Mustard Greens and Flea Beetles
By Bob Randall, Ph.D.
Fall 2002

 

The weather will soon be turning cooler and with it comes a hankering for greens.  Fall, winter, and spring are prime times for growing mustard, but often crops are destroyed by a perennial pest in these parts:  the flea beetle.

 

Flea beetles are shiny black beetles about the size of a pinhead, which jump like fleas when disturbed.  They eat tiny holes in leaves, transmit a number of diseases to the plants, and their larvae chew on the roots of the plants.  Once these critters get started, a bed of mustard greens, bok choy, or Chinese cabbage can vanish in a few days.

 

Flea beetles are one of the most challenging pests to control.  If you are not very greedy, you can simply plant when the beetles’ favorite temperatures are absent.  Plantings between mid October and mid January, or in shade during May and June have few problems.  As well, plants scattered around a garden rarely have trouble.

If you want to plant a lot of mustard greens in August, September, February or March, you will need to fight the beetles.  The easiest approach is to use a barrier.

 

• Plant in a bed that did not have mustard, turnips, radishes, or Chinese cabbage in the last 12 months.
• After you plant, put up a frame to keep the barrier above the plants.  The frame can be made out of wood, tomato cages, bamboo, or wire mesh.
• Purchase row cover.  Row cover can be found in small sizes at area garden supply stores.  It can be ordered by mail in many sizes from Peaceful Valley Farm Supply.  Locally, San Jacinto Environmental Wholesale sells row cover to businesses and to community gardens.
• Completely cover the bed with the row cover and weigh down the sides with old boards or other weights that can be removed for weeding and thinning.

 

If you didn’t get the row cover, you can still try to kill the huge numbers of flea beetles with a poison.  There are many poisons of questionable safety on the market, but an organic one made from the neem tree has fairly low toxicity and is said to work well on flea beetles.  One brand is Bio-Neem.  As with all pesticides, cover skin and head, use rubber gloves, and minimize all types of contact.