Sweet Corn

Catches of European corn borer (ECB) have declined through much of the state.  Remaining areas of highest activity include parts of Monmouth, Mercer and Salem counties (see ECB map).  ECB infestations are now rising in sweet corn plantings, but are well below normal levels.   Feeding ranges from single digits to 20% in areas where IPM personnel are operating, but many plantings have no detectable feeding at all.  Be sure to begin monitoring plantings for ECB feeding while they are still in the whorl stage.  Consider treating when the number of infested plants in a 50 plant sample exceeds 12%.  Feeding in the whorl stage will appear as numerous small holes (called “shot-hole”) on leaves, with damage present on consecutively younger leaves. As plants progress to pre-tassel and beyond, the actual larvae may be found in or on the emerging tassels (see photo).  Any planting remaining at or above threshold as it proceeds to full tassel should be treated, as this is the last stage at which ECB larvae will be exposed and vulnerable to insecticidal sprays. Often, early sweet corn plantings suffer from “split set”, in which germination does not occur in a uniform

Sweet corn tassel with ECB larvae.
Photo: Kris Holmstrom

fashion. The result is a planting where all plants do not reach full tassel at the same time.  This situation may require an extra tassel spray if there are several days difference in the time full tassel is reached on a significant number of the plants.  Insecticides that are acceptable in organic production include the spinosyn based material Entrust (IRAC-5) and Dipel (IRAC-11a).  The 10G formulation of Dipel is particularly useful when granules can be dropped or broadcast such that they get into the whorls of corn plants.  See the 2016 Commercial Vegetable Recommendations Guide for more insecticide choices.

The highest nightly ECB catches for the previous week are as follows:

  [Read more…]

Sweet Corn

European corn borer (ECB) adult catches have declined, and are now quite low throughout the state.   The most consistent catches at this time range from southwestern Burlington County through Cumberland County (see ECB map).  The earliest sweet corn plantings are now silking in southern NJ, and are approaching full tassel in some northern sites.  Feeding percentages are still very low (to 4% in central counties), but growers should expect that eggs are now hatching, and larval infestations could appear on all corn whorl stage and older.  Be sure to begin monitoring the earliest plantings for ECB feeding while they are still in the whorl stage. Consider treating when the [Read more…]

• Late blight (US23) was reported on potato on the Eastern Shore last week. All tomato and potato growers in the region should scout on a regular basis.
• Cucurbit downy mildew has been reported on cucumber as far north as central North Carolina this past week.
• Pythium root rot has been reported on a number of transplanted crops this past week.

Sweet Corn

European corn borer (ECB) adults are being captured with more frequency in the northern half of the state now, but overall, catches are low.  Highest activity is now found in Cumberland and Morris counties with local hotspots elsewhere  (see ECB map).  The earliest sweet corn plantings are now the right size to support ECB larval infestations. Scouts have not reported seeing adults flying in plantings (a phenomenon that usually precedes larval infestations).  However, within the next week or so we should begin to see feeding in the most advanced plantings. Be sure to begin monitoring the earliest plantings for ECB feeding while they are still in the whorl stage. Consider treating when the number of infested plants in a 50 plant sample exceeds 12%.  Feeding in the whorl stage will appear as numerous small holes (called “shot-hole”) on leaves, with damage present on consecutively younger leaves. [Read more…]

Sweet Corn

European corn borer (ECB) adults are being captured with more frequency now, but most captures remain limited to the southwestern portion of the state (see ECB map), although scattered individuals have been captured as far north as Morris County.  Warmer nights for the rest of this week may result in increased catches for the next several days.   Most early sweet corn plantings are too young to support ECB larval infestations. However, over the next two weeks we could begin to see feeding in the most advanced plantings. Be sure to begin monitoring the earliest plantings for ECB feeding while they are still in the whorl stage.  [Read more…]