IPM Update 09/05/18

Sweet Corn

European corn borer (ECB) moth catches remain low.   Feeding signs in whorl corn are rare.  There will be no map in this edition.  Second generation feeding is often obscured by fall armyworm (FAW) feeding.  Once plants hit full tassel, any ECB larvae present will move downward on the stalk and re-enter the plant near the area where ears are forming.  This can result in direct injury to the ear.  Growers should consider an insecticide application at the full tassel stage to target ECB larvae as they migrate downward.  This application can eliminate larvae that have escaped any earlier insecticide applications.

Corn earworm (CEW) catches have increased substantially over the past week in all traps.   The CEW pheromone trap network in the southern counties has captured high numbers of moths in several locations  (see CEW blacklight map at left, and pheromone trap map at right).   There are many fewer pheromone traps than blacklight traps.  This results in much broader colored patches on the pheromone maps.  The green area on the blacklight map indicates an approximate 3-day silk spray schedule.  Red areas on this map are extremely high local populations, and there should be no deviation from the 3-day silk schedule.  On the pheromone map, the red area indicates a solid 3-day schedule depending on location.  The current pattern of winds from the south/southwest has allowed good CEW movement into our area.  As fontal systems approach from the west, the inflow of CEW often increases until the front passes.  We hope that with cooler temperatures over the coming weekend, this CEW population will decline at least temporarily.

Please note:  It bears repeating!!  A number of growers have experienced unsatisfactory control of CEW when using synthetic pyrethroid insecticides (IRAC class 3A) in the silk spray program.  CEW resistance to this class of insecticides is well documented and has increased in recent years.  Growers should rotate among IRAC class 28 materials (Coragen, Besiege (28+3A)), class 5 (Radiant, Entrust, Blackhawk), and class 1A (Lannate) for acceptable control.   Growers of Attribute I and Performance Series sweet corn (expressing B.t. traits) should consider adhering to silk spray schedules prescribed for non B.t. sweet corn.  At this time, Attribute II varieties are not known to support CEW larvae.

The highest nightly black light trap catches of CEW for the week ending 9/05/18 are as follows:

The highest nightly pheromone trap catches of CEW for the week ending 9/05/18 are as follows:

Silking Spray Schedules*:

South – 3 days

Central – 3 days

North – 3 days

*These recommendations are based on regional catches.  Adhere to tighter spray schedules if indicated by local trap catches.

Fall Armyworm

Fall armyworm (FAW) infestations remain light, although single digit infestations are becoming more common.  Pheromone trap catches are unusually low.   Continue scouting regularly for this pest.  Look for significant injury in whorls, with all damage leading directly into the center of the plant (see photo at left). FAW larvae consume lots of tissue, and grow rapidly .  Be sure to check seedling stage plantings as well, as FAW will attach even small plants.  Consider treating if plants infested with FAW alone, or in combination with ECB exceed 12%.  FAW is resistant to synthetic pyrethroid insecticides.  Effective materials include those in IRAC groups 5 (Radiant, Entrust (OMRI approved)), and 28 (Coragen, Exirel).

The wet weather that we had experienced earlier has created a perfect environment for the development of northern corn leaf blight (NCLB). This foliar disease of corn causes elongated, gray lesions on the leaves (see photo at left).  NCLB attacks older tissue first, but can move further up the plant when wet conditions permit spore production and germination.  Ultimately, NCLB can cause unsightly lesions on ear husks and even poor ear size if is uncontrolled.  If NCLB is detected in sweet corn prior to silking, one or more fungicide applications may be warranted.  See the Sweet Corn section of the 2018 Commercial Vegetable Recommendations for useful fungicides.

Corn leaf aphid (photo at right) is a fairly common insect pest of late stage sweet corn at this time, particularly if pyrethroid insecticides have been used.  To help manage this insect, and prevent it from becoming a possible contaminant at harvest, consider including Lannate early in the silk spray schedule.  Additionally, the neonocotinoid Assail is labeled for aphid control on sweet corn and is much less toxic to bees than other neonicitonoids.  Assail has no caterpillar activity, so it must be in addition to the worm material that is used.

Peppers

Several farms in the northern counties have developed anthracnose fruit rot infections in pepper fields.  This disease can spread rapidly under wet conditions.  Anthracnose causes a depression on the side of fruit, with pinkish curd-like spores (see photo at left). Ideally, infected fruit should be removed from the field, even if this means separate buckets for picking crews.  This will help limit inoculum in the field.  Additionally, anthracnose requires specific fungicides to limit spread.  These may be found in the Pepper section of the 2018 Commercial Vegetable Recommendations.

Pepper Weevil

To date, no weevils have been trapped outside the Hammonton area and as far as is known, there are no infested fields other than those in Hammonton.

Beet Armyworm (BAW)

Pheromone trap catches of BAW in southern NJ are low in general, with the only notable catch still in the Woodstown area of Salem County.  No crop injury has been detected.

Tomatoes

There remain localized fruit worm (CEW)  infestations in tomatoes, and with high CEW numbers now, the threat of this damage is significant. CEW moths lay eggs near flower clusters in the upper portion of the plant.  Larvae bore into developing fruit (see photo at left). If CEW moths are being caught locally in traps, and this type of injury or live worms (see photo at right)  show up in more than one site in a 10 site sample, growers should consider treating.  Insecticides in the IRAC 28 group (Coragen) or 5 (Entrust, Radiant) have very short harvest intervals and are effective at controlling these larvae.

Stink bugs and cabbage looper (CL) caterpillars are also fairly common in tomato plantings at this time.  The latter does little real damage to plants; feeding mainly on foliage.  However, stink bugs can cause extensive fruit blemishes, and nymphs of our native brown species are now occurring in scouted fields.  Stink bugs are most easily detected by taking a slow walk down tomato rows.  Look ahead as you walk, paying particular attention to sunny spots where bugs often bask in the morning.  Consider treating if these bugs are found in more than one location in the field.

Brown marmorated stink bug (BMSB)

BMSB catches in black light traps have again increased.  At the present time, the heaviest catches are in Hunterdon and Monmouth counties, although these are somewhat isolated.  While this pest has not had serious impact on vegetable crops like peppers in recent years, it is still a significant pest of tree fruits.

The highest nightly trap catches of BMSB for the week ending 9/05/18 are as follows:

Pumpkins and Winter Squash

 All growers should be applying appropriate downy mildew (DM) fungicides on all cucurbit plantings now.  CDM has been found on pumpkins and other cucurbit crops throughout the state.  CDM causes yellow “panels” to develop on the upper leaf surface (see photo at left) with dark sporulation forming on the lower leaf surface (see photo at right). CDM can defoliate fields in a matter of several days during wet conditions such as we are currently enduring.    Our present  weather pattern has New Jersey cucurbit crops under constant threat of CDM infection from spore sources locally and from more southern sources.  For detailed CDM forecasts, see the following website:  http://cdm.ipmpipe.org/  All growers are encouraged to check this website at least once a week.  NJ is considered to be at moderate risk of infection from outside areas as rain is forecast on Thursday, but with most fields now infected and/or being protected, there is little change necessary.  Heavy dews now occurring will increase in-field spread in currently infected fields.  IPM scouts frequently detect DM lesions on leaves, but when appropriate fungicides are being used, these lesions are not actively producing spores.  For a list of DM specific fungicides, see the Pumpkin and Winter Squash section in the 2018 Commercial Vegetable Recommendations.