Vegetable Growers’ School talks posted

Last week, about 60 growers attended the Vegetable Growers’ School: Focus on Cucurbits, in Concord NH. We heard about some terrific new updates from Dr. Brent Loy and Janel Martin about their research at the NH Agricultural Experiment Station. For those who couldn’t make it, or those who’d like to look back on all of the presentations, all of the info from the conference, including agenda and all of the talks, is now posted here.

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Winter cutworm, Noctua pronuba

by Alan Eaton, UNH Cooperative Extension

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Winter cutworm

In January 2017, we received several reports (some with photos) of cutworms on top of the snow in New Hampshire yards and fields. They came from Hillsborough county and at least 3 towns in Cheshire county. Where did they come from? What is this new insect? Well… this isn’t completely new. Noctua pronuba is a species that is more commonly known as the “large yellow underwing”. The moths I’ve seen have an orange color on the underwing, but I didn’t get to name the species. It is known in Europe and other regions, as well as in North America. Larvae are typical cutworms. I’ve found them in my garden and elsewhere. The first larvae I saw were collected on UNH campus walkways and submitted to me perhaps 15 years ago. The larvae have been reported feeding on a wide range of herbaceous plant species in many families. They can tolerate pretty cold conditions, and can feed during mild periods in our winters, in addition to the normal growing season. My larval photo (above) is from February 2013. I thought: good ice fishing bait!

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Noctua pronuba adult

It is unusual to see caterpillars on top of the snow, but this species can do that. Finding themselves exposed, they soon burrow deeper (it takes a while, in the cold), unless a lucky bird finds them. People ask if this portends some new, significant pest problem. No, it shouldn’t. The larvae are subject to many of the same natural enemies as our other cutworms. We can find this cutworm in spring and fall too. In our insect collection, we have New Hampshire specimens (the moths) from as early as 1990. Our specimens before that were collected in Canada. The adults are strong fliers. This species could very well have spread here on its own.

The adults have variable coloring & pattern in the forewings, but the hind wings are bright yellowish-orange with a dark band at the edge. Growers asked me: is this the beginning of a new major problem? I doubt it. There are lots of predators & parasites that attack cutworms.

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New research report added: Managing cabbage aphid in Brussels sprouts

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Brussels sprouts infested with cabbage aphid

by Becky Sideman, UNH Cooperative Extension

From 2013 to 2015, we performed experiments comparing different varieties of Brussels sprouts as well as different topping practices. In these experiments, we observed severe infestations of cabbage aphid. Although our research did not focus on the aphids, they were quite a nuisance and rendered most sprouts unmarketable. From conversations with growers in the region, we came to realize that many growers, especially organic growers, were struggling with cabbage aphid management.

As part of her senior thesis, undergraduate student Talia Levy conducted a study to compare two different methods of managing cabbage aphids: intercropping with beneficial flowers and using a rotation between two organic insecticides. The short story is that, while we observed lots of aphid predators and parasites on the flowering plants, they did not provide sufficient control of cabbage aphids. On the other hand, weekly scouting and application of organic pesticides when economic thresholds were reached DID provide good control of cabbage aphid.

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Talia Levy, scouting for aphids

Want to learn more, and get the full scoop? The entire report is available here.

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This closeup of a Brussels sprout leaf shows several things: aphids at all stages including winged adults with black bodies and non-winged adults with their waxy gray appearance, and many parasitized aphids (these look like golden shells).

 

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Spider mite management in high tunnel cucurbits

by Alan Eaton, UNH Cooperative Extension

Among the attendee feedback from the January 2017 cucurbit school were comments that growers wanted me to cover mite management, something I skipped because of our limited time that day. So I’ll cover it now.

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Mite-induced stippling on the leaves of a cucumber plant in a high tunnel.

Inside high tunnels, it is usually warmer and drier than outside, and the growing season is longer. These are especially conducive to problems with twospotted spider mite (TSSM). Cucumbers are the cucurbit where I see the most TSSM problems, but they can be on other cucurbits as well.

Growers typically think of pesticides as their first line of defense for this problem, but I suggest first looking at preventative measures. If possible, begin with a totally clean, bare greenhouse. This includes the floor area. That is difficult for a high tunnel where the plants are grown directly in the soil. In that situation, at least eliminate all traces of the previous crops. That means removing and disposing of all crop residues. If the tunnel or greenhouse has been given a good opportunity to completely freeze out for a couple of weeks or more, that makes it less likely that you are starting the season with a significant number of live TSSM’s. Cucumbers, legumes, roses, and sometimes petunias are among the crops where I see lots of TSSM problems.

Biological controls are an option to consider, especially for an enclosed greenhouse. I almost never recommend them for an outdoor crop, because the predators or parasites just disperse once released. One spot where you can look at a table of the various predator species and their needs/advantages/disadvantages is in the Greenhouse Manager’s Guide to Integrated Pest Management in Northern New England. We have run out of hard copies of this spiral-bound publication, but if you don’t own a copy, you can look at a copy on line. Here is a link to the UVM Entomology Research Lab’s web page on greenhouse IPM.

The guide is on the left side of the web page. Part of the biological control section (actually pages 65 and 66) show that information very concisely for spider mites, including optimal temperatures for each species to work. Dr. Michael Brownbridge of the Vineland (Ontario) Research and Innovation Center tells me that most Canadian greenhouses have switched to biological controls, rather than struggle with spraying chemicals and fighting pesticide resistance and re-entry rules. The biological controls can work very well if 1) you start with a relatively clean, pest-free greenhouse or high tunnel 2) you select the proper species for your conditions and 3) begin very early in the crop cycle, when mite numbers are very low. Unless you nuke them with a pesticide application, they can provide season-long control. Usually it takes several applications (of predators!) to do so.

Pesticides: Avoid using the same material repeatedly. That leads to resistance. Instead, rotate between materials with different modes of action. Many pesticide labels will direct you to make 2 applications, about 5 to 7 days apart. That is fine, but if another treatment is needed later, switch to something else in a different group. In the New England Vegetable Management Guide, we have included which group each miticide is in, so you can rotate easily. Under cucumber & muskmelons, I see 14 products listed, including two (Trilogy and M-Pede) that are OMRI-listed. Coverage is very important to get good control. That is difficult, because there are usually more TSSM’s living on the undersides of the foliage than on the upper surfaces. Monitor the levels of TSSM’s in your crop before and then a few days AFTER you have applied a spray. That allows you to evaluate how effective (or ineffective) a treatment was. In many cases, effectiveness is in direct relation to how well you got the crop covered (including the undersides).

Thresholds? The threshold is that size pest population where it is worthwhile to apply controls. There are no specific thresholds established for mites in greenhouse/high tunnel cucurbits, in part because each situation is a little different. I strongly advise regular checking of the crop. Look for the fine white speckling that these mites cause, and then pull out a hand lens or magnifier to confirm that the pests are present. Don’t have a magnifier? Check out my publication on that subject. It explains how to use them, what advantages and shortcomings the options have, and where to find some.

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Tunnel Conference Talks Posted

Did you miss the High Tunnel Conference last week in Manchester NH? For those who couldn’t make it, all of the info from the conference, including agenda and all of the talks, is now posted at our project website.

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Spinach Downy Mildew in the Northeast: See It?? Report It!! Manage It!!

by Margaret Tuttle McGrath, Plant Pathology and Plant-Microbe Biology Section, SIPS, Cornell University, Long Island Horticultural Research and Extension Center, 3059 Sound Avenue, Riverhead, NY 11901; mtm3@cornell.edu

Downy mildew has been found recently in spinach at several farms in the northeastern U.S. This devastating disease has not been confirmed in the region for several years, thankfully as it has been a major production constraint in California. Pathogens causing downy mildew are Oomycetes and thus are related to the late blight pathogen. They are similar in ability to produce an abundance of wind-dispersed spores capable of moving long distances and to not need leaves to be wet to infect (high humidity is sufficient), plus ability to devastate crops. 

All growers with spinach should inspect their plants for symptoms promptly NOW and also in spring plantings to catch if there is carry over or new outbreaks. If downy mildew is suspected, please contact your local extension specialist and send an e-mail to mtm3@cornell.edu.

It will be CRITICAL that all high tunnel and overwintering spinach crops with downy mildew be destroyed couple weeks before the start of the spring spinach production season in the region to avoid carry over into 2017.

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The characteristic purplish-gray fuzzy growth on the underside of a spinach leaf.

Symptoms. Purplish-gray, fuzzy growth of the pathogen, which is usually on the underside of leaves, is diagnostic. Early morning is the best time to see as the growth (which is spores and the structures holding them) is produced overnight, then during the day the spores are dispersed. On the top side of leaves, opposite where the growth develops, the leaf tissue will be yellow, initially dull becoming brighter and larger with time. Subsequently affected tissue will become dry and tan. If only leaf yellowing is seen, which could occur when humidity is low, put suspect leaves upside down on wet paper towel in a closed ziplock bag for a day. Keep the bag in the dark, such as inside a box, to further promote the pathogen if present to develop.

Management.   Resistant varieties have been an important management practice, but the pathogen has proven adept at developing new races able to overcome host resistance. Last year race 16 was discovered.

To maximize success of control with fungicides, start early in disease development (preventive best), and apply weekly. Conventional fungicides for this disease include: Actigard, Aliette, Merivon, Quadris and other QoI fungicides, ProPhyt and other phosphorous acid fungicides, Ranman, Reason, Revus, Ridomil Gold, and Tanos. Downy mildew is difficult to manage with organic fungicides based on experience of researchers and growers in CA. Labeled products include copper, Actinovate, Double Nickel, Regalia, Oxidate, Trilogy, and Zonix. Copper is considered most effective but based on few evaluations of organic products. Check REI and PHI when selecting conventional or organic fungicides to make sure fits production schedule.

Note that while leaves are held in plastic bag after harvest, affected leaves may rot and new symptoms may develop, especially if there is residual moisture from washing.

Promptly destroy infected, abandoned crops to eliminate this source of inoculum for other plantings in the region. The pathogen can survive a few years in soil when both mating types are present together enabling production of oospores.

Other Susceptible Plants. The pathogen, Peronospora farinosa f. sp. spinaciae, is only known to infect spinach. It is possible some Chenopodium weed species are susceptible to some races.

Pathogen Sources. It is possible contaminated seed or infected spinach produce from outside the region was the source of the current outbreak.

Favorable Conditions. Cool with high humidity. Optimal temperature range for this pathogen is 59 – 70 F.

Please Note: Any reference to commercial products, trade or brand names is for information only; no endorsement is intended. The specific directions on fungicide labels must be adhered to — they supersede these recommendations, if there is a conflict. Check state registrations and labels for use restrictions.

 Prepared 11/14/16

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Tree Assistance Program (TAP) in New Hampshire

by George Hamilton, UNH Extension Field Specialist and Tom Smiarowski, UMass Extension Risk Management Specialist.

Orchardists, grape growers and small fruit growers who experience losses from natural disasters during calendar year 2016 may be eligible for assistance under Tree Assistance Program (TAP), which is administered by the USDA – Farm Service Agency (FSA). Producers must submit a TAP application either 90 calendar days after the disaster event or the date when the loss is apparent.

TAP was authorized by the Agricultural Act of 2014 as a permanent disaster program. TAP provides financial assistance to qualifying orchardists and small fruit growers to replant or rehabilitate eligible trees, bushes and vines damaged by natural disasters.  This include all tree fruits, grapes, blueberries and raspberry. Eligible tree types include trees, bushes or vines that produce an annual crop for commercial purposes.  Strawberries are ineligible for the TAP. Trees used for pulp or timber are ineligible.

To qualify for TAP, orchardists/growers must suffer a qualifying tree, bush or vine loss in excess of 15 percent mortality from an eligible natural disaster. The 15 percent mortality can be determined on block or planting bases.  The eligible trees, bushes or vines must have been owned when the natural disaster occurred; however, eligible growers are not required to own the land on which the eligible trees, bushes and vines were planted. If the TAP application is approved, the eligible trees, bushes and vines must be replaced within 12 months from the date the application is approved. The cumulative total quantity of acres planted to trees, bushes or vines, for which a producer can receive TAP payments, cannot exceed 500 acres annually.

Interested growers should contact the FSA Office that serves their farming operation.  Questions regarding eligible trees, vines and bushes should be directed to the FSA Offices. Check this web site to contact your county FSA Office.

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