Sweet Corn
IPM Program personnel have re-established the black light trap network in New Jersey. With continued below normal temperatures, no corn earworm (CEW) or European corn borer (ECB) moths have been captured. As numbers increase, look for population maps of ECB, CEW, brown marmorated stink bug (BMSB) and CEW catches from pheromone traps in this weekly publication. The resulting full-state maps will include interpretive information.
With cold, damp conditions dramatically slowing down the growth of seedling corn, wire worms (see photo at left) have the potential to be more of a nuisance than usual. While we don’t often see this problem in sweet corn, it does occasionally happen when wire worms are present and the corn cannot grow quickly enough to become less susceptible to injury. Look for clusters of seedlings that exhibit wilted inner leaves. Wire worms often are discovered by digging up these affected seedlings. The incidence of this damage may be minor, but if growers determine that a field must be replanted, it may be necessary to include an in-furrow soil insecticide targeting this pest.
Cole Crops
Imported cabbage
worm (ICW at left), and diamondback moth larvae (DBM) have not yet been found in cole crop plantings in central and northern NJ. However, ICW butterflies are active on warmer afternoons, and these infestations should appear and increase rapidly once warm weather dominates. Check 5 consecutive plants each in 10 random locations throughout the planting, paying particular attention to the innermost leaves where ICW often feed (see photo at lower right). 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 grow to a length of approximately 1.25” and are covered with short 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/ 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 are very active in a number of plantings, but only on warmer days. Signs of “shot-hole” in leaves of host crops are an indication that flea beetles are present, even if the pests are not visible due to cold/wet weather. 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. Plants may be protected with at-planting, soil-applied neo-nicotinoid insecticides (see the 2020 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.
Allium leaf miner
Captures of allium leaf miner (ALM) adults on sticky cards have trended downward over the past two weeks.
Cards from chive plantings in Mercer and Hunterdon counties had 0 and 1 flies/week respectively, for the week ending 5/13/20. Damage has been excessive in chives with significantly less in garlic when the garlic plantings were not located near the chives. It is likely that the first flight is winding down now. However, continued protection on all alliums either with row covers, or weekly insecticide applications is warranted. IPM personnel will continue to monitor ALM cards and will conclude that this first adult flight is over when all adult activity ceases. Insecticides recommended for ALM management include:
Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom) and the insect growth regulator Trigard are labeled for miner control. The diamide, Exirel, is permitted in NJ under a 2ee label as well.
