In This Issue

Phytophthora Root and Crown Rot - Implications
of Fall Irrigation in Controlling the Disease

This past season has been one of the worst years for phytophthora root and crown rot that I have experienced. I have observed the problem on fruit trees of all ages and species, and in all types of soil.

Symptoms of the disease include leaf yellowing, overall weakening of scaffolds and shoots, small fruit, and eventual tree death. Diagnose the disease by cutting into the tree trunk just below the soil line. If the disease is present, the rootstock will be brown and decayed, and sometimes slippery. Unlike bacterial canker - there usually is no smell associated with the disease.

The common culprit in all instances of phytophthora infection is water. The phytophthora fungus is a water-loving pest that lives in and is spread by water. Because of this it is important to ensure that orchards are not over-irrigated, especially in the spring and fall when soil temperatures are cool and most favorable to the development of the fungus.

To help prevent this disease do not over-irrigate or saturate soils this time of year. Try to make sure that water never stands for more than 24 hours after an irrigation, and make sure that water never stands around the trunk of the tree. A good rule of thumb is to irrigate after mid-September only if necessary.

Average tree water use in October and later is negligible. Of the 36 to 40 inches of water required by the average orchard in our area, only about 1.5 to 2 inches are used after the first of October. And only about 3.5 inches of water are used in September. Compare this to the period of peak water demand - July - when about 8 inches are used.

Consequently, tree irrigation needs this time of year can generally be met with just very small amounts of water. This reduction can play an important role in limiting phytophthora infection.

After several years of work we are pleased to announce that this new UC IPM manual is available. Developed for growers and pest control professionals, this book contains the most up-to-date information available from University of California researchers, specialists, and farm advisors.

Topics covered in the book include:

• Insect Pest and Disease Management
• Nematode Management
• Vegetation Management
• Tree Training and Pruning
• Irrigation Scheduling
• Scheduling Management Activities
• Soil and Tissue Sampling
• Pheromone Mating Disruption
• Relative Toxicity of Pesticide to Natural Enemies and Honey Bees
• Organically Acceptable Pest Control Options
• Vertebrate Pest Control Options

The book is 264 pages long and contains more than 250 color photographs. It is now available at our office for $35. Please stop by our office to pick up a copy or call (559) 733-6363 to arrange to have a copy mailed to you today.