Sweet Corn

Increasing numbers of European corn borer (ECB) moths have been captured over the past week, although overall numbers remain low.  At this time, activity is highest in central Morris County and western Burlington County (see ECB map at left).  The number of traps registering moderate catches is fairly low, and catches are widely dispersed.  Overall, this year’s population is late, and whether numbers increase much or not remains an open question.  Early corn is now in whorl or pre-tassel stage and able to support ECB larvae.  It is time to begin scouting corn in these advanced growth stages.

 

 

 

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 6/03/20 are as follows:

Denville   2	Clinton   1	Milford   1
Asbury   1	Downer   1	Oldwick   1
Bellemeade   1	Eldora   1	South Branch   1
Califon   1	Medford   1	Springdale   1

 

Widely scattered, and low catches of corn earworm (CEW) occurred this past week.   While there was an increase in activity over the previous week, this pest does not pose a threat to sweet corn that has not yet reached the silk stage.

The highest nightly trap catches of CEW in black light traps for the week ending 6/03/20 are as follows:

Chester   1	Eldora   1	Milltown   1	Oldwick   1
Crosswicks   1	Elm   1	Morristown   1

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Sweet Corn

A few European corn borer (ECB) moths have been captured over the past week, though they are too few in number to generate a map image.  While some early corn is now in whorl stage and able to support ECB larvae, adult numbers do not indicate a significant threat as of this week.  We expect numbers to increase over the next 2-3 weeks, and will post maps and management suggestions as this occurs.

The highest nightly trap catches of ECB for the week ending 5/27/20 are as follows:

Asbury   1	Denville   1	Milltown   1
Bellemeade   1	Eldora   1	Springdale   1
Califon  1	Hillsborough   1	Tabernacle   1
Clinton   1	Milford   1

Two corn earworm (CEW) moths were captured this week (Eldora, Cape May County and Port Colden, Warren County) in blacklight traps.  It is possible that these individuals overwintered locally, but in any case, they pose no threat to sweet corn at this time.

There have been fields of seedling stage sweet corn exhibiting signs of slug injury this past week (streaks on leaves with tissue eaten away, but leaving one layer of epidermal tissue).  Generally the slugs responsible for this injury are a smaller species than the one in the photo at left.   Additionally, corn stem weevils have been discovered this week causing holes in leaves similar to those bill bugs make, but without the linear pattern across the leaf as with bill bug – see photo at right.  The former (slugs) have been found in northern counties on heavier soil for the most part, while the corn stem weevil injury is occurring in Cape May County.  Slug injury generally decreases as weather warms and the soil surface dries.  In rare instances of prolonged cool, wet weather, an application of slug bait may be warranted to limit injury to small plants.  In this case, damage should be found on the majority of plants, with slug-favorable weather in the forecast.  Corn stem weevil can sometimes causing severe damage from feeding on leaves and stems of seedlings. Adults are small, 1/8-3/16 inch, brown or black mottled. They hide during daylight beneath plants  or under debris on the soil surface. In recent years, they have been active only in May and June.  Consider an application of a labeled pyrethroid for beetle control in corn if injury is present on 12% or more seedlings.  For insecticide recommendations, see the Sweet Corn section of the 2020 Commercial Vegetable Production Guide.

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Sweet Corn

The black light trap network is  complete at this time.  To date, one corn earworm (CEW) was captured at Eldora, Cape May County.  A very few European corn borer (ECB) moths have been captured this past week, indicating that as warmer weather begins to arrive, we should see increasing numbers over the next several weeks.   This pest poses little threat at this time, as they are few in number and the earliest sweet corn plants are only just reaching suitable size to support larvae.

The highest nightly trap catches of ECB for the week ending 5/20/20 are as follows:

Downer   1

Hackettstown   1

Medford   1

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Sweet Corn

IPM Program personnel have re-established the black light trap network in New Jersey.  With continued below normal temperatures, no corn earworm (CEW) or European corn borer (ECB) moths have been captured.  As numbers increase, look for population maps of ECB, CEW, brown marmorated stink bug (BMSB) and CEW catches from pheromone traps in this weekly publication.  The resulting full-state maps will include interpretive information.

With cold, damp conditions dramatically slowing down the growth of seedling corn, wire worms (see photo at left) have the potential to be more of a nuisance than usual.  While we don’t often see this problem in sweet corn, it does occasionally happen when wire worms are present and the corn cannot grow quickly enough to become less susceptible to injury.  Look for clusters of seedlings that exhibit wilted inner leaves.  Wire worms often are discovered by digging up these affected seedlings.  The incidence of this damage may be minor, but if growers determine that a field must be replanted, it may be necessary to include an in-furrow soil insecticide targeting this pest.

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Sweet Corn

IPM Program personnel are currently finishing deployment of the black light trap network in New Jersey.  At present, we are approximately 70% operational and have begun to monitor traps.  With below normal temperatures, no corn earworm (CEW) or  European corn borer (ECB) moths have been captured.  As numbers increase, look for population maps of ECB, CEW, brown marmorated stink bug (BMSB) and CEW catches from pheromone traps in this weekly publication.  The resulting full-state maps will include interpretive information.

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