August 1, 2016

Potato | Tomato Disease Forecast 8-2-16

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Potato Disease Forecasting Report

We will be tracking DSVs for Late blight development and calculating P-days for initiating the first early blight fungicide application.

The first late blight fungicide application is recommended once 18 DSVs accumulate from green row. Green row typically occurs around the first week in May in southern NJ. An early season application of a protectant fungicide such as mancozeb (Dithane, Manzate, Penncozeb) or Bravo (chlorothalonil) as soon as the field is accessible is suggested. Please be vigilant and keep a lookout for suspect late blight infections on young plants. No late blight has been reported in our region to date.

Remember the threshold for P-days is 300!  Once 300 P-days is reached for your location, early blight fungicide applications should be initiated. Growers who are interested in using this model should choose the location above that is closest in proximity to their farming operation and should regularly check the Cornell NEWA website (http://newa.cornell.edu/) where this information is compiled from. Click on Pests Forecasts from the menu, select your weather station, and click on tomato diseases, set accumulation start date, and a table of daily and total DSVs will be generated.

Tomato Disease Forecasting Report

Disease severity values (DSVs) for early blight, septoria leaf spot, and tomato anthracnose development are determined daily based on leaf wetness (due to rainfall, dew) and air temperature.

On a daily basis DSV values can range from 0 to 4 where 0 = no chance for disease development to 4 = high chance for disease development.
DSVs are accumulated during the production season.

Fungicide applications are based on an individually determined DSV threshold. The first fungicide application for the control of these three diseases is not warranted until 35 DSVs have accumulated from your transplanting date. After that, growers can base fungicide applications on different DSV thresholds.

Reports generated by Ryan Tirrell

Rutgers, The State University of New Jersey

Filed Under: Disease Forecasting Tagged With: ,
May 17, 2016

Late blight confirmed on tomato in Western Maryland – 5/17/16

Late blight (US23) was confirmed on tomato in a small, retail greenhouse operation in western Maryland (Garrett Co.) today. This is the first report of Late blight on tomato or potato this growing season. US23 has been the most prevalent genotype found in the region the last few years and can infect tomato or potato. While the current report not an immediate threat to NJ, all tomato and potato growers should scout fields on a regular basis as long as wet weather pattern continues. At this time, general protectant fungicide programs that have been initiated will help protect against Late blight. Importantly, in order for Late blight to appear this early in our region it must either have survived on an infested potato tuber left in the field or in a cull pile. For more information on the control of late blight please see the 2016 Mid-Atlantic Commercial Production Recommendations Guide.

Filed Under: Commercial Ag Updates, Disease Forecasting, Organic Production, Vegetable Crops Tagged With: ,
July 10, 2015

Leaf Mold in Tomato

Leaf mold (formerly Fulvia fulva) has been confirmed in field-grown tomatoes in Cape May County.

Leaf mold occasionally appears in high tunnel or greenhouse tomato production in New Jersey. However, under ideal conditions the disease will develop in field-grown crops. The fungus will cause infection under prolonged periods leaf wetness and when relative humidity remains above 85%. If relative humidity is below 85% the disease will not occur. The pathogen can survive (overwinter) as a saprophyte on crop debris or as sclerotia in the soil. Conidia (spores) of the fungus can also survive up to one year in the soil.

Symptoms of leaf mold on infected tomato plant. Note the bright yellow leaves and the olive-green spores developing on the undersides of leaves.

Symptoms of leaf mold on infected tomato plant. Note bright yellow leaves and olive-green spores developing on undersides of leaves.

[Read more…]

Filed Under: Organic Production, Vegetable Crops Tagged With: ,
May 31, 2015

White Mold in Greenhouse & High Tunnel Tomato

White mold, or timber rot, caused by the soil-borne fungal pathogen, Sclerotinia sclerotiorum, was found this past week in a high tunnel.

High tunnel tomato plant with main stem infected by white mold.

The photo on right shows a high tunnel tomato plant with main stem infected by white mold. Over time the entire plant will slowly collapse looking similar to a wilt or root rot pathogen as the water supply is cut off to the plant.

White mold is common and once introduced into a field or high tunnel it can very difficult to control. The pathogen produces black sclerotia on the surface and inside infected stems. Sclerotia, if they make their way back into the soil, can survive for years causing significant problems.

Infected stems will turn a light brown color and dry up becoming brittle. If the main stem is infected the entire plant will collapse looking like a wilt or root rot issue.

Under hot, humid conditions white fungal growth will develop on the surface of the stems and in some cases sclerotia will develop on the outside of the stem. Breaking open the stem will reveal numerous black sclerotia.

All infected plants and or plant material need to be removed from the greenhouse or high tunnel immediately and disposed of properly. Preventative protectant fungicide programs beginning at flowering will help control white mold. Cool, wet weather and poor air circulation favors disease development.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

Filed Under: Vegetable Crops Tagged With: ,
April 21, 2015

Early-season Pythium and Phytophthora Control in Pepper and Tomato Crops

“What should I do to help prevent Pythium and Phytophthora in my pepper and tomato crops early in the season?” is a question most often asked this time of year. In the past, the answer was simple. Apply mefenoxam (Ridomil Gold SL, Ultra Flourish, 4) or metalaxyl (MetaStar, 4). Problem solved, right?

Not exactly, with resistance development in Phytophthora (P. capsici) to both mefenoxam and metalaxyl, the correct answer isn’t as simple anymore. It’s important to remember that both chemistries will work very well as long as resistance hasn’t been detected on your farm. How do you know if you have resistance? The easiest way is to follow efficacy. [Read more…]

Filed Under: Vegetable Crops Tagged With: , ,
October 13, 2014

Late Blight Still Active on Tomato

Late blight was confirmed in a homeowner garden today near Clementon, NJ (Camden County) and here at the Rutgers research station near Bridgeton, NJ (Cumberland County). This is a good reminder that as long as weather conditions are conducive, the threat of late blight in the state and region will continue until the first killing frost.

All abandoned tomato fields need to be destroyed either by mowing, discing under, or sprayed with a herbicide such as gramoxone to kill all living foliage. This is especially important if protectant fungicide programs have been discontinued. Homeowners can simply pull plants and put in their compost pile or discard in the trash.

Filed Under: Vegetable Crops Tagged With: ,