Rutgers Cooperative Extension
Pepper Anthracnose
In recent years, pepper anthracnose caused by Colletotrichum spp. has become a significant problem on some farms in southern New Jersey.
Unlike in tomato, where symptoms are only present in mature (red) fruit, pepper anthracnose can infect pepper fruit at any growth stage. Currently, there are no commercially-available bell or non-bell peppers with known resistance to anthracnose. [Read more…]
Anthracnose and Alternaria leaf blight can become problematic in cucurbit crops during long periods of wet, humid weather. Both can cause significant losses if not controlled properly. With the production season quickly approaching, now is a good time to review a few of these important diseases.
Symptoms of anthracnose on infected cucumber leaf.
Alternaria leaf blight on cantaloupe (NCSU – G. Holmes)
Anthracnose, caused by Collectotrichum orbiculare, and Alternaria leaf blight (Alternaria cucumerina) produce distinct spots on infected leaves, and in most cases, symptoms begin on the older leaves. With Alternaria, diagnostic concentric black rings will be develop within the spots on infected leaves, often there is a chlorotic (yellow) halo around margins. With Anthracnose, spots always develop on veins on the underside of infected leaves. Often, black setae (hair-like projections) will develop on the veins of infected tissue. These symptoms make for easily diagnosing which disease might be present.
Both pathogens can overwinter on infected plant tissue in the soil for 1 to 2 years, thus extended crop rotations are important. Conidia (spores) develop from dormant mycelium in the soil and are splashed into the canopy causing primary infections during prolonged periods of humid, wet weather causing extended leaf wetness. Secondary infections and spread of both diseases can occur during the production season under favorable conditions for disease development.
Deep plowing debris or the removing of plant debris after harvesting, avoiding overhead irrigation during the production season, and most importantly, choosing cucurbit varieties with resistance are important cultural practices all conventional and organic growers should consider.
Anthracnose and Alternaria are easily controlled with weekly protectant fungicides such as chlorothalonil and mancozeb as long as they are applied prior to the arrival of the pathogen and on a regular basis during favorable disease development. Organic growers can apply copper and other labeled products to help suppress development of these diseases. Complete foliar coverage is critically important for the control of these diseases.
For more information on the control of anthracnose and Alternaria leaf blight in cucurbit crops please see the 2020/2021 Mid-Atlantic Commercial Vegetable Production Recommendations Guide.
Additional Resources:
University of MN Extension: https://extension.umn.edu/diseases/alternaria-leaf-blight
University of Florida: https://plantpath.ifas.ufl.edu/u-scout/cucurbit/alternaria-leaf-spot.html – Images of Alternaria
University of Florida: https://www.growingproduce.com/vegetables/aim-to-keep-anthracnose-out-of-your-cucurbit-crops/ – Additional information on anthracnose
University of MN: https://extension.umn.edu/diseases/anthracnose-cucurbits – Additional information on anthracnose of cucurbits
Now that the weather is beginning to cooperate and temperatures are warming up, be cautious about sunscald developing on the stems of transplants, especially those being set onto black plastic mulch. With a little planning ahead potential losses to sunscald injury can reduced significantly.
Sunscald injury on stems of newly transplanted pepper seedlings caused by stems laying against edges of black plastic mulch on hot, sunny days.
A transplant coming straight out of the greenhouse and directly into the field has not been exposed to much direct sunlight. Add that with black plastic mulch and you have a lot of heat aim directly at the tender tissue of the transplant. All transplants should have some time to harden-off outside the greenhouse before going into the field, a day or two, is better than none at all, the longer the better if time and space allow.
Sunscald typically appears as the slow bleaching out of the stem that will typically appear only on one side. Often this starts to appear right where the stem meets the black plastic mulch. In many cases if the stem is touching the mulch, the sunburn will start there and the transplant will begin to fall over as if the stem was broken.
When transplanting, make sure the holes in the plastic are wide enough to keep the stem from coming into contact with it. In some cases growers will fill in the transplant hole with soil to help keep the transplant upright before between-row herbicides are applied. ‘Leggy’ transplants that lay across plastic mulch and even those transplanted onto bare ground are prone to sunscald injury.
The following video includes a review and update on important diseases for vegetable farmers in New Jersey.
Covered in this presentation are:
Take-Home Extension Talk: Updates on important vegetable diseases.
Please click here: Take Home – PPA 4-17-20
For commercial growers, fungicide recommendations can be found in the 2020/2021 Mid-Atlantic Commercial Vegetable Production Recommendations Guide. The new guide available FREE on-line or can be purchased in hardcopy form through your county agricultural office in New Jersey. The complete 2020/2021 Vegetable Production Recommendations guide or specific sections can be downloaded depending on your production needs.
Verticillium wilt is a common soil-borne fungal pathogen that once it has infested soil can remain for a very long time. Verticillium wilt is caused by either Verticillium albo-atrium or Verticillium dahlia and has a wide host range (over 200 plant species). Both pathogens can survive (overwinter) as microsclerotia in the soil. Verticillium wilt prefers cooler weather and drier soils and can be more severe in neutral to alkaline soils. Solanaceous weeds such as Nightshade may harbor the pathogen.
Diagnostic symptoms of Verticillium wilt in eggplant
Photo by Kris Holmstrom
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