Julie Jones  |   January 3, 2012

Here are some rough calculations concerning weeds and herbicide resistance….

 

Follow this scenario….

1)      Season 1:

a)      A single resistant waterhemp plant per acre survives a herbicide application and produces 100,000 seeds

i)        This is a conservative number since waterhemp can easily produce over one million seeds per plant!

(1)    100,000 seeds per acre equates to over 2 seeds per square foot, if spread evenly!

b)      Keep in mind that a couple escaped plants per acre is tough to see!

2)      Season 2:

a)      If only 25% of those seeds emerge and if only 10% of those plants are resistant, then 2,500 waterhemp plants per acre will be present at harvest

i)        If soybeans were planted and the stand is 180,000, then 1.4% of all plants will be waterhemp

3)      Season 3:

a)      If those 2,500 plants each produce 100,000 seeds and 25% of those seeds emerge and only 10% of those plants are resistant, there will be 6,250,000 waterhemp plants per acre at harvest!

i)        This is just two years after year 1!

 

This helps explain why growers have said there were no resistant weeds present last year, but now there is a severe problem. (It probably took a couple years, but resistance can happen very quickly!)

 

And this is why it is so critical to obtain 99 to 100% weed control.

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