April 30, 2015

by Terence Bradshaw

Cool weather has kept bud development in orchards behind ‘normal’, and I’m hearing reports ranging from late dormant in high elevation inland orchards through early half-inch green in the warmer valleys. Bud development will be moving fast with expected warm temperatures through Tuesday, when rain showers are expected to arrive. Ascospore maturation is increasing fast as well, and a significant infection period can be expected if wetting hours are sufficient. Because buds are developing so quickly, protective fungicide coverage should be applied as close to Tuesday as possible the ensure that material is on emerged tissue going into the infection period. Most orchards have applied little if any fungicide this season, so coverage will good spray coverage is critical since any ‘base coat’ of material is limited. Saturday through Monday look to have good weather (i.e. low wind speeds) for spray application. The point is, if you are among the majority of orchardists with green tissue showing, you should be applying a fungicide this weekend. With the dry weather and adequate warning going into this event, protective fungicides (EBDCs, Captan or sulfur (for organic growers)) should be adequate. Remember, do not use Captan or sulfur if oil was applied within the past 7 days.

Green tip through tight cluster is a good time to apply nitrogen fertilizers in the orchard. Applications are best informed by foliar nutrient analyses which should have been conducted last summer. Many orchards on heavy soils with high organic matter content may not need any nitrogen applications in most years. Another concern is that overapplication of nitrogen may increase susceptibility of trees to fire blight infection. A conservative rate of nitrogen to apply in most orchards is 30 of actual nitrogen per acre. Recommended fertilizer materials can be found in the 2015 New England Tree Fruit Management Guide.

I go away for a week and nothing happens in the orchard. Not quite, but with the cool weather, trees have been advancing slowly. We reached green tip on McIntosh on Friday, April 24 at the UVM Hort Farm in South Burlington. This signals the real start of pest management season for us. Other, warmer sites likely had green tip earlier and I have heard a few reports of half-inch green showing.

Last week’s rains likely occurred before emergence of green tissue susceptible to apple scab, but rain today and tomorrow cause enough wetting for an infection period. Estimated ascospore maturity based on degree day modelling is relatively low right now at 2-3%, but actual maturity may be higher. If you sprayed copper in the last week, you should be okay, but if not, and significant wetting occurs, application of a fungicide with kick-back activity may be important, especially if you had high levels of scab last year which would provide ample inoculum for infection this spring. Strobilurin and DMI fungicides may be effective if resistance is not an issue in your orchard, but they would be better used later in the season when their activity against other diseases that aren’t yet a threat such as cedar apple rust and powdery mildew are active. The anilinopyrimidine (AP) fungicides Scala and Vangard would be better choices now because they are effective at cool temperatures (<50 F) and have little to no activity against fruit scab which limits their at later times. Kick-back fungicides should be combined with at least a half-rate of a protectant material (EBDCs or Captan, but no Captan within 10 days of an oil application) to reduce development of resistance in the local apple scab population.

White rectangle traps may be hung at three traps per ten acre block any time for monitoring tarnished plant bugs in the orchard. A cumulative capture of three bugs per trap for wholesale orchards or five per trap for retail orchards by tight cluster may indicate a need to treat before bloom.

Weather continues to look good for tree planting this week.

-Terry

Friday, April 17:

I will be away starting Saturday April 18 through the 25th. I am sending this notice in anticipation of activity next week in my absence, but please recognize that it is made based on a fairly long-range prediction.

We have seen no green tissue yet in South Burlington on any cultivars, and most are at early/just barely silver tip. Degree day accumulation since January 1, base 43 F is just about 47, and green tip is expected at about 100. Warmer sites than South Burlington have little more accumulated degree days, including Dummerston (50) and Shoreham (54). Other sites are at or below this level generally. Daily accumulations are in the 5-10 range when temperatures range from lows in the 30s to highs in the 60s. This is all estimations, guesses, and (informed) conjecture, but the point is that there is little to no green tissue out there now, and I don’t expect much development over the weekend, although the warmest sites may see some green tissue by Monday.

Next week we’re expecting two days (Monday & Tuesday) of rain followed by three days of showers, all with highs in the 50s and lows in the upper 30s and low 40s. Bud stages will advance slowly, and although scab ascospore maturity is likely very low to zero as of today, the fungus matures just a little faster than your trees so that when green tissue emerges, mature inoculum may be present in the orchard.

I recommend that growers in the Champlain and Connecticut Valleys use any time this weekend or between rains next week to get a copper fungicide on for management of fire blight, which will also buy you a week or so of time before scab season really hits. If you have time, go slow and add your spring oil treatment to thoroughly wet the canopy at dilute-2x concentration. If green tissue emerges by mid-late next week and copper coverage was questionable, nonexistent, or washed off from 1″ or more of rain since application, and you had any scab last year (or didn’t conduct a thorough evaluation in fall to assess), you may want to follow up with a kickback fungicide after the rains stop. Vangard and Scala are recommended particularly for the cool weather that is expected next week.

Anything else I offer is pure speculation based on very extended weather forecasts. Keep your eye on NEWA in the coming weeks (I mean every morning), there are a few new stations that have added in recent years. If you need to extrapolate very far for a station, and that includes on host site farms with varied topography, remember that NEWA is just one tool to help you in your pest management decisions, but to also use your experience and to trust observation made on your own farms.

I’ll make another plug for the 2015 New England Tree Fruit Management Guide, which has the specific answers an any materials I have suggested or alluded to.

Other activities next week: if your site is prepped, it looks like good timing to plant trees. If anyone is planting cider apple trees, please let me know what you have and how you have planted them, and I may also be able to visit when I get back. We need to set the stage for good cider apple research now so that it may pay off down the road in good, scientifically-sound research results.

Thanks. Remember, I will not have email access next week, so avoid sending me anything until April 27. Questions regarding spray guides or administrative issues can be sent to Sarah Kingsley-Richards at: skingsle

Where trade names or commercial products are used for identification, no discrimination is intended and no endorsement is implied. Always read the label before using any pesticide.
The label is the legal document for the product use.
Disregard any information in this newsletter if it is in conflict with the label.

The UVM Apple Program is supported by the University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM Grant, and USDA Risk Management Agency Funds.

I think it’s safe to say that spring is officially here, and the business or managing our orchards is about to pick up pace real fast. In walking the orchards at the UVM Hort Farm yesterday, I saw a lot of swollen, delayed-dormant buds, but only one cultivar, Zestar, which had reached silver tip. Given the warm weather expected all week, I would expect to see at least some cultivars reach green tip by early next week if not this weekend. Thus begins the disease management season.

I know many growers are still catching up on pruning after a difficult winter, and at this point, you should wrap up what you can and get your brush pushed to make room for sprayer access. I am a believer in using copper at green tip for disease management. The timing of this spray is very important- too soon (no green tissue showing) and you risk ‘wasting’ some of the effectiveness of the material against apple scab when susceptible tissue isn’t present. Too late (beyond ½” green tip) and you risk fruit russeting, which can be quite severe. Given that, it’s better to err a bit on the early side, but you should have green tissue showing in the orchard before applying. Copper applied at green tip will give about seven days’ protection against apple scab.

Copper’s primary benefit is in reducing overwintering populations of fire blight bacteria. Fire blight has become a regular disease to manage in Vermont, and a multi-pronged approach will be needed to keep it at bay. Copper should be applied to all trees in the orchard, not just susceptible varieties, and in as dilute a spray as possible. The specific copper material is less critical than the amount of metallic copper that is applied in the spray, and copper sulfate, copper hydroxide, copper oxychloride sulfate products all will be effective when used at label rates. A good primer on spring copper applications to pome fruit by Dr. David Rosenberger can be found in the March 28, 2011 issue of Scaffolds. Addition of one quart oil per 100 gallons can help improve penetration into bark crevasses where fire blight may reside. However, this could be a good time to apply a full oil spray to manage overwintering mites, and a 2% solution is recommended at this timing. Oil and copper products are compatible for tank mixing at this time of the year, but likelihood of phytotoxicity increases as more green tissue emerges. One benefit of applying oil in your first spray is that it allows more time for it to degrade or wash off before incompatible fungicides such as Captan and sulfur may be used as primary scab season ramps up.

Now that the ground is clear and firming up, it also would be a good idea to perform spring orchard sanitation to reduce overwintering scab inoculum. Leaf shredding with a flail mower is an effective practice that also may be used to reduce small pruning wood to mulch, but the mower must be kept low in order to lift and grind leaves that harbor overwintering inoculum. Alternatively, there is still time to apply urea (40 lbs/100 gal water/acre) to leaf litter which aids in decomposition and breakdown of inoculum. Leaves should be wetted thoroughly and the majority of material directed into the tree row. This application would add 18 lb actual nitrogen per acre which should be accounted for in your fertilizer applications later in the season.

/*Where trade names or commercial products are used for identification, no discrimination is intended and no endorsement is implied. Always read the label before using any pesticide.
The label is the legal document for the product use.
Disregard any information in this newsletter if it is in conflict with the label.

The UVM Apple Program is supported by the University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM Grant, and USDA Risk Management Agency Funds.

The 2015 edition of the New England Tree Fruit Management Guide is in and may be ordered at: https://www.regonline.com/newenglandtreefruitmanagementguide.

This guide represents the work of IPM professionals throughout New England, and is our primary resource for IPM and general production information available to growers. If you think your old guide will cut it, it won’t. There have been numerous changes in product registrations and recommendation in recent years, and an up-to-date guide is your best investment in helping to keep your management program up-to-date.

Guides are $40 each, delivered.

-Terry

Cornell Cooperative Extension will host two IPM trainings for Apple Growers later this month:

Champlain Valley: April 21st, Clinton County CCE Office (Plattsburgh) Upper Hudson Valley: April 22nd, Saratoga County CCE Office (Ballston Spa)

This training will provide a review of the basics of Integrated Pest Management in a classroom style setting. Multiple presentations will cover the theory of IPM, major pests requiring management in commercial orchards, and resources available to make management decisions (including NEWA).

Please see the attached flyer for registration information of contact CCE Fruit Specialist Anna Wallis at aew232@cornell.edu or (443)421-7970.

Announcement Apple IPM Training.pdf
2015 DEC Agenda Apple IPM Training.docx