By Terence Bradshaw

May 14, 2017

Orchards in the Champlain and Connecticut valleys are in full bloom now, and it looks like a good one. After my worrying comments last week about poor weather for bee flight, one grower last Monday told me, “You’re worrying too much. It’ll happen.” And it looks like Thursday and Friday the bees were flying. Although I am not trapping for native pollinators this year, I did notice some small native bees in trees in Putney Thursday afternoon. I wasn’t at the UVM orchard Friday, but my technician told me the bees were moving well. Orchards in cooler upland and inland spots will likely be flowering later this week, which also looks like a period of decent (>60° and sunny)bee weather.

Since we are talking bees, we need to continue to keep them in mind as we begin to think about petal fall and insect pest management. We have found extremely low levels of the usual pink/petal fall insects, tarnished plant bug (TPB) and European apple sawfly (EAS), in orchards all across the state. Some growers predicted and I confirmed a suspicion of a protracted bloom and therefore applied prophylactic insecticides at pink. In terms of bee protection, that is a valid response as long as those who applied a broad-spectrum, non-neonicotinoid material at pink use that extra protection they applied to give a little more time for all petals to drop and to clear out other attractive blooms by mowing before applying the next insecticide. This is our most dangerous timing for potentially damaging bees, because we need to get in to protect the developing crop, but there is still potential for a lot of pollinator activity in the orchard. Remember, pollinators aren’t just the honeybees you bring in to the orchard, and as we have been developing softer, more pest-specific spray programs in recent years, we are encouraging pollinator conservation in the orchards (good), which increases the number of pollinators that could be impacted when we apply that important post-bloom insecticide (not good).

I have been advising growers who are either still at pink or approaching petal fall who have below-threshold populations of TPB and EAS but who have concerns about lepidopteran pests now to consider using only a Bt spray like DiPel. Green fruitworms and obliquebanded leafroller are active now and may be monitored by inspecting 100 blossom/fruitlet clusters and terminal tips in multiple sections of the block and looking for larvae (small green caterpillars). Bt is very effective against moth larvae but has no known effect against most other insect orders, including bees.

Speaking of moths, if you have not already done so, now is the time to hang codling moth (CM) traps in the orchard. These traps are baited with either a pheromone (most common) or fruit volatile (used where CM mating disruption is used) lure and is used primarily to set the biofix date for use in the CM development model in NEWA, so daily or at least 2-4 times per week inspection is needed until the first moths are caught. Trap counts may be collected for the rest of the season to gauge population size and flight patterns. I mentioned CM mating disruption. We have been using this tactic since 2011 after suffering 65-75% damage in our organic orchards at the UVM Hort Farm. This year we have started using a Trece product, Cidetrack CMDA Meso, which reduces the needed number of applicators per acre from up to 200 to 36. This greatly affect the ability of larger-acreage orchards to hang the dispensers. Eric at CPS can provide details on availability and pricing, but growers who wish to try them must be prepared to treat the whole orchard, and should get them up as soon as possible before CM start flying and mating. A good background on using mating disruption in orchards can be found here. It’s a little bit old so the products listed may not be available or registered for use in Vermont.

Fire blight continues to be a non-issue for now, but increasing temperatures forecast for next weekend may trigger an infection, I’ll keep you posted as things develop. Keep in mind that bacteria need open blossoms to cause blossom blight, so as your petals fall, so does your risk. Scab- it’s still active, and I assume everyone is protected for today’s rain. As we get into the late bloom/petal fall window, addition of a material to the usual protectant (mancozeb/captan/sulfur if organic) schedule may be prudent. Consider a strobilurin (IRAC class 11), SDHI (7), or, if the bees are all gone, DMI (3) fungicide in your next spray or two.

Thinning is going to be interesting this year. Every orchard I have seen will need thinning, and I am going to work up some thoughts on recommendations later this week.

Finally, I have been asked to pass on to the orchard community that Dave Boyer, from Boyer’s Orchard in Monkton passed away last week. His obituary can be found here.

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 message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

May 5, 2017

Ugh. Vermont orchards are largely at tight cluster (inland, cooler sites and cider cultivars) to pink (most of the Champlain Valley, Honeycrisp of course is lagging) to early king bloom in a few spots and even a little full bloom in the warmest spots. Yesterday was a decent but not great ‘bee day’

for those with open flowers, but an extra 3-5 degrees would have moved their activity up a bit. My greatest concern going into the 2017 crop is this weather we’re facing as we go into bloom- gray, wet, and cool. Hopefully bud development will slow sufficiently so that by the time we get king or at least full bloom, we’ve got good bee weather. Pollen viability extends quite a bit in this weather, up to five days or more after a flower opens, so that’s a good sign as well. If you have the ability to get any extra bees in the orchard, consider doing so. And of course if you have any bees flying in the orchard, treat them right- no insecticides, especially neonics and any materials rated highly toxic to bees; lay off sterol inhibitor/DMI fungicides, at least until we learn more about their effects on pollinators; and mow competitive flowering weeds, if necessary, to funnel them to your apple blossoms. I wish I had a magic bullet that would improve pollination/fertilization/fruit set in a tough bee year, but there just isn’t any proven snake oil you can throw at the trees to compensate for this weather, so the best you can do is to promote and protect the pollinators (managed and wild) that we do have.

That said, this may be a year to consider supplemental pollen application. We have blown pollen at the UVM orchard as long as I have been around (over twenty years), and while it’s not a commonplace practice, it’s something I’ve done partly out of tradition (it was one of the first jobs I did when I started at the UVM orchard as an undergrad in May 1995) and partly to improve our overall pollination since we don’t bring in migratory bees (but we do have seven hives on the property). I was going to skip manual pollination this year, but this bad weather had me calling Firman Pollen to order some up to apply next week. I cannot point to a good peer-reviewed study that says it works in all conditions, but supplemental pollination has, anecdotally anyway, been successful for us. Application method is a little tricky and I don’t know if Firman has the leaf blower guns anymore, but it’s worth checking with them. They also have hive inserts that you add to bee hives to increase the amount of pollen that bees are carrying as they travel through the orchard.

Thursday’s weather provided an ideal spray day between rain events, and I assume everyone took the chance to get covered up. We maintained our spray coverage at the UVM orchards- scab sprays (mancozeb + Vangard) on the IPM and cider blocks, and insecticide (Aza-Direct and Dipel) in the Vf-gene scab resistant organic block where scab isn’t a problem but European apple sawfly and green fruit worn perennially are. Those two sentences covered most of what you need to be thinking about as far as pest management in the next week. Apple scab is the primary threat now, and I expect that when it’s all over, the models will call the period from April 30 through May 10 or so one long infection period. We are entering peak ascospore maturity right now, which means the guns are loaded and each wetting event will release more spores and infection will occur unless you’re protected. Keep covered with a protectant fungicide- mancozeb, captan if you haven’t applied oil recently, or sulfur if you’re organic (and same warning with oil). Five to seven days, max, between applications, and remember that an inch or two of rain removes the coverage you just put on. If you have another perfect, dry day like we has yesterday, add in a more broad-spectrum material with kickback activity (i.e. activity after an infection has occurred but before spores penetrate the leaf cuticle) that can broaden activity against rusts or powdery mildew. Remember the tables in the new spray guide to help guide your decisions. This is a good time to use your strobilurin or SDHI materials.

Notice that I just mentioned a disease concern, but didn’t bring up fire blight. Despite my warning last week to have some streptomycin on-hand for bloom this year, the onset of cool weather has almost completely shut down concern of blossom blight infection, for now anyway. Remember that in order to have a fire blight blossom infection, you need four conditions to occur: 1) open blooms through which bacteria can enter the plant; 2) wetting events during bloom to move bacteria into susceptible tissues; 3) sufficient heat (daily average over 60°F) during an infection event to permit bacterial reproduction in susceptible tissues; and 4) sufficient levels of bacteria present going into bloom. The cold weather has shut down bacterial population growth so the last condition isn’t a concern, and I don’t see any window in the next week anyway where mean temperatures will be over 60°F in any stretch of more than a few hours. Until I say otherwise, put fire blight out of mind, but remember that a warm/hot spell during bloom could turn the situation around quickly. In the meantime, this past week’s Scaffolds newsletter from the fruit team at Cornell has a great synopsis of the fire blight situation in the region.

Insect trap captures are very low across all monitored sites, nothing that I would treat anyway. That said, we are looking like we’re entering an extended bloom period, and that means that those pests waiting in the wings can start doing damage on early-blooming cultivars while you’re waiting for petals to drop on the later ones. Growers with low tolerance for cosmetic injury or history of European apple sawfly may consider a prophylactic pink spray, but I only say that because of the drawn-out bloom. Ideally, sprays will be based on quantifiable trap data, and in no orchard have we caught even remotely enough of either to warrant a pink spray.

In between sprays, this is still a great window to get your trees in the ground, apply herbicide, and fertilize orchards. We did all three this week at the UVM Hort Farm, or at least my technician Jess and chief engineer Andy did. I had one of those days yesterday when it took me as long to spray seven gallons of material (herbicide in the vineyard() with an electric backpack sprayer as it did Jess to spray 600 gallons of materials from three sprayers in multiple orchards. The lesson here is to make sure your equipment is ready to go the day before you need it. And maybe to not let the Professor play Farmer, but I’d say I still do all right at it when I prepare properly.

-TB

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 message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.