Reduce Blossom End Rot
Now that tomatoes are setting fruit, watch for a physiological disorder that causes the bottom of the tomatoes to develop a sunken, brown or black, leathery spot. This disorder is termed "blossom end rot," and it's caused in part by inconsistent soil moisture, combined with calcium deficiency. This can occur when the plants are watered well and then the soil is allowed to get too dry. The best way to prevent blossom end rot is to mulch tomato plants to help maintain uniform moisture in the soil, and to water plants thoroughly and deeply on a regular basis to minimize fluctuations in soil moisture.
Midsummer is the time to watch for signs of the tobacco/geranium budworm. Geraniums, petunias, and nicotiana flowers and buds can be quickly devoured by these tiny caterpillars. The caterpillars will often take on the color of the flowers they are eating, which makes them difficult to find. While they are still small, you can control them with Bt (Bacillus thuringiensis), the biological control sold under various trade names. Bt is very effective at controlling young caterpillars, and is harmless to other creatures.
During the heat of summer it is important to check soil moisture at the root zone of newly planted trees and shrubs. To do this, dig down 8 to 10 inches with a trowel or soil probe. Don't overwater or water too frequently; this can damage the root system. It is better to water trees and shrubs deeply and less frequently, which encourages a healthier and more drought-enduring root system.
Plant Fall Crops
If you want a fall crop of lettuce, peas, spinach, beets, and cabbage, now is the time to plant. These crops can be sown directly in your garden and will germinate quickly in warm soil. Many pests, such as root maggots, and soil-borne diseases have had their season and are now gone. These crops prefer the cooler weather of fall and will continue to yield even after a light frost.
Watch For Bean Beetles
Keep a watchful eye out for Mexican bean beetle larvae. The beetles are beginning to hatch, and the young larvae will feed on bean leaves. Though similar in appearance to the beneficial lady bird beetles, Mexican bean beetles are yellow with rows of dots across their wing covers. Look for orange eggs on the undersides of the foliage. Both larvae and adult beetles cause damage as they skeletonize leaves. You can reduce plant damage by hand-picking egg masses and beetles.