In California the pink bollworm overwinters as a late-stage larva in trash, at the base of cotton stalks and in soil cracks. Though rare, it can also overwinter in the seeds of an unopened boll.

When done properly, conventional plow down activities will kill the pink bollworm in these overwintering sites, according to Fresno County Agricultural Commissioner Les Wright.

Officials urge conventional plow down methods because it is not known whether reduced tillage practices can give the pink bollworm a foothold for next season. For that reason, Wright said Fresno County will scrutinize fields under reduced tillage methods during the host-free period and in next trapping season.

Growers in the other counties using conservation tillage methods need to contact their local ag commissioner for specific protocols related to plow down.

Proper plow down protocols include:

• Stalks must be shredded by a power-driven shredder that effectively reduces stalks to a particle size, permitting burial and rapid decomposition. Shredding must incorporate materials into the soil;
• Following shredding, tillage must be completed in a manner that all stubs are loose from the soil around the roots and will prevent re-growth;
• Conventional plow down is done by discing all roots, plant stubs, shredded debris and trash;
• Reduced tillage does not require the incorporation of all roots, plant stubs, shredded debris and trash remaining from harvesting or clean-up operations. Fresno County growers selecting this option must submit a notification 10 days prior to tillage of their intentions to do reduce tillage on their acreage. Contact your local agricultural commissioner’s office for specific information if utilizing reduced tillage methods;
• Once plow down is completed by either method, any volunteer cotton must be destroyed that may appear during the host-free period, even if it is on ground that was not planted in cotton this season. Cotton regrowth is subject to violation and citation. Growers are urged to check fallow fields and easements for volunteer regrowth.

Growers not in compliance with plow down requirements can be fined a base fine plus a per-acre fine for every acre not in compliance. Depending on the county, those fines can start at a base of $500 plus $5 per acre, with subsequent fines double those amounts.

Growers in Imperial County need to be aware of their specific location as that county has several different plow down dates, ranging from Dec. 1 through Jan. 1, depending on location.

Plow down dates are as follows:?

• Dec. 20: Fresno County south of Shields Avenue and the counties of Kings, Tulare and Kern;
• Dec. 31: The counties of Merced, Madera, San Benito and the portion of Fresno County north of Shields Avenue; and,
• Jan. 1: Riverside County (except the UC Riverside campus) and parts of San Bernardino and Imperial County?.

For specific answers to plow down procedures by county, contact your local agricultural commissioner’s office. In Arizona, contact the state department of agriculture.

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