Forage growers 'get the drift' of spray calibration - state hay show winners named

By MANDY JOHN | Central Texas Edition

December 26, 2002 -- The Texas Forage and Grassland Council held their 2002 annual meeting and State Hay Show on Dec. 5-6 in Fredericksburg. Dr. Charles Stichler, professor and agronomist for Texas A&M University, was at the event to discuss spray calibration and drift minimization.

"One of the main things that you must pay attention to when spraying your field is the type of sprayer that you use," explained Stichler.

He said that a weed is any plant out of place and drift is the movement of a pesticide away for the target area. The two kinds of drift are vapor drift and physical drift.

"The three different types of vapor drift are amine, high volatile ester butyl and low volatile ester. Of the low volatile ester there are two kinds: butox-ethanol and isoocytle."

Stichler stated that the different factors that cause drift are:

• the size of the droplet, which is the number one issue related to drift,

• the pesticide carrier,

• the wind speed,

• the shape and size of the target,

• the weather conditions, and

• the distance to the target.

He also said that when spraying a pasture, distance does make a difference.

"The sprayer option and your care are what's really important.

"When reducing drift you must think of things such as making sure that you avoid spraying in windy conditions, using the lowest recommended pressure range, using the lowest possible boom height, using drift control additives, using a nozzle that produces the largest droplets, using shields to reduce wind drift, spraying early or late when temperatures are low and humidity is relatively high, and leaving buffer strips.

"The size of the spray droplets, from an actual spray to a light mist, all has to do with the type of nozzle you use. One thing to remember is that using flat fan nozzles causes a lot of drift. They have a poor nozzle and are not really that good to use.

"A drift guard puts out large droplets and reduces drift. An extended range tip is a good one to use because it has uniform coverage at low pressure.

"A nozzle I really like is a Turbo Tee Jet because it reduces drift significantly."

He explained that the two spray activators are ionic and non-ionic. An ionic activator forms electric charges because of phosphate in water, which may react to some pesticides. A non-ionic activator is neutral when it's added to water, which will not react to pesticides.

"It's good to try and have both drift retardants and foam retardants on the sprayers. Drift retardants reduce drift from 50 percent to 80 percent and foam retardants cuts foam in the sprayers."

Stichler said that most pesticides like a pH balance of seven.

He stated that two necessary accessories to have when spraying are a wind gage and a toothbrush.

"You must record the wind speed and direction, so it's important to have a wind gage. A toothbrush is used to clean the spray tip when it clogs up. You must use care and common sense when putting out pesticides."