Vegetable IPM Update 5/26/21

Sweet Corn

European corn borer (ECB) moths are now being captured in parts of the state.  As yet, numbers are low, and the next 7-10 days will likely tell whether this flight will be of any significant size.  Current “hot spots” are around Salem County and southern Hunterdon into Mercer and Ocean counties (see map at right).  Whorl corn is the primary target for egg laying, but as yet, scouts have reported no signs of feeding injury.  We expect to encounter feeding over the next week.  .

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 5/26/21 are as follows:

Several corn earworm (CEW) moths were captured this past week.  Although there is little impact from these moths, their presence is a reminder that we sometime get a low, early population that lingers into the silking period of our first sweet corn plantings.  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 trap catches of CEW for the week ending 5/26/21 are as follows:

Black cutworm – 1% damage in early planted sweet corn in Cape May County.  The caterpillar burrows up to the soil line and feeds in that area of the corn plant, often tunneling up the corn stem resulting in a wilted plant.  The threshold for spraying would be 6%.  See the Sweet Corn section of the  2020/2021 Commercial Vegetable Production Recommendations for useful insecticides.

Cole Crops

Low numbers of imported cabbage worm (ICW at left) continue in cole crop plantings in central and northern NJ, and adults are evident everywhere.   With warmer temperatures on the way, these infestations should increase rapidly.   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 now appearing in 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)

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 remain very active in a number of plantings, and warmer days will 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.

Tomatoes

Field scouting of outdoor and high tunnel tomatoes has begun.  Low level  aphid populations (see photo at right) have been found in a number of recently transplanted fields.  With plants in the vegetative or early flower stages, it is often acceptable to allow natural predation and parasitism to take its course.  Beneficial insects such as syrphid fly maggots, ladybird beetles and parasitic wasps will frequently limit the advance of these early aphid populations before the advent of fruit production.  This is particularly true if broad spectrum insecticides are avoided at this time.  If aphid populations persist into the early/enlarging fruit stage, and their droppings are accumulating on fruit, aphid specific insecticides may be advisable.    Growers should check tomatoes at least weekly, and note the presence of spider mites or aphids.  Mites in particular should be treated early, so that they do not build to a population that becomes difficult to manage.   Consider treating if aphids are found on multiple sites in a 5-site sample, and fruit are beginning to develop.

Peppers

With ECB moth activity now increasing, 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.

Pepper weevil – Pheromone traps are being set out across southern New Jersey.  As yet, no weevils have been trapped.  Weevils escaping from processing facilities could be present as soon as transplanting is finished.  A new fact sheet is now available for anyone interested in monitoring for pepper weevils on their own:  FS1330: Monitoring and Management of Pepper Weevil in New Jersey (Rutgers NJAES).