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New menace on the muck: sowthistle

By Tom Rivers, Editor Posted 13 August 2013 at 12:00 am

‘This is a very serious weed problem.’- Christy Hoepting, Cornell vegetable specialist

Photos by Tom Rivers – Christy Hoepting, a vegetable researcher and specialist with the Cornell Cooperative Extension, holds a sowthistle plant that she dug up from the muck today. The sowthistle grows taller than onions, and the weed has stems that stretch horizontally, competing with onions.

BARRE – The enemy grows tall – and sideways. It blocks light from onion plants and encroaches on their space.

Perennial Sowthistle is a new muck menace and it has onion growers and researchers worried. Growers don’t have herbicides in their arsenal that can kill it without hurting the onions. Some trials are showing some chemical sprays can slow the weed. The only proven way to take out the plants within an onion field is to dig them up. But plucking the weeds could multiply the plants if the underground stems are ripped.

“This is a very serious new weed problem,” said onion researcher Christy Hoepting, a specialist with the Cornell Vegetable Program.

She is working to develop tactics to take out the plant that can tower 4 or 5 feet high. She is starting at the beginning because the powerful weed hasn’t been studied in onion regions outside of New York. Some fields in Oswego and Livingston County also are contending with the problem.

“We’ve seen it before in New York, but this year it has just exploded,” Hoepting said on the muck today.

Onion growers and researchers met today for “donut hour” on the muck, a weekly gathering when they share about challenges and successes in raising the annual onion crop. Pictured, clockwise from bottom left, include: Chuck Barie of CY Farms; Guy Smith of Triple G Farms; Elizabeth Buck, a program assistant with the Cornell Vegetable Program; Courtney Hill, a technician with the Cornell Vegetable Program; and Christy Hoepting, a vegetable specialist for Cornell.

Some crops such as corn are fighters and can compete with weeds for nutrients in the soil. But onions aren’t in that category. Weeds can overpower them, hogging nutrients.

Growers worry the sowthistle will result in smaller yields because of the weed’s suffocating underground stems that can reach 6 feet sideways. Those stems are called rhizones and Hoepting said they have “explosive reproductive capabilities.”

The plant also towers over onions, shielding sunlight that the onions need to grow.

The muck farmers have spent more time hand weeding their fields this year, only to see the sowthistle pop back. The weed is a perennial and it can easily survive a brutal Western New York winter.

Farmers plan to fight the sowthistle once the onions are done. Some of the growers are planning a chemical burn-down of the weed after the harvest. Growers will let the sowthistle grow back until it has enough critical mass to absorb an herbicide that will burn back all the top growth. The herbicide will move underground where it will kill the roots, Hoepting said. Those herbicides will also kill onions, so they must be applied after the onions are harvested.

Hoepting and Cornell researchers also are experimenting with herbicides, varying applications at different stages of the sowthistle’s development to figure out the right strategy to kill the weed within an onion crop and also after harvest.

One grower rotated onions this year from his field in Livingston County. Corn was able to better compete with sowthistle, said Matt Mortellaro who also grows onions on the Elba muck. He doesn’t want to rotate the onions in the Elba muck because they are a high-value crop. But the persistence and strength of the sowthistle may force him to switch to corn.

The Elba muck includes the towns of Barre and Clarendon in Orleans County. Most of the onions are grown in the Orleans part of the muck, where the muck is deeper.

Despite the struggles with the sowthistle, and a very rainy spring, growers say they expect a decent crop this year.

“Early in the year we had wind damage and then all the rain,” said Guy Smith, co-owner of Triple G Farms. “But we’ve had good weather in July and August. It looks like it will be a good year, but we still have a ways to go.”