MAY
2006

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

05-04-06

Question and Answer

Q. I am hoping that you can give me some advice on my yard. I think I may have a fungus. Nothing grows very well. Last year I planted bell peppers and tomatoes, and they were inedible. They were full of white veins. All of my trees have small holes in the leaves. And my grass has small pale patches all over the yard. My income is limited. Can you suggest a treatment that is not too expensive?

A. Well, the good news is that there is no one organism that would attack all of the different types of plants that you've mentioned. Most diseases and insect pests are what is referred to as "host specific," meaning they attack a particular, or sometimes a few different, species. When that many different plants are affected, it's more likely to be something related to environmental factors, such as weather, poor soil conditions, etc., or management, such as improper watering, fertilizing, etc. And, there is no one solution to all of these various problems. You must first diagnose the problems before any recommendations for treatments can be made.

For assistance in diagnosing these various problems, contact the Purdue Extension office in your county and take them some samples of the various affected plants. You can look up the contact information for your county online at http://www.extension.purdue.edu/counties.htm.

Q. I have two forsythia bushes that I started from cuttings. They are about 3 years old and are growing quite well. They are nice and bushy, but they have never bloomed. The bush that I got the cutting from blooms every year. Do you have any ideas as to what could be wrong? I would appreciate any advice.

A. Flowering is the reproductive phase of plant growth, and so plants need to reach a certain degree of maturity to be able to flower. While there is no one specific age at which all woody plants become mature enough to flower, 3 years is pretty young for most trees and shrubs. Other reasons for lack of flowering can include insufficient light (too shady), excessive nitrogen (promotes excess leaf growth and delays maturity) and, in the case of forsythia, the flower buds are often damaged by late spring frosts. If these cuttings are near the parent plants and exposed to all the same conditions, then I would assume they just need a few more years to reach maturity.

Q. I am surrounded by corn and wheat fields. I seem to have more weeds in my garden than they do in their fields. They just got through spraying for something. I have pretty blue weeds taking over the garden now. Can I put "preen" all over to cut the weeds? I want to plant potatoes, peppers, cukes, squash, tomatoes, carrots and beans.

A. Ah, beauty is in the eye of the beholder! Those “pretty” blue weeds are likely either henbit or the closely related purple deadnettle. They both have similar purplish-pink flowers and square stems, but the purple deadnettle has a spade-shaped, stalked leaf, and the henbit has more of a scalloped-shaped, stalkless leaf (leaves clasp the stem). They are both winter annuals, meaning their seeds germinate in the fall, flower and produce their seed in early spring. By the time you see them flowering in the spring, the best means of control is manually by hand pulling, hoeing or tilling.

Preen® contains trifluralin as the active ingredient, which is ONLY effective at preventing some weeds (mostly annual grasses and some annual broadleaves) from germinating. It will not provide any control once the weeds are already growing.

For trifluralin to be effective against either of these two weed species, it would have to be applied in the fall before their seed germinates. Trifluralin is labeled for use on many but not all vegetable crops, and the appropriate time for application depends on the specific crop, so it can be tricky to use in a small garden. As always, be sure to read the label before you apply.

Q. I have a problem with my muskmelon. The problem arrives when the vines are fully grown and the fruit is in various stages of development. Overnight, the vines wilt and hopes for a melon are gone. Can you offer a solution?

A. The most likely culprit is bacterial wilt, a disease that clogs up the water conducting tubes that in turn causes irreversible wilting. The bacteria is transmitted to the plant by cucumber beetles (both striped and spotted types) as they feed on the foliage. Once the plant is infected with the bacteria, there is no cure. Infected plants should be removed. There are a few cultivars of cucumbers that are resistant to bacterial wilt but none yet in melons. So the only hope is to prevent the cucumber beetles from feeding.

Early-season use of floating row covers can help reduce beetle feeding, but covers will need to be removed when plants are blooming to allow bees to pollinate. Yellow sticky-cup traps can reduce beetle feeding, if placed around the borders or about every 20 feet within the row and replaced as needed when they are no longer sticky.

A promising new product called "Surround At Home®" contains fine kaolin clay particles as the active ingredient. Neem oil is also labeled for beetle control on melons. More traditional insecticides that are labeled for cucumber beetle control on melons include carbaryl (very toxic to bees) and methoxychlor (less toxic to bees). Always read and follow label directions before applying.

Q. I have a 10-year-old snowball bush that was taken from a cutting of a cutting from my grandmother's dating back probably 100 years. Last year, some of the sections growing up from the ground wilted and died. This year, when one of the three remaining sections failed to bloom (and the other two looked like Charlie Brown's Christmas tree), I investigated and found a white caterpillar hidden in little sawdust sacks burrowing in grooves up inside the bark around the entire base of the three sections. I cut the dead section out and I tried to pull the little buggers from the two surviving sections, but the softened bark came off with them. What kind of bug is this, and is there anything I can do to save this bush, or is it doomed? Is there anyway to get a cutting from this plant to start a new one?

A. Sounds like one of the viburnum borers, which as an adult is a clearwing moth that emerges from the tunneling larvae in midsummer. Affected plants are, at best, weakened and, in serious cases, can dieback as you've experienced. Plants that are injured and/or stressed are most susceptible to attack by borers. Avoid pruning plants during the growing season and keep mowers and weed whips well away from the stems. Remove all affected stems, preferably during the dormant season; however, now is better than midsummer. Plants can be sprayed with either permethrin or bifenthrin (Ortho) in midsummer, just after the adults emerge.

As insurance, in case the plants do not recover, take cuttings anytime in late spring or early summer, selecting the healthiest-looking twigs. Take a 6-inch or so length of the stem tip, remove the lower pair of leaves and dip the cut end of the stem in rooting hormone. Insert the cuttings into moistened potting soil or vermiculite, and keep the humidity high around the cuttings with a ventilated plastic bag. Gently lift the cuttings out of the mix in 3-4 weeks to check on rooting status. Once the new roots are an inch or so long, you can either transplant them in a protected outdoor location, or repot and raise them in containers until early fall.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,