Aphids also feast on a smorgasbord of vegetables. The most popular aphid is the green peach aphid, plus lettuce (red) aphid, foxglove aphid, potato aphid, and cabbage aphid. Luckily, all of these aphids usually appear in the field at the same time.

Green peach aphid management in desert leafy greens and cole crops can be successfully accomplished with insecticides. In Palumbo’s field trials conducted at the Yuma Agricultural Center, insecticides with the best residual control included Platinum, Assail, Admire Pro (upgraded Admire 2F), Voliam Flexi, Beleaf, and Movento.

The Leptidopterous insect complex can be a tough nut to crack with insecticides. In fall lettuce, PCAs on average treat 100 percent of the acreage two to three times per crop cycle.

Over the last several years, PCAs, growers, and Palumbo have noticed a sharp decline in beet armyworm pressure in fields in the low desert, the California Central Valley, and other vegetable-growing areas in the U.S.

Palumbo has several theories for the reduced worm numbers.

The first is the increased use of Bt (biotech) cotton seed which includes the insect-control trait Bollgard II. The trait is highly effective against the beet armyworm and corn earworm.

As part of the pink bollworm insect eradication efforts in 2008 and 2009, the percentage of acreage planted in Bt cotton in Yuma County and nearby Mexicali in Mexico’s State of Baja California increased to about 95 percent. The technology likely reduced insect levels in cotton and other nearby crops including vegetables.

Another theory is related to alfalfa. With higher alfalfa hay prices in recent years, Palumbo says alfalfa growers have invested more dollars into effective insecticides to gain higher hay yields and quality. The end result is likely fewer armyworms marching from alfalfa fields into nearby vegetables.

Yet another potential reason is the use of pyrethroids and other insecticide products in fall melons to control whitefly populations. The adult whitefly is the major vector for the virus which causes cucurbit yellow stunting disorder (CYSDV) virus which reduces melon size. The insecticides target a variety of pests including cabbage loopers.

In summary, many effective insecticides on the market control Lepidopterous larvae in desert vegetables, Palumbo says. These products include a total of eight different modes of action and more than 20 active ingredients which help reduce insecticide resistance potential over the long run.

“The take-home message is there are many highly-effective insecticides on the market today which not only provide good insect control in winter vegetables, but are environmentally friendly as well,” Palumbo concluded.

“These products provide excellent knockdown plus good residual activity which benefits a wide range of desert-grown crops.”

cblake@farmpress.com