Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

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What are the most common problems of potatoes in this area?

The most common problems associated with growing potatoes in Missouri are Colorado potato beetles, flea beetles and early blight. Adult Colorado potato beetles are about 3/8 inch long, yellowish-orange with black stripes. The larvae are fat, red and humpbacked. The larvae may also have 2 rows of black dots along each side. Both the adults and larvae feed on leaves and stem. Several methods of control can be used. Early in the season, hand picking can be effective. Also look under the leaves and collect and destroy any leaves with clusters of yellow-orange eggs. Vegetable garden insecticides such as rotenone, a botanical insecticide can also be used. Bacillus thuringiensis var. san diego also just called "BT" is an effective biological control for the larvae. A good control method to use in combination with crop rotation is to cover the young plants with a polyester row covering and secure the sides and edges well to exclude the pest.

Not as devastating as the Colorado potato beetle, but nevertheless a common pest is the flea beetle. Flea beetles are small insects only about 1/8 inch long which chew tiny holes in the leaves. Protection is most important early in the season when the plants are small. Polyester row coverings and rotenone are good control measures.

Early blight is a common disease of potatoes. Irregular dark brown spots 1/8 to 1/2 inch in diameter appear on lower leaves. Concentric rings develop and the leaf my die and fall off. Infection is most severe towards the end of the growing season when the vines approach maturity and the tubers are formed. Many leaves may be killed and yield may be reduced but the plants seldom die. If the disease is detected early, spraying with a fungicide registered for use on potatoes can be used. At the end of the season, collect and dispose of all dead vines. Next year plant certified seed and grow your potatoes in a new location. Also, do not use overhead watering which can spread the disease.

Several other diseases affect potatoes but they are best controlled by using only certified, northern-grown seed each year, rotating where you plant your potatoes and working to keep your soil's pH around 5.2 or lower. Do not apply lime to soil where you will be growing potatoes.