Veg IPM Update: Week Ending 7/05/17

Sweet Corn
European corn borer (ECB) catches continue to be extremely low, and no map will appear in this edition.  Feeding in NJ sweet corn plantings is highly variable, but with second and third plantings now reaching the silk stage, we find that later plantings have much less damage.  Check 5 plants each in 10 random locations for a 50 plant sample.  Look  for “shot-hole” injury, and  consider treating when the number of infested plants in a 50 plant sample exceeds 12%.  As infested plants proceed to the pre-tassel stage, live larvae and damage may be found in the emerging tassels.  Once plants hit full tassel, ECB larvae 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 ECB catches for the previous week are as follows:

Corn earworm (CEW) moth catches continued to decreased in the southern half of the state this past week.  As we enter the latter half of June and into early July, we would expect only scattered catches of CEW moths.  This is historically our CEW-free period.  However, even very low CEW catches represent a threat where sweet corn is silking.  At present, the highest activity remains along the Atlantic-Camden County border (see CEW map at left), although catches have occurred as far north as Morris County.

The highest nightly CEW blacklight trap catches are as follows:

Southern NJ CEW pheromone traps have also registered slight declines in catch relative to the previous week.  This more conservative network is also indicating a similar threat level to last week  (see CEW pheromone map below at right).

At present, the highest nightly pheromone trap catches are as follows:   

Fall Armyworm

Fall armyworm (FAW) infestations in NJ have remained fairly low in severity, but are increasing in occurrence.  We should expect FAW to increase in the near future.  This pest favors smaller whorl stage plants, and will even infest seedling stage plants if the population is high.  At present, infestations have been identified  from Cape May and coastal Monmouth County west to the Delaware river in Camden County.  This pest is capable of serious injury to plants, and scouting should commence immediately on whorl corn throughout the southern half of the state.  Look for plants with “window-pane” type feeding that leads from the outer leaf surface down into the whorl (see photo at left).  As larvae grow, this damage will progress to obvious ragged holes, with lots of caterpillar droppings in the whorl.  The larvae are tan and brown (see photo at right), with a conspicuous upside down “Y” on the head capsule.  If FAW alone or in combination with ECB are found to infest 12% or more plants in the sample, consider an insecticide treatment.  FAW do not respond well to synthetic pyrethroid insecticides.  In general, IRAC Group 5 materials like Radiant or Entrust (OMRI approved) or IRAC Group 28 materials like Coragen work very well on FAW and other caterpillar pests.

Silking Spray Schedules*:

South – 4-5 days

Central – 6-7 days

North – 7 days

*These recommendations are based on regional catches.

Pepper Weevil Update

No pepper weevils were trapped in the past week.  So far as is known, there are no infested fields in the region.

Brown Marmorated Stink Bug 

Blacklight trap catches of the brown marmorated stink bug (BMSB) remain at very low levels this past week, and no map will appear in this addition.  It is important to note that late June and early July are typically the time our native brown stinkbugs become more active and will seek cultivated hosts.  This is of increasing importance if dry weather degrades forage in areas surrounding fields.  Scouting for stinkbugs in peppers requires stealth, as the bugs will retreat into the canopy if they perceive a threat.  While scouting for other insects and diseases, approach each sample site slowly.  Before disturbing the foliage to search for ECB eggs, aphids, etc., observe the upper canopy for the presence of stinkbugs.  Often, they will bask on the upper leaves.  If adults, nymphs or egg masses are found in 2 or more sites in a pepper planting, consider treating preventively to limit feeding injury to fruit.  There are several insecticide options listed in the 2016-17 Commercial Vegetable Production Recommendations.

Pumpkins and Winter Squash

Bacterial leaf spot (BLS) lesions have appeared in some plantings.  This seed-borne disease is fairly common in pumpkin plantings, but growers with affected plantings should begin applying copper hydroxide materials to try to limit it’s impact.  Older leaves are the first to become noticeably infected.  Dark lesions will form, having water-soaked margins (see photo at left).  These ultimately will dry and fall out.

As per Dr. Wyenandt’s Disease Alert, cucurbit downy mildew (CDM) is active on cucumber in southern NJ.  A CDM sentinel plot has been established at the Snyder Research and Extension Farm in Hunterdon County.  This plot consists of cucumber, watermelon, cantaloupe, acorn and butternut squashes and giant pumpkins.  This is just one of a network of sentinel plots in the eastern half of North America that will contribute information to the CDM forecast (http://cdm.ipmpipe.org/).  An identical plot will be established at RAREC.  These plots are scouted weekly for the presence of CDM.  If found, the disease is reported to NC State Univ., the organization managing the forecast.  Affected crops are also identified.  The purpose of this is to provide early warning to growers of these crops so that they may react proactively to the disease, and treat the appropriate crops.  A this time, it is important for all cucurbit growers to check the above website at least weekly for updates on the movements of CDM in the eastern U.S.   While the imminent threat appears to be confined to cucumber, note that contributors to the CDM forecast page have logged in occurrences of CDM on cantaloupe as near as east-central Pennsylvania.  As of 7/4/17, the CDM forecast issued by NC State had NJ at moderate risk to develop infections from regional sources.  ALL cucurbit crops should be scouted for the presence of CDM, and treat all cucumber plantings preventively.  CDM causes yellow lesions to develop on the upper leaf surface (see photo above at right).  Lesions are confined within veins initially, but coalesce quickly to kill the entire leaf when moist conditions prevail.   Beneath these lesions (lower leaf surface),  dark gray spores will be produced.  If discovered, please report any incidence of CDM to your county agent as soon as possible.

Tomatoes                                                                                  

Recently, tomato plantings both in high tunnels and in the field, have developed low level infestations of tomato  hornworm (THW).  This caterpillar is often first detected by observing the damage it causes to foliage, where it tends to strip branches of their leaflets, leaving bare stems.  THW will also feed on green fruit as the caterpillars grow large enough to take large scoops of tissue out of the fruit.  All recently detected larvae have been small (see photo at right), but these caterpillars will grow to about 3 inches long and can cause significant injury to individual plants.  While this damage is frequently more a nuisance than an economic threat in the field, their population can become high enough to warrant treatment in the high tunnels.  If characteristic feeding is appearing in multiple sites within tunnels, or under rare circumstances in the field, consider treating for THW.  Spot treatments may be effective in high tunnels.  There are a number of useful materials, including those in IRAC group 28 (Coragen) and IRAC group 5 (Radiant, Entrust – OMRI listed).  A complete list may be found in the 2016-17 Commercial Vegetable Production Recommendations.