Originally created 08/18/00

Tomatoes need six hours in sun



I get calls this time of year from homeowners concerned about spots that appear on tree leaves. These folks are afraid that their trees are going to die if they don't do something.

There are a number of spots that appear on different species of trees, but in almost all cases they are nothing to worry about.

One of the most common leaf spots is oak leaf blister, a disease that occurs on red and white oaks. Symptoms include light green to yellowish blisterlike, roughly circular bulges on upper leaf surfaces (depressions as viewed from the lower leaf surface). These blisters tend to brown as the season progresses.

Spores over-winter on leaf buds and infect leaves as they open. This is the only infection that occurs each season, and leaves become resistant to infection as they mature. This infection tends to be worse in a mild, moist spring. There's usually no reason to treat with a fungicide.

Tar spot infects maple trees. The fungus over-winters on fallen leaves, then infects the upper surfaces of leaves in the spring. This disease causes raised, black tar-like spots that develop on the upper side of mature leaves in mid to late summer. Infected leaves may drop prematurely. To control, rake and dispose of fallen leaves.

Phyllosticta also infects maples. Its circular spots develop into tannish spots with purple to red borders. Later in the season the spots often contain black fruiting bodies of the fungus arranged in rings inside the lesion.

It's quite noticeable, especially on silver and red maples, but damage is minimal and fungicides are rarely necessary. As with tar spot, rake and remove the fallen leaves.

Tomatoes

Many gardeners are having problems with tomatoes developing blooms but no fruit.

One problem could be in pollination. Tomatoes are self-pollinating and need wind or some movement to pollinate. If it stays calm for several days, gently shake the plants and this will ensure pollen transfer and fruit set.

Another reason fruit may not set is extreme heat. When it's 92 to 95 degrees in the daytime and stays around 75 at night, blooms drop.

Too much fertilizer, particularly nitrogen, also will cause blossom drop. A 20-20-20 fertilizer is probably too high in nitrogen. The ideal tomato fertilizer is a 5-10-15, or something similar.

Tomatoes need a minimum of six hours of sun to do well. Many people grow them in shadier places, but the less sun you give them under six hours, the fewer tomatoes you tend to get.

One final culprit could be dry soil. Keep your plants watered when they need it.

Spraying with a commercial blossom set that you can buy at a garden center has helped solve this problem for many tomato gardeners.

Sid Mullis is director of the University of Georgia Extension Service office for Richmond County. Call him at 821-2349, or send e-mail to smullis@uga.edu. The offices that serve Richmond and Columbia counties have a Web page at www.griffin.peachnet.edu/ga/columbia.