Vascular diseases of trees; pumpkin planting; Japanese beetle control

By John Fulton

[June 25, 2009]  Many major tree diseases cause vascular system blockage. Verticillium wilt, oak wilt and most of the canker diseases fall into this group. Usually a fungus "plugs the pipes" so there is reduced movement of water up and food down. This leads to dead areas above the blockage. Of course, if the blockage is on the main trunk, you end up with a dead tree. It is often possible to see streaking of the wood or a dark ring around the center portion of the branch or trunk with verticillium wilt, but a lab analysis is needed for definite confirmation.

The list of trees affected by verticillium is very large, but good-quality maples are very susceptible. There have been many affected trees this year, including maples and ashes.

There are no cures for any of these diseases at this time. To help prevent transfer from root grafting, it is recommended to remove and destroy trees severely infected with verticillium.

The only treatment is to water and fertilize to try to get new growth, with new water- and food-carrying tissues.

We have really had 20-plus years of stressful weather. Just like us, trees like moderate weather. When we have extreme heat and cold and no moisture or a flood, the trees are stressed. This stress makes them more susceptible to things that are always in the environment.

Try to even out some of the extremes by watering when it is dry, fertilizing when you do the lawn (or just fertilize the tree) and mulching to even out the soil temperature in the root area. Remember that many diseases can be passed with pruning equipment, so disinfect your equipment between cuts.

Pumpkins

Many pumpkins are already on their way, with seeds being sown a month ago. While this practice is great for producing pumpkins for pumpkin pie, it really doesn’t work very well for producing the Halloween jack-o’-lantern pumpkins. The Halloween pumpkins are best planted around Father’s Day. This timing helps prevent the pumpkins from rotting before we get to the end of October.

Many different varieties are available, and they come in many sizes and shapes. The small pumpkins, ranging from 2 to 5 pounds, are called "pie" types. They are normally used for cooking and fall decorations and include the Baby Bear variety. Intermediate and large varieties are primarily used for jack-o’-lanterns. Many of the newer varieties have stronger side walls to aid in display and carving. The flesh of these varieties is generally poor in quality and not used for cooking. Processing pumpkins, which are canned commercially, make poor carving pumpkins and are more like a buff-colored watermelon in appearance. The jumbo or mammoth varieties are mainly used for exhibition. These jumbos can weigh in the 900-pound range. For most homeowners, you might want to pass on these, since moving a 900-pound pumpkin isn’t for everyone. The other option is to try and grow one in place.

Pumpkins should be planted about now for carving or fall decoration. Vining pumpkins need at least 50-100 feet per hill, with the larger pumpkins requiring the larger area. Hills should be five to six feet apart, and rows of hills should be 10-15 feet apart. Each hill should have about four seeds per hill, planted about an inch deep. The miniature varieties such as the Jack-Be-Little are sometimes grown in rows with seeds planted every eight to 12 inches, then thinned to about two feet apart in the rows.

Fall decoration pumpkins should be cut from the vine after the color is acceptable but before the vine dries, in order to have a good stem attached to the pumpkin.

Keep the pumpkin bed free from weeds by shallow hoeing, and make sure it is watered during extended dry periods.

Major pests are squash bugs, cucumber beetles and vine borers. Most often, frequent applications of an insecticide such as carbaryl will help protect the new runners from the vine borers and also control the beetles that transmit the wilt virus. Apply insecticides in late afternoon or early evening to make sure no applications are made to open blooms, which attract the bees for pollination.

Japanese beetles

Japanese beetles are growing in number at a rapid pace. Peak emergence should happen over the next two weeks. Start control early on plants you want to protect, to avoid having the beetles emit the pheromones that attract others to the same plant.

Small plants can have the beetles hand-picked and dropped into a bucket of soapy water. Chemical controls of carbaryl (Sevin), permethrin or bifenthrin are among those that are effective. The extreme heat will greatly reduce the length of time the products are effective, especially the permethrin or bifenthrin, to as little as three to four days.

[By JOHN FULTON, University of Illinois Extension, Logan County]