Disease Management

California almonds are susceptible to many diseases, which can reduce crop yield and quality in both current and subsequent years. They also can weaken and, occasionally, kill trees. Almond diseases are caused by a wide variety of microorganisms including fungi, bacteria, and viruses. They also can result from certain environmental stresses or genetic disorders. Some occur only at particular times of the year; others remain in the tree and exhibit yearlong symptoms. Disease infections may be more or less severe depending on age of the tree, variety, and environmental conditions such as rainfall, temperature, humidity, soil type, and soil moisture content. In order to fully understand the impact of disease organisms and environmental conditions on almond trees, it's important to understand the tree's seasonal cycle, growth processes, and crop development. The purpose of this course is to provide an update on current diseases that occur in California almonds--everything from branch and root diseases to vascular disorders--and the latest disease management practices that can protect valuable orchards and crops.

As of January 2018, there were approximately 2.63 million managed honey bee colonies in the U.S. Over 500,000 make their home permanently in California, while another 1.5 million hives are moved into the state annually to augment the pollination demands of California’s almond crop alone. This means slightly fewer than 79 percent of the managed hives in the U.S. are used to pollinate a single California crop.

In 2019 there are about 1.16 million planted acres of almond orchards in California, with mature trees on bearing acreages capable of producing more than 2.27 billion pounds of almonds annually. Growers usually rent two colonies of honey bees per bearing acre.

“Honey bees are essential to almond production,” said Bob Curtis, pollination consultant and retired director of Agricultural Affairs for the Almond Board of California. “Every almond we eat exists because a honey bee pollinated an almond blossom so it’s in farmers’ best interest to keep them safe. Our livelihood depends on it.”

As important as managed honey bees are to almonds and the more than 100 other crops they pollinate, pesticides and insecticides used to protect crops against pests are also important. Farmers and crop protection specialists recognize that and work diligently to ensure that pollinators and pesticides can co-exist in balance.

This course will examine the stressors on the honey bee population such as Colony Collapse Disorder, nutrition, pesticides, parasites and pathogens as well as rules and legislation to protect honey bees. 

When people hear the words, fungus or fungi, they tend to think mushrooms or, perhaps, molds, or yeast. While mushrooms, molds, and yeast do fall in the fungi family, the term actually refers to a much broader spectrum of organisms.

A fungus is a member of the Fungi Kingdom, a group of eukaryotic organisms (organisms whose cell nucleus is enclosed within membranes). Biologists have identified more than 100,000 different species of fungi. More than 1.5 million species are estimated to now exist on planet Earth.

Fungi are the number one cause of crop loss worldwide. Management and control of fungi is vital to the agriculture industry as well as to the grower’s harvest yield and marketability of the crop.

This course discusses types of fungi and appropriate biological controls.

Potassium nitrate is used in agriculture, industry, solar energy plants, food and pharma. In agriculture, the main uses of potassium nitrate are related to the supply of plant nutrients via fertigation, foliar and field applications. Potassium nitrate has also proven to be a valuable tool in crop pest and stress management and has shown positive effects on the control of plant pests and diseases when applied or as an additive to crop protection agrochemicals, thus allowing the grower to practice more effective and judicious use of pesticides. When used correctly, potassium nitrate can be a valuable and economic source in any Integrated Pest Management (IPM) strategy, not only for its effective and environmentally sensitive aspects, but for its effects on overall plant health, thus creating a stronger, more resistant plant. This is demonstrated in this course by a number of examples of pest management with potassium and nitrate sources. This course also has a section on the role of nutrients in IPM and is sponsored by SQM.

Grape Powdery Mildew is the number one disease in California vineyards. More dollars are spent on powdery mildew control and, yet, this disease still accounts for more crop losses than any other grape pest. This course, sponsored by Western Farm Press, explores the different fungicide classes; treatment options for powdery mildew in California; resistance management, and regional differences in disease development. It also includes a detailed approach to using the UC Powdery Mildew Risk Assessment Index (RAI) to predict infections. Seasonal patterns of disease development differ from region to region (as well as year to year), and cost-effective management strategies must be based on local conditions that favor or inhibit pathogen reproduction. Season-long control depends on reducing early-season inoculum and subsequent infections with well-timed fungicide applications. Spray timing and frequency (and coverage) is everything; these vary depending on local weather, temperature, varietal susceptibility, vine growth stage and material choice.