Vegetable IPM Update 08/17/22

Sweet Corn

European corn borer (ECB) moth catches are largely unchanged; remaining at low levels throughout the state.    Only occasional feeding in sweet corn has been detected by field personnel.

The highest nightly trap catches of ECB for the week ending 08/17/22 are as follows:

Corn earworm (CEW) moth captures from both blacklight traps and pheromone trap captures are increasing now, with a few large increases in pheromone traps.  While the highest catches are still from Burlington County southward, there have been sharp increases in parts of Hunterdon and Warren counties as well.  Both trap types are in general agreement as to spray schedules.  We are now in the high activity portion of the summer.  CEW populations can increase or decline with changes in night temperatures.  Growers should be on alert for large CEW migrations should NJ experience strong low pressure fronts approaching from the west.    Check this publication weekly for CEW status.  The number of pheromone traps deployed is much lower, resulting in much broader color bands on the map. It is also important to understand that pheromone traps are more sensitive than blacklight traps, and thresholds are adjusted to account for the higher catches typical of this trap type.  Silking  corn is at risk of CEW infestation at this time.  On the blacklight map (left), green areas represent a 3-day silk spray schedule and blue represents a 4-day schedule.  On the pheromone map (below right), red represents a 3-day spray schedule, green represents a 4-day schedule. Be sure to access information from this publication in the upcoming weeks to determine how frequently you should treat silking sweet corn to protect it from CEW infestation.

The highest nightly blacklight trap catches of CEW for the week ending 08/17/22 are as follows:

The highest nightly pheromone trap catches of CEW for the week ending 08/17/22 are as follows:

Silking Spray Schedules*:
South – 3 days

Central –  3 days

North – 3 – 4 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.  Utilize materials in IRAC groups 5 and 28, or combination products that include IRAC group 28 for best control.  See the Sweet Corn section of the 2020-21 Commercial Vegetable Production Guide for selections.

Fall armyworm (FAW) continues to infest whorl and  seedling stage corn at low to moderate levels throughout the state.  Cape May county continues to experience the highest  levels of infestation, but damage around 20% is not unusual.  Sweet corn plants in the 6-12″ range have been targets for egg laying in some areas.  This can result in terminal injury to the plants if not controlled.   Injury from newly hatched larvae shows up as “window panes” or areas where leaf tissue has been eaten down the the lower epidermis (see photo at far left).  This injury leads down into the whorl.  As larvae gain size, they begin to consume leaf tissue in its’ entirety, creating ragged holes and lots of droppings (see photo at near left).  FAW can be tough to manage because it is resistant to synthetic pyrethroid insecticides (IRAC 3A) and because larvae are often covered by their own droppings, making contact with the insecticide more difficult.  Treat when 12% or more plants exhibit FAW injury alone, or in combination with ECB injury.  As a rule, insecticides that are most effective on CEW will also adequately control FAW.

Two-spotted spider mites (TSSM) are infesting sweet corn plantings as they approach the silk stage.  Insecticide applications for CEW control often intensify these infestations.  Check plantings prior to the onset of silks.  Mite populations in corn will result in lower leaves first appearing “dusty”, and ultimately turning yellow.  This condition progresses up the plant as mite populations increase.  If mites are detected in any plantings, the addition of the miticide Oberon (5-day PHI) to the normal silk spray schedule can help minimize injury.  Zeal is also labeled in corn but must be used early in the silk schedule as it carries a 21 day PHI.

Tomatoes

With CEW numbers increasing, consideration should be given to protecting tomato plantings from this pest (called the fruitworm, when found in tomatoes).  Larger populations locally, (>20 CEW/night) in local pheromone traps are a signal that growers should be inspecting tomato plantings at least weekly for signs of fruit injury.  Typically, the female CEW moth lays eggs in blossom clusters near the outer canopy of the plant.  Larvae hatching from these eggs begin feeding on the nearest fruit (photo at left), making damage very visible while walking the planting.  At the first sign of this injury, growers should initiate control, with insecticides in the IRAC 5 and 28 classes most effective, with short PHIs.  There are a number of effective insecticides listed in the Tomato Section from the 2022-23 Guide.

Two-spotted spider mites (TSSM) will remain a threat in nearly every scouted tomato field with hot, dry weather.    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 current 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.

Peppers

Weevil counts in traps are increasing in one of the East Vineland farms, so there seems to be an established population there.  No other infested fields have been reported.

The best control rotations include Vydate, a neonicotinoid (Actara, Admire, Assail, others), a diamide (Exirel, Harvanta), and possibly Torac.  University of Georgia researchers have found that all populations of pepper weevil that they have tested are resistant to pyrethroids. Since we don’t know where the weevils come from that we find here in New Jersey, farmers probably shouldn’t rely on pyrethroids being effective.  Refer to the Rutgers Fact Sheet,  FS1330: Monitoring and Management of Pepper Weevil in New Jersey (Rutgers NJAES) for more details on monitoring pepper weevil populations.

Beet armyworm adults (BAW) continue to be captured over the past week.  Nightly counts include:

Growers in Gloucester, Salem and Cumberland counties should monitor pepper fields weekly for signs of feeding.  BAW larvae feed in the developing foliage in terminal growth of plants.  Initially, leaves are skeletonized (photo at left, courtesy of Univ. of Ga.), but as larvae grow, they will move onto fruit and damage these as well.  As with other armyworms, BAW is difficult to control with pyrethroid insecticides.  Effective materials include spinosyns (IRAC 5) and diamides (IRAC 28).

Pumpkins and Winter Squash

Cucurbit downy mildew (CDM) is active on cucumbers in all parts of the state.  As yet, other cucurbits, including pumpkins, butternut squash, acorn squash and watermelons are NOT affected.   As of Monday 8/15, the CDM forecast was for low risk of new infection in NJ.  For regional information on this important disease, see the Cucurbit Downy Mildew Forecast webpage:  http://cdm.ipmpipe.org/.    It is advisable that all growers treat preventively for CDM on cucumbers and muskmelons.

Powdery mildew (PM) infections are now present in nearly all scouted pumpkin and winter squash fields, and protectant spray programs for this fungal disease have been initiated.  While it is not necessary to spray preventively for this disease, it is advisable to begin the program when lesions are first detected (2/50 older leaves).  Growers should include protectant and systemic fungicides for powdery mildew management.  For a review of PM control, see Dr. Andy Wyenandt’s article on PM control from earlier this season.

Cole Crops

Host availability and elevated temperatures have made diamondback moth larvae ((DBM) see photo at right) the dominant caterpillar pest in many cole crop plantings.  This pest can multiply quickly, with a generation completed in under 2 weeks with high temperatures.  Furthermore, it is apparent that this pest is not responding to chlorantraniliprole (Coragen) in many parts of the state.  Effective materials continue to be IRAC 5 materials (spinosyns), other IRAC 28 products like Exirel, and the IRAC 6 material, ememectin benzoate (Proclaim).  Be sure to check the Cole Crops Section of the 2022-23 Commercial Guide for specifics, as PHI’s and crop labels vary.  It is important to return to treated fields within 2-3 days to assess the efficacy of the insecticide applications.  Effective materials should eliminate DBM larvae within 48 hours.

Brown Marmorated Stink Bug (BMSB)

BMSB numbers have decreased to very low levels with cooler evening temperatures over the past week.    Should numbers rebound, information will appear here.  BMSB has not been a major pest of vegetable crops in NJ for a number of years, but is still of concern to tree fruit crops.

Kristian Holmstrom and Joseph Ingerson-Mahar would like to gratefully acknowledge the efforts of field technicians:

Claire Chapeau

Travis Kaye

Gabe Torres

Without the hard work of our field technicians, much of the information presented weekly in the IPM Update would be unobtainable.