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 in full swing, now is a good time to review a few of these important diseases. [Read more…]
Vegetable Crops Edition
Seasonal updates and alerts on insects, diseases, and weeds impacting vegetable crops. New Jersey Commercial Vegetable Production Recommendations updates between annual publication issues are included.
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July 16, 2023 Andy Wyenandt
Important resources for cucurbit disease control in 2023
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 2023
Preparing for cucurbit powdery mildew in 2023
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 15, 2023 Andy Wyenandt
Diagnosing Important Diseases In Tomato – Reference Guide
The following images consist of important diseases in tomato. These images can be used as a quick reference for diagnosing important fungal and bacterial pathogens. For best results, please turn your device (i.e., cell phone) sideways. For information on commercial control recommendations, please visit the tomato section of the 2022/2023 Mid-Atlantic Commercial Vegetable Production Guide. Additional information for home gardeners is located at the bottom of the Table.
| Early blight | Septoria leaf spot | Anthracnose fruit rot |
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| Early blight lesion on fruit | Ground rot infected green fruit | Ground rot sporulating on fruit |
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| Bacterial leaf spot | Bacterial canker | Bacterial speck |
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| White mold | Southern blight | Late blight on foliage |
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| White mold sclerotia in infected stem | Southern blight sclerotia on infected stem | Late blight infected fruit |
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| Collar Rot caused by Alternaria spp. | ||
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For the homeowner or non-commercial grower there are a number of Rutgers/NJAES Fact Sheets available on-line:
For other Rutgers University/NJAES Fact Sheets for tomato please click here.
July 14, 2023 Michelle Infante-Casella
What Can Summer Cover Crops Do for Soil Health and Future Crops?
Now that some of our spring planted crops have finished, rather than leaving fields fallow or replanting fields that may have had some issues with plant diseases or insect pests, consider replanting with a summer cover crop. It is not too late to take advantage of summer cover crop benefits. What do summer cover crops do for soil health or future crop improvements? See below:
1. Increase Soil Organic Matter– One of the best attributes of having organic matter in the soil is improvement in soil structure. Adding organic matter improves tilth, water infiltration, water holding capacity, nutrient holding capacity and reduction of soil crusting. Also, as important is the increase in beneficial soil microbes and earthworms. Beneficial microbes can compete with pathogens and help release nutrients. Earthworms can cycle nutrients and improve pore spaces in the soil.
2. Reduce Soil Erosion – Just like with winter cover crops, summer cover crops can also reduce wind and water erosion in fields, especially those with slopes. During summer rainfall events, that can be significant if resulting from tropical storms, runoff may not just include soil loss, but also fertilizer and chemical movement. Therefore, keeping cover on a field during non-production times in any season is an excellent practice.
3. Nitrogen Cycling in the Soil – Nitrogen is often the most limiting nutrient for crop production, since it is so readily lost through nitrification and leaching. Storing nitrogen through plant cycling is an excellent way to improve fertility management. Whether it is a grass or non-leguminous cover crops N is still kept in the mix by the cover crop taking up residual N that would
otherwise be lost. The cover crop plant takes up the nitrogen and after the crop is incorporated it decomposes, thus releasing the N for subsequent crops to use. If legume cover crops are planted, they have the ability to “fix” nitrogen from the atmosphere and through the same decomposition process will provide N for subsequent crops. Be sure to inoculate legume seed just prior to planting with Rhizobium bacteria in order to gain the maximum N fixation benefits.
4. Reduce Weeds – When fields are left fallow after crops are harvested, weed growth can occur. If left to produce seeds, these weeds will multiply in subsequent crops. Therefore, managing the field by planting cover crops between cash crops is a great weed management option. As the cover crop grows, it will suppress the germination and growth of weeds through competition and shading. Some cover crop species can also suppress weeds biochemically, either while they are growing or while they are decomposing, which may prevent the germination or growth of other plants (allelopathy). Research has shown some cover crops like wheat, barley, oats, rye, sorghum, and sudangrass may suppress weeds. In some cases, it has also been reported that residues and leachates from crimson clover, hairy vetch, and other legumes have shown weed suppression.
5. Impacts on Plant Diseases – Cover crop residues could possibly be beneficial when it comes to plant pathogens, or can in some cases increase plant disease organisms. Some cover crop species are in the same plant families as cash crops and may be susceptible to the same disease organisms. Therefore, carrying the pathogen to the next crop. This is why paying attention to crop rotations is so important. In other cases, the cover crop residue can improve soil health in order to produce a better environment for beneficial microbes. By improving soil health, water infiltration, air pore space and other positive attributes, some soil pathogens may not survive as well, as in the case of water molds and water fungi. Some cover crops, like sorghum-sudangrass and sunnhemp, have been reported to reduce nematodes in soils. There are multiple positive factors from cover crops that can combat plant diseases.
6. Impacts on Insects – Like with plant diseases, cover crops can be susceptible to the same insect pests as cash crops. However, they may also attract beneficial insects into an area. Insect pests should be monitored in cover crops, just like in cash crops in order to not let populations get out of control and then move into nearby fields after the cover crop is killed.
For more resources on the us e of cover crops check out these resources: Cover Crops for Sustainable Crop Rotations – SARE
July 14, 2023 Andy Wyenandt
Diagnosing important diseases in Pepper – Reference Guide
| Phytophthora blight causing plants to wilt and die | Phytophthora blight – crown rot | Phytophthora crown rot. Note the blackish-brown necrotic tissue at base of the stem |
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| Phytophthora sporulating on infected bell pepper fruit. | Phytophthora fruit rot (L) and Pythium blight (R) | Symptoms of Phytophthora blight on infected leaves. Under ideal conditions leaf infections can occur. |
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| Anthracnose fruit rot | Anthracnose fruit rot. Note the salmon colored spores being produced in the lesion of the lesion. | Sunscald on pepper fruit (L) and Anthracnose fruit rot (R) |
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| Bacterial leaf spot on leaves | Bacterial leaf spot. Note the infected leaves falling off of plant. | Bacterial leaf spot infection of pepper fruit. Note the irregular raised scabby spots on fruit. |
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| Southern blight on infected stem. Note the numerous small fruiting bodies (sclerotia) developing on the stem | White mold infecting pepper stem. Infected stems come brittle and hollow | White mold sclerotia present on inside of infected stem |
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| Blossom end rot | Cucumber Mosaic Virus | Cyclamen mite feeding injury. Symptoms resemble virus infection |
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| Others: | ||
| Mefenoxam injury on a young pepper transplant | Sunscald on stems of pepper recently transplanted into black plastic mulch. | Cyclamen mite damage on immature pepper fruit |
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| “Silvering” on mature bell pepper fruit. | “Silvering” on the right and thrips feeding injury on the Left | Edema on pepper fruit |
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The following images consist of important diseases in pepper. These images can be used as a quick reference for diagnosing important fungal and bacterial pathogens. For best results, please turn your device (i.e., cell phone) sideways. For information on commercial control recommendations, please visit the pepper section of the 2022/2023 Mid-Atlantic Commercial Vegetable Production Guide.
Andy Wyenandt, Wesley Kline, and Kris Holmstrom
July 13, 2023 Andy Wyenandt
Avoiding Plectosporium blight in cucurbit fields in 2023
Plectosporium blight, also known as Microdochium blight or White speck, caused significant problems in some pumpkin fields the last few summers in New Jersey. The soil-borne fungal pathogen, although somewhat uncommon, can unexpectedly show up in some years and cause significant losses if left uncontrolled. The fungus survives in the soil on decaying plant debris where it can remain saprophytic by surviving off organic matter. Infection is characterized by the production of numerous light tan to “bleached” spindle shaped lesions that develop on vines and the undersides of infected leaves. Heavily infected vines and leaves can die leading to premature defoliation and subsequent sunscald on fruit. In cases of heavy disease pressure, spores that are produced on the bottom sides of leaves fall and infect the topsides of fruit laying beneath the canopy. Infection of stems leads to premature browning and drying reduce their longevity. Fruit infection, in most cases, remain mostly cosmetic in nature reducing fruit quality and may predispose fruit to other opportunistic fruit rots. Plectosporium blight often shows up during periods of prolonged wet weather where the soil remains wet for extended periods. “Hot spots” typically appear in fields before the pathogen is further spread by driving rains and wind.
From a production standpoint, stay away from fields with known history of the disease for as long as possible; provide adequate spacing between plants in- and between rows (i.e., avoid the overcrowding of plants); avoid over (pre-plant) fertilization that can lead to thick, dense canopies; avoid overhead irrigation (if possible); avoid planting in area of a field that remains heavily shaded where soils tend to dry too slow.
Controlling Plectosporium blight begins with regular scouting, recognizing symptoms, and identifying “hot spots” in the field. Protectant fungicides, such as chlorothalonil, as well as those used in weekly maintenance spray programs for cucurbit powdery mildew control will help control Plectosporium blight as long they applied on a weekly schedule with a high volume of water with thorough coverage. To help improve control on the undersides of leaves, a FRAC code 11 fungicide such as Quadris Top or Pristine, can be added to the tank mix. Remember, FRAC code 11 fungicides have translaminar activity and will move from the top surface of the leaf to the bottom. Growers who grow powdery mildew resistant varieties need to remember to scout their fields regularly even if cucurbit powdery mildew has not been detected on the farm or if regular maintenance sprays haven’t begun.
White speck lesions covering the surface of immature and mature pumpkin fruit. White speck will only cause cosmetic injury to fruit.
White speck on vine and stem of infected pumpkin plant. Note the numerous small, white diamond shaped lesions.
