spray nozzle drplet size

mes111(5b -Purling NY & 7b -Nassau County NY)February 23, 2013

I am 35 miles south of Albany, NY.

Last summer I finished planting my 60 tree orchard. I will attempt to grow them all as espaliers. A photo is attached. 35 different apples with the rest being Cherie's, plums, pears, peaches and apricots.

Now I am planning my spray schedule and realized that I have seen no discussion as to the size of the spray droplets. Do we need a fine mist, fog, or larger droplets making up the spray.

I have a Wagnerair powered spray paint applicator that sends out a really nice fine spray which I am sure will get into all the nooks and crannies.

Any suggestions?????

This post was edited by mes111 on Sat, Feb 23, 13 at 0:58

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olpea(zone 6 KS)


It's a good question and the answer is that it depends. Ultimately your goal is to get good coverage throughout the canopy with a minimal amount of drift, a minimal amount on the ground, with a reasonable amount of labor.

Basically there are two different spray delivery methods - hydraulic and air.

Hydraulic relies on the water to penetrate the canopy. Water is the carrier of the pesticide. For water to penetrate the canopy, you need a coarser droplet size. Fine droplets don't travel very far by themselves, using a projectile force. It's the equivalent of shooting bird shot in a shotgun, or buck shot. The buck shot will go farther because it 's larger in diameter.

The other method is air delivery. Here, air is primary carrier of the pesticide. For air to push the pesticide, the water droplets need to be finer. Coarser droplets are heavier and fall out of the air current before they can penetrate the canopy.

It sorta sounds like your paint sprayer is an air delivery system, but I'm not sure how well it will work for spraying trees. My guess is that it's made for close up work and doesn't have enough "ummph" to really blow the pesticide through the canopy. Most air delivery systems need a lot of CFM to create a large air current, which I doubt your paint sprayer has the capability to do.

As your trees get larger, labor may well be a consideration in using your paint sprayer as well. You may be able to get good coverage with your paint sprayer getting in really close, but it may take a lot longer to get it done.

For the orchard area you show, I think a good quality backpack sprayer would probably work fine. A small 15 gal Fimco pull behind sprayer would be another option if you wanted something powered.

    Bookmark   February 23, 2013 at 12:08PM
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mes111(5b -Purling NY & 7b -Nassau County NY)


Keep in mind that these will be espalier no more than 6 feet high anh I WILL be getting up close.

One of the metrics for the sprayers that I noticed being used is GPM. Going from 1 to 6 GPM. I don't see any discussion of droplet size. I wonder if the GPM rating is the consider. Spraying my trees will be akin to painting a fence. Its just that I will be spraying a leafy wall.


    Bookmark   February 23, 2013 at 9:15PM
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