How to Manage Pests
UC Pest Management Guidelines
Phytophthora Root and Crown Rot
Pathogen: Phytophthora spp.
(Reviewed 4/13, updated 4/13, pesticides updated 6/16)
In this Guideline:
Symptoms and Signs
Symptoms of Phytophthora root and crown rot commonly occur in spring and include reduced terminal shoot growth, chlorotic and/or undersized leaves, and an open canopy. As temperatures increase in summer, vines may collapse suddenly, or alternatively, vines may decline slowly over a few seasons. Roots and crowns of infected vines exhibit a red-brown rot that is easily observed by cutting into the cortical tissue. Often a margin where healthy, white tissue meets diseased tissue may be found. Feeder roots are lacking and active lesions often progress above ground on one or more sides of the lower trunk resulting in sunken areas.
Comments on the Disease
The pathogens survive in soil and can be carried in irrigation water obtained from surface sources. Prolonged periods of saturated soil are optimal for the pathogen to infect roots. Disease development is enhanced in poorly drained soils or where vineyards receive long durations of flood irrigation. Several species of Phytophthora are known to attack kiwifruit roots and crowns.
This disease can be managed using strict planting practices, water management, and fungicide treatments. Plant on raised berms in well-drained soil to allow for rapid water drainage following irrigation or rains. Duration of irrigations should not exceed six hours in fields where disease occurs. Intervals between irrigations may be shortened as needed as long as the soil has drained adequately since the last irrigation.
Fungicides with efficacy that are currently registered in California for the control of root and crown rot include mefenoxam and phosphonates. Hydrogen dioxide is also registered, but yields variable results.
UC IPM Pest Management Guidelines: Kiwifruit
J. E. Adaskaveg, Plant Pathology, UC Riverside
Acknowledgment for contributions to Diseases:C. Arredondo, Plant Pathology student, UC Davis
K. Conn, Plant Pathology, UC Davis