Vegetable IPM Update 7/29/20

Sweet Corn

European corn borer (ECB) adults continue to be very low, although a few traps in Cape May and Burlington counties have shown initial signs of a second flight.  Numbers are low and isolated such that no map will appear in this edition.

The highest nightly trap catches of ECB for the week ending 7/29/20 are as follows:

Fall armyworm (FAW) larval infestations are generally low, but IPM technicians report more frequent occurrences in the central counties.   This is the time of the summer when FAW can show up, resulting in significant injury to whorl and even seedling stage corn.  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.

Corn earworm (CEW) moth captures have remained largely unchanged in blacklight traps this past week.  This moderate mid-Summer population poses a significant risk to silking corn.  Blacklight catches were highest overall along the Atlantic coast (see map at left), with blue areas on this map representing a 4-5 day spray schedule.

The highest nightly trap catches of CEW in black light traps for the week ending 7/29/20 are as follows:

CEW pheromone trap catches have increased somewhat, with the south seeing consistently higher catches (see CEW pheromone map at left).  Areas in white generally represent populations requiring 6-7 day spray schedules to manage, while blue areas are in the 5-6 day range.  Green areas represent  a 4-5 day schedule and red areas indicate a 3 day schedule.  Note that in the southwestern corner of the state, the pheromone network is indicating a tighter silk spray schedule than is the blacklight network.  The number of pheromone traps deployed is much lower, resulting in much broader color bands on the map.

The highest nightly trap catches of CEW in pheromone traps for the week ending 7/29/20 are as follows:

Silking Spray Schedules*:
South – 3 – 4 days

Central – 4  days

North – 4 – 5 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.

Pepper weevil (PW)

No new farms reported with infestations.  One of the early infested farms may have eliminated the population of weevils, which is possible where there are few weevils initially.

As for control materials, Florida insecticide trials indicate that Actara, Vydate, Harvanta, and Torac provide the best results, however, there is a broad range of materials including pyrethroids and neonics that can kill the adults.  The hope is to eliminate the weevil population before it becomes established in the field.  A combination of spraying, trapping, and removal of aborted fruit would help to manage this pest.

If anyone wants pheromone traps or participate in a project of evaluating different lures, please contact Joe Ingerson-Mahar, mahar@sebs.rutgers.edu; phone: 856-889-5718.

Pheromone trap catches of beet armyworm (BAW) have remained steady in southern NJ.  There was one report of very light feeding in peppers from the southern counties this week.  It is important to remember that this pest is capable of causing rapid and significant injury to pepper plants.  Look for clusters of plants with lace-like damage to foliage near growing points (see photo at upper left).  The green caterpillars will be found among these damaged leaves (see photo at lower left).  After consuming foliage, BAW can begin to damage fruit directly.  It is also important to note that BAW, like FAW, is resistant to synthetic pyrethroid insecticides.  For this reason, materials in the IRAC 5 and 28 classes should be used in response to an infestation.

The highest nightly trap catches of BAW in pheromone traps for the week ending 7/29/20 are as follows:

Pumpkins and Winter Squash

A cucurbit downy mildew  sentinel plot  at Snyder Farm in Hunterdon County has thus far remained free of CDM.  This plot, consisting of pumpkin, watermelon, cantaloupe, butternut, acorn, cucumber and kabocha squash is used to indicate the presence of cucurbit downy mildew in the region, and what crops are affected.  As of 7/28/20, there was no CDM detected in this plot.  For regional information on this important disease, see the Cucurbit Downy Mildew Forecast webpage:  http://cdm.ipmpipe.org/.  As of this Tuesday (7/28/20), New Jersey was rated at moderate risk for new infections by CDM.  Regional infections to date have been on cucumber.

Several of the earlier planted pumpkin/gourd fields in the scouting program hit the powdery mildew (PM) threshold this week.  When scouting 50 plants (5 consecutive plants each, in 10 random locations), look within the canopy and observe the upper and lower surface of two older leaves per plant.  PM generally doesn’t appear until fruit enlargement is occurring.  Initial lesions will be fairly small and isolated (see photo at far left).  As the disease progresses, lesions will spread out, giving the leaves a dusty appearance (see photo at near left).  A PM fungicide prpogram incorporating both protectant and locally systemic materials should be initiated when PM is found on two or more leaves in a 50 plant (100 leaf) sample.  Fungicides and suggested rotations are found in the Pumpkin and Winter Squash section of the Commercial Vegetable Production Recommendations.  Consider the addition of copper hydroxide to the fungicide program if bacterial leaf spot has been detected in the field.

Tomatoes

Thrips feeding on foliage and fruit is becoming more common, with the onset of very hot weather.  Fruit injury resembles a gold speckling on the surface of ripe fruit (photo at center left below), while thrips feeding on leaves results in cleared areas on the surface with conspicuous dark specks (droppings) (photo at far left below).  Any increase in the incidence of foliar feeding at this time of year should cause growers to consider an insecticide application to limit fruit injury.  A complete list of insecticides for this pest may be found in the Tomato Section of the Commercial Vegetable Production Recommendations.  Note that the insecticide Entrust is OMRI approved.  Avoid applying insecticides that carry a “M” or “H” designation for  bee toxicity while bees are active in the field.  As we progress through July, and dry weather dominates, brown stink bug injury also increases.  These true bugs (see photo of Euschistus sp. nymph below at center right), move into irrigated tomato fields as forage in the surrounding environment dries out.  Feeding results in “cloudy spot” (see photo at far right below).  Increases in stink bug injury are often found by crews picking the fruit.  Growers should consider 1-2 insecticide applications to limit fruit injury if this damage is increasing in harvested fruit.  If actively scouting fields, insecticides should be considered if stink bug adults, nymphs or new fruit injury is found in 2 or more sample sites in a 10 site sample.  Insecticides that are effective on stink bugs include pyrethroids and neonicotinoids, so care should be taken to avoid contact with foraging bees.

Two-spotted spider mites (TSSM) are now a common occurrence in tomato fields with this stretch of prolonged hot weather.  These pests can build to high populations quickly and are a particular nuisance in high tunnels.  Check two complete leaves each on 5 consecutive plants in 10 random locations in a planting.  Look for the characteristic mite “stipple”, or whitish pin spots on the upper surface of the leaf (see photo at left).  A check of the underside of the leaf should reveal the actual mites (photo at right).  Be sure to take some samples from field or tunnel edges as this is often from where TSSM will enter the planting.  Consider an miticide application if TSSM are found at more than one site in the sample.  Miticide choices are found in the Tomato Section of the Commercial Vegetable Production Recommendations.

Brown Marmorated Stink Bug

Brown marmorated stink bug (BMSB) activity has increased further in blacklight traps throughout New Jersey.  It is likely that these trap catches do not reflect population levels in a given area, but rather the activity of the bugs themselves.  We often see numbers increase dramatically during heat waves like the one we are now experiencing.  While this pest has generally declined as a threat to peppers, it remains a significant threat to tree fruit.

The highest nightly catches of BMSB in black light traps for the week ending 7/29/20 are as follows: