Herbicide Resistance Testing

[Rosie]

I'm interested in learning about testing weeds for herbicide resistance; finding out if a weed has become more resistant to certain types of pesticides. I've read that after a while, the weeds become more resitant to the pesticide, and that using larger amounts simply doesn't work. Apparently they can test to see if the plants have become resistant, and then I could modify the type of pesticide I was using. This would save time and money, so that sounds great but...

Do you guys have any experience with pesticide resistance testing? What do you know about it? Would you have pesticide resistance testing done, or do you have other methods of dealing with weeds becoming resitant? How much should I expect to pay for something like this?

I've read about the tests, but I'd like to hear about it straight from the horses mouth, rather than from a company promoting its services.

Thanks very much,

Rosie!

[BA Deere]

For corn and soybean weed control, lambsquarter and waterhemp are tough to kill. The key is they have many growing points so it`s important to have good spray coverage to hit each growing point. Spray early, small weeds have less growing points. Never reduce rates, if it escapes, what doesn`t kill it makes it stronger. Mix chemicals according to label with different modes of killing action, conditions may favor one mode over another. Don`t spray if weeds have shut down growing in a dought, they have to be growing to get killed   .  Most chem salespeople will tell you what will work in your situation and probably guarantee it to work. Good Luck.  

[Rosie]

Great info BA Deere, I will certainly keep that in mind!

However, if the plants become resistant to the herbicide, wouldn't even the younger weeds be harder to kill? After a few years of them building resitance, they'd be unstoppable!

[BA Deere]

Yes, however alot of the "herbicide resistance"  is caused by farmers thinking they can spray their beans one time in a season. So they wait till the weeds are older, slightly above the label heights. Then they use low drift nozzles, low pressure...that`s just a perfect recipe for raising resistant weeds. In the case of waterhemp, if you just plan on spraying Roundup twice when the weeds are <4" with a good 40 psi and not more than 10 gal water (ams added for pH lowering). Then with corn add a Calisto, Status, Atrazine, ect for a different mode of action, you`ll do good. Small weeds absorb chemicals easier, they don`t have a waxy coating and just a few growing points. Where as big weed may have 200? growing points, each and every one requiring a taste of spray to totally kill the weed