In the Garden:
Western Mountains and High Plains
July, 2012
Regional Report

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A three to four inch layer of straw mulch helps to maintain uniform soil moisture and moderate soil temperature.

Prolonged Heat and Drought Hard on Tomatoes

I can't remember a summer so hot, and so early in the season. Tomatoes love the heat, but when temperatures hit the triple digits for a prolonged period, problems can result.

I've been watering my garden diligently to reduce moisture stress during these periods of dry, hot weather. Deep watering is more effective than frequent light waterings. My layer of organic straw mulch is helping to maintain uniform soil moisture and moderate soil temperatures.

One of the most common problems of tomatoes in summer is blossom end rot (BER). It causes water soaked, sunken spots near the blossom end of the tomato. As the spots enlarge, they will become dark brown to black and feel leathery.

Blossom end rot can be caused by a variety of cultural problems. A calcium imbalance as the fruits are developing can be the result of improper irrigation and prolonged dry, hot weather. High levels of nitrogen from fertilizer or disruption of the root system by deep cultivation can also cause BER.

You can prevent blossom end rot by keeping your tomato plants well mulched to maintain uniform moisture and avoiding high nitrogen fertilizer.

Hot, dry weather can also cause sunscald on the fruits. White or yellow patches on the side of the tomato fruit exposed to the sun are typical when it is exposed to direct sunlight. Stifle the urge to prune off foliage, as it is needed for natural shading and protecting the ripening fruits.

Summer heat invites a variety of tomato insects that can wreak havoc, sometimes overnight. Hornworms are the most noticeable pest. These large (3-4 inch) caterpillars devour the foliage starting at the top of the plant. Handpicking is an easy way to control hornworms. The bacterial control Bacillus thuringiensis is effective if it is applied when these critters are small, as are natural predatory wasps that deposit their eggs on the caterpillars.

Aphids, psyllids, and flea beetles are other pests of summer. Aphids suck plant juices from the plant and deposit sticky honeydew on the leaves. Psyllids cause the foliage to turn yellow and leave a sugar-like residue on the leaves. Insecticidal soaps and sulfur dust can be applied for controls. Flea beetles chew tiny holes into the leaves, leaving them looking as though they were blasted with fine shot. Diatomaceous earth, neem-based insecticides, and horticultural oils are effective against flea beetles.

As the summer continues to sizzle, make sure your garden is mulched and watered properly to keep your plants healthy and more resistant to problems. This heat can't last forever!


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