May 31, 2015

by Terence Bradshaw

After last night’s rains, I would say that every orchard in the region experienced an infection period last night that will likely continue through Tuesday. Because it has been so dry this spring, few opportunities have been available to release of apple scab ascospores, so a large amount of this season’s inoculum is releasing during this event. Orchards protected with a protectant fungicide applied Thursday or Friday may be fine through this event without recovering, depending on the amount of rain that falls. It would still not be a bad idea (and is a very good idea for anyone going into this with questionable coverage) to apply a good kick-back fungicide (strobilurins, DMIs, or SDHIs) when things dry out and you can next get back in.

Apple scab, plum curculio, thinning

May 28, 2015

by Terence Bradshaw

I was a bit absent earlier this week when some of this information may have been relevant, but here’s my take on the situation in Vermont orchards:

Apple scab:
Although there has been little moisture this season, infection periods have occurred, and I saw my first primary scab lesion on unsprayed McIntosh trees at the UVM Hort Farm this morning. Although the NEWA apple scab model shows near-complete ascospore maturity and release across the majority of the state, the model isn’t always accurate in these seasons of low rainfall. Researchers at UMASS have reported “plenty” of mature ascospores in their trapping, and the next soaking rainfall will likely lead so a major spore release and infection period. To date, the infection periods we have seen this season have generally been from combined, intermittent wetting events. These events require just as much protection as a full rain, and I recommend maintaining fungicide coverage for another couple of weeks until we are comfortable that the primary inoculum is expended.

Fire blight: With the warm weather we’ve been having, fire blight bacteria has had an excellent opportunity to continue developing in Vermont orchards. Growers, especially those who had fire blight anywhere on their farm last year, would be advised to have an application of streptomycin on-hand and be ready to apply immediately following a traumatic weather event (very high wind with rain, hail). Blossom blight symptoms from the May 9-11 infection event should be showing up any day now, so scout your orchards closely and be prepared to cut out diseased tissue using appropriate caution to prevent disease spread (cut 8-12 inches below visible symptoms, clean pruners with alcohol or 20% bleach solution between cuts, prune on a dry sunny day). DO NOT apply strep to visible fire blight infections- you will not get control of the disease, and you will be setting your orchard up for strep resistance in the local fire blight population.

Thinning: Bloom was heavy and pollination good across most of the state, and Vermont orchards will need to thin aggressively this year to break the alternate bearing pattern we have gotten into. Many orchards should have put a second thinner on at the beginning of this week when fruit were at 8-12 mm size and subsequent warm weather conducive to thinner activity. Good spray conditions should be coming this evening and tomorrow and relatively warm weather tomorrow and Saturday will provide a decent window of opportunity. By next week, many orchards will have fruit reaching 15-20 mm in size which are significantly more difficult to thin.

Insects: Plum curculio is still active, so keep covered for that one. Orchards that received a full-block spray of an effective curc material may get away with border row sprays for the next week or two. Codling moth are beginning egg laying in the Champlain Valley so materials that target early instar larvae may be applied any time. European apple sawfly are largely completed with their activities this season but if your orchard has problems with this pest, consider keeping covered with an effective material for another week or so.

Horticulture: Water any trees you can, especially new plantings. Now is the time to apply nitrogen fertilizers, and trees may benefit from potassium applications at this time as well. Foliar fertilizers may also be applied now, since nutrient demand is very high given the high fruit load and rapidly developing canopy.

Prebloom disease management and frost prevention (?)

May 28, 2015

by Terence Bradshaw

Grapes in the Champlain Valley will soon be approaching the ‘immediate prebloom’ stage which is a critical time for management of multiple disease, including black rot, downy mildew, powdery mildew, phomopsis, and anthracnose. Spray applications may be made any time now to help prevent these diseases. Remember, you cannot generally treat these diseases successfully after you see symptoms. A combined application of an EBDC fungicide (mancozeb, polyram, etc.) and a sterol-inhibitor (Rally, Procure) at label rates will help to manage these diseases at this critical time.

For organic growers, the options are much more limited: copper products have a small amount of efficacy against black rot but are potentially phytotoxic (cause damage to the plants), require multiple applications season-long, and are a heavy metal that may accumulate in the soil. Sulfur products also may have phytotoxicity issues but are generally effective against powdery mildew. If using an organic program, strict vineyard sanitation is absolutely critical. This means removal of all overwintering berry mummies from the canopy and burying or burning them. Dead or otherwise infected wood also must be removed from the canopy to reduce phomopsis inoculum.

Other vineyard activities that should be performed at this time: shoot thinning to 3-5 shoots per foot of cordon on healthy vines, weed control (avoid herbicide application to bases of vines with leafed-out renewal shoots), tying vines and trellising.

There has been some recent discussion among growers about frost control measures after the May 22 cold snap that affected some vineyards. Questions about irrigating for frost control came up, and I’ll give my take on the subject: it is rarely worth it. Unless the irrigation system is carefully designed specifically for frost control (i.e. capable of outputting sufficient water to provide protection to the whole canopy), is run during the entire freezing event, and conditions such as low dew point or wind do prevent effective heat release from forming ice, then the significant effort likely won’t pay off and may cause even more damage than doing nothing at all. Frost fans are more commonly used in larger production regions, but they are very expensive and require their own specific conditions to be effective. I’ll echo comments made by others on the matter: the best frost control is good site selection, followed by good vine management. Row covers may be effective in mitigating frost conditions, but have their own infrastructure needs particularly a wire suspended above the canopy at 7-8 feet on which to hang the cover, and significant labor to apply and remove. I do not have experience to suggest a fabric type that would work best.

Hoping your vineyards are frost and disease-free,

Marginal yellowing on apple leaves

May 22, 2015

by Terence Bradshaw

This is just a quick note to help explain a condition you may be seeing on your orchards this year. Yesterday, while passing through the orchard quickly, I noticed marginal yellowing on many leaves, similar to the picture below. My first thought was to go back and diagnose a nutritional deficiency, but Mary Concklin at University of Connecticut reminded me that this damage is common on trees treated with streptomycin and regulaid for fire blight management (and thanks Mary for the photo). No negative impacts are expected or documented from this.

May 2015 Northern Grapes Project Newsletter

The May issue of Northern Grapes News is now available at:


In this Issue:

-When Species Matters: All Is Not Equal in the World of Wine Tannins.

-Impact of Spring Frost Damage on Marquette in Michigan.

-NGP Team Profile: Anna Katharine Mansfield.

-NGP Team Profile: Chris Gerling.

-Results from the Northern Grapes Project Baseline Survey – A Series. Growth and Development of Wineries.

Petal fall: scab, insects, and thinning

May 19, 2015
by Terence Bradshaw

Most orchards in the ‘traditional’ growing regions in Vermont are at or near petal fall, although the cool weather may be extending bloom a bit. This is a critical time for orchard management, so be ready.

Apple scab: Ascospore maturity is high and with few wetting periods lately many mature spores that have not yet been released are ready to cause infection. Rain overnight and more expected today will likely provide conditions for infection. Fungicides applied as late as last Thursday will likely have protected your orchard during this infection period, but we are in a period of rapid shoot and leaf expansion so newly emerged tissue may not be covered. Wind conditions do not appear favorable for spray applications until Wednesday evening or Thursday morning, so a material with ‘kick-back’ activity such as strobilurins (Sovran, Flint, etc.), DMIs (Rally, Inspire Super, Procure), or the newer SDHIs (Luna Sensation/Tranquility, Merivon, Fontelis) is suggested. Each of these materials also has at least some activity against cedar apple rust and powdery mildew. As always, kick-back materials should be combined with a protectant fungicide to reduce risk of developing resistance. I do not recommend combining Captan with Fontelis due to incompatibility issues. This may be an appropriate time for a final EBDC/mancozeb application if you have been using the lower three pound/acre rate, since an application made on Thursday will allow for harvest on August 7, given the 77-day preharvest interval. Organic growers would apply micronized sulfur, or consider using liquid lime sulfur (2% solution) which will provide some thinning action if combined with a low rate of oil (0.5%).

Insects: Plum curculio, European apple sawfly, and the earliest flying codling moth are active. If you have significant bloom or bees flying in the orchard, you should not apply an insecticide in your orchard. This is always a tough spray to time. particularly in orchards with many varieties or extended bloom. There are many options for insecticide materials at petal fall, please consult the table in Chapter 7 of the New England Tree Fruit Management Guide to make your selection. One material of note to consider is the old standby carbaryl which may be applied for thinning purposes (see below), but a low thinning rate of 1 pt/acre may not be sufficient as an insecticide, so another material may be combined to provide better efficacy. Organic growers should have started applying Surround and may consider adding an azadiractin material to improve efficacy, especially against European apple sawfly.

Thinning: Virtually all orchards had heavy bloom and good pollination weather. This is the year to break the biennial bearing cycle that many orchards have gotten into in the last few years. This means thinning early and often, Starting at petal fall. Each orchard is different, so it is very difficult to make blanket thinning recommendations that apply to everyone, so please consult the thinning section in Chapter 11 of the New England Tree Fruit Management Guide. Complicating thinning decisions are weather conditions recently and in the next several days. The NEWA Apple Carbohydrate Thinning Model may be of use in planing your strategy. Cooler, cloudy weather in the next few days will reduce thinner activity, so higher rates of materials may be in order in your orchard.
Where petals are off and no bee activity is present in the orchard. an application of carbaryl plus NAA is warranted, please check the Guide for appropriate rates. 6-BA thinners (Maxcel, Exilis) are not particularly effective in cooler weather, and may be saved for the 10-12 mm fruit size window next week. If you still have blooms or bee activity in the orchard, a higher rate (5-10 ppm) of NAA may be used without the addition of carbaryl, with carbaryl included in the 10-12 mm spray. It is important to check thinner effectiveness before making the next spray. Fruitlets that are thinning will not close their sepals and will develop yellow stems before abscission. Also, fruitlets stop growing before visual thinning indicators appear, so measuring a sample of fruitlets daily in the 3-5 days following application will indicate whether or not fruit are likely to drop. This measurement should be made on the same fruitlets for each measurement. Dr. Philip Schwallier from Michigan State University Extension has a good outline of thinning activities that would be appropriate to consider in this season which has the potential fore orchards to overset fruit: http://apples.msu.edu/uploads/files/Schwallier_Thinning_EXPO_2013.pdf.

Good luck, Terry

Fire blight risk

May 15, 2015

by Terence Bradshaw

With all credit to Dan Cooley from UMASS, I am sending along a comment of his for Massachusetts growers that is equally pertinent to Vermont:

Fire Blight update May 15 – it’s not done quite yet

With the refreshingly cool weather, the tendency is to think fire blight is no longer an issue and worry about the potential for a major scab infection. But fire blight risk remains high into early next week. Risk has dropped over the last few days, but the drop was from unusually high levels. Both MaryBlyt and CougarBlight say that infection risk is still high on those trees that still have open flowers, and the risk will increase somewhat over the weekend. If you add in a shower or two, then there is definitely a high risk of infection over the next few days.

The Hudson Valley and southern parts of New England may no longer have open flowers, but we have yet to see petal fall at UMass Cold Spring Orchard. In cooler parts of the MA and in other parts of northern New England, bloom is happening now. Even as Macs reach petal fall, it’s important to monitor all trees for open bloom, and keep an eye on fire blight risk until the flowers are gone.

If it does rain over the next few days, then it will be a major apple scab infection period, requiring fungicide protection or post-infection treatment. Again, be careful about using Regulaid or other spray adjuvants that increase chemical uptake with captan. It’s better to stay away from captan for a week or two to avoid phytotoxicity. Add mancozeb as a broad-spectrum protectant instead. If you’ve already applied streptomycin and need another streptomycin application on open flowers in the next few days, consider leaving Regulaid out of the mix and applying strep alone at the 24 oz/A rate to decrease risk of russet or other phytoxicity.”

We’ll discuss petal fall management needs later this weekend.


Organic options for disease management in Vermont vineyards

May 15, 2015

by Terence Bradshaw

I have received several requests for information on organic disease management in Vermont vineyards. I must say from the beginning that organically-certified options for managing some diseases are very limited. For some diseases, primarily powdery mildew and to some degree downy mildew, organic options are available to manage the disease fairly well. However, for phomopsis, anthracnose, and especially black rot, you will face an uphill battle. This does not mean it cannot be done, but expect significant frustration.

The first line of defense for organic disease management is strict vineyard sanitation. This entails removal of all diseased and dead wood during pruning and removal of spur stubs (blind or dead wood on spurs beyond the point where shoots emerge in spring) after bud break. It is too late in this season to apply now, but a dormant application of liquid lime sulfur may reduce inoculum for some diseases, however this material is unpleasant to apply (to put it mildly), as it is extremely caustic to applicators and equipment and requires much care in its use. During the growing season, removal of diseased berries and clusters must be completed on a regular (i.e. weekly) basis. Application of biological or (more effectively) mineral-based copper and/or sulfur fungicides will be required in most vineyards on a regular 7-10 day schedule, season-long, to reduce disease incidence on fruit and foliage. The most effective materials are copper-based products, which do not degrade and will accumulate in the soil.

Coming from a background in apple production, where disease management typically requires 8-12 applications of synthetic fungicides for disease management, I have been encouraged by the reduced spray schedule of as few as four sprays of conventional/non-organic materials that may manage disease in grapes. However, organic disease management will require many more applications in the vineyard to produce reasonable results. Growers who pursue this strategy should refer to the 2014 Cornell Production Guide for Organic Grapes, and prepare to be vigilant in vineyard sanitation and application of mineral and/or biologically-derived products whose efficacy is questionable.

Early season disease management in Vermont vineyards

May 13, 2015

by Terence Bradshaw

With bud burst in cooler sites and grape shoots ranging from 1-3″ in the Champlain Valley is the time begin thinking about disease management. I’ll put it simply: the next four fungicide applications, combined with good vineyard sanitation, will ‘set the stage’ for your vineyard in 2015 as far as diseases are concerned.

Disease Management at the 3-5 Inch Shoot Growth Stage – The following was written by Dr. Wayne Wilcox of Cornell University and appeared in the article “Grape Disease Control, 2013”: [Note:   Ph = Phomopsis; PM=
powdery mildew; BR= black rot; DM= downy mildew]

“3 – to 5-INCH SHOOT GROWTH. A critical time to control Ph rachis infections if it’s raining or likely to be soon, especially in blocks with any history of the disease. Early is better than late if it looks like some rain is setting in. Late is much better than nothing if those are the only two options , i.e., you’re past this stage, haven’t gotten anything on, and wonder whether it’s too late . This spray can provide significant benefit against fruit infections as well, since many of them originate from movement into the berries from infected rachises and berry stems. Also an important time to control basal shoot infections, since this is where the fungus will establish itself for the future if infected tissue is retained in canes, spurs, or pruning stubs.

Now is the time to start thinking about control of PM on vinifera varieties if temperatures remain above 50 °F for long stretches of the day… This spray is much more likely to be important in vineyards that had significant PM last year (we’re talking late season foliar disease more than fruit infections here) than in those that were “clean ” into the fall; however, it may be beneficial even in relatively clean blocks of highly susceptible cultivars, which tend to be relatively valuable as well… If already spraying for Ph, most growers of highly susceptible (and valuable) varieties include something for PM while they’re at it. I would too.

In NY, spending extra money for BR control is almost never justified this early unless you’re trying to clean up a severe problem block AND weather is wet and reasonably warm. In general, the farther south you go, the more important early sprays can become. Still too early for DM.

Disease Management options for the 3-5 Inch Shoot Growth stage are listed on pages 55-58 of the printed version of the 2015 New York and Pennsylvania Pest Management Guidelines for Grapes.

Unless you have had issues with anthracnose or extensive black rot on your vineyard, an application of a protectant fungicide such as mancozeb or captan should be sufficient at this time.

Terence Bradshaw, UVM Tree Fruit and Viticulture Specialist

IMPORTANT: Conservation Compliance and Crop Insurance Subsidies

Further clarification on the Conservation compliance requirement for receipt of crop insurance subsidies (referenced in my 5/12/2015 message), from Bob Parsons at UVM Extension:

“Producers with crop insurance must have Form 1026 on file with their FSA office by 1026 to qualify for subsidized crop insurance rates. The form certifies they are in compliance with conservation requirements for highly erodible land and wetlands. This form must also be in the same name that the crop insurance policy is in. For example, if the crop insurance policy is in Dad’s name but the Form 1026 lists Dad and son, its not identical. Needs to be identical. If you don’t have crop insurance in 2015 but think you may consider crop insurance for 2016, you need to have Form 1026 on file in the FSA office to qualify for subsidized crop insurance rates.”