Knowing Your Roots

Blog 21a

It’s the growing season in the Central Sands and a new crop is emerging; carrots are peeking up amid the oats, a “nurse crop” that is used to protect the delicate young carrot seedlings from damaging winds and all of us have an expectation for another great crop.  Although most Wisconsin farmers are keeping an eye on the carrots, they are also concerned with what’s happening in southwest Arkansas.  Why?

Aster yellows.   This bacterial-like disease is one of the major threats to the carrot crop each year and the only way this pathogen can get into a carrot is through the needle-like mouthparts of an insect:  the aster leafhopper.  In April, young infected leafhoppers are just unfurling their wings on grain crops in the warm, sheltered valleys of the Ozarks.  As they mature, their wings harden up, and the urge to fly kicks in.  As soon as the south winds top 60 degrees, off they go on a remarkable northerly migration that will take them all the way to Canada, or with a little nudge from the west, directly into the carrot fields of the Central Sands.

Blog 21cBlog 21b
This could mean disaster for aster yellows and can also be a threat to other important Crops in the Central Sands such as potatoes, and home garden staples like lettuce and onions. But, thanks to a 30-year investment in Integrated Pest Management (IPM), Wisconsin farmers will be ready!  They have worked closely with UW researchers and can predict when these leafhoppers become adults in Arkansas, when they will fly, where the winds will take them, and when to be aware of them in the fields in Central Wisconsin.  Once there, trained professional IPM scouts will be in the fields waiting and ready to control them before they transmit this destructive disease into the carrot crop.

For Randy VanHaren, an IPM specialist who has worked in the Central Sands, just knowing when the leafhoppers arrive was not enough.  Randy wanted to know just how many were carrying this disease, which would ultimately tell him how serious the threat would be to the crop here in Wisconsin.  To find a solution, Randy worked with UW plant pathologists to develop a completely new technology in crop protection circles that used a rapid, DNA-based assay that tells farmers exactly how many leafhoppers are infectious (carrying the pathogen).  Armed with this critical piece of information, farmers know exactly when and how much control is needed to protect the carrot crop. As Randy notes, “It took us years to perfect this technology but it was worth it, now farmers can help the bottom line while doing something really good for the environment.”

This is a great example of IPM.  Understanding the biology and ecology of the aster leafhopper and using DNA- technology to assess the crop risk took many years of collaboration between carrot farmers, UW scientists and crop consultants like Randy. Not only has this system saved millions of dollars for the farmer, but it has greatly benefited the local ecosystem. By not applying chemical controls unless absolutely necessary, the early-season biodiversity is preserved.  This is an essential factor for providing natural pest predators for control later in the year.

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