Veg IPM Update: Week Ending 8/31/16

Sweet Corn 

A few European corn borer (ECB) adults have been captured this past week.  At the present time, highest activity is in the Cape May-Cumberland County border area (see ECB map). Earlier ECB catches were extremely low, and these moths, likely representing a partial third flight, will not present much of a threat to host crops.  This is particularly true in light of the dominance this year of fall armyworm (FAW). FAW will probably remain the larger threat, and treatments for this pest will eliminate ECB in the process.  As always, consider treating when the number of infested plants in a 50 plant sample exceeds 12%. Any planting remaining at or above threshold as it proceeds to full tassel should be treated, as this is the last stage at which ECB larvae will be exposed and vulnerable to insecticidal sprays. See the 2016 Commercial Vegetable Recommendations Guide for insecticide choices.

The highest nightly ECB catches for the previous week are as follows:

There has been no change in the fall armyworm (FAW) situation.  Infestations continue throughout NJ, with high infestation rates in all parts of the state.  This pest is devastating to small corn plants, and in fact the worst infestations are currently in shorter whorl stage plantings.  Fields down to seedling stage should be scouted weekly for signs of infestation.  We should expect this pest to be with us for the remainder of the sweet corn growing season.  Treat when FAW alone or in combination with ECB damage exceeds 12% plants infested.  FAW do not respond well to pyrethroid insecticides.  The most useful products are those in the IRAC group 28 class (Coragen, Exirel) or the IRAC group 5 class (Radiant, Entrust), or combination products including these classes.  See the 2016 Commercial Vegetable Recommendations Guide for insecticides effective against FAW.

There has been little change in corn earworm moth (CEW) activity over the past week.  We have experienced a solid week of high pressure with no transport systems to help deliver moths to us.  Despite this, weekly averages remain moderately high.  If any of the tropical storm systems tentatively forecast to head northward along the coast actually reach us, we would expect increased CEW numbers to result.  Activity is highest in south and central counties but pockets with higher catches may be found anywhere in the state (see CEW map).  Many North Carolina traps continue to registering high catches, although Delaware’s network is showing catches similar to ours.  It is advisable to incorporate materials into the spray program that have different modes of action from the pyrethroids.  This includes IRAC 28 materials like Coragen, Exirel and Besiege, as well as IRAC 5 (Radiant, Entrust (OMRI approved), and Blackhawk)). Our current population is still lower than we traditionally get in mid-August.  Growers should be checking CEW activity frequently, and adjust spray schedules according to local activity.

The highest nightly CEW catches for the previous week are as follows:

The limited CEW pheromone trap network in the southern counties registered lower catches over the past week.  Despite this, CEW moth populations are present throughout southern NJ (see CEW pheromone map).  The low number of traps results in broad areas of color within the map.  It is critical that growers monitor local CEW moth numbers.  At present, this population constitutes a significant threat to silking corn.

The highest nightly CEW pheromone trap catches for the previous week are as follows:

For silking sweet corn, the following spray schedules are warranted.

Silking Spray Schedules*:

South – 3 days

Central – 3-4 days

North – 4 days

*These recommendations are based on regional catches.

Corn leaf rust and northern corn leaf blight (NCLB) are now present in many late plantings.  Both of these diseases are favored by leaf wetness, which increases with longer nights.  Rust causes reddish, powder (spore) filled pustules to erupt from the leaf surface, while NCLB causes elongated tan lesions (both may be seen on one leaf in photo at right).  Both diseases can reduce the amount of productive leaf surface, which can result in shorter ears to be produced.  At less destructive levels, both can still cause unsightly lesions on the husks.  The 2016 Commercial Vegetable Recommendations Guide lists several fungicides for these diseases.  Be sure to observe pre-harvest intervals, as some are quite long.

Brown Marmorated Stinkbug (BMSB) 

BMSB numbers continued to fall in NJ blacklight traps this past week.  This is the time of the summer when BMSB catches in light traps generally decline, while increasing in pheromone traps as the bugs begin to aggregate.  It is still important that host crops like peppers be scouted regularly for the presence of BMSB and other stinkbugs at this time.  It is often most productive to walk slowly down pepper rows, scanning plants ahead.  BMSB and other stink bugs tend to bask near the tops of plants, especially in the morning hours.

The highest nightly BMSB trap catches for the previous week are as follows:

Pumpkins and Winter Squash

Powdery mildew (PM) (see photo at right) is active on pumpkin and winter squash fields throughout NJ. The action threshold for commencement of the protectant fungicide program for PM is 2 lesions per 100 older leaves. This pathogen kills tissue very slowly, and needs to be managed.  Elimination of the disease is unrealistic.  If not managed appropriately, premature death of foliage gradually occurs, resulting in poor fruit size, color, and handle quality.  See the 2016 Commercial Vegetable Recommendations Guide for a list of appropriate protectant fungicide rotations for PM control.

Downy mildew (DM) is present on cucumbers in all parts of  NJ (see photo at left).  DM has been reported on the eastern shore of Virginia on butternut squash.  While this site may not currently be a direct threat to NJ pumpkin and winter squash acreage, it is an indication that races of the pathogen that are capable of infecting these important crops are getting closer.  All growers should be applying appropriate protectant fungicides plus DM specific materials to cucumbers  and cantaloupes at this time, and scouting frequently and preparing to make DM applications on pumpkins and winter squash.   RCE personnel have still not been able to confirm DM on
crops other than cucumber, and the only crop in the DM sentinel plot at Snyder Research Farm in Hunterdon county that is infected is cucumber.  DM lesions appear as yellow areas on the upper leaf surface with leaf veins making distinct borders to the lesions.  On the lower leaf surface, beneath the lesions, dark spores may be seen if conditions are moist (see photo at right).  For more information on the regional presence of DM as well as comprehensive, weekly forecasts, see the following website: http://cdm.ipmpipe.org.  At this time, with the current weather pattern, NJ is at low risk of new infections according to the Cucurbit Downy Mildew Forecast.

Peppers and Tomatoes

Stinkbug injury continues to be found in scouted fields along with two-spotted spider mites (TSSM). This latter pest is particularly favored by the heat we are now experiencing. Check fields regularly for the appearance of yellowing on leaves, or whitish pin-spots.  Both are indications that TSSM may be present.  If TSSM is present, the actual mites will be found on the lower leaf surface.  It is best to treat for TSSM before the population gets too widespread.  Spot treatments may be adequate to achieve satisfactory control. There are a number of good miticides available, and growers should choose products based on efficacy and pre-harvest interval.  See the 2016 Commercial Vegetable Recommendations Guide for miticides effective against TSSM.

If stink bug fruit injury is increasing in harvests, or stinkbug adults, nymphs  or eggmasses are found in more than one of 10 samples in a field, consider treating for this pest to limit injury.   See the 2016 Commercial Vegetable Recommendations Guide for insecticides effective against stinkbugs.

As nights lengthen, and dews are heavier and longer, early blight (see photo at right) can increase dramatically.  Be sure to be on a strict protectant fungicide program to preserve foliage into the later part of the season.  Early blight (alternaria) generally attacks mature foliage first, but if not managed, it can move up the plant rapidly.  Several fungicides and appropriate rotations are found in the 2016 Commercial Vegetable Recommendations Guide.

Pepper weevil

No weevils have been trapped in the past week. As far as known there are no infested fields.  There is a species of weevil that is present in the pepper fields that has caused some confusion as it is about the same size and coloration as pepper weevil, but this weevil is not a pest.

To recognize pepper weevil, look for the spines on the underside of each leg and the body will be pear-shaped, 1/8 to 3/16 inch long.