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:
| Asbury 1 | Denville 1 | Milltown 1 |
| Bellemeade 1 | Eldora 1 | Springdale 1 |
| Califon 1 | Hillsborough 1 | Tabernacle 1 |
| Clinton 1 | Milford 1 |
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.
Cole Crops
Diamondback moth larvae (DBM) have been increasing in cole crop plantings in central and northern NJ this week, with several plantings going over threshold. These infestations should increase rapidly as the spring season progresses. Check 5 consecutive plants each in 10 random locations throughout the planting. Consider treating if caterpillars are found on 10% or more plants that are in the 0-9 true leaf stage. From 9-leaf to the early head stage (in broccoli, cauliflower, and cabbage) infestations up to 20% may be tolerated. Once heads begin to form, a 5% threshold should be observed to protect the marketable portion of the plant. For leafy greens such as collards and kale, 10% plants infested is the threshold throughout. 
Some populations of DBM are resistant to carbamate and synthetic pyrethroid insecticides. The lack of DBM control with these insecticides has been noted in NJ previously. It is important to distinguish between common cole crop pests for this reason. DBM larvae grow to a length of approximately 0.5”, and taper toward both ends (see photo at right). These caterpillars thrash violently when disturbed. Newer chemistries that specifically target caterpillar pests are effective against DBM as well as all other caterpillar pests of cole crops. These materials include (active ingredient – trade name (IRAC* code)):
Spinosad/Spinetoram – Entrust(OMRI)/ Radiant (5)
Chlorantraniliprole – Coragen (28)
Cyantraniliprole – Exirel (28)
The IRAC group 5 insecticide, Entrust, is OMRI approved for organic production. Insecticides based on the soil-inhabiting bacterium Bacilllus thuringiensis (B.t.) may also be effective on caterpillar pests of cole crops. Examples include Xentari and Javelin.
Flea beetles continue to be active in many plantings, particularly during the warmer days. These pests have a preference for the “hotter” flavored crops like arugula, mustard greens, and turnip greens. They also attack Tuscan or lacinato kale frequently. Large populations of this pest may build up in areas of the farm where cole crops have been planted frequently over the past several years. Rotation of host plantings with as much distance as possible is important. Weed hosts like rocket, wild mustard, etc. should be discouraged. Plants may be protected with at-planting, soil-applied neo-nicotinoid insecticides (see the Commercial Vegetable Production Recommendations for products). An OMRI approved foliar material for flea beetle management is Pyganic. This product will provide knock-down of flea beetles, but may need to be applied frequently on preferred host crops.
