Rutgers Cooperative Extension
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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White mold, or lettuce drop, caused by Sclerotinia sclerotiorum, can cause serious losses in lettuce and other susceptible crops if left uncontrolled. Disease development is favored by wet, humid conditions (especially in high tunnels and fields) with known histories of the disease.
White mold on lettuce. Notice the white fungal growth and black sclerotia developing on the base of the stem. The sclerotia can survive in the soil for up to 10 years.
Copper resistance in bacterial leaf spot of tomato and pepper crops has been detected at a high level in New Jersey the past few summers. While not surprising, copper resistance has been known to develop for decades now. Copper applications for the control of bacterial diseases in many crops has been a mainstay for decades now and is often applied in weekly protectant fungicide programs. With help from Dr. Nrupali Patel and Dr. Don Kobayashi, bacteriologists in the Department of Plant Biology located on the New Brunswick campus, a (NJ-VGA funded) survey was initiated to determine which species of bacterial leaf spot are most prevalent in New Jersey tomato and pepper crops. Bacterial leaf spot can be caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri. Currently, there are four races of BLS found in tomato (T1-T4; one for each of the 4 species stated above) and eleven races found in pepper (0-10). Differential tests in southern New Jersey using various bell pepper lines over the past 15 years has suggested that the number of races of BLS in pepper has increased over time; with all races present in the State to date. Lab testing results from samples collected from the small number of NJ vegetable farms the last three summers has shown the presence of X. euvesicatoria in pepper, as well as X. euvesicatoria and X. perforans in both tomato and pepper in the state, with ~60% of all samples testing positive for copper resistance.
Edema is often expressed as off-color swellings or galls that appear on leaves and stems. Edema develops when epidermal cells hold excessive water due to a slowing of evapotransporation when hot, muggy days are followed by cooler, wetter weather. Edema develops because the plant takes in more water (due to a high soil moisture content) faster than it can get rid of it through evapotranspiration causing cells to rupture which results in the blistering of the leaves. Edema is strictly caused by environmental factors and can appear whenever these conditions are met. Properly monitor soil conditions, irrigation cycles, and the weather to avoid over irrigating on warm, hot early spring days, especially when quick cold fronts/temperature drops and cloudy weather are expected.
Symptoms of edema on top side of
collard leaf.
Note the off-color appearance of leaf surface.
Edema, bottom side of collard leaf.
Note irregular, “corky” appearance due to leaf cell rupture.
Sweet Corn
European corn borer (ECB) moth captures have increased in northern and central county light traps. Numbers are low, as they have been in recent years, and no feeding has been detected on whorl and pre-tassel stage sweet corn as far south as northern Burlington County. Whorl corn is the primary target for egg laying. If the peak of the first flight is late, it sometimes results in heavier infestations on 2nd and 3rd plantings than on the first. Feeding may be present in the southern counties, and should rise over the next 3 weeks.
Look for the characteristic “shot-hole” type of feeding (photo below at right) and consider treating when infested plants exceed 12% in a 50 plant sample. As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels (see photo at left). It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time. This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.
Useful insecticides for this particular application include synthetic 
pyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen or Vantacor (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen. It should be noted that Coragen or Vantacor, used alone, are not toxic to bees that may be visiting corn tassels during this stage. Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn. Control with these materials is very inconsistent.
The highest nightly trap catches of ECB for the week ending 5/29/24 are as follows:
| Bellemeade 1 | Hillsborough 1 |
| Califon 1 | Sergeantsville 1 |
| Farmingdale 1 | South Branch 1 |
| Georgetown 1 |
As the summer heats up in New Jersey, the control of Phytophthora blight in cucurbit plantings can be extremely difficult (even with the use of fungicides) as hot, wet weather finally sets in. Mitigating losses to Phytophthora blight in cucurbit crops begins with long crop rotations, where recommendations suggest crop rotations longer than 5 years if possible. Other cultural practices include avoid planting in low areas of the field where water may persist after rain or overhead irrigation, rogueing out infected plants as soon as possible, cutting the plastic to help dry out the soil, proper weed control, and proper preventative fungicide programs.
Septoria leaf spot (SLS) in Parsley can cause significant losses in fields where it has become established. Like other Septoria’s, the leaf spots produced on parsley look much like the leaf spots produced on tomatoes and other crops. Septoria leaf spot overwinters from year to year on infected debris so long crop rotations of 2 or more years are important to help reduce disease pressure. During the season, SLS will spread rapidly with each subsequent rainfall and/or overhead irrigation event. Therefore, early detection and preventative fungicide applications are key to successfully controlling SLS. There have been a few new fungicides labeled for SLS control in the past few years.
Septoria leaf spot of Parsley
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