Q: What can I do to grow healthier tomatoes this season? — Roger Eberhart, San Luis Obispo
A: One of the best ways to grow healthy tomatoes is to plant varieties well adapted to your local climate. Many tomatoes set fruit only with warm nights (above 55˚ F) and days less than 90˚ F. Last year’s cool summer caused late, small harvests in many areas. Ask local nurseries and neighbors what variety might prosper in your location.
Although many gardeners enjoy experimenting with heirloom tomatoes, it is probably wise to plant at least some hybrid tomatoes labeled VFN. These varieties have been bred resistant to common tomato diseases caused by fungi in the soil (Fusarium and Verticilium wilts), and also nematodes. Both fungal diseases cause yellowing of leaves and severe decline.
If you suspect your tomatoes suffered from these diseases last year, plant in another part of the garden or in containers. Tomatoes are also susceptible to other diseases caused by fungi and to several viral diseases. Avoiding overhead watering may prevent some diseases promoted by wet foliage.
Unfortunately many insect pests also target tomato plants and fruit. With daily inspection, you may be able to identify and control the worst of these pests. If you have only a few plants, hand picking of horned worms and other large pests is quite effective. Sometimes a magnifying glass will help spot smaller scales and mites. For online help identifying pests and suggested treatment, go to http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/tomato.html.
Local Master Gardeners may also be able to identify your problem when given a sample of leaves or fruit. Strong plants can often survive pest or disease attacks and still bear fruit; so start by giving tomatoes optimal amounts of sunshine, water and nutrients.