middle only. Is there anything I can do to save it? — Connie C.

A: Ninebark are shrubs that definitely need rejuvenation every few years by pruning them back drastically. For now, prune out all branches that are dead, down to their point of origin. It was a tough winter on plants, as many of us have found.

To inspire the ninebark to regain its pleasing, well-rounded shape, rejuvenation is needed. Such pruning is best done in early spring before they leaf out. Prune all branches to about 4 inches above ground level. Some sources recommend pruning one-third of the branches each year for three years, but that hasn’t worked for me as successfully as cutting all branches back at once, which stimulates fresh growth over the entire structure.

If you don’t mind a slightly greater risk, I’ve done rejuvenation pruning on ninebarks in early July, but there’s a greater chance of something going wrong.

Rejuvenation of ninebarks is needed every five to seven years. At that point, the branches become old and woody, and prone to die-out. If rejuvenation pruning isn’t done, the shrubs can weaken and die.

Ninebarks are a colorful addition to any home landscape. A favorite of mine is Amber Jubilee with its mix of copper, orange and green-toned leaves. Some cultivars are lime-colored, and some are burgundy. There’s a color shade for nearly everyone, and although they require pruning, they are well worth the occasional effort.

Q: My potato plants are being eaten by the round, fat, black and yellow striped potato bugs. I tried the insecticide I use on some of my other vegetables, but it’s not working. What can I do? — Tom T.

A: You’ve described the situation with Colorado potato beetle very well. They’ve become resistant to many of the common garden insecticides that are effective against other pests.

Check local garden centers for products that contain the active ingredient Spinosad, which will be listed in fine print on the front of the product label. It’s a relatively new insecticide, developed from a naturally occurring bacterium discovered at an old rum distillery and is labeled for most organic insect control situations.

Spinosad is very effective for Colorado potato beetle control, and is available in both dust and liquid form. I prefer the liquid form, as I feel spraying achieves better plant coverage.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.