Solanaceous crops: Late blight continues to spread, with new outbreak confirmed this week from a tomato field in Worcester Co. MA. Several samples from MA were genotyped as clonal lineage US-23, which is generally sensitive to methanoxam (Ridomil) and attacks both tomato and potato. For a map of late blight reports and photos of symptoms, see usablight.org.
Table 1. European corn borer (ECB), fall army worm (FAW), and corn earworm (CEW) trap captures for the week ending 7/17/14.
Cucurbits: Frequent rains and humid weather are highly conducive to development of Phytophthora blight. Scout low-lying, wet, fields or fields where the disease has previously occurred. Plow under any areas that are infected, along with a non-infected border area, to slow the spread of this disease.
Sweet Corn: European Corn Borer: Captures for the week rose in some locations (eg Sunderland, Amherst, Leominster) and dropped in most others compared to last week; we are nearing the end of the first flight. Continue scouting for borers in pretassel and green tassel and spray if 15% of plants are infested. To use a quick decision tool see scouting sheets in the Record Keeping Booklet of the
Squash Vine Borer moths (see article) have been captured in pheromone traps in Hampshire and Franklin County, MA, Hillsborough County, NH, Saunderstown, RI and in Burlington VT so we know that regionally, the flight has begun. SVB populations are very site specific, so make treatments based on scouting or trap captures.
European Corn Borer: The earliest corn has emerging tassels and now is the key time to scout for ECB & apply controls. First silk has been seen in warm areas; set out corn earworm traps when corn has first silk. For the ECB-ZI or ‘Iowa’ strain, flight peaks at 631 GDD at base 50 F. Most of our trapping sites have reached the peak moth flight according to degree day models.
European Corn Borer: ECB moths continue to be captured in pheromone traps around MA and egg laying has likely begun in many locations. Eggs take 5-7 days to hatch. If moths are being captured in your area or you have reached 375 GDD at base 50 F and you are using Trichogramma ostriniae wasps in sweet corn, you should be making your first release if you have not done so already.
European Corn Borer: ECB moths are being captured in pheromone traps and egg laying has begun. Eggs take 5-7 days to hatch. If you are using Trichogramma ostriniae wasps in sweet corn, it is time for the first release (Table 1). High tunnel peppers could be at risk from first-generation ECB caterpillars, which will begin boring into the top of fruit when it is about ping-pong ball size.