IPM for field-grown rose plants in California

Approximately half of the U.S. rose plant production is located in the southern San Joaquin Valley around Wasco, California. The production of insect-, disease-, and nematode-free plants is required both for product quality and by state regulation. IPM methods are favored wherever practical, and field studies have been executed to investigate both chemical and non-chemical alternatives to current practice. Recent work has included investigation of methyl bromide alternatives for management of soil-borne pests and pathogens, development of sampling strategies and treatment thresholds for spider mites, which are the most important invertebrate pests of roses, and evaluation of acaricides and herbicides. In the current cropping system for roses, methyl bromide is routinely used as a pre-plant soil fumigant to minimize production losses due to soilborne pests including plant parasitic nematodes, fungal and bacterial pathogens, and weeds. Both chemical and non-chemical alternatives for this fumigant are being sought, due to its impending US production and importation ban. Cultural practices for roses are organized around furrow irrigation systems, and the absence of summer rains minimizes disease pressure from several foliar pathogens.