Cucurbits: Powdery mildew is well established in older MA and RI cucurbit fields and is starting to spread into new plantings. Conditions favoring infection include a dense plant canopy, low light intensity, high nitrogen fertilization, relative humidity >50%, and 68-80° F.
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.