Q: I’m worried about my garden. There are black spots on my tomatoes, rust colored spots on my roses — nothing is looking great. What am I doing wrong? — Norinne Morris, San Luis Obispo
A: Finally, after a long, wet winter, an almost nonexistent spring and our notorious “June gloom,” summer is officially here. Most gardeners look forward to the typical, rewarding chores of the July garden: deadheading, pinching back chrysanthemums, harvesting beautiful produce and flowers — even planning for the fall garden.
This year, however, gardeners on the Central Coast are faced with special challenges. We’re experiencing unusually high levels of plant disease, from early blight of tomatoes (the likely cause of your spotted tomato plants) to rust spots on rose leaves, to mildew on vegetable plants.
Generally the problems are caused by various types of fungus. While there are many species of fungal diseases, most of them share certain characteristics. Their growth is encouraged by cool, damp weather and spread by wind and rain. In other words, this has been a banner year for fungus development. While not all fungal diseases will kill the plant, many of them can do damage in our gardens — and are not fun at all!
The University of California website (www.ipm.ucdavis.edu ) offers information on specific fungal diseases and management strategies for specific types of vegetable, fruit or ornamental plants. In general, control is similar for most of them and demands a bit more than the usual amount of attention to our gardening in July.
While judicious use of fungicides may occasionally be helpful, they are best used as a preventative measure.
At this point, impeccable management of irrigation and cleanliness in the garden will be your best approach. Avoid overhead watering, and do not allow the ground to stay soggy. Minimize contact between the plant and the wet soil. Carefully clear out all diseased plant material and dispose of it rather than compost it. Clean up all dropped flowers, fruits and vegetables. Leave space between plants for good air circulation. When possible, plant resistant species.
Because many fungi will overwinter in the soil, it is advisable to rotate crops to minimize the contact of certain pathogens with susceptible plants.
The development of disease from most fungi stops in hot, dry weather, so let’s keep our fingers crossed and hope for a warm, sunny July!