Vegetable scouting sheets can be found on the UMass Extension Vegetable Program website. When not given here, refer to the New England Vegetable Management Guide for scouting thresholds and treatment options.
Allium: Onion thrips pressure was very low in an onion field scouted in Worcester Co., MA and just at threshold in untreated fields in RI. Periodic (just about weekly) heavy rains may be to thank for keeping thrips, which are favored by hot, dry weather, off of plants. A field in Bristol Co., MA, however, was well above threshold, so even with the rain, continue to scout and treat if thrips reach 1 per leaf. Salt marsh caterpillars were found on onions in ME. Onions in a field in Worcester Co., MA were diagnosed with an as-yet undetermined bacterial disease. Symptoms were water-soaked, brown leaf tissue in the center of otherwise healthy-looking plants. Warm, humid, wet weather favors bacterial diseases. Leaf infections can move down into onion scales, making the bulbs unmarketable. No good chemical controls exist for bacterial disease in onions, but one option is to scout for and pull any affected plants. Bulbs can be sold fresh if they are still unaffected and have reached marketable size. A number of reports of garlic bloat nematode have come in from locations in ME; symptoms are dwarfed, yellowing plants, with significantly reduced roots.
Basil: No cases of basil downy mildew have been confirmed in New England so far, but reports of the disease on the online monitoring site maintained by Meg McGrath of Cornell University indicate that the disease is being observed at garden centers and in home gardens across the US. Scout plants regularly and please alert us if you are fairly certain you have the disease so that we can alert growers. You can send a photo to umassvegetable@umext.umass.edu. Symptoms are yellowing of the leaves between veins and dark furry sporulation on the underside of the leaf.
Brassica: In an untreated cabbage field in Franklin Co., MA and untreated Brussels sprouts field in Bristol Co., MA, severe damage from imported cabbage worm was observed but the first generation seems to have been completed or large larvae present now will soon be pupating. Small diamondback moth caterpillars are starting to move in. An untreated field in Washington Co., RI was 40% infested with either ICW or DBM. Before head formation in heading crops, use a 35% infestation (% of plants with one or more caterpillar present); for leafy greens or after head formation, the threshold for treatment is 15% infestation. Continue to scout for flea beetles; use a threshold of 1 beetle per plant if plants are <12” or if leaf damage exceeds 10%. Scouts in MA have not seen much in the way of brassica diseases, but conditions are favorable for black rot, which has been diagnosed in kale and Brussels sprouts in VT. Scouts in RI observed a brassica field where 70% of plants were affected by Alternaria on their lower leaves. Destroy and incorporate older plantings to hasten decomposition; rotate! Apply fungicides to long season brassicas.
Corn: European corn borer trap captures continue to be low to none in MA and NH, except for a count of 16 moths in Sharon, MA. According to growing degree days, a second generation should start soon: with flight at 1400 GDD; first eggs at 1450 GDD; and egg hatch at 1550 GDD. Scout fields with tasseling and silking corn now and treat at a threshold of 15% infestation. Corn earworm moths are being captured where traps are up, at numbers ranging from 3 in NH up to 20 at one site in Southeastern MA, with only a couple sites reporting no moths. Recommended spray intervals range from 4 to 6 days. See article in the July 2nd issue of Vegetable Notes on corn earworm management options. Fall armyworm larvae were found in tassels in VT, and traps in NH are beginning to catch moths in low numbers. FAW traps are also capturing a number of different look-alikes; be sure to confirm the identity of captured moths before making spray decisions. We’re seeing breakdowns in sweet corn herbicide programs after so much rain.
Cucurbit: Squash vine borer trap catches are high again in NH, averaging almost 20 moths per trap. Catches went down last week, but were up again this week. We may start seeing damage soon, as young larvae in plant stems reach 3rd or 4th instars. Scouts are beginning to see squash bug egg masses – 1.8 egg masses per plant at a field in RI; there is no threshold set for adults or nymphs, but scout for egg masses and treat to target nymphs when you see one egg mass per plant. Crops most susceptible to squash bug are yellow summer squash, zucchini, Hubbard squash, and thick-stemmed pumpkins. Continue to scout young cucurbit plants for striped cucumber beetle. SCB vectors bacterial wilt, and will feed on stems and fruit as well as leaves; stem feeding can make stems more vulnerable to wind damage. Protect young succession plantings with kaolin (Surround) sprays. Cucurbit downy mildew continues to spread in New York, and conditions are favorable for disease development in MA, though no infections have been reported to date. No new cases of powdery mildew found in MA, but this is the time when we usually start to see it, and the threshold for treatment is low, so scout now to stay ahead of this disease (see article this issue). Fruit rot caused by the fungus Choanephora cucurbitarum was diagnosed on zucchini in VT, and Septoria was diagnosed on pumpkin in MA, in a field that had been in pumpkins for the past three years – time to rotate this field to a new crop group.
Solanaceous: A second case of late blight was diagnosed on potato in Northern VT, in Orleans Co. Protective sprays should be applied to both potatoes and tomatoes now. See the MA late blight DSS for spray intervals. Black leg of potato, caused by the bacterial pathogen, Erwinia carotovora subsp. atroseptica, was confirmed last week in Hampshire Co., MA and seen in Plymouth Co., MA this week. This disease is most often introduced on infested seed. If symptoms are scattered in the field, rogue out infected plants including tubers to minimize spread of disease. All stages of Colorado potato beetle were present in potato fields scouted in the region, but in relatively low numbers, though a field scouted in VT averaged 4 large larvae per plant where they haven’t been able to get in to spray because it was too wet. Potato leafhopper numbers are going up, as are reports of hopperburn; PLH nymphs seen in high numbers on multiple crops, including apples, beans, and small fruits, as well as ornamental plants such as hollyhocks (a good indicator plant for PLH). The UMass diagnostic lab has confirmed reports of the bacterial diseases pith necrosis (Pseudomonas corrugate) and bacterial canker (Clavibacter michiganensis pv. michiganensis) on tomatoes from several locations in MA. The plant bug, garden fleahopper, an uncommon pest in the Northeast, was found feeding on greenhouse tomato leaves in Worcester Co., MA. Damage was originally thought to be caused by Western flower thrips. Another relatively new pest in the Northeast, yellow striped armyworm were found in tomato high tunnels in RI. These can do a lot of defoliating, often right around the same time as tomato hornworm. Bt products are effective against both pests.
Multiple: Oriental beetles and Japanese beetles were seen on eggplants, cucurbits, and other crops. See article this issue for more on scarab beetles.