Studies funded by the California Lettuce Research Board on management of purslane on iceberg lettuce have generated a three-point program for control of the hard-to-kill, succulent weed.

Steve Fennimore, a Salinas-based Extension weed control specialist with the University of California, says his recommendations begin with a bed-top application of Prefar or Kerb plus Prefar herbicides.

Second, purslane must not be allowed to persist in fields longer than three weeks after emergence or it will set seeds.

Third, special attention to control should be given during May and August plantings since these are times when most purslane emerges and wider banded applications have greatest effect.

Increasing problem

Fennimore said untreated purslane can produce two million seeds per acre and his research showed that Prefar applied in a 22-inch band on the bed top reduced purslane seed production to 35,000 per acre as opposed to a five-inch band reducing the count to 350,000.

No difference in seed production was observed for Kerb applied as a band or a bed top application.

Purslane has become an increasing problem in Monterey County lettuce fields. When a field has small amounts, growers should try to uproot it and remove it, and the potential seeds, from fields.

In other studies to evaluate the brush hoe cultivator on 80-inch beds for lettuce, Fennimore found it was removed more effective than standard cultivators for removing weeds close to the seed line.

“The big advantage is you can get close to the plants and still it is easier on the plant roots than steel shovels,” he said.

The disadvantages of the brush hoe are the slower speed of operation, dust created by it, and the need for a second operator (in addition to the tractor driver). Fennimore added, however, that an electronic guidance system for the device conceivably could be designed.

E-mail: dan_bryant@intertec.com