Summer garden problems explored

Squash bug life stages: eggs, nymphs and adults, Photo courtesy of Missouri Botanical Gardens.

Heat and tomato fruit set: The hot streak we had recently was not good for a lot of plants, but in particular not good for fruit set in tomatoes. Tomato blossoms drop off when daytime temperatures exceed 95 and night-time temperatures are above 70. Tomatoes in the sun may experience temperatures as much as 10 to 15 degrees higher than a shade measurement. Hence, there likely will be some time slots of no tomato harvest. Cool summers are best for consistent tomato production in our valley.

Some things that might help would be to use shade cloth which will keep plants cooler while only partially blocking light; misting them at midday also helps. Planting some varieties early to get some early tomatoes before hot weather comes and planting others late for fall tomatoes. However, most indeterminate varieties will start producing again in the fall or in cooler weather, without planting new plants. There are also some varieties more heat tolerant than others: Arkansas traveler, Early Girl, Marvel Striped, Thessaloniki, Roma are a few, for more information see: .

Squash bugs: The squash bug (Anasa tristis) is a garden pest that many of us battle annually Squash bugs feed on cucumbers, melons, pumpkins and summer and winter squash. It will often cause wilt of zucchini or squash plants. If you garden organically, here is one approach that helps. Spray water with a hose or watering can over your zucchini plants. This will cause the bugs to crawl out of their hiding places and move upward on the plant where you can see them and pick them off. Another approach is to place boards or wood shingles under the plants where the bugs will hide overnight. In the early morning, turn over the boards and squash the bugs.

If you are lucky enough to kill the overwintering adults before they reproduce, then you may enjoy a bug-free summer. Be sure to check underneath leaves for their shiny orange-brown eggs and rub them off before they hatch. It takes about a week or more for eggs to hatch. If they hatch, the nymphs can be killed by neem oil or horticultural oils, but it is difficult to spray under the leaves where they hang out. If nymphs are present, you may have lost the chance to be free of squash bugs this year.

I have noticed that the bugs show up first and most abundantly in my Caserta variety of zucchini, so some plants may be more susceptible than others; hence planting more resistant varieties can help ease the problem. To reduce the overwintering of adult squash bugs, it is advisable to clean up garden debris and vines in the fall by removal or composting them.

Stink Bugs: A tomato pest that resembles the squash bug is the stink bug. Both have stinking odors when squished, but the stink bug make a bad odor when disturbed. The most common species statewide is the consperse stink bug (Euschistus conspersus). It is the most important species in the northern San Joaquin valley. If you have yellow spots or splotches on your ripe tomatoes, the stink bug is the likely culprit and the stings that cause the yellow spots may be delivered when the tomato is green. They then show up as dark pinpricks surrounded by a slightly discolored area.

Deterring these pests include: cleaning out weeds and debris around the vegetable garden where adults overwinter or hide, encourage beneficial predators: birds, assassin bugs, praying mantis. You can also use pheremone traps designed for stinkbugs. Hand picking, neem oil and insecticide soaps can also be used to kill stink bugs. Planting decoy crops will help keep them away from your tomatoes or other crop of interest. Decoy plants are mustard, millet, buckwheat, sorghum, sunflower, marigolds, lavender and chrysanthemums.

Blossom end rot: If you have a brown spot of tissue on the blossom end of the tomato it is likely blossom end rot. This is not a pathogen caused problem, but is produced by a calcium imbalance in the plant. It is often brought on by inconsistent watering. It is best to water tomatoes 2 times per week and water deeply each time. Tomato roots can go four feet deep so shallow watering is not advisable.

Tomato Spotted Wilt Virus (TSWP): For some gardener especially in the Linden area, TSWP   virus overwinters in weeds in orchards and it is carried to the tomatoes or peppers by tiny, 1 mm long, thrips. The plant declines over time with bronzing and curling of leaves and fruit have a mottled appearance. It is best to remove the infected plants. To avoid this problem, plant TSWP resistant tomatoes, but they are not readily available to gardeners unless you grow your own. For more info go to: .


If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:

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