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Neighbors Growing Together | Nov 23, 2014

Garden Talk: Plant problems galore

By JEAN THOMSON, Master Gardener | Jul 25, 2013

The term “plant problem” is an understatement for this month’s news that the emerald ash borer has been confirmed in neighboring Des Moines County, specifically on the north side of Burlington. Previously, the borer was known to be present in Allamakee County and in Knox County in Illinois, but it had not been seen in Southeast Iowa.

Once the emerald ash borer appears, it kills ash trees in two to four years. If you have one or two healthy ash trees that you are determined to save, you might wish to contact tree services now. Ask for information about injections administered in the spring, and gather estimates.

There is absolutely no benefit to any pesticide application this late in the season. Technically treatment is not suggested at all until the ash borer has appeared within ten to 15 miles of a site, but some parts of Henry County are close to that distance from Burlington.

Another source of problems for plants has been the very meager rainfall this month. In some parts of Henry County, there had been no measurable rainfall prior to Sunday and only a few tenths of an inch then.

The rain that fell on Sunday was, fortunately, enough to replenish rain barrels, offering gardeners another water source. Everything planted this year has needed watering, and we are well-advised to consider water for all of last year’s plantings and for all plants, such as hydrangeas, that are especially thirsty.

If you are able to add mulch or compost in garden areas, that will help a bit in conserving whatever moisture is available.

Tomato growers may have begun to see leaf spots on their plants. There are three possible sources of this problem. Identification of the specific source is necessary for planning effective treatment.

Septoria leaf spot is a fungal infection that characteristically begins on the plant’s lower leaves. These spots have dark margins and gray areas in the center; they affect leaves and stems but not the fruit.

Bacterial spot starts as greasy-looking small spots that affect all plant parts. On the fruits, raised black spots evolve into large sunken scab-like areas.

Bacterial speck affects all plant parts. On fruits, tiny black specks appear, slightly raised above the fruit surface.

Several widely available fungicides are effective against septoria leaf spot but not against the others. Fixed copper sprays can help control bacterial spot and bacterial speck if started when first observed.

Cultural practices are very important in controlling leaf spots. Keep tomato leaves dry by spacing plants widely and watering at soil level. Do not handle plants when they are at all wet.

Pathogens causing leaf spot do over-winter in infested plant tissues, so plant debris should be gathered and disposed in the fall.

In addition, never plant tomatoes in the same area in a subsequent year.

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