Archives for June 2016

• Basil downy mildew has been confirmed in southern and central New Jersey.
• Cucurbit downy mildew has been confirmed as far north as Maryland this week.
• Bacterial canker in tomato has been reported.
• Angular leaf spot of cucumber has been reported. Water-soaked lesions similar to cucurbit downy mildew appear on the bottom of the leaves at first. In the case of angular leaf spot, caused by a bacterium, no spores will develop on the underside of leaves.
• Reports and sampling for Dickeya dianthicola  in potato across the east coast continue.

Sweet Corn

European corn borer (ECB) moth catches remain very low now.  The first flight is over, and growers are now managing subsequent infestations, which are generally lower than normal.  Present adult activity is too low to generate a map image (<0.5 moths/night in all traps).  Larval feeding ranges from single digits to above 20% in areas where IPM personnel are operating, although many plantings still 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, droppings and  larvae may be found in or on the emerging tassels.  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.    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.  Other effective insecticides include Coragen (IRAC 28), and the synthetic pyrethroids (IRAC 3).  See the 2016 Commercial Vegetable Recommendations Guide for a more complete list of insecticides.

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

In addition, several low-level infestations of fall armyworm (FAW)  were discovered this week.  These were in Hunterdon and Middlesex counties, but it is likely that there are other light infestations throughout the state.  These infestations have not exceeded 4% in the whorl stage, and are likely the result of a few FAW moths arriving in advance of weather fronts.  This is somewhat early for FAW infestations in NJ, and we would expect to see little injury until mid-July.  FAW feeding is much more obvious than that of ECB larvae, with large ragged holes and conspicuous droppings found in the whorl.  FAW is resistant to synthetic pyrethroid insecticides (IRAC 3), and can be effectively managed with insecticides such as Radiant/Entrust/Blackhawk (IRAC 5) or Coragen/Besiege (IRAC 28).  Consider treating if damage from ECB and/or FAW reaches 12%.  [Read more…]