Much of California and the Southwest is experiencing the driest period in over a century, according to the National Oceanographic and Atmospheric Administration. This is the fourth year of drought, and there is no end in sight. California’s coniferous forests and oak woodlands as well as its urban forests are being affected. Drought is not only the result of subnormal rainfall but also of temperature and plant transpiration. Although most trees are adapted to moderate seasonal droughts, acute or chronic droughts can cause severe damage, direct mortality or predispose trees to invasion by secondary pathogens. Drought is also relative‒some species are adapted to dry soils, others no so much. This presentation will focus on the how trees respond to soil water deficits, how drought effects trees, and it predisposes them to opportunistic pests. Diagnosing the signs and symptoms of drought stress, common secondary insects and plant pathogens affecting stress-weakened trees, and ways to mitigate drought stress will be discussed.
Bruce Hagen resides in Sonoma County, California. His received an MS in Entomology from San Diego State University. He Retired from California Dept. of Forester and Fire Protection (21 years), were he worked as an Urban Forester and Forest Pest Specialist and was an Economic Entomologist with the California Dept. of Food and Agriculture (10 years). Bruce was formally a Board Member for the WCISA. He is the current editor for the Western Arborist Magazine, newsletter for WCISA. He has written extensively for CDF, ISA, WCISA on urban forestry, arboricultural, pest management, tree preservation, oak woodland issues, ‘FireSafe’ landscaping, plant health, pest management, etc. Bruce Co-authored a book on Care of Oaks in the Landscape – a University of California Publication.