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Late Blight Confirmed In Two Northern New Jersey Tomato Fields

By Beth K. Gugino
 
On Monday, late blight was confirmed in two tomato fields in Morris Co. in Northern NJ. These are the first reports on tomato in the mid-Atlantic and Northeast regions.
 
Previous reports, the closest of which were in western NY, were on potato. One of these samples has already been characterized as US-23, the predominant genotype since 2012. Since the major outbreak in 2009, in PA we seen late blight very year and have confirmed it as early as 17 May in 2010 and as late in the season as 12 July 2012.
 
 
Irregularly shaped greasy gray-brown late blight lesions as well as some small circular tan lesions from Septoria leaf spot on tomato (Photo credit: Beth Gugino).
 
 
Irregularly shaped greasy gray-brown late blight lesions as well as some small circular tan lesions from Septoria leaf spot on tomato 
 
Symptoms on tomato and potato are very similar and any plant growth stage is susceptible. It is important to be scouting your crop regularly looking for irregularly shaped water-soaked lesions that are initially pale green before turning gray- brown. Under humid conditions, the lesions on the underside of the leaf will sporulate giving them a white fuzzy appearance. The lesions will tend to develop on the upper to middle part of the plant as opposed to early blight and Septoria leaf spot (tomato only) that start on the lower leaves and progress up the plant.
 
Keep in mind, unless you have planted a late blight resistant tomato cultivar (e.g. Plum Regal, Mountain Magic, Mountain Merit, Defiant, Iron Lady) the only way to manage late blight during the growing season when conditions are favorable for disease is with the use of protectant and/or late blight specific fungicides. Without careful scouting and the use of fungicides, you could potentially lose your crop in as few as 5 days. Given the persistent high relative humidity and frequent rain events, protectant fungicides are recommended. For organic production, copper is still one of the most effective in-season tools and is most effective when applied before symptoms are observed. Copper tank mixed with Actinovate and alternated with copper tank mixed with Regalia would be one suggested organic program. Since Regalia functions to boost the plants defense system, initiating applications early in the season is recommended.
 

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