One item that’s at top of mind is the heat we are expecting early this week could provide substantial stress to trees, not to mention farmers and farm workers. Plan ahead and take care of yourselves. If you have irrigation, is should absolutely be running this week. Even with drip irrigation, well-watered trees will have cooler canopies due to increased transpiration and evaporation from leaves. High temperatures combined with many pesticides can lead to phytotoxicity ranging from minor leaf burn to fruit finish damage to tree defoliation- I’ve done them all. Pay attention to any warning on labels and do not spray during the heat wave.

Heat stress on trees not only contributes to general tree decline, but also predisposes fruit to certain rots. I have visited some orchards and haven’t seen any substantial apple scab, so most can step back from regular sprays for that disease. However, protection should still be applied to reduce fruit rots. Captan is the standard summer fungicide for its efficacy against the cosmetic diseases sooty blotch and flyspeck as well as against fruit rots, and is more effective when mixed with topsin, a strobilurin fungicide (FRAC code 11, e.g., Flint, Sovran, Merivon, Pristine, etc.), or a phosphite fungicide (e.g. Rampart, OxyPhos, Prophyt, etc.). Summer fungicides should be applied every 10-20 days depending on rain, and I find that most well-managed orchards that market direct to consumer and don’t store fruit for long with trees pruned and grass mowed to allow for good airflow can get by with 2-3 post-scab summer fungicides. That’s a lot of qualifiers, but it works for us and for many other farms. Farms that will store fruit or process on a packing line and thus have greater likelihood of disease development in storage and / or lower tolerance for cosmetic diseases may need to cover more and would do best to follow the NEWA SBFS model.

We are seeing a bit of fire blight shoot blight symptoms. It is important to cut these out as soon as possible before infection can spread. Cuts should be made at least 10 inches below the symptoms. If you have a lot to cut, get it out of the tree and on the ground and keep working; if you have time, collect that material and burn it. Be careful to not drag infected shoots through the canopy either while taking out of the tree or when they are sticking out of the back of a utility vehicle. If you have fire blight, do not apply streptomycin except in the event of trauma such as hail or extremely high wind, in which case treatment may reduce the spread of new infections. Once trees set their terminal buds in mid-late July, shoot blight susceptibility drops substantially. If you have fire blight and want to consider options for reducing its spread, reach out to me this week as we can discuss.

Insect pests of note right now include the beginning of second generation flight and increasing obliquebanded leafroller activity. For the former, we need to wait for emerging moths to mate, lay eggs, and the eggs to hatch, so a targeted application toward second-generation codling moth is likely a couple of weeks away. OBLR may require treatment in many orchards, it would be good to take a close look at terminals for feeding and the characteristic leaf rolling to see if treatment may be warranted. If warranted, a lepidopteran-specific material like Delegate, Intrepid, Altacor, Belt, Exirel (DON’T mix that one with captan) would best (be sure to rotate FRAC codes with each application). This is a good time to think about applying trunk sprays targeting dogwood borer and other trunk boring insects if you haven’t yet. Assail is the most commonly-recommended material, especially since Lorsban / clorpyrifos is no longer labeled for use in Vermont.

Check apple maggot traps at least weekly, unbaited traps that catch one fly per block (as an average of all the traps in the block) would warrant treatment; the lure (Gemplers, GL IPM) makes them much more attractive such that you can wait until an average of five flies per trap are caught before treating. For most growers, the main insecticide used against AMF is Assail, Imidan also works but it has a long reentry interval and tends to leave visible residue on fruit. Remember to rotate your insecticide chemistries to avoid resistance development in pest populations. Resistance isn’t a huge issue with apple maggot fly that has one generation per year, but codling moth and other lepidopteran pests are still about and subjecting successive generations of them to the same class of materials can induce resistance. For organic growers, Surround works well, but its use in midsummer may increase European red mites, and it can be hard to remove at harvest; spinosad (Entrust) works pretty well too.

Keep scouting for mites, they can really flare up in hot, dry weather. Treatment with a miticide may be called for if you observe more than five mites per leaf (average).

Now that we’re into July, any weed management sprays should not include glyphosate which can cause substantial, systemic damage to trees when used this late. Growers often use post-emergent contact herbicides at this time of the season to keep weeds down, these may include glufosinate (several trade names, controls grasses and broadleaf weeds); sethoxydim or clethodim (Poast, controls grasses); or 2,4D, pyrafluen, clopyralid, or fluroxapyr (several trade names, controls broadleaf weeds). I am not an expert on all of the available herbicides that may be used in tree fruit, so a discussion with your chemical representative may be in order. Notice on material that I left off that list—paraquat. This is a somewhat commonly-used herbicide in apples that has recently come under pressure due to its toxicity to humans, and as such has been banned for use in the state starting next year, with some exceptions. We will be discussing the ban alternatives to paraquat in the coming months and especially during the winter season.

Foliar nutrient analysis – It is the time in the growing season to collect leaf samples for analysis. 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: http://anlab.umesci.maine.edu/. Direct link to the leaf sampling form here.
2. Agro One: https://dairyone.com/services/forage-laboratory-services/plant-tissue-analysis/

Instructions on collecting leaf samples can be found here.

That’s all for now. Stay cool out there this week- it’s a good time to do fieldwork ‘farmer’s hours’ in early morning (or ‘hobby farmer’s hours’ in the evening).

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Terence Bradshaw (he/him)
Associate Professor, Specialty Crops

Chair, Dept of Agriculture, Landscape, and Environment
(formerly Plant and Soil Science)
College of Agriculture and Life Sciences

University of Vermont
117/210 – Jeffords Hall | 63 Carrigan Dr
Burlington, VT 05405

(802) 922-2591 | tbradsha
https://go.uvm.edu/alebradshaw

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