Vermont Apple IPM: Mid-late summer apple insects and diseases

Apple maggot fly captures are increasing in some orchards. At this point, unless you know you have really low or no AMF in your orchard, I would consider applying an effective material when you next apply a fungicide or foliar nutrient. This will allow for activity and eventual wash off prior to harvest. Check the options in the New England Tree Fruit Management Guide.

Second generation codling moth are due for management in many orchards. At UVM HREC, we caught our first codling moth on May 26. Using NEWA’s codling moth model, I know that I have accumulated 1215 degree days (base 50°F) since then. Sprays against a second generation should be applied around 1260 DD after first capture. I sprayed this morning. If you’re a little further behind, you can use NEWA’s degree day tool to calculate present and estimate near-future degree days, just enter your start date (first moth capture, or use the one generated in the CM model), end date (usually today), and base (50°F). This will allow you to use the six-day forecast to plan your best-timed spray. Precision tools like this allow for better use of fewer or more selective sprays. Using NEWA, monitoring, and knowledge of my market (retail with fairly high tolerance for cosmetic blemishes but not for wormy fruit) should allow me to get away with three insecticide applications this year. That’s half as many as we used to put on when I started 25 years ago.

Today I applied the Exirel I purchased earlier in the season. I only mention this product as a cautionary note to read your labels, every time you use a product and preferable a few days before. I bought this material for use against first generation CM, but it comes in an oil-based emulsion which will cause phytotoxicity when used with captan, which was my early summer fungicide of choice. I held off applying until this spray, but of course failed to order the more compatible fungicide I plan to use for my final fruit rot and sooty blotch / flyspeck spray. So, I was all set up, material already in the tank, so I sprayed anyway but now will need to put my fungicide on separately next week. Plan ahead.

On that note, I would consider one last fungicide against sooty blotch and flyspeck, but moreso against the summer fruit rots. The latter can be worse in doughty conditions with high heat and humidity- remember last week? Captan, especially combined with Topsin or a phosohorous acid product, are good summer fungicides, but leave visible residue on fruit surfaces at harvest if not washed off. Strobilurins (FRAC group 11) are also very effective, including some of the premix materials like Merivon and Luna Sensaton. The biological resistance promoter Lifegard is reported to have some efficacy as well. I had that left over in the shed from our fire blight management this spring so applied it this morning to improve natural resistance in the plant to disease. I don’t know how well that works, but there is some evidence of efficacy. I’ll be following up with a strobilurin next week.

For organic growers, the options get slim. I have seen where sulfur and high heat can damage fruit and actually allow fruit to rot more easily. A rotation of Lifegard with biologicals like Regalia or Serenade may help reduce disease.

Fruit need calcium now, especially Honeycrisp and other large-fruited varieties, so I’m okay making another trip out there to apply that again as well.

Peru Orchard Weed Management and Soil Health Field Day Weds, July 20

Forwarding on this excellent learning opportunity from our friends across the make in New York. -TB

Peru Orchard Weed Management and Soil Health Field Day

July 20, 2022

1:00pm – 4:00pm

The Don G Orchard Block

333 Route 22B, Peru, NY

Join us in Peru on July 20th as we discuss orchard weed and soil management! Speakers will be joining us from across Cornell’s research and extension teams. Topics will include the results of our herbicide timing trials, new vision-guided technologies for orchard weed spraying, organic weed management options, soil health demonstrations, and a discussion on our statewide orchard soil health survey.

1.5 DEC credits available in categories 1A, 10, and 22

Free to attend.

Register here:

Vermont Apple IPM: Midsummer management

This has really been a bit of a goldilocks season, with relatively mild, or dare I say ‘normal’ temperatures, few significant weather calamities, and just enough rain to keep us from complaining too much. That generally means low tree stress, and with the reports I’m hearing from growers and the observations I’ve made around the state, it appears that we’re headed toward a decent apple crop for 2022. But there’s still work to be done.

While it has been dry, there have been enough showers that we do need to think about keeping some fungicide coverage on against the summer diseases. The first that comes to mind is the purely cosmetic sooty blotch / flyspeck complex. If you are growing apples for cider, this disease is of no concern to you, but if you are selling fresh fruit, it does need to be considered. That said, if you follow the standard recommendations for management of a fungicide applied every 10-14 days or after 1-2 inches of rain, you will likely have visible fungicide residue on the fruit at harvest, which in a PYO or direct sales situation is just as tough to explain as a few spots are. That doesn’t mean that I suggest ignoring the disease. There is a good NEWA model for planning your sprays to manage it. Dr. Dave Rosenberger gave a good synopsis of SBFS management in a 2014 issue of Scaffolds. In it, he mentions considering both this summer disease complex as well as black rot, which can be especially bad on Honeycrisp, Cortland, and Northern Spy. The take-home message is to consider keeping your fungicide coverage up at least every three weeks or after 180-200 hours of leaf wetting. Captan plus a phosphite is a good option, but for better black rot control, captan plus a DMI (e.g., Inspire Super), strobilurin (e.g., Flint), or the old standby Topsin would be a better choice.

For organic growers, sulfur remains the material of choice, although Lifegard may have some efficacy. Bitter rot is another disease of concern that is caused by a different fungus which thrives in hot conditions and is more common when fruit finish is compromised by sprays (e.g. summer oil, lime sulfur) or when trees are drought or heat stressed.

This brings up water. It is essential, especially on young or dwarf trees, to maintain adequate water to ensure good tree growth. NEWA has a good apple

irrigation tool, but a god rule of thumb is one inch of rain per week. If you receive less than that, it is good to make up the difference with irrigation. One inch of rain equals about 27,000 gallons of water. However, if using drip irrigation, you can assume that you only need to irrigate the dripline of the tree canopy, which I’ll say requires about 15,000 gallons of water per week. The actual amount needed is more complicated than that determined in my quick calculation there, and takes into account many factors- soil type; soil organic matter content; temperature, wind, and solar radiation; tree size; tree age; crop load; etc. The point is, if it’s still dry and you have the capability, consider watering your trees.

On the insect from, we’re still in a bit if a between period, where codling moth has finished its first generation activity and we’re waiting on apple maggot. Apple maggot flies have started to be trapped in some high pressure orchards, so keep on-guard and be ready to treat when an average of one fly per four unbaited traps or five flies per four baited traps per block is reached. In the meantime, if you have seen lepidopteran larvae (caterpillars) on growing terminals, you may have a population of obliquebanded leafroller which can be managed with a cheap, effective, and low-risk application of Bt insecticide. Sprays are typically timed for 360 degree days (base 43°F) from first trap capture of the ‘summer generation’. In my experience, we don’t get strong peaks in weekly monitoring for this pest, so I like to include some Bt in any sprays in June and July that don’t have another insecticide in the mix.

Every spray this time of year should contain a calcium product for optimum fruit quality, and varieties highly prone to bitter pit- Honeycrisp, Northern Spy, Cortland, William’s Pride- should get sprays of calcium even when you’re not spraying for diseases or insects. While we’re talking about nutrients, it’s time to start thinking about foliar tissue testing to assess orchard nutrition. Samples are usually collected between July 15 – Aug. 15. The UVM Agriculture and Environmental Testing Lab can provide analysis, but at this time their output does not generate fertility recommendations. The following are potential options of labs for analysis. It is recommended that you contact the lab for instructions and costs before samples are sent. Plus, it is important to confirm that they will send recommendations along with the analysis.

(1) University of Maine Analytical Lab:
(2) Agro One:

Samples should be collected separately per variety, per block. Each sample should contain 25-50 leaves collected from the middle section of current season’s terminal leaves- do not collect young pubescent leaves nor the oldest leaves on a shoot. Leaf samples should be washed quickly and gently in a basin of warm water with one crop of detergent, then double or triple rinsed. Wet leaves can ne loosely placed on a paper lunch bag left open in a breezy or sunny area to dry before shipping.

That should be enough for now. Please let me know if you’re seeing anything of interest in your orchards. I do have a little time left this and next month for field visits, so if you’re interested in one, let me know that, too.


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