Spinach Gets New Protection Against Pesky Leafminers

Spinach and lettuce—favorite greens of many salad lovers—are also top choices of troublesome insects known as leafminers. That's why California-based plant geneticist Beiquan Mou of the Agricultural Research Service (ARS) has developed two kinds of parent spinach plants with impressive natural resistance to the insects.

Natural resistance offers an economical, effective and environmentally friendly way to battle leafminers, according to Mou. He's with the ARS Crop Improvement and Protection Research Unit, Salinas, Calif. The Salinas Valley is world-famous for the top-quality leafy greens grown there.

New, leafminer-resistant lettuces are in the works, Mou noted.

Adult leafminers—shiny black flies about one-tenth-inch long—sport a bright-yellow triangle on their backs. They can ruin spinach, lettuce and other greens when they puncture leaves to feed on the sap, creating unsightly holes called "stings."

Female flies cause additional damage by inserting their eggs between the upper and lower layers of a spinach leaf, for instance. The hungry, wormlike larvae that hatch from the tiny white eggs feed voraciously on the leaves. Their munching creates winding, whitish tunnels, the signature "mines" for which leafminers are named.

Though the new plants aren't resistant to the stings of the flying adult leafminers, they have many fewer mines than the other kinds of spinach that Mou's team tested.

The new spinach plants, designated "03-04-09" and "03-04-63," rate as the world's first spinach breeding lines with significant leafminer resistance. Mou has been making seeds of the plants available to other researchers and plant breeders worldwide since late 2006.

These parent plants serve as an invaluable source of resistance that can be bred into spinach types already popular with growers, home gardeners and shoppers.

Read more about the research in the October 2007 specialty crops issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.