potato 5-9-12 CLEAN - Vegetableipmasia.org

ORGANIC POTATO PRODUCTION temperatures are high. High temperatures and moisture on tuber surfaces promotes disease in storage.Key characteristics: This fungal disease is also referred to as “black dot” because of the numerous black, fungal structuresthat appear on tubers, stolons, roots, and stems both above and below ground. Root growth is reduced and appears brown toblack in color. Tuber infection appears as brown to gray discoloration over a large part of the tuber surface or as round spotslarger than 1/4 inch in diameter. Black dot survives up to 2 years on infected plant debris and soil. See HUfact sheetUH (Reference65), HUinteractive black dot potato photoUH (Reference 66) and Michigan State University HUlife cycleUH (Reference 67).Relative risk: Black dot root rot occurs sporadically but can result in 75% yield loss in severely infected fields. Can bedestructive because it causes symptoms on all plant parts.Management Option Scouting/thresholds Crop rotation Resistant varieties Seed selection Site selection Postharvest Notes Recommendation for Black Dot Root Rot Record the occurrence and severity of root rot. Thresholds have not been established for organic production Minimum 3-­‐4 year rotation that includes a grain crop. Maintain good management of solanaceous weeds in rotational crops. Do not rotate with tomatoes. No resistant varieties are available, but late-­‐maturing varieties are more vulnerable to yield reduction. Varieties that appear to be moderately resistant (based upon tuber ratings) include Eva, Genesee, Keuka Gold, Lehigh, Norland, and Norwis. Varieties that are moderately susceptible to susceptible include Andover, Banana, Chieftain, Monona, Pike, Reba, Superior, and Yukon Gold. See Section 6: Varieties. Plant phytosanitary certified seed. See Section 7.1: Seed sources. Choose well-­‐drained field if possible. Deep plowing will bury infected debris and promote decomposition. Provide adequate water and fertilizer because crop stress increases vulnerability to black dot. At the time this guide was produced, the following materials were labeled in New York State for managing this pest and were allowable for organic production. Listing a pest on a pesticide label does not assure the pesticide’s effectiveness. The registration status of pesticides can and does change. Pesticides must be currently registered with the New York State Department of Environmental Conservation (DEC) to be used legally in NY. Those pesticides meeting requirements in EPA Ruling 40 CFR Part 152.25(b) (also known as 25(b) pesticides) do not require registration. Current NY pesticide registrations can be checked on the Pesticide Product, Ingredient, and Manufacturer System (PIMS website) http://pims.psur.cornell.edu/ (Reference 3). ALWAYS CHECK WITH YOUR CERTIFIER before using a new product. Table 12.7 Pesticides Labeled for Management of Black Dot Root Rot Class of Compounds Product Name (active ingredient) BIOLOGICALS Sporatec (rosemary, clove and thyme oils) Product Rate 1-­‐2 pints/A in 100 gal spray PHI (days) REI (hours) Efficacy Comments 0 0 ? 25(b) pesticide. Applications should be made once the disease is observed. PHI = pre-­‐harvest interval, REI = restricted entry interval. -­‐ = pre-­‐harvest interval isn't specified on label. Efficacy: 1-­‐ effective in half or more of recent university trials, 2-­‐ effective in less than half of recent university trials, 3-­‐not effective in any known trials, ?-­‐ not reviewed or no research available 12.8 Canker and Black Scurf, Rhizoctonia solaniTime for concern: Growing season. Cool wet soils favor disease development.Key characteristics: This fungus causes a variety of symptoms on tubers including cracking, malformation, and russeting. The‘black scurf’ symptom found on infected tubers appears as numerous dark, hard reproductive structures, called sclerotia. Thesclerotia may be flat and superficial or large, irregular, and lumpy. Sclerotia on stored tubers do not cause damage or spreadthe disease in storage. However, sclerotia in soil or on seed pieces can germinate and infect young, susceptible sprouts andstolons, causing lesions, or cankers. In cool wet soils, when plants are growing slowly, disease can progress rapidly, causingreduced stands and stunted plants. See Cornell HUfact sheetUH (Reference 68), Michigan HUfact sheetUH (Reference 69), and HUinteractiveblack scurf potato photoUH (Reference 66).392012