University of Vermont

by Terence Bradshaw

We’re in a bit of a quiet window for pest management in Vermont orchards. Apple scab primary ascospore release is done, and if you have no scab in the orchard, you’re done for the year managing that disease. For anyone with a scab issue, maintaining fungicide coverage every 10-14 days or after 2″ of rain will be important until terminal bud set when leaves and fruit become less susceptible to secondary infections. I’ve seen little fire blight, despite the infection periods predicted in the pest models. I’ve said this before- cut out any fire blight strikes as soon as you see them, and feel free to contact me to evaluate any questionable strikes. I have seen several instances of Nectria twig blight this season that look much like fire blight, but are caused by a relatively weak fungal pathogen. Nectria often infects winter-damaged wood, which I am seeing a lot of this year. The most notable characteristic that identifies Nectria compared to fire blight is that Nectria-infected shoots will have a very distinct delineation between dead (brown) and live (green) tissue at the base of the dead shoot. Fire blight shoot blight will typically show a gradation between dead and living tissue as well as water soaked cambial tissue in the area of visible infection. The only management technique for Nectria is to prune it out, and maintain the orchard with good pruning and nutrition to ensure good cold hardiness. Summer diseases such as sooty blotch/flyspeck and fruit rots are the main concern now. Dr. Dave Rosenberger’s comments from June 23, 1014 issue of Scaffolds provide good insight into managing these diseases. Take home message (read the article for specifics): Captan alone or with another material will likely be in your spray program every 2-3 weeks for the next month or two, especially if this wet weather continues.

Apple maggot traps should be hung any time now to monitor for this pest. I observed my first trapped apple maggot fly at the Hort Farm yesterday in an especially problematic block, so they will be flying in commercial orchards any day now. Other insect pests of concern potentially include obliquebanded leafroller and codling moth. skingsle ASAP.

-Terry

by Terence Bradshaw

Please see the attached itinerary for the June 30 Champlain Valley Orchard Tour. Cornell Entomologist Peter Jentsch will be with us on the tour to discuss summer insect pest management.

We will begin at 9:30 AM at Hick’s Orchard in Granville, NY, then travel north to Champlain and Sentinel Pine Orchards in Shoreham, VT. This will be a self-driven, caravan-style tour. We will provide drinks and light refreshments, but please plan on packing a lunch for the day.

RSVPs are requested, please email Sarah Kingsley-Richards with your name and the number of persons who will attend at: skingsle

150630_SummerOrchardTour.pdf

by Terence Bradshaw

Apparently I need to go away for a week for us to get any significant moisture, and boy did we get it. The good news is that apple scab ascospores should be all released now, so if you maintained good protection during the primary infection season, You should be done by now. If you have any question about fungicide coverage, be sure to carefully inspect the orchard for lesions that could cause secondary infections during the summer. Lesions from the May 28 infection period should be visible by now. The bad news is that no matter what was last sprayed, there is likely zero fungicide residue in orchards unless they were treated recently. Sooty blotch and flyspeck (SBFS)are the main diseases of note now, and will require treatment to manage them. Dr. David Rosenberger wrote a good summary article on SBFS management in the June 23, 2014 issue of Scaffolds. Fire blight infections should be visible in orchards by now. Please let me know if you are seeing this disease in your orchard. At this point, if you have it, the primary management strategy is to cut it out.
Codling moth eggs are hatching now, and insecticides targeted at larvae should be applied as soon as possible.
Results from apple thinner applications should be evident by now, and I am hearing from many growers that there is excessive fruit in their orchards. I do not have enough experience with ‘rescue thinning’ at this point to recommend it, your best option to reduce crop load may be to hand thin. Hand thinning at this point will have little effect on return bloom. For growers who are concerned about poor blossom bud development for next year’s crop, especially on biennial-tending cultivars (Honeycrisp especially), application of a return bloom enhancer such as Fruitone or Ethrel may be considered. Specific materials, rates, and timings are found in Chapter 11 of the New England Tree Fruit Management Guide.

by Terence Bradshaw

Please consider joining us for a tour of Champlain Valley orchards sponsored by the UVM Fruit Team, UVM Extension Risk Management Agency, Vermont Tree Fruit Growers Association, and Cornell Cooperative Extension on June 30, 2015. Final details are still being arranged, and an agenda will be forthcoming.

Cornell Entomologist Peter Jentsch will be with us on the tour to discuss summer insect pest management.

We will begin at 9:30 AM at Hick’s Orchard in Granville, NY, then travel north to Champlain and Sentinel Pine Orchards in Shoreham, VT. This will be a self-driven, caravan-style tour. We will provide drinks and light refreshments, but please plan on packing a lunch for the day.

More details will be coming soon. RSVPs are requested, please email Sarah Kingsley-Richards with your name and the number of persons who will attend at: skingsle@uvm.edu

TB

June 2, 2015

by Terence Bradshaw

We are coming out of the biggest apple scab infection period of the season in Vermont orchards, and despite model predictions, I and many others in the region are assuming that there were plenty of mature ascospores that were released since rains started on Sunday. For orchards that were recently covered going into the infection, you can assume that fungicides were washed off after the first 1.5-2″ of rain, and that there was no protection for the latter half of this rain event, nor for showers that are expected this weekend. Spray conditions look good to excellent from this afternoon through Friday. I strongly recommend coming in with a fungicide with kick-back activity (DMIs, SDHIs, or Strobilurins, check your spray guide for specifics) as soon as possible. As always, these materials should be combined with a protectant fungicide to increase efficacy and reduce the development of resistance.

Plum curculio is still active, so a final application of an insecticide may be appropriate in problem blocks. Codling moth egg hatch is still about a week away, so specific materials against this pest should be held out until 250 degree days have passed since the first moth capture, which we expect in another couple of weeks.

Fire blight strikes have been observed at the UVM orchards, likely from the blossom infection that occurred May 9-11. Scout your blocks carefully and remove any strikes in dry weather.

The window for chemical thinning id rapidly closing as king fruit approach 15 mm in size. Cool weather for the remainder of the week and cool, cloudy weather the last few days have allowed the trees to build up significant carbohydrate reserves that will making chemical thinners less active. If you need more thinning, apply carbaryl + NAA as soon as possible. Higher rates (1 pint cabaryl 4L, 4-8 oz/acre NAA) would be prudent in blocks which had heavy bloom and good fruit set.

I will be away at a conference next week, so likely will not send out updates. Next week may be the first that we’ll take a break in the spray schedule anyway, assuming that we get good spray coverage on this week and the rains that come are not the downpours we just experienced.

Good luck with it.

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.

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.