New research report: Overwintering scallions with heavy rowcover

by Becky Sideman, UNH Extension


Scallion varieties, all lined up for a photo shoot.

After several years of research, we know that it is possible to plant bulbing onion (Allium cepa) in the fall, overwinter them in low tunnels, and harvest bulbs by late May in Durham, NH (see info about this system here). In response to grower inquiries, we expanded this work to look at non-bulbing onions, also known as green onion or scallion (Allium fistulosum). We were particularly intrigued by reports that growers successfully overwinter scallions using just row cover, no low tunnels involved.

What we did: We grew over a dozen varieties of scallions, planted at different dates, and protected them overwinter using heavy row cover. We then evaluated percentage of survival in the spring.

We found: that there were dramatic differences between varieties, and that some varieties survived very well in this system. We were encouraged enough to do some more work with this system to learn more!

Want all the details? Check out the full research report !


Scallions tucked in for the winter, under their 1.25 oz/yd2 row cover. 

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Cucurbit downy mildew update

August 16, 2017 Update from Cheryl Smith, UNH Plant Diagnostic Lab:


Cucurbit downy mildew on cucumber; photo courtesy GJ Holmes via CDMpipe.

Cucurbit downy mildew (CDM) has been identified in NH in both Hillsborough county (on cucumber) and Cheshire county (on muskmelon).

CDM symptoms begin as vein-delimited spots, but then expands and causes rapid collapse of vines. Excellent photos can be seen in the CDMpipe photo gallery. Cucumber and melon are susceptible to all pathotypes of CDM; for squash and pumpkin, reaction to pathotypes can vary, as can varietal resistance.

To control this disease with fungicides, growers should use fungicides specific for downy mildew. Commercial producers should reference the New England Vegetable Management Guide for fungicide options.

Options for organic producers are limited to copper fungicides (some of the Bacillus products may provide some suppression).

Home gardeners are also limited to copper, Bacillus products, and Agri-fos (Agri-Fos is not approved for organic production, and should not be mixed with copper products or applied immediately after a copper product).

Commercial producers and home gardeners in counties other than Cheshire and Hillsboro County should send samples of suspected CDM to the UNH Plant Diagnostic Lab for free confirmation, and to assist in the tracking of this disease. A sample submission form can be downloaded at  (be sure to write CDM confirmation at the top of the form).

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Late blight nearby

by Cheryl Smith, UNH Plant Diagnostic Lab and Becky Sideman, Vegetable & Berry Specialist.

As of July 31, 2017, Angie Madieras from the UMass Diagnostic Lab just diagnosed late blight on cherry tomatoes (‘5-star grape’ and ‘purple bumble bee’) in Hampshire County, MA.

We encourage any growers with tomato and potato in Southern NH (esp. Rockingham, Hillsborough, and Cheshire counties) that plan to protect their plants to apply protectant fungicides now, and consider having late-blight specific fungicides on hand prior to the next spell of cloudy/humid weather. 

If you believe you have late blight on either tomato or potato, you may send photos (details below) OR submit a sample free of charge. Write “late blight confirmation” on the top of the UNH-PDL submittal form.

For a current list of fungicide recommendations, please see the New England Vegetable Guide.

Please scout for symptoms. If you suspect late blight in your tomatoes and/or potato crops, please have it checked out. One way to do this quickly is to send digital images to either your county field specialistCheryl Smith, or Becky Sideman You can also send or bring samples to the Plant Diagnostic Lab in Durham.

For home gardeners: At this point in the season, if symptoms begin appearing on tomato or potato plants and you are sure that it is late blight, follow these steps:

  1. Remove plants.
  2. Place in a plastic bag.
  3. Seal bag and discard in trash OR completely bury plants deep enough underground so plants will decompose and will not re-sprout. DO NOT put the plants in a compost pile, as spores will still spread from this debris.

If you are not sure whether it is late blight, e-mail photos to the UNH Cooperative Extension Education Center, Cheryl Smith, or Becky Sideman.

Fungicides must be applied BEFORE symptoms appear. Fungicides containing chlorothalonil, or copper formulations are relatively effective for late blight prevention. For organic production, copper-based formulations are effective.

For more details, images, and management options, watch this video or visit Cornell’s Long Island Horticultural Research & Extension Center. This page showing other diseases that are often confused with late blight may be particularly helpful. If you have any questions, please get in touch.

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July 20, 2017 Insect Pest Update

From Alan Eaton, UNH Extension IPM Specialist

July 20, 2017 Sweet corn pests – This year our sweet corn trapping network is basically in Hillsborough county, with a couple of sites in Merrimack & Cheshire counties.  We detected our first corn earworms (just a couple) in late June.  The week of July 9, it increased to 20.  By July 19, the catch had jumped to 32, out of about 14 sites.  So fresh silking corn is at risk of earworm attack in much of southern New Hampshire.  Fall armyworm prefers younger corn, and we found our first ones in the last few days (10 as of 19th). They create messy holes with lots of visible frass.

We don’t know how far North these moths are now, but you can view the recent catches at our IPM Trapping Data website.  The data is updated on weekends.

Spotted wing drosophila (SWD) – SWD was first detected, and is increasing, earlier in the growing season than in prior years. This appears to be the case throughout New England. George, Alan and Linda are seeing potentially damaging numbers of SWD in traps present in cherry, raspberry, blueberry, and also in late varieties of strawberry. While you can look at the NH trapping data, growers intending to manage this pest should set up their own traps, in order to make effective decisions about when they need to make insecticide applications.

Directions for making an SWD trap (plus lots of other good information) are available at the UNH SWD page. However, an effective commercial trap and bait is now available from Scentry.  The trap is reusable and the bait lasts 4-6weeks.  Cost for both is about $15 plus shipping, it is available from Great Lakes IPM Company ( Other good resources for SWD information include Michigan State University, and the University of Maine.

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Keep an eye out for pepper maggot

by Becky Sideman, UNH Extension Vegetable & Berry Specialist

Pepper maggot (Zonosemata electa) is a pest that is found throughout southern New England; but in recent years, it has been found in several locations in southern New Hampshire as well. Peppers growing in southern counties (Cheshire, Rockingham and Hillsborough) may experience this pest, and should know what to look for.


These little dimples are the characteristic “stings” (oviposition scars) from pepper maggot.

The pepper maggot adult is a fly with striped wings. It lays its eggs in pepper fruit, producing characteristic “sting” marks on the fruit, typically in July. The eggs hatch within the fruit, producing maggots that feed within the fruit (and reduce marketability). This is not the same pest as European corn borer, which is frequently found within pepper fruit as well. The July 20, 2017 issue of UMass Veg Notes has an excellent article that discusses both pepper maggot and European corn borer damage in pepper.


This is a pepper maggot egg, on the inside of a pepper fruit.

It is difficult to use traps to monitor this pest, because the effective trapping protocols require that traps be installed high up in trees near production fields. However, pepper maggot is highly attracted to small round peppers, such as the varieties Cherry Bomb. Work in CT by Jude Boucher showed that these varieties can be successful used as a perimeter trap crop to protect other varieties of pepper from the pepper maggot. Jude also has found that these varieties work as an indicator, telling you when the pepper maggot is present.

This year, we have indicator peppers at our research farm in Durham, and are keeping an eye on them. Indicator plants are also in use at commercial farm sites in southern NH; Alan Eaton tells me that stings were first observed in Hillsborough county this week (July 20, 2017), suggesting that the pepper maggot fly is active now. If you have pepper fields and are in these southern locations, keep an eye out for this pest.

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Garlic harvest reminders


freshly harvested garlic

by Becky Sideman, UNH Extension Vegetable & Berry Specialist

Garlic harvest time is upon us, or fast approaching!

Determining time of harvest. Figuring out when to harvest can be tricky. The longer you wait, the bigger the bulbs, BUT the higher the risk of cloves separating. Harvesting too early results in smaller heads, with cloves not entirely filling their wrappers – and it can be more difficult to thoroughly dry garlic with numerous moist wrapper leaves. Here are some suggestions:

  • The 3-4 older (bottom) leaves on the plants should have yellowed and senesced, but over half of the leaves should still be green and healthy. These healthy leaves make up the wrappers on the harvested bulb.
  • Cloves should be wedge-shaped, and should fill their wrappers. The only way to see this is to pull a few test heads, and cut them in half to examine the cross-section. You can see a good photo of a mature head  by Crystal Stewart, from Cornell University.
  • Check maturity every week or so, beginning in late June/early July. It is better to harvest too early than too late; bulbs that have split apart are less marketable and will not store well.

Best harvesting practices.

  • Harvest when the soil is slightly dry. This will make it easier to pull, clean, and dry the garlic.
  • Lift garlic with an undercutter bar, mechanical harvester, or hand tools prior to pulling. Avoid bruising by being gentle during harvest. Remove excess soil by gently rubbing or shaking; don’t bang the heads against harvest baskets or anything else to remove the soil.
  • Harvest garlic when it’s as dry as possible, to avoid bringing extra moisture into your drying and curing area.

Drying, curing and storing garlic.

  • Immediately after harvest, move garlic into a shady spot (to avoid sunscald) to allow soil to dry in a well-ventilated area. Avoid direct sunlight and temperatures over 90F.
  • High tunnels or greenhouses covered with shadecloth, or well ventilated barns, can make good drying spaces. Good air circulation is important. It will take 10-14 days to cure garlic.
  • Garlic roots and stems may be trimmed before or after curing. If trimming while still green, leave stems about 6” long, and trim to final length once dry.
  • The ideal long-term storage conditions for garlic are cool and dry conditions; 32F, 60-75% relative humidity. Seed garlic should be stored at warmer temperatures (50F).

Assessing garlic health. Harvest time is a good time to pay attention and look for signs of pathogens and diseases. This is especially true if you save your own seed garlic, or if you sell garlic that will be used as seed. For most garlic pathogens and diseases, the only effective management strategy is to be vigilant and cull problems quickly – so it pays to keep an eye out. Some of the most problematic pests & diseases are described below.

Leek Moth. Leek moth is a new pest for our region. Thus far, it has been found in Vermont, and in Coos County in NH. Signs of this pest on garlic include feeding damage on the scapes and leaves. See the Leek Moth page maintained by Cornell University for more information and photos. If you see something that you suspect is leek moth, please reach out to any member of the Vegetable & Fruit Team, or to Piera Siegert, the NH State Entomologist (contact info here).

Stem & bulb or garlic “bloat”nematode (Ditylenchus dipsaci).  This pest has been found throughout NH, and is particularly damaging because it’s easily spread by saving and selling or replanting seed. Cool, moist conditions favor infestation by this tiny roundworm, and many parts of NH experienced prolonged periods of cool and wet conditions this year. Signs of this pest include 1) stunted plants that die prematurely and 2) stunted, underdeveloped, and misshapen bulbs. Some excellent photos are found in this University of Maine publication by Steve Johnson. If you believe you have this pest, please get it identified – one way to do this is to send it to Cheryl Smith at the NH plant diagnostic lab. This pest can spread quickly from seed stock that appears to be clean, so it pays to be vigilant.

White rot (Sclerotium cepivorum). This fungal disease is favored by cool and moist condition. Symptoms include yellowing leaves or stunted plants. Affected bulbs may rot, and fungal mycelia or sclerotia (black resting structures) may be visible on the bulbs. Some photos are found here. Because it spreads so quickly and is so destructive, this disease should also be diagnosed if you think you have it (NH plant diagnostic lab).

Fusarium basal plate rot (Fusarium oxysporum f.sp. cepae). Cheryl has received several samples of this disease already this year. As with the other issues mentioned above, one of the first indications of this disease is early senescence and yellowing of infected plants. Often, the basal plate and roots of heads are rotten, and there may be some discoloration of the bulbs. It can be difficult to distinguish between this disease and other problems (photos here), so submitting samples to a lab is really the only way to get a truly accurate diagnosis. 

Resources/Additional Information:

C. Stewart, Cornell University, Harvest considerations for garlicS. Johnson, University of Maine, Bloat nematode in Maine garlicS. Johnson, University of Maine, White rot in garlic and onionsM. Celetti, OMAFRA, Fusarium basal plate rot of onion and garlic , and R. Hazzard, UMass, Garlic harvest, curing and storage.



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2017-2018 Small Fruit Guide Available


2017-18 Small Fruit Guide

The new 2017-2018 edition of the New England Small Fruit Management Guide is now available! The guide is a cooperative publication authored by Extension specialist from the New England Cooperative Extension systems. It describes basic cultural practices and up-to-date pest and disease management recommendations for most berry crops: strawberry, highbush blueberry, brambles, currants and gooseberries, and grapes.

As always, you can access the online version of the guide for free at any time, by clicking here.

If you would prefer a print version, they are available for $16 plus $4 if you’d like it shipped. To order, please contact Suzanne Hebert or call 603-862-3200.

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