Sweet Corn
Increasing numbers of European corn borer (ECB) moths have been captured over the past week, although overall numbers remain low. At this time, activity is highest in central Morris County and western Burlington County (see ECB map at left). The number of traps registering moderate catches is fairly low, and catches are widely dispersed. Overall, this year’s population is late, and whether numbers increase much or not remains an open question. Early corn is now in whorl or pre-tassel stage and able to support ECB larvae. It is time to begin scouting corn in these advanced growth stages.
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 (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen. 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 6/03/20 are as follows:
| Denville 2 | Clinton 1 | Milford 1 |
| Asbury 1 | Downer 1 | Oldwick 1 |
| Bellemeade 1 | Eldora 1 | South Branch 1 |
| Califon 1 | Medford 1 | Springdale 1 |
Widely scattered, and low catches of corn earworm (CEW) occurred this past week. While there was an increase in activity over the previous week, this pest does not pose a threat to sweet corn that has not yet reached the silk stage.
The highest nightly trap catches of CEW in black light traps for the week ending 6/03/20 are as follows:
| Chester 1 | Eldora 1 | Milltown 1 | Oldwick 1 |
| Crosswicks 1 | Elm 1 | Morristown 1 |
Cole Crops
Diamondback moth larvae (DBM) and imported cabbage worms (ICW) have have increased significantly in cole crop plantings in central and northern NJ this week. Threshold levels of infestation are now common. 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. These caterpillars thrash violently when disturbed. ICW can grow to over an inch in size, and are covered in short, felt-like hairs. 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 (see photo at left) 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.
