Dear Master Gardener: I have bugs feeding on my potatoes and eggplants. Their body shape is oval and there is yellow-orange behind their heads. Their wings are yellowish with black stripes. What are they and how do I get rid of them?
Answer: From your description, it sounds like you have Colorado potato beetles. These insects feed on potato as well as eggplant, tomato, pepper and other related plants. First found in Colorado — as the name implies — in the 1850s, they had spread across the country by 1875. Both larvae and adults feed on foliage and can completely defoliate plants. Adults are active from June through September and can cause significant damage. Potato plants can tolerate up to 30% defoliation before flowering, but only 10% defoliation at the onset of tuber initiation. Severe defoliation can reduce plant vigor, size, and yield.
The adult is about half the size of a thumb nail, oval in shape, yellow-orange in color, and has 10 narrow black wing stripes. Adults overwinter in the soil and emerge in the spring at the same time as the plant does. They then mate and the female lays clusters of 10-30 yellow eggs, up to a life total of 350, on the underside of leaves. Depending on temperatures, the larvae hatch in 1-2 weeks and begin to feed. The larvae molt four times, getting larger and hungrier each time. Each molt results in a change in appearance. In the fourth stage the larvae drop to the ground and pupate. Adults emerge 1-3 weeks after pupation and the cycle begins again. Depending upon temperatures, a potato patch can contain beetles in all stages of development.
Controlling Colorado potato beetles is a challenge. Once you have them, they will always be around. It is wise to keep an eye on their numbers, and when damage is becoming too much for your plants to handle, you can intervene. A good time to spot the beetles is when they first show up in spring. They are resistant to most insecticides available to homeowners but you can reduce their numbers several ways. Clean up your garden at the end of the year to make it harder for adults to overwinter. Go a year without potatoes in your garden and that can reduce their numbers. In a small garden, pick them off by hand and destroy adults and visible larvae by dropping them in a pail of soapy water. Crush the yellowish-orange eggs found on the underside of leaves. Row covers can be placed over your rows of potatoes to prevent the beetles from feeding and laying eggs on plants. It is most effective if you do this before you see any beetles, and if you are putting your plants in a different spot than last year. Make sure to remove the row covers when temperatures and humidity increase, or it will promote plant disease.
Dear Master Gardener: How do I take care of the yellow spots in my yard caused by dog urine?
Answer: Dogs often cause brown spots of dead grass in the lawn. Their nitrogen-rich urine acts just like fertilizer burn. The treatment is the same. Thoroughly water the area to dilute the urine and wash it through the soil. It may not be practical, but it is effective. The surrounding grass will eventually fill in these brown areas. Nature and time do heal many landscape problems. There are mixed reports on some of the urine-neutralizing products. Several people have reported great success while others find that watering works just as well. Some gardeners train their dogs to go in a specific area.
Yellowjacket wasps are numerous in August and are attracted to sweet, ripe and rotting food. Be watchful of cans and glasses of beverages, which may harbor yellowjackets you don’t see or expect before your next sip! Keep picking zucchini, cucumbers, snap beans and other vegetables from your garden, even if they are past their prime because the plants remain more productive. Also, the rotting produce attracts yellowjackets.Blossom end rot is a disorder that is characterized by a black, leathery sunken area at the bottom of tomatoes and peppers. It’s caused by inconsistent watering which causes the minerals in the soil to not reach the fruit consistently. To avoid it, water deeply and regularly and don’t fertilize too heavily with nitrogen. Slice off the affected tissue — the rest of the tomato is perfectly good.Continue to dead-head perennial flowers to prevent seed set and enable the plant to retain more energy reserves for next year’s bloom.Divide and replant perennials that are overgrown and no longer blooming well. Discard the central part of any clump that has become woody, then replant the outer portions. Wait until spring to divide fall-blooming plants, such as mums.Iris become dormant and slow their growth this month, so now is the time to divide them if needed. Bearded iris flower better when they are regularly divided. Cut the foliage back to 6-8 inches and keep one or two foliage clusters per rhizome.Watch for delightful sphinx moths in the early evening. They look a lot like hummingbirds. They are about the same size, also flap their wings rapidly and hover, and suck nectar from impatiens and other flowers with their long proboscises. Late summer is an excellent time to plant evergreen trees and shrubs, giving them several months to grow new roots. Evergreen trees such as pines, spruces and firs can help save energy when planted on the northwest side of your home, will provide shelter for birds, and are beautiful covered with fresh snow. It is important to water evergreens until the ground freezes any week in which we do not receive an inch or more of rain.Raise the height of your lawn mower blades to 3 inches. As heat builds in the summer the taller grass protects the roots and allows deeper root development. Shorter cut levels lead to shallower root systems, making the plants more susceptible to water and heat stress. Mid-August is a good time to plant grass seed. Warm soil and less weed competition greatly improve the chance for successful establishment before winter.Create a compost pile with grass clippings, leaves, garden debris (plant material), egg shells and fruit and vegetable scraps. Warm August weather encourages the rapid breakdown of materials by bacteria. Keep it moist and turn it frequently to maintain an aerobic environment to speed up the breakdown process. According to the EPA, home composting can divert 700 pounds of waste per household per year from municipal waste. And — you’ve just created your own “gardener’s gold” to enrich your soil!
You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, email me at
umnmastergardener@gmail.com
and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.
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