Sweet Corn
IPM personnel have deployed black light and corn earworm (CEW) pheromone trap networks in central and northern New Jersey counties. In areas from central Burlington County southward, grower cooperators have been provided with CEW pheromone traps and will be monitoring these traps on their own properties and reporting catch data to IPM personnel. This is an effort to maintain a statewide reporting program for the most significant economic pest of sweet corn despite a shortage of professional staff this year. The IPM program thanks these growers in the southern counties for their assistance in maintaining this necessary service.
Black light trap derived maps for European corn borer (ECB), CEW and brown marmorated stink bug (BMSB) will not appear in the Plant and Pest Advisory, as there is no statewide blacklight trap network. Data from existing black lights in the central and northern counties will appear in table format, with associated information on the relevance of the populations. Provided that data from the southern CEW pheromone traps is available on a regular basis, maps will be generated for this pest/trap type. Limited collections from traps thus far have not contained any target pests.
Cole crops
Recently transplanted crops of broccoli, cabbage, etc. as well as newly emerged seedlings are at risk of damage from flea beetles (see photo at left). Flea beetle activity occurs primarily on warm, still days, and the heat during the first half of this week has resulted in threshold levels being reached in several scouted fields. Inspect plantings under these fair conditions to get an accurate assessment of population in the field. Flea beetles can do considerable damage to small plants, and have a 
preference for the “hotter” flavored crops like arugula and mustard. They will feed on all brassicas however, and broccoli and Tuscan kale are also favored hosts. Site rotation is critical to managing flea beetle populations because they can build to high numbers in the repeated presence of host crops or host weeds (see photo at right – cabbage transplants with brassica weeds). Scout early and consider treating when 50% or more plants are showing injury and flea beetles are present on plants. Respond quickly to limit injury. Systemic insecticides such as the neonicotinoid (IRAC 4A) class, used at planting, can provide protection from flea beetles for the first critical weeks. Check the Cole Crops section of the 2022/23 Commercial Vegetable Production Guide for a complete list of insecticide recommendations.
Low numbers of imported cabbage
worm (ICW at left) have been discovered in a few cole crop plantings. With warmer temperatures, these infestations could increase rapidly and continue for the duration of the growing season. 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.
Diamondback moth larvae (DBM) thus far have only been found associated with kale production in high tunnels in central and northern NJ counties. They could well be active in southern county fields now, but certainly will be within the next two weeks. Remember that 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 lower right).
These caterpillars thrash violently when disturbed. ICW grow to a length of approximately 1.25” and are covered with short hairs. Some chemistries that specifically target caterpillar pests have been 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)
Emamectin benzoate – Proclaim (6)
Tolfenpyrad – Torac (21 a)
Cyantraniliprole – Exirel (28)
There are reports from the field that some growers have had success with Spear-Lep (IRAC 32). Note that this material must be combined with a B.t. based foliar insecticide to allow the toxin to enter the body if the target caterpillar.
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. It is important to return to treated fields within 24-48 hours to assess the DBM control. If significant numbers of larvae remain, it is an indication that your population may be resistant to the material most recently used. The critical message here is that growers’ spray programs should incorporate as many effective products as possible in rotation. Reliance on 1-2 active ingredients could result in the development of resistance to those materials.
Allium Leaf Miner
No sticky card captures of allium leaf miner (ALM) adults in central and northern NJ have occurred over the past 10 days. This is a strong indication that the first flight is over. In southern NJ allium fields, this is likely the case as well. We will attempt to identify the onset of the second flight by placing sticky cards in allium fields during the second half of September.
