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Maple (Acer spp.) - Bleeding Canker
Cause The fungus-like organism, Phytophthora spp., has been found in rotted maple (especially Acer palmatum) roots and branch tip diebacks by the OSU Plant Clinic. In addition, P. cactorum was found by the OSU Plant Clinic associated with bleeding trunk cankers. Phytophthora gonapodyides and other species have been found in symptomless roots of Acer rubrum shipped from the west coast. Other organisms, such as Pythium spp., have also been found in association with rotting maple roots.
Flooded or poorly drained soil or media encourages disease development. These organisms survive unfavorable periods within soil, media, and infected plant debris. Under favorable conditions, spores germinate and infect roots. After infection, the microorganism spreads mainly in the inner bark tissues of the root. They survive as various spores in the soil, container media, or infected roots. Movement of infected plants and/or soil can spread the microorganism.
Symptoms Aboveground symptoms are generally slow or poor growth, which can be mistaken for other problems such as nutritional deficiencies. Root systems; however, are rotted with few if any feeder roots. In advanced cases, many roots are in various stages of decay. The vascular cambium near the root crown shows a brownish discoloration that has a distinct border with healthy tissue. Stem lesions may also accompany rotted roots.
Cultural control
- Container production should be on raised benches or gravel covered beds sloped to quickly drain excess water.
- Avoid reusing pots from a previous crop for propagation. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
- Avoid ponding of water around plants.
- Avoid over- or under-watering plants.
- Plant in a well-drained area or container media.
- Avoid leaving trees on the ground during rainy winter weather.
- Remove and destroy all infected plants and plant debris.
- Prevent mechanical injury to trees, especially late in the season.
- Do not let sprinkler irrigation wet landscape tree trunks.
Chemical control To minimize the development of resistant fungi, alternate or tank-mix fungicides from different groups that have different modes of action. Use fungicides as preventative treatments, they generally do not save heavily infected plants. The phenylamide and phosphonate fungicides (Group 4 and P7 fungicides) do not kill these organisms. They can only prevent establishment of the organism before it gets into the plant. They can also prevent continued growth if the organism is already inside the plant thereby delaying symptoms that might have developed. Once chemical activity has subsided with time, the organism can resume growth within infected plants.
- Aliette at 5 lb/100 gal water. Do not use with adjuvants. Group P7 fungicide. 24-hr reentry.
- ArborFos is registered for tree injections. The number of capsules used is based on tree size. Group P7 fungicide.
- Fosphite at 3 quarts/100 gal water. Do not use copper products within 20 days of treatment. Group P7 fungicide. 4-hr reentry.
- Phospho-Jet is registered for tree injections. Rates are based on tree size. Group P7 fungicide. 4-hr reentry.
- Rampart at 1 to 3 quarts/100 gal water/A. Do not use copper products within 20 days of treatment. Can also be trunk injected. Group P7 fungicide. 4-hr reentry.
- Segovis at 0.65 to 3.2 fl oz/100 gal water as a soil application. Group 49 fungicide. 4-hr reentry.
- Subdue MAXX at 1 to 2 fl oz/100 gal water as a drench. Apply 1 pint of solution per 1 sq ft. Group 4 fungicide. No restrictions on reentry when used as a soil drench.
References Bienapfl, J.C., and Y. Balci. 2014. Movement of Phytophthora spp. in Maryland's Nursery Trade. Plant Disease 98:134-144.