Gardening inside and out: Cabbage worms; grubs in gardens; peach leaf curl

This is the time of year we normally start seeing damage from cabbage worms. The imported cabbage worm is usually the first cabbage worm species to appear and is a fuzzy, elongated green worm. Larvae come from eggs laid by the white butterfly often seen flitting around the plants.

Early control is essential to reduce injury. BT (Bacillus thuringiensis) is an effective organic product that is labeled for this pest. It can be found in Dipel, Thuricide and other similar materials.

Be sure to hit the underside of leaves because this is where insects feed. Also, direct sunlight deactivates the product quickly so it is helpful to spray late in the day or on a cloudy day. Conventional insecticides such as carbaryl (Sevin), malathion and methoxychlor are also effective but will kill natural enemies of these pests as will rotenone, an organic product.

White grubs in gardens and flower beds 

We have had a number of calls this spring from gardeners who are finding white grubs in the vegetable garden or flowerbed. Usually, populations of grubs are low enough that they will not cause appreciable damage. Unfortunately, if populations are high, there isn't much you can do once the garden is planted other than try to keep the plants healthy until the grubs pupate. I have not been able to find information on how many grubs per square foot are needed to damage vegetables. In turf, you normally assume it will take 9 to 10 southern masked chafer or 3 to 4. May beetle grubs per square foot to cause damage.

White grubs are most often a problem when a lawn is converted to a garden or flower area in the spring. If the lawn was heavily infested with grubs, many survive to cause problems for the new plants. Working lawn areas in the fall that you plan to convert to another use the next spring can help prevent problems by eliminating food for the grubs and exposing the insects.

Peach leaf curl and plum pocket symptoms

Peach leaf curl is a fungus disease that causes developing peach leaves to become puckered and distorted and show a reddish-green hue. A similar disease called plum pocket may develop on American and sand hill plums. Plum pocket results in formation of distorted, light green, bladder-shaped fruit. Asian and European plums are not susceptible to the local strain of plum pocket. It is too late to control these diseases with fungicides this year.

Trees that are severely infected with peach leaf curl are likely to lose many leaves. If trees are healthy, new leaves will grow. Indicators of a healthy tree are large leaves with a deep green color and last year's growth being at least 18 to 24 inches long. If these tree vigor indicators are not present, especially if there was only 12 inches or less of growth last year, then a fertilizer application would be helpful. The fertilizer should be spread on the soil under the branch area.

Apply 1 and 1/3 to 2 cups of a 13-13-13 fertilizer under the branch area. If a soil test indicates that only nitrogen is needed, use 1/3 to 1 and ´ cups of nitrate of soda (16-0-0) instead of the 13-13-13. You may also substitute a high nitrogen fertilizer such as a 27-3-4, 30-5-4 or something similar for the 13-13-13 but use only half the amount used for nitrate of soda. The sooner fertilizer is applied, the more immediate benefit it will have in promoting new leaf growth. Both peach leaf curl and plum pocket can be controlled with a single fungicide application applied this fall after leaf drop or early next spring before bud swell. Effective fungicides include Bordeaux, liquid lime sulfur and chlorothalonil (Bravo, Daconil and others). Be sure to cover the entire tree including the bark and trunk.

Peaches and apricots

It is relatively rare in Nebraska to have both a peach and apricot crop that isn't badly hurt by late frosts. This is perhaps one of the best fruiting years I have seen in a long time for Nebraska -- perhaps Mother nature is making up for the terrible fruit year last year. We will want to take advantage of our good fortune. Following are certain things you should do as the fruit matures to insure a good harvest.

Control insects and diseases: Though we are too late to control peach leaf curl, we do need to control scab and brown rot. The insects we need to be concerned with are plum curculio, oriental fruit moth, plant bugs and stink bugs. Use Captan or Immunox to control the diseases and malathion or Thiodan to control the insects. Spray every 10 to 14 days. Pay attention to the waiting period between the last spray and harvest. See a Kansas publication, "Fruit Pest Control for Home Gardens" at www.oznet.ksu.edu/library/hort2/c592.pdf  for more detail including organic controls.

Thin peaches: You may want to thin your peaches to 1 every 4 inches to maximize fruit size and to decrease the load on the branches. Peaches are borne in clusters, so calculate how many a branch can support by dividing the length of the branch in inches by 4. As long as there is an average of 4 inches of branch length per peach, it doesn't matter whether the peaches are in clusters or not. Prop up branches if needed: Prop up branches if the fruit load is so heavy that the tree may break apart. Use boards with a "V" cut in one end to support the branch.