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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Vegetable IPM Update 8/02/23
Sweet Corn
Occurrences of Fall armyworm (FAW) injury are becoming more common, with infestations discovered as far north as Warren County this week. Some infestations in whorl corn are in excess of 20%. It is likely that economic infestations are present in much of southern New Jersey now, and could occur anywhere. Growers are advised to check whorl and seedling stage corn plantings weekly for signs of FAW. Consider treating if infestation rates exceed 10%. This pest is capable of significant injury to sweet corn plants, resulting in severe stunting and failure to produce viable ears.
Newly hatched FAW larvae cause holes and scratches on leaves that are similar to European corn borer (ECB) feeding, except that they tend to be more concentrated and always lead down into the whorl (see photos at left). As the larvae grow, the feeding becomes more destructive, with large ragged holes and obvious droppings deposited in the whorl (see photo at right). 
We will provide updates on new FAW appearances and severity as reports come in. FAW are resistant to synthetic pyrethroids. Effective sprays should include IRAC grp. 5 (spinosyns) or IRAC grp. 28 (diamides). The carbamate (IRAC grp. 1A) Lannate is also still effective. Sufficient water should be used in the applications to allow the solution to penetrate the layer of droppings that may have formed above the caterpillar.
European corn borer (ECB) moth activity remains extremely low in areas where blacklight traps are operating in the northern and central counties. Many plantings exhibiting no ECB injury at all. We will report on ECB activity should numbers rebound to potentially damaging levels during the second flight. In recent years, this later flight has not required targeted control in sweet corn.
Vegetable Disease Update: 07-29-23
- Basil downy mildew has been reported in New Jersey.
- Rhizoctonia root rot has been reported in tomato and other vegetable crops.
- Phomopsis and Phytophthora fruit rot has been reported in eggplant.
- Collar rot has been reported on tomato. For more information please click here.
- Pythium cottony leak has been reported on pepper. For more information on controlling Pythium and Phytophthora please click here.
- Pepper anthracnose has been reported in southern New Jersey. For more information on controlling anthracnose fruit rot please click here.
- Cucurbit downy mildew has been reported on cucumber and cantaloupe in New Jersey with more being reported on the East Coast and Ontario, Canada. For more information on CDM control please click here.
- Blackleg has been reported on potato in New Jersey.
- There have been no reports of Late blight in potato or tomato in the region to date. Late blight has been reported in Ontario, Canada. To follow the progress of Late blight in the US please click here.
- Bacterial leaf spot has been reported in pepper. More more information on BLS control please click here. Rutgers is surveying tomato and pepper fields throughout the state this summer to help determine the makeup of the bacterial population and for copper resistance development.
- Powdery mildew has been reported in cucurbit crops. For more information on the control of CPM please click here.
- Southern blight has been reported on pepper.
- Bacterial canker has been reported in tomato. For more information on diagnosing important tomato diseases please click here.
- For information on diagnosing important diseases in pepper, tomato, and cucurbit crops please click on links.
- 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.
Understanding and controlling Rhizoctonia root rot
Even though much of New Jersey has had wet weather recently, which is more favorable to Pythium and Phytophthora development, Rhizoctonia root rot has been reported over the past few weeks in a number of crops. Rhizoctonia root rot, caused by Rhizoctonia solani, is an important soil-borne fungal pathogen with a very large host range. The pathogen can survive saprophytically on living or dead plant material (organic matter) or as sclerotia in the soil (for more than 3 years). Disease development is favored by warm temperatures, dry (or very well drained) soils and stressed plants. Symptoms of Rhizoctonia root rot may begin as stunted plant growth (with poor root systems) with the appearance of brown lesions at the base of the stem causing wilting with lesions eventually girdling the stem and killing the infected plant. Rhizoctonia root rot infections only extend about an inch above the soil surface (Figure 1), unlike Phytophthora blight infection which can extend much farther up the stem. [Read more…]
Controlling Phytophthora blight in eggplant
Phytophthora blight, caused by Phytophthora capsici, can cause crown and fruit rot in eggplant. Unfortunately, most of New Jersey has been plagued by heavy rains and pop-up thunderstorms these past few weeks making conditions ideal for pathogens such as Phytophthora blight on pepper, eggplant, tomato, and cucurbit crops.
Control of Phytophthora blight is extremely difficult (even with the use of fungicides) in the very hot, wet weather conditions that most of New Jersey has been through during the month of July. In the past few years a number of new fungicides, with new active ingredients, have become commercially-available for use on multiple crops. Mefenoxam and metalaxyl, both once widely-used to effectively control Phytophthora blight have been hit by resistance issues around much of Southern New Jersey. Growers with a known history of mefenoxam-insensitivity on their farm should use Presidio or Ranman plus a Phosphite fungicide in rotation in their drip application programs for the control of the crown rot phase of Phytophthora blight. 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, and the phosphite fungicides are the most systemic of the group and should readily be taken up the by plant via application through the drip. Orondis Gold (OXTP + mefenoxam) is also systemic. Presidio is locally systemic, and Ranman has protectant activity and can also be applied via drip.
[Read more…]
Phomopsis fruit rot in eggplant
Phomopsis blight is caused by the fungal pathogen, Phomopsis vexans. It survives between seasons in the soil on infested plant debris. Although the pathogen can infect stems and older leaves, fruit infections are most prominent. Cankers that develop on stems and branches can cause the entire plant to collapse and die. Circular, grayish spots may develop on infected leaves. On fruit, the pathogen causes brownish-black spots that can quickly enlarge causing flat spots that can produce black pycnidia (e.g., fruiting bodies) that produce masses of conidia (spores) which are rain dispersed onto healthy plants and fruit. Phomopsis blight is favored by hot, wet weather (85 – 90 F). Spores germinate in free water on leaves and fruit causing infections. The pathogen can survive on solanaceous weeds such as nightshade, so good weed control is necessary. Crop rotations of 3 to 4 years are recommended. If possible, infected fruit should be harvested and removed from the field to help reduce to inoculum and the spread of the disease. Fields should be scouted on a regular basis, especially fields with a history of Phomopsis blight. Fungicide applications include Quadris Top (difenoconazole + azoxystrobin, 7 +11) or Priaxor (fluxapyroxad + pyraclostrobin, 7 +11) rotated with chlorothalonil every 7 to 10 days. For more information please see the 2022/2023 Mid-Atlantic Commercial Vegetable Production Recommendations Guide.
