Sweet Corn
European corn borer (ECB) moth catches have declined over the past week despite increasing temperatures. At this time, activity is highest near the Hunterdon/Warren County border, although this is still a low level population (see ECB map at left). The number of traps registering moderate catches remains low, and catches are widely dispersed. Another week of trapping will clarify whether this decrease in activity signifies the end of the first flight. A number of corn plantings are now in whorl through tassel stages and able to support ECB larvae. Larval infestations as high as 12% were detected as far north as Hunterdon County this week. As moth catches fall, larval development and damage increase. We expect that with a few more warm days, these infestation rates will climb quickly in many parts of the state.
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 6/10/20 are as follows:
| Allamuchy 1 | Crosswicks 1 | Milford 1 |
| Blairstown 1 | Denville 1 | Milltown 1 |
| Califon 1 | Downer 1 | Springdale 1 |
| Chester 1 | Eldora 1 | Tabernacle 1 |
Widely scattered, but slightly increased catches of corn earworm (CEW) occurred this past week. As the earliest plantings (mainly in the south) proceed to full tassel and on to silk, even this low population can present a limited threat.
The highest nightly trap catches of CEW in black light traps for the week ending 6/10/20 are as follows:
| Califon 1 | Downer 1 | Green Creek 1 |
| Dayton 1 | Georgetown 1 | Tabernacle 1 |
This increase in the blacklight network is corroborated by catches that have occurred in the partially established CEW pheromone trap network. While the number of traps deployed currently is low, some have recorded low-to-moderate catches, indicating a fairly significant late spring flight. We hope to have the remainder of this trap network deployed by the end of next week.
The highest nightly trap catches of CEW in pheromone traps for the week ending 6/10/20 are as follows:
| Berlin 19 | Woodstown 9 | Beckett 5 |
| Monroeville 15 | Pedricktown 8 | Springdale 5 |
Silking Spray Schedules*:
South – 5-6 days
Central – 7 days
*These recommendations are based on regional catches. Adhere to tighter spray schedules if indicated by local trap catches. Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn, or for fall armyworm (FAW) management at any stage. Control with these materials is very inconsistent.
Cole Crops
Diamondback moth larvae (DBM) and imported cabbage worms (ICW) are the main pests in cole crop plantings, with ICW increasing dramatically in the warmer weather. Threshold levels of infestation are now common and re-infestations can occur within 7-10 days. 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.
Tomatoes
The first signs of bacterial infections in tomatoes occurred this week in scouted plantings. The photos at left show symptoms consistent with bacterial canker (dark lesions at the margins of lower leaves, with obvious involvement of the hydathodes – pores at the leaf edges). This pathogen, as well as bacterial leaf spot are readily spread through the actions of field workers. Materials that may be helpful at mitigating the impact of bacterial infections include Actigard, copper hydroxide, and hyrogen dioxide products (in response to trauma events like tying, pruning or severe weather). Be sure work crews enter fields from youngest plants to oldest. This prevents the spread from older (and more likely symptomatic) plants to younger ones. The later in the life of a plant that it acquires an infection, the less likely there is to be negative yield impact. Remember, bacterial lesions are typically very dark in appearance, while physical injury, paraquat burn or other desiccation events result in light colored lesions. Bacterial infections rarely occur on single plants, but rather clusters or down entire rows. See the 2020 Commercial Vegetable Production Recommendations for advice on mitigating bacterial infections in tomatoes.
