Sweet Corn
Due to continued cold night temperatures, European corn borer (ECB) moth captures have been extremely low in northern and central county light traps. Thus far this flight has been weak, and no feeding has been detected on whorl and pre-tassel stage sweet corn as far south as northern Burlington County. An increase in nighttime temperatures (even temporarily) may result in somewhat higher numbers over the next week. Whorl corn is the primary target for egg laying. If the first flight is late rather than nonexistent, this sometimes results in heavier infestations on 2nd and 3rd plantings than on the first. Feeding levels could be somewhat higher in the southern counties, and should rise over the next 3 weeks.
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 or Vantacor (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 5/30/23 are as follows:
Blairstown 1 | Princeton 1 |
Chester 1 | Sergeantsville 1 |
Morristown 1 | South Branch 1 |
No Corn earworm (CEW) moths were captured in blacklight traps in the northern and central counties this past week. While data from the pheromone trap network in southern NJ is not yet available, northern traps are only capturing scattered individuals. There is little risk from this pest currently, but as as the earliest plantings in southern NJ begin to silk, even low numbers will be impactful. Be sure to access information from this publication in the upcoming weeks to determine how frequently you must treat silking sweet corn to protect it from CEW infestation.
The highest nightly pheromone trap catches of CEW for the week ending 5/30/23 are as follows:
Allamuchy 1 | Dayton 1 | Georgetown 1 |
Califon 1 | Farmingdale 1 | Matawan 1 |
Cole Crops
Low numbers of imported cabbage worm (ICW at left) continue in cole crop plantings everywhere. With warmer temperatures on the way, these infestations should 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) are becoming the dominant pest in a number of scouted plantings. 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 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)
Emamectin benzoate – Proclaim (6)
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. 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.
Flea beetles remain very active in a number of plantings, and warm, sunny days accelerate injury. 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 2020/21 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.
Peppers
With potential increases in ECB moth activity over the next few weeks, growers should be looking for ECB egg masses (see photo at left) on the underside of pepper leaves. The larvae that hatch from these eggs will bore into the central stem of pepper plants in the absence of suitable fruit. This damage causes the tops of the plant to die, and eliminating the crown set of fruit in the process. Check 2 leaves per plant on 5 consecutive plants in 10 random locations. Consider treating if 2 or more leaves are found to have ECB larvae on the lower surface.
Tomatoes
Tomato pests have been largely absent in scouted fields, although two-spotted spider mites (TSSM) have appeared in a few high tunnels recently. This is a typical response to higher heat and dry conditions. Initial, low-level infestations result in a mite “stipple” on the upper leaf surface (see photo at right). In these cases several mites may be found on the lower leaf surface. With hot, dry conditions and no control applied, mites multiply rapidly. A large population will create webbing that can cover entire plant leaves and branches (see photo below). Large populations can become quite difficult to manage, so treatment should be applied upon finding a mite infestation at any level. This can limit future problems with this pest. There are a number of effective miticides listed in the Tomato Section from the 2022-23 Guide.