Nozzle selection is not always the foremost thought when preparing to make a weed control application. However, it can have a significant impact on the effectiveness of the herbicide.  This is especially true with contact herbicides like fomesafen or glufosinate.  Choosing the correct nozzle can be the difference between having a weedy mess or an effective application.  Compounding the issue, flow rate control systems on different sprayers (pulsation controlled vs. pressure regulated) can cause the same nozzle on one sprayer to have a different droplet size from another sprayer under identical operating conditions.

We tested Liberty + Dual and Prefix alone through Wilger DR and ER (droplet size similar to Spraying Systems AIXR and Flat Fan, respectively), Spraying Systems AIXR and TTI, and also GreenLeaf Dual Fan nozzles both with and without the air-induction (AI) caps.  All nozzles were tested at a 50 and 100% (100%=constant flow) duty cycles with each herbicide.  The application was made at 15 GPA to Palmer pigweeds ranging from 3 to 6 inches in height.

Manufacturer recommendations advise against using AI type nozzles with a pulsating sprayer system. This recommendation may clash with proposed new herbicide technology labels (Enlist and Xtend) which specify AI nozzles that generally provide larger droplets and reduced driftable fines.  Surprisingly, these AI nozzles in this test were still functional when operated on the pulsating system, however, control was generally 5-10% less for AI type nozzles on the pulsating system.  For all non-AI nozzle types, there is little to no difference between the flow control systems for Palmer control.

For each herbicide control was greatest from the Wilger ER and GreenLeaf Dual Fan without the AI cap with the AIXR and Wilger DR being only slightly behind.  The Wilger ER provided the smallest droplet size which translates into greater plant coverage.  The GreenLeaf Dual Fan nozzle gives a slightly larger droplet size, however, since it has two orifices projecting patterns at different angles it also provides improved coverage which would explain the increased control.

Although nozzles like TeeJet Flat Fans and Wilger ER give the best plant coverage and weed control, drift can occur much more easily from these type nozzles.  In general, nozzles like the Wilger DR, AIXR, or the GreenLeaf Dual Fan (Coarse droplet size; 350 – 400 micron range) still give very comparable control while potentially reducing the chance that a drift event will occur.