Vegetable IPM Update 8/12/20

Note: Cucurbit downy mildew has now been identified on cucumber in southern and northern NJ. See the pumpkin and winter squash section below for more information.

Sweet Corn

European corn borer (ECB) adults remain very low, and no map will appear in this edition.

The highest nightly trap catches of ECB for the week ending 8/12/20 are as follows:

Califon 1	Farmingdale 1
Cinnaminson 1	Medford 1
Downer 1	Tabernacle 1

Fall armyworm (FAW) larval infestations continue, although at low to moderate levels around the state, with infestations as high as 26% in Cape May County. FAW could increase dramatically in the late summer, 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 are increasing gradually in blacklight traps. This moderate mid-Summer population poses a significant risk to silking corn. Catches remain somewhat variable (see map at left), with blue areas on this map representing a 4-5 day spray schedule. Note that there is disagreement between blacklight and pheromone trap maps with regard to the southwestern counties. See pheromone trap information below.

The highest nightly trap catches of CEW in black light traps for the week ending 8/12/20 are as follows:

Morristown 3	Green Creek 2	Farmingdale 1
Allamuchy 2	Bellemeade 1	New Egypt 1
Califon 2	Downer 1	Old Bridge 1
Georgetown 2	Elm 1	Princeton 1

CEW pheromone trap catches have also increased somewhat over previous week (see CEW pheromone map at left). The blacklight network is indicating a more conservative schedule in Morris, Warren and Sussex counties, while the pheromone network indicates a more conservative schedule in Salem and Cumberland counties. Areas in green areas represent a 4-5 day schedule and red areas indicate a 3 day schedule. The number of pheromone traps deployed is much lower, resulting in much broader color bands on the map. At this time of the summer, organized storm fronts moving from west to east can result in dramatic increases in CEW in our area. As of this week, there is no particular indication that a large adult population is active in states to our south. Our resident population remains a serious economic threat, however.

The highest nightly trap catches of CEW in pheromone traps for the week ending 8/12/20 are as follows:

Monroeville 90	Beckett 32	Matawan 11
Woodstown 54	Dayton 23	Crosswicks 5
Pedricktown 35	Snyder Farm (Hunterdon) 21	East Vineland 5
Elm 33	Green Creek 16	South Branch 5

Silking Spray Schedules*:
South – 3 – 4 days

Central – 3-4 days

North – 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.

Pepper weevil (PW)

No additional farms have reported with infestations and the known infestations appear to be light. August is when most infestations are discovered so hopefully there will not be anymore.

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.

Although pheromone trap catches of beet armyworm (BAW) have increased somewhat in southern NJ traps. Growers should be alert to the potential for infestation from this pest. 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 8/12/20 are as follows:

Woodstown 32	East Vineland 2
Pedricktown 6	Folsom 2
Cedarville 3

Pumpkins and Winter Squash

The cucurbit downy mildew (CDM) sentinel plot at Snyder Farm in Hunterdon County has CDM on cucumbers as of 8/11/2020. 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 8/11/20, there was no CDM detected on any of the other cucurbit types. For regional information on this important disease, see the Cucurbit Downy Mildew Forecast webpage: http://cdm.ipmpipe.org/. As of this Tuesday (8/11/20), New Jersey was rated at low risk for new infections by CDM. Regional infections to date have been on cucumber.

Nearly all pumpkin/gourd/winter squash fields in the scouting program have now reached the powdery mildew (PM) threshold. 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

Two-spotted spider mite (TSSM) infestations continue to appear in tomato fields, with populations frequently rebounding about 2 weeks after initial control. 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. Continue to scout for TSSM, even after a control application. 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 decreased 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. While this pest has generally declined as a threat to peppers, it remains a significant threat to tree fruit.