All Pests in Low Numbers, but Most Silking Corn Needs Protection

SITUATION
Some fields have been hit hard by thunderstorms during the past week while others saw only moderate temperatures and little, if any rain.  The later plantings are looking better than early seeded fields with better uniformity and growth.  Pests have been relatively quiet.  Although we have started to catch a few fall armyworm moths in our traps, we have not yet found any larvae feeding on corn.

European corn borer:  Moth counts were pretty low this week, although several sites were over the threshold of 5 moths in silking corn.  We did find more feeding injury from larvae in whorl and pre-tassel stage corn, with fields scouted in Biddeford, Lewiston, Sabattus and Wells over the recommended spray thresholds.

European Corn Borer Larva, photo by David Handley

European Corn Borer Holes, photo by David Handley

Corn earworm:  Moth counts remained low this week, and many fields do not have corn in silk, so the moths do not yet pose a significant threat to those fields.  A 6-day spray interval was recommended for silking fields in Cape Elizabeth, Dayton, Dresden, and New Gloucester.

Corn Earworm Moth, photo by David Handley

Fall armyworm:  We captured our first fall armyworm moths of the season this week in two southern Maine fields.  However, at these low levels, fall armyworm is not yet a threat.  Fall armyworm moths tend to lay their eggs on the youngest corn available.  When the larvae hatch, they chew large, ragged holes in the leaves, and may bore into developing ears.  This damage is scouted for along with European corn borer injury, and a spray is recommended if the injury exceeds 15% of plants in a pre-silking field.  Larvae may also move into the ears through the silk channel, behaving similarly to corn earworm.  Pheromone trap catches of 3 or more moths per week indicate a spray is needed to protect silking corn, unless it is already under a spray schedule for corn earworm.

Male Fall Armyworm Moth, photo by David Handley

Late blight alert for potatoes and tomatoes

Late blight has recently been reported in tomato and potato plantings in coastal and central Maine.  Growers should be on the alert to catch any early symptoms and be ready to apply appropriate control measures.  Typical symptoms will be water-soaked lesions on the leaves with fine, white cottony mycelium on the undersides.  Infections on the stems appear as dark, almost black lesions.

Late Blight on Tomato, photo by James Dill

Please report any suspicious symptoms to the Pest Management Office 581.3883 (1.800.287.0279), or email PMO@umext.maine.edu.  The latest control options for late blight on tomatoes are on the University of New Hampshire Extension web site .

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                      Pest Management Office
P.O. Box179                          491 College Ave
Monmouth,ME 04259            Orono,ME 04473
207.933.2100                        1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary