Sweet Corn

A few European corn borer (ECB) moths have been captured over the past week, though they are too few in number to generate a map image.  While some early corn is now in whorl stage and able to support ECB larvae, adult numbers do not indicate a significant threat as of this week.  We expect numbers to increase over the next 2-3 weeks, and will post maps and management suggestions as this occurs.

The highest nightly trap catches of ECB for the week ending 5/27/20 are as follows:

Two corn earworm (CEW) moths were captured this week (Eldora, Cape May County and Port Colden, Warren County) in blacklight traps.  It is possible that these individuals overwintered locally, but in any case, they pose no threat to sweet corn at this time.

There have been fields of seedling stage sweet corn exhibiting signs of slug injury this past week (streaks on leaves with tissue eaten away, but leaving one layer of epidermal tissue).  Generally the slugs responsible for this injury are a smaller species than the one in the photo at left.   Additionally, corn stem weevils have been discovered this week causing holes in leaves similar to those bill bugs make, but without the linear pattern across the leaf as with bill bug – see photo at right.  The former (slugs) have been found in northern counties on heavier soil for the most part, while the corn stem weevil injury is occurring in Cape May County.  Slug injury generally decreases as weather warms and the soil surface dries.  In rare instances of prolonged cool, wet weather, an application of slug bait may be warranted to limit injury to small plants.  In this case, damage should be found on the majority of plants, with slug-favorable weather in the forecast.  Corn stem weevil can sometimes causing severe damage from feeding on leaves and stems of seedlings. Adults are small, 1/8-3/16 inch, brown or black mottled. They hide during daylight beneath plants  or under debris on the soil surface. In recent years, they have been active only in May and June.  Consider an application of a labeled pyrethroid for beetle control in corn if injury is present on 12% or more seedlings.  For insecticide recommendations, see the Sweet Corn section of the 2020 Commercial Vegetable Production Guide.

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• Sand blasting has been reported on a number of leafy green and other crops these past few weeks. Injury from sand blasting predisposes plants to bacterial infections. Remember, all bacteria need a wound or a natural opening, such as a stomata, to gain entry into the plant. Fields with extensive injury need to be scouted regularly, and most likely will need to be sprayed regularly with a copper fungicide or disinfectant-type product to help mitigate infection and spread.
• For a review on how to avoid sunscald injury on transplanted crops please click here.
• Bacterial leaf spot has been reported in sweet basil. BLS of sweet basil is a relatively new disease of basil in the US. The bacterium has a large host range and can survive and overwinter in the soil on infested plant debris. Disease development is favored by hot, humid, rainy weather. Periods of hot, dry weather will help mitigate disease development.
• Club root has been reported in southern New Jersey.
• Cucurbit powdery mildew season is quickly approaching as more cucurbit crops are planted. For a review of CPM control strategies please click here.
• Cucurbit downy mildew has been reported as far north as southern Georgia on cucumber and cantaloupe. To track the progress of CDM please visit the CDM forecasting website.
• With the on and off again rains we have been getting, along with warmer weather this week, all growers should consider applying at-transplanting fungicides for root rot control. Please click here to see this article.
• Weather conditions have been ideal for fruit rot infections in strawberries. For more information on controlling fruit rots in strawberry please click here.
• The following is a nice article by Jeanine Davis from NCSU about mixing Serenade with coppers.
• The 2020/2021 Commercial Vegetable Production Recommendations Guide is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
• 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.