IPM Update 08/22/18

Sweet Corn

European corn borer (ECB) moth catches remain unchanged.  The second flight is weak, with many traps catching no individuals.  Feeding signs in whorl corn have been exceptionally low.  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.

The highest nightly trap catches of ECB for the week ending 8/22/18 are as follows:

The corn earworm (CEW) situation has intensified in southern NJ, while declining slightly in the northern counties over the past week.   While CEW numbers have been inconsistent, we continue to have significant black light trap catches even in the north.   The CEW pheromone trap network in the southern counties is showing a significant increase in some traps (see CEW blacklight map at left, and pheromone trap map at lower right).   There are many fewer pheromone traps than blacklight traps.  This results in much broader colored patches on the pheromone maps.  The blue area on the blacklight map indicates an approximate 4-5 day silk spray schedule, while green would be 3 days.  On the pheromone map, the green area corresponds to a 3-4 day schedule, with red indicating a solid 3 day schedule depending on location.  Trap catches from North Carolina appear to be rising now, while reports from Virginia are inconsistent.    While cooler, drier weather forecast for the second half of this week may bring us some relief from CEW inflow, we should expect another increase any time prevailing winds shift to the south.  Late August into September is traditionally when these second generation CEW moths arrive in high numbers.

Please note:  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 8/22/18 are as follows:

The highest nightly pheromone trap catches of CEW for the week ending 8/22/18 are as follows:

Silking Spray Schedules*:

South – 3 days

Central – 3 days

North – 4 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 continue to be light, with coastal regions experiencing slightly higher activity.  Pheromone trap catches remain 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 (see photo at right).  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).

Continuous wet weather 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.

Pepper Weevil

We continue to trap weevils only in the Hammonton area.

Beet Armyworm (BAW)

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

Tomatoes

With very warm, wet weather, foliar diseases of tomatoes are increasing to extreme levels.   Be sure to monitor the tomato/potato disease forecasts generated from the RAREC station.  This information appears weekly via the Plant and Pest Advisory and is useful for calculating spray schedules necessary for early blight.  Bacterial infections are particularly common now. Bacterial leaf spot (BLS) (see photo at left) is showing up to some degree in most scouted plantings in the northern counties, and bacterial canker is present in a number of locations as well.  BLS causes small, very dark lesions on all ages of foliage.  When these lesions occur on juvenile tissue, the leaves often become distorted as they expand and mature.  Bacterial canker can cause a marginal necrosis, typically on older foliage.  Pale streaks form on petioles and a characteristic fruit lesion called bird’s eye spot (see photo at right), forms on the fruit.  Labeled products are found in the tomato section of the 2018 Commercial Vegetable Recommendations Guide.  Maintaining our accustomed level of disease control will be difficult under these very wet conditions.  Good coverage is essential.

The inconsistent CEW population of the past two weeks has resulted in localized fruit worm (CEW)  infestations in tomatoes. This has primarily been observed in Monmouth and Ocean counties, but may be happing elsewhere; especially in coastal areas.  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.

Brown marmorated stink bug (BMSB)

BMSB catches in black light traps have fallen further over the past week.  At the present time, the heaviest catches are in Cape May and Somerset counties.  Although 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 8/22/18 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.  Through Wednesday of this week, NJ was considered to be at high risk for spread from existing known sites, but the threat drops to low risk by Thursday, as drier weather arrives.