Downy mildew is caused by the oomycete Peronospora belbahrii. Recent research has revealed light exposure is most important during the first 6 hours of night. There is a 2(ee) recommendation allowing use of the new botanical fungicide EcoSwing (extract of Swinglea glutinosa) for downy mildew in field-grown basil. Global production is at significant risk because of the lack of genetic resistance to this disease and the ability of the pathogen to be distributed on seed. If you must spray, water the plants more deeply and less often, preferably early in the morning so that plants have plenty of time to dry during the day and between waterings. Subdue MAXX can be applied once to foliage and must be tank-mixed with another fungicide labeled for this use and applied at full label rate. Downy mildew of basil was first reported in 1932 from Uganda, Africa as Peronospora spp. Basil downy mildew is caused by a pathogen called Peronospora belbahrii. The disease was first reported on basil in Uganda in 1930, but did not attract international attention until it appeared in several new locations; Italy (2003), France (2004) South Africa (2005), Iran (2006) United States (Florida, 2007) and Argentina (2008). Long Island Horticultural Research and Extension Center (LIHREC) If you suspect that your basil plants have been affected by basil downy mildew, what do you do next? Plants that are affected by downy mildew, may be stunted or have leaf loss. The fungus may appear raised from the leaf surface or “fluffy” in appearance. Procidic (3.5% citric acid) is specifically labeled for basil downy mildew. The cucurbit downy mildew forecasting web site might be useful for predicting when conditions are favorable for basil downy mildew since both pathogens likely have similar requirements for successful wind dispersal long distances (e.g. OxiDate has limited residual activity and thus if used should be combined with or followed by another product. Revus can be applied 4 times with no more than 2 consecutive applications. Fig. Downy mildew caused by Peronospora belbahrii Thines is one of the most destructive diseases of sweet basil (Ocimum basilicum) of the family Lamiaceae Lindl. Famous for being vineyard owners’ #1 enemy, downy mildew is a constant threat to grape harvests. Basil crops should be disked under or otherwise destroyed as soon as possible after last harvest, or when abandoned because of disease, to eliminate this source of inoculum for other plantings. Basil that has become infected with downy mildew may have a yellowish appearance, similar to a nutritional problem. Introducing "One Thing": A New Video Series, The Spruce Gardening & Plant Care Review Board, The Spruce Renovations and Repair Review Board. Recent efforts to develop a seed test have resulted in a genetic-based procedure specifically for Peronospora belbahrii that is now being validated (suspected contaminated seeds are needed for this step, see information about submitting samples below). Because spores are produced during the dark night period, early morning is the best time to inspect basil for downy mildew. Many of the fungicides currently labeled for this new disease, plus others not registered yet, have provided limited suppression in some fungicide evaluations, demonstrating the difficulty in controlling this disease, especially in a research setting with applications made with a backpack sprayer, and thus the importance of starting before disease onset. It is important to use a fungicide resistance management program including alternation among as many chemistries based on FRAC code as possible. Pull up the entire plant, remove it from the garden area, and destroy it. Practices that minimize leaf wetness and reduce humidity may contribute to control. These are the same leaves in Fig. Downy mildew is in the list of foliar diseases controlled by this OMRI-listed product. Pathogen isolate from these plants was found to be genetically different from other US isolates examined. 2. Practices to achieve this include base watering, wide plant spacing, circulating fans, lights, and increasing temperature. It was reviewed and determined to be NOP compliant by Washington State Dept of Ag. Onset of downy mildew development at LIHREC is very regular, with first symptoms found between 4 and 19 August since 2009; in contrast, first symptoms of downy mildew were found in … When you first notice signs of the mildew, it is best to remove the entire plant and remove and cook only the healthy leaves, if you want to eat them. First observations of basil and cucumber downy mildews at LIHREC. (Originally prepared for Vegetable MD Online.). Red light was shown to be the most inhibitory under laboratory conditions. Please email. Fig. All sweet basil varieties evaluated before breeding for resistance was started were found to be very susceptible. Infected leaves also can show irregular black spots as well as gray, fuzzy spores on the underside of the leaf. The first step in preparing for basil downy mildew is learning the symptoms (Fig. There are several phosphorous acid (phosphanate) fungicides labeled for this disease with no use restrictions, including ProPhyt, Fosphite, Fungi-Phite, Rampart, pHorsepHite, and K-Phite. 5: Yellowing, necrosis, and sporulation on basil leaves and flower bracts. Generally speaking, basil leaves infected with downy mildew are not poisonous, but it is not advisable to eat leaves that are clearly affected. Sweet basil is among the most popular and economically important culinary herbs, but by 2010, US production began to feel the impact of a newly emerging destructive disease: basil downy mildew. Fig. Sealed plastic baggie for transport in protected culture can infect the seeds and affect the year. During the dark night period, early morning is the best time to inspect basil for downy mildew to. 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