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Verticillium Wilt, Potato Leafhopper Damage, AND Wilt of Vining Crops
By John Fulton

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[July 24, 2015]  Verticillium Wilt - Many major tree diseases cause vascular system blockage. Verticillium wilt, oak wilt, and most of the canker diseases fall into the 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. There are no cures for any of these diseases at this time. It is recommended to remove and destroy trees severely infected with verticillium, to help prevent transfer from root grafting. 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, as well as shrubs such as smoke bush and viburnam. The only treatment is to water and fertilize to try and get new growth, and new water and food carrying tissues.

We have really had twenty-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.

The following is a recommendation from the University of Illinois Plant Clinic: “Once a plant has succumbed to Verticillium wilt, we recommend replanting that area with non-susceptible species. Apple, pear, crabapple, gingko, sycamore, walnut, willow, rhododendron and azalea, and oaks in the white oak group are some woody plants that are considered non-susceptible to Verticillium wilt. In addition, all conifers are considered resistant to Verticillium wilt.”

Potato Leafhopper Damage Is Now Evident



A few weeks ago, I wrote about damage from the potato leafhopper. The damage symptoms are now more evident on all types of plants. Symptoms include yellow or brown “v” shaped areas at the tips or points of leaves, possible discoloration of leaves (evident on red maples with red leaves already), and shrunken and distorted leaves – particularly on the youngest leaves.

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 Once symptoms are noticed, you get to ride things out. The damage has already been done. Control of leafhoppers on trees in particular is very difficult. You are looking at spraying on a regular basis to cover the entire tree. Think at least every two weeks. It is easy to see the cost of treatment would probably outweigh the benefits. Of course, spraying a prized rose bush or something smaller is probably something you are doing anyway.

Wilt of Vining Crops

With the growing season entering the home stretch for vining crops such as squash, pumpkins, cucumbers, and melons, there are few things worse than having your vines wilt suddenly. I’ve noticed the population of the striped cucumber beetles have exploded in the past few weeks. These beetles can be green, black and yellow striped, or black and yellow spotted. The importance of the beetles is not that they eat small holes in the leaves, but that the beetles can transmit a bacterial wilt to the plants as they eat. The first thing you see is you have a plant that suddenly wilts on various runners, or the entire plant. The best means of controlling this disease is a good beetle control program. Current homeowner recommendations would include these products with the days to harvest restrictions in parenthesis: carbaryl (0), bifenthrin (3 days), or rotenone (1 day).

[By JOHN FULTON, COUNTY EXTENSION DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]

 

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