Hort Shorts

Rudbeckia Leaf Spot

Many rudbeckia species are available to gardeners. You may know them as black-eyed Susans or orange coneflowers. One particularly unappealing disease of this species is Septoria leaf spot, caused by a fungus, septoria rudbeckiae. It is prevalent now in Illinois. The dark brown leaf spots are hard to miss, starting as 1/8-inch spots but quickly merging into large, brown areas on otherwise dark green leaves. The disease begins on lower leaves and progresses up the plant.

Another problem that might look similar is a bacterial disease, angular leaf spot. Angular leaf spot produces bacterial streaming from sections observed with a microscope. Septoria leaf spot produces fruiting bodies embedded in the spots. The fruiting bodies produce diagnostic, long, narrow spores.

Disease spread depends on leaf moisture. With recent rainfall in Illinois, there is not much you can do to stop spore splashing. Still, you can help prevent further disease spread by watering the soil, as opposed to syringing the foliage. Also try to prevent overcrowding of plants and keep weeds under control. Preventive fungicide applications protect new growth from Septoria leaf spot. Sprays should begin before symptoms appear, but there may be some benefit to newly forming leaves. Copper-based fungicides have some effect against both Septoria and the bacterium causing angular leaf spot. Copper products have protective-contact activity. A systemic product registered for this use by homeowners is Heritage. The active ingredient is azoxystrobin.

Author: Nancy Pataky, University of Illinois Extension

 

Don’t Use Pet Manure in Vegetable Garden

Occasionally we get a call from a gardener about using pet manures as an organic amendment in soil. A recent question had to do with adding dog manure to soil in a vegetable garden and if it was safe to grow vegetables in the site. It is never a good idea to apply manure from cats or dogs to soil that will be used for growing vegetables. Some organisms that are harmful to humans can survive a cat or dog’s digestive system and if their manure is applied to garden soil, can later contaminate vegetable surfaces. There are several parasites that can be transmitted to humans via dog or cat feces including roundworms, tapeworms and occasionally toxoplasmosis. Other pathogens include E. coli bacteria and salmonella, as well as others. There is also disagreement among sources as to whether composting pet manures will eliminate harmful organisms. Some say it does if the pile is “hot” composted and others say not. Since the risk of illness can be high, it is recommended that pet manures not be used at all in vegetable gardens.

Manure from cows, sheep, horse and poultry is often used to amend garden soil and is inherently less pathogenic to humans, although these manures have been reported to harbor microorganisms as well. Even after composting, manure mixes have been show to harbor disease-causing organisms. Animal wastes contain “pathogens to which humans are vulnerable, including salmonella and cryptosporidium” (Animal Water Pollution in America – 1997). There appears to be a consensus recommending that these animal manures and manure compost should not be used within 60 days of being produced. This waiting period may be critical when using these manures in vegetable gardens. In addition, be wary of hog manure; pigs carry parasitic roundworms that can be transmitted to humans.

It is imperative that vegetables be washed thoroughly before consumption, especially root crops and salad crops like lettuce, chard, radishes, onions, etc., that grow in the soil or close to the soil surface, as they may pick up soil and manure particles in rainy periods or as the gardener works with the plants.

Source: Weekly Garden News, June 2003

 

Leaf Roll on Tomato

It’s not too surprising that we are seeing some tomato leaf roll this summer. Older tomato leaflets roll inward toward the mid-vein and the leaflets are somewhat leathery to the touch. This is not a disease or insect problem, but is physiological in nature. Leaflets take on a cupped appearance and eventually; the margins may touch or overlap. As much as three-fourths of the foliage may be affected on a single plant.

This is caused by a fluctuation in moisture in the root zone, going from ample moisture to a shortage, or by excessive pruning. Fortunately, this problem does not adversely affect the production of tomatoes. Leaves remain green and hang on the plant, though affected leaflets do not unroll. If you are irrigating, try to keep the soil moisture level consistent and account for rainfall when irrigating. Some tomato varieties are more susceptible to leaf roll than others, such as ‘Beefsteak’, ‘Big Boy’, and ‘Floramerica’.

Source Ohio State Weekly Gardening News, June 2003

 

Fertilizing Tomatoes

We had many calls from gardeners late last season that had grown lush and massive tomato bushes, but the plants had set few, if any, fruits. Tomato growers should remember not to over fertilize plants. Only one application of fertilizer is made once the first blooms set fruit and that is all that is required for the season. Over fertilizing with nitrogen will grow lots of lush foliage, but few fruits. Use a fertilizer with a 1:2:2 ration such as 5-10-10, 6-12-12 or similar analysis fertilizer. The same is true for pepper and eggplant; only one application of fertilizer is needed after the first fruits set.

Source: Ohio State Weekly Gardening News, June 2003

Summer 2003
Hort Shorts | Hort Tips | Did You Know… | Did Winter Kill My Trees? | Unlocking the Medicinal Secrets in Plants | Herb of the Year 2003: Basil | Bug Bites: Carpenter Ants in Trees | Cybergarden Sites | Lawn Care Calendar | Tomatoes: Can, Freeze or Dry | Fruits With Bad Seeds | Trans Fat on the Food Label | Health & Household Tips

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