IPM Update 6/17/20

Sweet Corn

European corn borer (ECB) moth catches increased somewhat over the past week although higher numbers were recorded in a relatively low number of locations.  At this time, activity is highest in Gloucester and central  Morris counties (see ECB map at left).  Catches remain widely dispersed.   Larval infestations into the 30+% range were detected as far north as Morris County this past week.  As moth catches begin to fall, larval development and damage increase.  We expect that these infestation rates will continue to climb for the next 1-2 weeks in many parts of the state.

Look for the characteristic “shot-hole” type of feeding (photo below at right) and consider treating when infested plants exceed 12% in a 50 plant sample.  As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels (see photo at left).  It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time.  This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.

Useful insecticides for this particular application include synthetic pyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen.  Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn.  Control with these materials is very inconsistent.

The highest nightly trap catches of ECB for the week ending 6/17/20 are as follows:

Increased catches of corn earworm (CEW) moths were recorded this past week.   As early plantings proceed to full tassel and on to silk, they will need protection from this pest.  Blacklight catches (see map at left) were scattered, but higher in locations than the previous week.

The highest nightly trap catches of CEW in black light traps for the week ending 6/17/20 are as follows:

This increase in the blacklight network is corroborated by catches that have occurred in the nearly complete CEW pheromone trap network (see CEW pheromone map at left).  While the number of traps deployed is much lower, and the northernmost traps are not operational yet, some have recorded low-to-moderate catches.   This indicates a fairly significant early flight.

The highest nightly trap catches of CEW in pheromone traps for the week ending 6/17/20 are as follows:

Silking Spray Schedules*:

South – 3-4 days

Central – 4-5 days

North – 6 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.

Peppers

With continuing ECB moth activity, growers should be looking for ECB egg masses (see photo at left) on the underside of pepper leaves. The larvae that hatch from these eggs will bore into the central stem of pepper plants in the absence of suitable fruit.  This damage causes the tops of the plant to die, and eliminating the crown set of fruit in the process.  Check 2 leaves per plant on 5 consecutive plants in 10 random locations.  Consider treating if 2 or more leaves are found to have ECB larvae on the lower surface.

Pepper weevil

So far no weevils have been trapped at any farm.  Trap deployment will continue on farms.  Any grower who wants to have traps set for detecting pepper weevils can contact Joe Ingerson-Mahar at mahar@sebs.rutgers.edu

Pumpkins and Winter Squash

With pumpkin and related crop fields now being planted, it is important to remember that the initial threat will be from striped cucumber beetles.  Most seeds now come with a pre-applied insecticide to limit injury from this pest.  However, growers should be alert to the possibility that untreated seeds may be fed upon heavily by cucumber beetles, resulting in bacterial wilt in a few weeks, or outright death of seedlings from excessive feeding.  Scout 5 plants each in 10 random locations.  If beetles are found to be feeding at more than two sites, consider an insecticide application to limit damage.  It is unlikely that this situation will occur if seeds were pre-treated.

A cucurbit downy mildew sentinel plot is now established at Snyder Farm in Hunterdon County.  This plot, consisting of pumpkin, watermelon, cantaloupe, butternut, acorn, cucumber and kabocha squash will be used to indicate the presence of cucurbit downy mildew in the region, and what crops are affected.  For regional information on this important disease, see the Cucurbit Downy Mildew Forecast webpage:  http://cdm.ipmpipe.org/.

Potato Leafhopper

Potato leafhopper (PLH) adults (see photo at left) have appeared in snap beans and other crops over the past  week.  This pest is a particular problem because it often goes unnoticed until foliar distortion and burn occurs.  Once this damage appears in beans and some potato varieties, yields have already been compromised.  It is critical that beans be monitored regularly for the presence of PLH.  If a sweep net is available, consider treating if more than 100 nymphs and adults are present in 20 sweeps of pre-bloom stage plants.  This threshold increases to 250 during bloom and to 500 per 20 sweeps during pod development.  If no sweep net is available, check plants in 10 random field locations and consider treating if adults and nymphs are found throughout.  Adults are pale green, and will fly out from foliage when disturbed and immediately fly back into the plant canopy.  Nymphs are wingless and bright green and may be found on the underside of leaves.