Cucurbit Downy Mildew Update

Cucurbit downy mildew (CDM) was discovered by IPM technician Chris Cloutier in Morris County, just south of Morristown on Friday.  Suspect leaves from pumpkin plants were incubated and ultimately produced spores on Sunday.   All NJ growers of pumpkins and winter squash should treat fields accordingly.  Look for chlorotic areas bordered by veins on the upper leaf surface (photo at lower right).  If conditions are moist, dark sporulation may be found on the lower leaf surface (photo at lower left).

Useful materials for CDM may be found in the Pumpkin and Winter Squash Section of the 2024/25 Commercial Vegetable Production Recommendations.  Downy mildew specific fungicides should be added to the existing powdery mildew fungicide program.

Sweet Corn

Fall armyworm (FAW)  infestations remain present, although they have become lighter and more sporadic in most scouted locations in central and northern NJ counties.  Re-infestations following treatment can and have occurred.    Because FAW moths are highly mobile, it is important to monitor fields at least weekly for signs of infestation.   Whorl stage plants are prime targets for egg laying.  Delays in treating whorl stage infestations can lead to stunted plants and poor ear size.

Newly hatched FAW larvae cause holes and scratches on leaves that are similar to ECB feeding, except that they tend to be more concentrated and always lead down into the whorl  (see photo at left).  As the larvae grow, the feeding becomes more destructive, with large ragged holes and obvious droppings deposited in the whorl (see photo at right). 

We will provide updates on new FAW appearances and severity as reports come in.  FAW are resistant to synthetic pyrethroids.  Effective sprays should include IRAC grp. 5 (spinosyns) or IRAC grp. 28 (diamides).  The carbamate (IRAC grp. 1A) Lannate is also still effective.  Sufficient water should be used in the applications to allow the solution to penetrate the layer of droppings that may have formed above the caterpillar.

[Read more…]

Sweet Corn

Fall armyworm (FAW)  infestations remain present, although in fields where growers responded with appropriate insecticides, control has been good.   Re-infestation is occurring rapidly in Cape May County fields, and is likely happening elsewhere in the southern part of the state.  Because FAW moths are highly mobile, it is important to monitor fields at least weekly for signs of infestation.   Whorl stage plants are prime targets for egg laying.  Delays in treating whorl stage infestations can lead to stunted plants and poor ear size.

Newly hatched FAW larvae cause holes and scratches on leaves that are similar to ECB feeding, except that they tend to be more concentrated and always lead down into the whorl  (see photo at left).  As the larvae grow, the feeding becomes more destructive, with large ragged holes and obvious droppings deposited in the whorl (see photo at right). 

We will provide updates on new FAW appearances and severity as reports come in.  FAW are resistant to synthetic pyrethroids.  Effective sprays should include IRAC grp. 5 (spinosyns) or IRAC grp. 28 (diamides).  The carbamate (IRAC grp. 1A) Lannate is also still effective.  Sufficient water should be used in the applications to allow the solution to penetrate the layer of droppings that may have formed above the caterpillar.

[Read more…]