JUNE
2002

 

 

 

By
Beverly Shaw
 
Advanced
Master Gardener
Purdue University

 

 

 

 

 

6-6-02

Question and Answer

Q. Our family likes growing pumpkins every year. The problem is all the weeds! The weeds take over the pumpkin patch, so much so that the pumpkins can't grow and rot before time to harvest them. What could we use to spray or use on the ground to kill out the weeds? -- Gayla Merry, Mitchell, Ind.

A. Preventing weed establishment is the most effective means of control. Black plastic mulch or a 2-4-inch layer of organic material will keep weed seeds from germinating.

Pre-emergent herbicides are effective for annual weed control, if applied before seeds germinate. Make sure the one that you select is labeled for your crop, and follow the directions carefully. You cannot directly seed your garden plants into soil treated with a pre-emergent herbicide, so use these herbicides around vegetable transplants or after germination of seeded crops. Unfortunately, by the time the vegetable seeds germinate, so will many of the weeds, but this will prevent future weeds from germinating.

After weeds have sprouted, regain control by pulling, tilling or hoeing. A scuffle, or action hoe, works well where mulch is thin before the pumpkins begin to vine. This tool has a flat blade on the bottom of a handle-shaped loop of metal. It provides a relatively easy way of slicing off the tops of plants, which eventually starves the roots.

Outside the vegetable garden, you can reduce the weed seeds that infest your pumpkin patch by spraying actively growing weeds with a nonselective post-emergent herbicide. These kill all green plant tissue, so use care, and follow label instructions.

Q. I have an Eastern Redbud tree, which was planted seven or eight years ago. Last fall, I noticed that the tips on the leaves, for about a quarter inch, were black and curled under. I first noticed this in the fall, but it could have been happening earlier. Is this fireblight? I didn't notice any distorted twigs. How can I help this tree? -- Mike Klinger, Abion, Ind.

A. It's most likely verticillium wilt, one of the most common and destructive diseases of shade and ornamental trees in Indiana. Redbud and hard maple trees are especially susceptible.

During midsummer, leaves turn yellow at the margins, then brown and dry. Sudden wilting of leaves on one or several branches may occur. Frequently, the foliage on only one side of a tree wilts. The wood under the bark of wilting branches is discolored in streaks, usually brown streaks on redbuds. To examine for streaks, cut a problematic branch, and look for a ring of dark discoloration.

If you're unsure of the diagnosis, take a sample to the Extension office in your county or submit one to the Purdue Plant and Pest Diagnostic Laboratory. Your local Extension office has submission forms and detailed instructions for submitting samples. Photographs are very helpful, in addition to the plant sample itself.

Verticillium is a soil-borne fungus, infecting plants through the root system. It produces resting structures that can survive and re-infect plants for many years. Once it invades the host plant, it blocks the water-conducting tissues.

Don't be too quick to remove the plant. Prune out affected limbs, and water and fertilize to maintain tree vigor. In some cases, these tactics may delay progression of the disease for a number of years; however, infection is not cured since the disease originates in the roots.

If the tree dies or you choose to remove it, never replant a susceptible tree or shrub back in the same location, or it will meet the same fate. For a list of woody plants resistant and susceptible to verticillium wilt, contact the Extension office in your county and ask for "Verticillium Wilt of Shade Trees," BP-6-W or find BP-6-W online in pdf format.

Q. I have two apple trees in my orchard. Both apple trees become infected midway in the season with some kind of insect that bores a small hole all the way into the core. The apples then rot from the inside out and become lumpy. What can be done to alleviate this condition? -- Lawrence O'Brien, Cutler, Ind.

A. There are plenty of insects that find apples as appealing as we do! For a certain diagnosis, you will need to take a sample to the Extension office in your county, but most of the common pests in our area will be prevented with the same orchard practices. Once apples are infested, it's impossible to kill the insect inside.

You can protect healthy apples by spraying with a multi-purpose fruit spray, containing insecticides and a fungicide, at regular intervals. It's a detailed process, and I highly recommend downloading a copy of "Managing Pests In Home Fruit Plantings" (ID-146). It covers most fruits grown in home gardens and orchards. Following the schedules listed will provide relatively insect- and disease-free fruit.

 

Contact: B. Rosie Lerner
Editor: Olivia Maddox,