Crop Scene Investigation - 24 Solved: Why has Stan's wheat stalled?

Monday, April 5, 2010

by BERNARD TOBIN

Stan's wheat field failed to meet his expectations because he didn't clean out the sprayer tank after applying his weed control.

While the tank only contained 90 to 115 litres (20 to 25 gallons) of the Pardner/MCPA 500/Tilt herbicide and fungicide application, this leftover spray packed enough wallop to injure Stan's wheat and reduce yields by 50 to 75 per cent.

The big problem was the fact that the tank still contained about 100 to 120 ml of MCPA 500, an estimate based on the amount of leftover spray in the tank. This went back out onto the 23-acre wheat field – at a rate of 5.2 ml per acre – during a critical time in its development.

"MCPA 500 gives you very effective weed control, but it's a potent Group 1 phenoxy herbicide that you can't spray on vulnerable wheat heads as they are about to pollinate," explains crop advisor Merv Erb. "If you apply it at pollination, it basically sterilizes the male flower, which leads to the poor performance we saw in Stan's field."

Erb says there's a simple lesson here for growers: "It's dangerous to leave something in your spray tank, thinking you are going to get rid of it here or there. If you're going to do that, tape a note to the cab window that alerts you there is something in the sprayer," he recommends.

Erb also cautions growers to be aware of areas in their sprayer where herbicide can hide.

"A lot of our sprayers have dead ends in their booms. Every year, people get hit with something coming out of their spray line and giving them crop injury or crop death due to herbicide hiding in the corners or inadequate flushing."

Proper rinsing is very important. "It's a busy time of the year and people are in a rush and corners get cut," says Erb. "You have to have things set up so you can move quickly and effectively. That could include some extra rinse water on the sprayer or a little water tank on top of the sprayer to allow you to quickly flush, rinse or clean out the boom when you're stretched for time."

Congratulations to Sid Atkinson Roseneath Ont. for his correct answer. BF