Vegetable IPM Update 8/07/19

Sweet Corn

European corn borer (ECB) moth captures have increased slightly for a second week in parts of the state (see ECB map at left).  The second flight is very weak and spotty, as is consistent with recent years’ second flights.  Limited feeding has appeared in whorl and pre-tassel corn.

Growers should continue to scout whorl and pre-tassel stage plantings weekly 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.  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 black light trap catches of ECB for the week ending 8/07/19 are as follows:

Corn earworm (CEW) moth catches are increasing now in blacklight traps in southern and central portions of the state.  Pheromone trap catches have increased as well, with significantly higher catches in southwestern NJ.  There are now economically important populations of this pest throughout the state (see blacklight map at left, and pheromone trap map below at right).   CEW numbers are likely to continue to increase steadily throughout August, with the potential for a dramatic increase in the event of a strong storm system hitting our state.  Red areas on the on the pheromone trap map indicate a 3-day silk spray schedule, while green indicates a 4-5 day silk spray schedule. Blue areas represent a 5-6 day schedule, and white areas are 6-7 day.  There are far fewer CEW pheromone traps than blacklights, and the resulting map has much broader color bands as a result.  It should also be noted that the pheromone traps are much more sensitive than blacklights.  Therefore, the number of moths caught in pheromone traps required to generate a specific spray interval is much higher than the number caught in blacklight traps.   It must be stressed that there is high variability in these catches, and growers should consult with their IPM practitioner on recommended spray schedules.

The highest nightly CEW pheromone trap catches for the week ending 8/07/19 are as follows:

Fall armyworm (FAW) feeding is now increasing, although infestations remain fairly low and widely dispersed. We are entering the time of the season when FAW populations can get heavy.  Growers should scout all fields from pre-tassel stage down to early whorl stage.  This pest causes extensive foliar damage on whorl stage corn (see photo  at left), can also infest ears, and is capable of killing small plants.  FAW larvae are brown in color (see photo at right), with an inverted “Y” pattern on their head capsule.  They are much larger than ECB when fully developed.  FAW is even more consistently resistant to pyrethroid insecticides.  For this reason, the same insecticides classes now recommended for CEW control should be utilized for FAW management.

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.  To repeat: 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

As yet, no pepper weevils have been captured on traps placed near southern NJ pepper fields.

Pheromone traps established for beet armyworm (BAW) in the southern counties continue catching adults, with regional catches generally increasing.

The highest numbers for the week ending 8/07/19 are:

BAW can reach levels that result in damage to pepper plants, and low level injury has been reported in southwestern NJ.  Growers in the southern counties should be alert for the appearance of severely defoliated terminals (see photo above at left) on pepper plants.  Small BAW larvae feed on these leaves before turning to fruit as they increase in size.  As with FAW, beet armyworm is resistant to pyrethroid insecticides.  Insecticides now recommended for CEW and FAW control are useful for BAW management.

Pumpkins and Winter Squash

Cucurbit downy mildew (CDM) is active on cucumbers, pumpkins, acorn squash and butternut squash in numerous parts of the state.     All growers should be applying appropriate fungicides for downy mildew on all cucurbit crops at this time.    For regional information on this important disease, see the Cucurbit Downy Mildew Forecast webpage:  http://cdm.ipmpipe.org/.   In addition, many pumpkin fields are now exhibiting signs of powdery mildew (see photo at right), and  thresholds (2 lesions/50 older leaves) are being exceeded.  Growers should include materials in their spray program that target powdery mildew as well.  See the Pumpkin and Winter Squash section of the 2019 Commercial Vegetable Production Guide for suggested materials

Brown Marmorated Stink Bug (BMSB)

BMSB numbers in blacklight traps have increased in south and central NJ over the past week (see BMSB map at left).  Blacklight catches are likely a better indicator of stink bug activity (movement) than of actual numbers in a given area.  Growers with crops that are potential targets of this pest should be scouting for BMSB or increases in stink bug injury.  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 8/07/19 are as follows: