- White mold has been reported in tomato and Southern blight in pepper in southern new Jersey this past week. Click here for more information.
- Early blight is being reported in tomato.
- Rhizoctonia root rot has been reported in summer squash. Click here for more information.
- Powdery mildew has been reported in cucurbit crops. For more information on the control of CPM please click here.
- Cucurbit downy mildew has been reported on cucumber in southern and central New Jersey and Eastern PA. For more information on CDM control please click here.
- Bacterial leaf spot has been reported in pepper. More more information on BLS control please click here.
- Bacterial canker has been reported in tomato. For more information on diagnosing important tomato diseases please click here.
- Early blight has been reported on potato.
- Phytophthora blight has been reported on pepper. For more information please click here.
- Dickeya dianthicola has been reported in potato in Virginia and Massachusetts.
- The 2022/2023 Commercial Vegetable Production Recommendations Guide is available for free online or for sale in hardcopy form at many County offices.
- For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and information on FRAC group 4, FRAC group 7, and FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
July 11, 2022 Andy Wyenandt
Vegetable Disease Update: 07-11-22
July 10, 2022 Andy Wyenandt
Identifying and controlling leaf mold in high tunnel & greenhouse tomato production
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. Therefore, the proper venting of high tunnels and greenhouses on a regular basis is important. 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 bright yellow leaves and olive-green spores developing on undersides of leaves.
July 9, 2022 Andy Wyenandt
Important resources for cucurbit disease control in 2022
The cucurbit growing season is well under way in New Jersey and the rest of the mid-Atlantic region. Below are links to useful resources for the identification and management of important cucurbit diseases.
Diagnosing important diseases in cucurbit crops
Cucurbit Powdery and Downy Mildew: A Tale of Two Pathogens
The downy mildew forecasting website
Preparing for cucurbit downy mildew in 2022
Preparing for cucurbit powdery mildew in 2022
Preparing for Anthracnose and Alternaria Leaf Blights in Cucurbit Crops
Recognizing and controlling Angular leaf spot in cucurbits
Recognizing and controlling Plectosporium blight in cucurbits
Controlling Phytophthora and Pythium root rots
Destroying cucurbit plantings after harvest
July 8, 2022 Andy Wyenandt
Phytophthora and Pythium control during wet weather
Most of New Jersey has been plagued by heavy regular rains and pop-up thunderstorms making conditions ideal for pathogens such as Phytophthora and Pythium. Unfortunately, Pythium and Phytophthora blight can be found on most farms in the southern part of the state. Poor crop rotations with susceptible hosts only make matters worse. The Phytophthora pathogen has an increasing host range that now includes snap and lima beans; and all crops, other than a few resistant bell pepper cultivars, lack any resistance to the pathogen.
Control of Phytophthora blight and Pythium are extremely difficult (even with the use of fungicides) in the wet weather conditions. In the past few years a number of new fungicides, with new active ingredients, have become commercially-available for use on multiple crops. Mefenoxam or metalaxyl, both once widely-used to effectively control Phytophthora blight has been hit by resistance issues around much of Southern New Jersey the past decade. Growers with a known history of mefenoxam-insensitivity on their farm should use Presidio, Previcur Flex, or Ranman plus a Phosphite fungicide in rotation in their drip application programs. Importantly, if mefenoxam has not been used in particular fields on any crop for a number of years (more than 5+) the fungus may revert back to being mefenoxam-sensitive and control with these products may return. Mefenoxam, metalaxyl, Previcur Flex, and the phosphites are the most systemic of the group and should readily be taken up the by plant via application through the drip. Presidio has locally systemic and has translaminar activity and should offer some protection of the root system via drip. Ranman has protectant activity and thus will offer some root protection where it comes into contact with. Orondis Gold (oxathiapiprolin + mefenoxam, 49 +4) is the newest fungicide available with a new active ingredient in a new FRAC group. Additionally, in past research trials, mefenoxam, Orondis Gold, Presidio, Previcur Flex, Ranman, Revus and the phosphites in rotation and/or tank mixes have offered very good control of the fruit rot phase of phytophthora blight.
[Read more…]
July 7, 2022 Andy Wyenandt
Controlling fungal leaf blights of Carrot
Powdery mildew, Alternaria and Cercospora are three important fungal foliar pathogens that can cause early defoliation in carrots, thus reducing yields and making harvest difficult. Each pathogen produces distinct symptoms. [Read more…]
July 6, 2022 Andy Wyenandt
Diagnosing Southern blight and White mold in tomato and pepper
There have been a few reports of Southern blight (Sclerotinia rolfsii) and White mold (Sclerotinia sclerotiorum) on tomato and pepper in New Jersey. Southern blight is much more common in vegetable areas south of the state where summer temperatures remain hotter (above 90°F) for longer periods of time. Like white mold, it can survive in the soil for many years. Symptoms of Southern blight include infection at the base of the stem at the soil line. The resulting infection will girdle the plant causing wilt and death. The fungus will produce white, cottony mycelium and very small, spherical sclerotia which are often have a tannish, brown color.
White mold is more common than Southern blight in New Jersey, and like Southern blight, once introduced into a field or high tunnel it can very difficult to control. The pathogen produces large black sclerotia on the surface and inside infected stems. If sclerotia of either pathogen make their way back into the soil, both can survive for years causing significant problems.
All infected plants need to be removed immediately and disposed of properly to help reduce the chances of sclerotia returning to the soil.
For more information on chemical control please see the 2022/2023 mid-Atlantic Commercial Vegetable Production Recommendations Guide.
Symptoms of Southern blight on infected pepper plant. Note the numerous, small white to tan colored sclerotia on the stem.
White mold of tomato. Note the large black sclerotia developing inside the brittle stems.
