Veg IPM Update: Week Ending 6/21/17

Sweet Corn
European corn borer (ECB) catches remain low generally, with a few remaining hot spots in southern Hunterdon County and on the Cumberland-Salem border (see ECB map).  Feeding in NJ sweet corn plantings has risen, with some plantings exceeding 40%.  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 (see bottom photo at right).  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 increased slightly in the southern half of the state this past week.  This may have been the result of the strong southerly winds in advance of the storm front we experienced Monday afternoon and  evening.   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, recent CEW catches indicate a real threat where sweet corn is silking.  At present, the highest activity remains along the Atlantic-Camden County border (see CEW map at right), although catches have occurred as far north as Hunterdon County.

The highest nightly CEW blacklight trap catches are as follows:

Southern NJ CEW pheromone traps have registered low to moderate catches.  This more conservative network is also indicating  a significant economic threat to silking corn (see CEW pheromone map below at right).

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

Silking Spray Schedules*:

South – 4 days

Central – 5-6 days

North – 7 days

*These recommendations are based on regional catches.

Recently, two-spotted spider mites (TSSM) have been discovered in whorl and pre-tassel stage sweet corn.  This pest sometimes flares up in corn, but typically after silk sprays have begun.  To find them so early in the life of a planting is an indication that if not addressed, a significant infestation will develop later on.  TSSM can infest the husks, making ears unmarketable.  At very high populations,  TSSM can reduce the vigor of a planting enough to reduce ear size.  While scouting for other pests, check to see if there are irregular yellow blotches developing on lower leaves (see photo at left ).  If any are found, turn over the leaf to see if actual mites are present (see photo at right). TSSM are quite small, but will be yellowish in color and will move slowly.

Peppers 

Pepper plantings in some areas continue to be at risk from ECB infestation, as moths lay eggs on the underside of pepper leaves (see photo at left).  Larvae will hatch and bore into central stems of these small plants, causing the tops of the plants to die.  While this is not terminal, it will prevent the production of crown fruit on affected plants.  Scout 5 plants each in ten random locations.  Check the underside of 2 leaves per plant.  If 2 or more ECB eggmasses are found in this sample consider treating with a foliar insecticide or a soil applied insecticide such as Coragen.  There are several options listed in the 2016-17 Commercial Vegetable Production Recommendations, including the OMRI approved spinosyn material, Entrust.

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) have increased to levels that permit the creation of population maps (see BMSB map at right).  At present, catches of adults are relatively low, but growers of tree fruit are aware of how serious a pest this is in orchards.  In addition, BMSB has occasionally been an economic pest of peppers in NJ.  It is also 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

Early planted pumpkins are now beginning to emerge.  It is critical that these fields be scouted while plants are in the 0-4 true leaf stage.  Striped cucumber beetle (see photo at left) is the most serious pest of these crops in this stage, not only because they cause direct injury to seed leaves and true leaves, but because at this stage, the beetles can transmit the bacteria that cause in bacterial wilt.  Check 5 plants each in 10 random locations.  If beetles are found actively feeding in 2 or more sites, consider an insecticide application to reduce the likelihood of bacterial wilt setting in later.  Many pumpkin and winter squash seeds are purchased with a seed treatment that includes a neonicotinoid insecticide.  In this case, cucumber beetle feeding should be seriously limited for the first 2-3 weeks of  growth.  This is typically long enough to get the plants close to the stage where vines begin to run or bush out.  At this point, it is much more difficult for the plants to acquire a large enough bacterial load from the beetles to cause wilt.  Organic growers of these crops should consider covering plants from emergence through just before vine run.  This should limit beetle feeding and permit bee access to blossoms when the covers come off.

A cucurbit downy mildew (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.   CDM has been reported on cucumber and cantaloupe in North Carolina.  The weather pattern in advance of Monday’s storms put southern NJ at some risk for infection, but since that time, the threat has been reduced.  It is important to monitor all cucurbit fields (especially cucumber, is this host is the most frequent host) at this time.  CDM causes yellow lesions to develop on the upper leaf surface (see photo 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.