On top of it all, we have a large marketing effort by Crop Life companies to create awareness and action on the disease control front.

Dr. Tom Wolf, a spray technology specialist, has studied fungicide application in a number of crops in western Canada and offers these insights from his research experience.

1. Timing is the most important part of fungicide application. Diseases can develop and spread quickly. Most fungicides cannot cure a disease infection, they can only protect against it. If an application misses the window, yield is lost. Remember your priorities – become familiar with disease symptoms, the susceptibility of your crop and key growth stages. Make sure your sprayer is ready. Hire an agronomist to help scout and make recommendations. Make the right decision about whether to spray or not.
2. Water Volume is the most important application parameter for fungicide application. In years of study, optimizing water volume had a greater effect on fungicide performance than droplet size or spray pressure. More water is needed for fungicides than herbicides because of the greater amount of plant material present. Getting coverage on larger leaf areas requires more water. Although finer sprays can also help with coverage, this practice is riskier due to drift potential and higher evaporation rates.
3. Double nozzles, in particular the asymmetric types, are becoming more popular with fungicides, but data on their performance remains scarce. Double nozzles are proven effective and recommended primarily for fusarium head blight, or any other disease where an exposed vertical part of the plant canopy is the primary spray target. Double nozzles are also useful for preventing the spray quality from getting too coarse as higher flow-rate nozzles are used.
4. Travel speed is important with fungicides. Canopy penetration improves with slower travel speeds, and this has certain advantages For example, some applicators don’t use a separate nozzle for fungicides, they simply use the same one they had for their herbicide application at say 8 gpa and 15 mph at 70 psi (assume air-induced tips). For fungicides, this same nozzle and pressure will deliver 12 gpa simply by slowing down to 10 mph.
5. Boom height and spray quality are both important for angled sprays or double nozzles. The angle at which a spray leaves a nozzle diminishes quickly as air resistance and gravity do their work. If the boom is too high, any angle will be lost and the spray droplets deposit with gravity and wind. However, if the spray is a bit coarser and the boom is low, the angle of attack is retained for long enough to make a difference in spray deposition.

Despite these suggestions for making the spray more effective, there is no substitute for an informed decision regarding fungicide use. It’s possible that spraying is unnecessary for a number of reasons, and you should seek professional advice help to make that call. If you decide to go ahead, ensure that your sprayer is properly calibrated and will deliver the fungicide uniformly to the target.

A new product that is helping extend spray application hours and lets you see the spray much better under low, or no light conditions is spray nozzle lights. An important consideration when spraying extended is hours is to watch out for inversion as this can cause increased spray drift.

1. Do a visual inspection first. Are there any cracked hoses or broken nozzle bodies? Broken or frayed wires? Loose clamps? Are hydraulic fluid levels correct? Grease all points – this directs your attention to places that may need work.
2. As you re-install the flow meter, filters, and nozzle bodies you removed for the winter, pay special attention to the filters and make sure they are clean and in good shape.
3. Fill tank with clean water. If you’ve changed your water source, and especially if you use well water, make sure you know the level of hard water cations (primarily Mg2+ and Ca2+). These can antagonize some herbicides. Also observe the cleanliness of the water for the same reason.
4. Run pump to flush antifreeze out of boom and gradually increase spray pressure while observing all hoses, clamps, and fittings to make sure there are no leaks. A remote boom control is very useful for this operation.
5. Inspect your nozzles and nozzle screens, to make sure they are clean. If you’re not already sure, note the brand (TeeJet, Hypro, ComboJet, etc.), model (XR, ULD, AirMix, etc.), and flow rate (03-blue, 05-brown, etc.).
6. Measure the flow rate of each nozzle while spraying at 40 psi. Note any nozzle that differs more than 5% from the average flow. If flow is higher, replace it with a new one. If the flow is lower, check for a plug. Measure the flow of the new nozzle.
7. It is possible that the new nozzle you installed will have a lower flow than the rest of the set, especially if the old set has sprayed more than 30,000 acres or so. If the new nozzle is more than 5% outside the average, consider replacing the whole set.
8. Raise the pressure as high as it will go and take note of this number. This will help set the target spray pressure later. Repeat for all nozzle sets, as the max pressure will likely decrease at higher flow rates. Max pressure should be near 80 to 100 psi. If it is lower, reduce agitation or spurge flow.
9. Set the pressure to the minimum you expect to operate at (for most low-drift tips, this will be about 30 psi). Set the boom to the lowest height you expect to operate and observe the nozzle pattern width at ground level. It should be twice the nozzle spacing. Increase boom height if necessary. This step will ensure that your weed control is still adequate at the slowest travel speeds.
10. When spraying begins, make sure you are operating the nozzle in the upper-middle of its recommended pressure range. For example, many low-drift nozzles have an operating range from about 20 to about 100 psi. These nozzles should be operated at about 60 – 80 psi on average.

A few more words on nozzle calibration. Although step (6) is least popular of all, it is the only way to identify a problem nozzle or boom section. Some operators rely on the rate controller to handle this step, but that can be a mistake. The rate controller measures the total boom flow, and can’t tell if any part of the boom is different from the rest. The only way to be sure is to check the flow of each nozzle.

Computerized calibration tools link to that make this task a bit less time consuming are now available, and are well worth it.

To extend your spraying hours you may also want consider adding nozzle lights.

Dr. Tom Wolf is a former scientist with Agriculture and Agri-Food Canada, and is now heading up his own company that specializes in spray technology research and training.