Tips for keeping tomatoes healthy, insect free

Tomato problems are plentiful this week. The harsh climate, poor cultural practices, diseases and insects bring on disorders that are discouraging. Here's how you can minimize these concerns.

Tomatoes love temperatures between 70 and 90 degrees and hate temperatures below 55 and above 75 degrees at night. Our temperatures are more outside those parameters than in.

Relative humidity plays a major role in setting fruit. Tomatoes like humidity between 40 percent and 70 percent, and ours runs below 20 percent.

Here is a partial solution to improving blossom set until it gets real hot: Direct a jet of water at your blossoms each morning. The water lowers temperature, raises humidity and vibrates flowers so the pollen becomes stickier to improve fruit set.

Sunscald becomes a factor when tomatoes are exposed to extreme heat and bright sun. The tissue develops a blistered, water-soaked appearance and leads to scalding. Either plant heavy-foliage tomatoes such as Patio or Better Bush or shade the fruit.

Fruit cracking occurs when temperatures exceed 90 degrees and plants become stressed for water. When you do irrigate, moisture promotes rapid growth within the fruit and cracks result. Mulching under plants helps to maintain a more uniform soil moisture and stops cracking.

The tomato russet mites bring on bronzed tomato leaves. It's impossible to see this mite with the naked eye. If you must see them, get a 20x hand lens. We rarely notice this damage until we see the bronzed leaves at the base of plants. These mites move up the plant sucking sap out of the leaves and causing the bronzing. You'll find the highest concentration of mites above the bronzed tissue on healthier leaves.

These mites multiply like wildfire. Newly hatched larvae begin laying eggs within 48 hours, so it is imperative you get them with a miticide. Direct it just above the bronzed leaves. These mites took care of my tomatoes last year while I was on vacation.

Three-inch-long tomato hornworms scare many gardeners to death. They come from mammoth grayish moths that lay eggs near your tomatoes at night so you don't see them. The hornworm feeds on foliage at night and returns to the soil during the day, so go out at night to find them. Pick them off or spray them with Bt (organic product), sold at nurseries. Don Fabbi throws them in the road and lets cars eliminate them. I remove any damaged leaves so I know if they're still around.

Curling leaves is a disease called curly top virus. It causes infected leaves to curl and twist. Leaf veins turn purple, foliage becomes dull yellow, the fruit prematurely ripens without increasing in size, and plants eventually die. Leafhoppers cause this virus. It affects only one or two plants, never the entire crop. Remove infected plants so leafhoppers can't spread it to others.

White flies cause sticky substances, similar to aphid honeydew on tomatoes. Disturbing vines flushes these small powdery-white insects out in the open so you see them. They suck juices from plants and secrete the honeydew. This stunts plants and reduces yields.

Yellow attracts the whiteflies. Place several yellow boards around the garden above the foliage and smear heavy oil on them. Vigorously disturb foliage to flush flies out. They head for the boards seeking cover and become stuck in the oil and die. Insecticidal soap and pyrethrum, both organic insecticides, will control them, but make repeated applications. The trick is spraying the underside of leaves where they hang out.

IRIS PLANT SALE

The Las Vegas Iris Society's iris sale will run from 8 a.m. to 5 p.m. Saturday and from 9 a.m. to 3 p.m. June 26 at Plant World Nursery, 5311 W. Charleston Blvd. Society members have tested all the irises so you'll go home with winners.

GARDEN CLASSES AT PRESERVE

On Saturdays and Sundays throughout June, gardening demonstrations are always happening at the Springs Preserve, 333 S. Valley View Blvd. Here's what's going on.

Exploring Trees Inside and Out: This exhibit is open every day until September. You climb through the inside of larger-than-life trees, soar over the treetops using an entertaining "green screen" experience, jump into a giant bird's nest and take in the aroma of an orchard.

Grow Your Own (11:30 a.m.): Can you create a beautiful desert flowering landscape from seeds? Sure. Learn how to collect and harvest seeds and then grow your own successfully.

Container Gardening (1:30 p.m.): I will show you how containers let you have a green thumb even if you have a small yard or patio.

Plants for Lazy People (2:30 p.m.): Take the hassle out of gardening with these plant-'em-and-forget-'em plants.

Water-wise Gardening (3:30 p.m.): Get healthy plants with less water. Learn the secrets of water-wise gardening.

Linn Mills writes a garden column each Sunday. He can be reached at linn.mills@ springspreserve.org or 822-7754.