May be applied as a soil or trunk spray or by chemigation. This disease can be caused by different species within the genus Phytophthora, a water mold in the Oomycete class, and can be found around the world. All other trademarks are the property of their respective owners. COMMENTS: For use on trees in nurseries only. The pathogen infects the root cortex, which turns soft and separates from the stele. Trees should be sprayed to wet at the time of planting. ©2020 Syngenta. Phytophthora citrophthora is a winter and summer root rot that also causes fruit brown rot and gummosis. Sign up for the Know More, Grow More Digest to receive twice-monthly agronomic e-mail updates pertinent to your area. Do not plant for at least 3 months. Apply in 100 to 250 gal/acre; spray to wetness when conditions favor disease development. Damage from mowers and jagged cuts from dull tools may leave an opening for the water mold pathogen to enter. COMMENTS: Use lower rate on sandy loam and high rate on heavier soils or high clay. According to the University of Florida Institute for Food and Agricultural Sciences (IFAS), Phytophthora root rot is one of the most important diseases threatening citrus yield. If a tree growing on susceptible rootstock looks stressed, dig up some soil and check the feeder roots. Citrus growers need every available tool to fight disease, reduce tree stress and keep groves healthy against Phytophthora root rot. Phytophthora root rot damage begins below the soil, then extends through root systems and ultimately affects entire trees. They can survive adverse conditions as persistent spores in the soil. When replanting or establishing new plantings, choose resistant rootstocks where possible, but also consider tolerance to other diseases, nematodes, and cold. According to the University of Florida Institute for Food and Agricultural Sciences (IFAS), Phytophthora root rot is one of the most important diseases threatening citrus yield. Apply in a banded surface spray under tree canopy. The most tolerant rootstocks are trifoliate orange, swingle citrumelo, citrange, Alemow, and sour orange. Apply 0.5 to 1 inch water after application. Fumigants such as metam sodium are a prime source of volatile organic compounds (VOCs), which are a major air quality issue. This tool creates a perfect opening for the water mold (previously labeled a fungus) to enter. Enter your email address to subscribe to Citrus Industry and receive notifications of new posts by email. Phytophthora parasitica is active during warm weather when roots are … Phytophthora parasitica is active during warm weather when roots are growing. Disease symptoms are often difficult to distinguish from nematode, salt, or flooding damage; only a laboratory analysis can provide positive identification. Dead bark tends to break away from the trunk in vertical strips. Phytophthora citrophthora is most damaging when citrus roots are inactive and their resistance to infection is low. Ohr (emeritus), Plant Pathology, UC Riverside, Fungicide Resistance Action Committee (FRAC). The symptoms commonly seen above ground include yellowing of foliage, abscission of leaves, dying shoots and reduced fruit size and yield. COMMENTS: Apply with 6 to 12 inches of water. Put composite samples in a sealed plastic bag, but do not refrigerate or overheat. The leaves turn light green or yellow and may drop, depending on the amount of infection. Apply in 100 gal water/acre to susceptible varieties as a foliar spray when conditions favor the disease. Phytophthora root rot is most often found on citrus trees that are overwatered and have cuts from lawn equipment, such as from a weed whacker. Preharvest interval (PHI) is the number of days from treatment to harvest. Performance assessments are based upon results or analysis of public information, field observations and/or Syngenta evaluations. COMMENTS: Apply in March to April followed by one or two applications at 3-month intervals to coincide with root flushes; rate depends on tree size and the number of applications per year.