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University of Arizona
March 2nd 2014 Vegetable IPM Updates
Insect Management
Weed Science
Question to the IPM Team
Some Videos to Check Out
Pheromone/Sticky Trap Monitoring Network
Insect Management:

Thrips on Fall Lettuce

The weather this fall is as warm and humid as I can ever remember. These conditions are no doubt one of the main reasons insect pressure continues to be heavy on our local produce crops as we approach November. Thrips and their associated scarring damage on leaves are beginning to show up on leafy vegetables throughout the desert. Their presence on these crops is not unusual in the fall and will likely remain steady until the weather breaks or we get a good winter rain. We have observed predominantly two species on lettuce this fall; the typical western flower thrips, Frankliniella occidentalis, and the bean thrips, Caliothrips fasciatus. Both are common in the fall, but bean thrips are the predominant species we’re currently seeing on lettuce at the Yuma Ag Center. It’s has also been causing significant damage to small organic lettuce in the Imperial Valley (see image below). Adult bean thrips are uniformly dark, almost black in color and their wings have two black and two white bands which can easily be distinguished with a 10-15X hand lens. Alfalfa, melons, cotton, lettuce and a number of grasses are all known host crops for the bean thrips. The good news is based on my research experience, they can easily be controlled with available insecticides such as Radiant, Lannate (methomyl), acepahate and Entrust/Success. Note: the key to preventing thrips from significantly scarring leafy vegetable plants is to prevent the larval populations from becoming established. With the temperatures we’re currently experiencing, western flower thrips larvae can complete development in about 7 days. Applying back-to-back spray applications ~ 5 days apart is an effective approach for controlling nymph populations once they become established. For more information on the identification, biology, ecology and management of thrips on desert produce please visit these links:
  1. Insect Management: Western Flower Thrips
  2. Thrips Management in Desert Leafy Vegetables

Remember, When in Doubt . . . . . “SCOUT”

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To contact John Palumbo go to:



Comparison of Two Lettuce Wilt Diseases

Fusarium wilt of lettuce, caused by the fungus Fusarium oxysporum, f. sp. lactucae, was first detected on lettuce in Arizona during the 2001-02 growing season and continues to be found in lettuce fields from mid-October through early January. There is another wilt disease of lettuce called Verticillium wilt, caused by the fungus Verticillium dahliae. This disease has occurred in the Salinas Valley since 1995 but has not yet been found in Arizona. The primary symptoms of each disease are similar and consist of internal discoloration of the root cortex and plant wilting followed by death. The internal root discoloration ranges from green, brown to black in plants infected with Verticillium and reddish-brown to black in plants infected with Fusarium. Since symptoms of both wilt diseases are similar, true disease identity only can be achieved by bringing symptomatic lettuce plants to The University of Arizona Yuma Agricultural Center, where the causal pathogen can be isolated from infected root tissue and identified by microscopic examination. Both wilt pathogens are soil inhabitants which can persist there for many years. Both pathogens also can be seed-borne. The lettuce Fusarium pathogen can only infect and cause disease on lettuce, although it may sustain itself on roots of other plants without causing disease symptoms. Verticillium dahliae, in comparison, can infect and cause disease on numerous crops other than lettuce. Management strategies for diseases caused by Fusarium oxysporum and Verticillium dahliae are similar. When available, genetic resistance in host crop plants can provide effective disease control. Soil fumigation and soil solarization can reduce disease levels by lowering viable populations of both pathogens in soil. On the other hand, no known fungicides applied after planting have consistently and effectively managed diseases caused by Fusarium oxysporum or Verticillium dahliae.

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Weed Science:

Satellite HydroCap Herbicide on Lettuce

Satellite HydroCap is a generic form of Pendimethalin (Prowl) that is registered by UAP. It is registered in Arizona on direct seeded leaf lettuce that is at least at the 3 leaf stage. It is not registered on leaf lettuce in California. Severe crop injury can occur when this product is applied preplant or preemergence to the crop. (See attached picture). It is far safer after the 3 leaf stage but unacceptable injury can still occur at this time and caution should be used. Weeds are likely to have emerged when lettuce has reached the 3 leaf stage and these will not be controlled. This product can likely be used most effectively and safely with transplants prior to transplanting and on weed free beds. Transplanted lettuce is rare in Arizona however.

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Area wide Insect Trapping Network

Oct 15, 2014

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: Corn earworm moths remain active and were particularly numerous in the Dome Valley, Wellton and near Texas Hill in the past 2 weeks. Compared to this time in 2013, corn earworm is much more active this fall. Unseasonably warm temperature is likely influencing this difference in activity.

Beet armyworm: Beet armyworm moths remain active in most areas, but remain particularly heavy in the Yuma Valley and Dome. Moth activity is similar to trends we saw last fall (2013).

Cabbage looper: Cabbage looper moth activity continues to increase in most area-wide traps, whereas last fall, trap catches began to decline at this time. Again, temperature is likely the reason.

Whitefly: Adult activity continues to decline in all areas, at levels similar to what we experienced in late August. However, larger numbers of whiteflies were still actively moving this time last year, particularly in the N. Gila Valley and Wellton.

Thrips: Thrips numbers in general are beginning to pick up in most areas, and movement remains high in the Yuma Valley. Current trends are similar to what we saw last fall.

Leafminers: Numbers on traps were generally down, except for high numbers of adults captured on the trap located at 47E adjacent to harvesting melons and cotton recently shredded.

Aphids: Alate (winged) aphids are still showing up in traps in lower numbers than previous weeks, and are trap catches have been steady in the N. Gila Valley. An occasional cabbage aphid was found on the traps, all others were species not important to produce crops. Anticipate numbers increasing as temperatures decline and N, NW winds pick up.


Click picture to listen to John’s update video link

To contact John Palumbo go to:


Check Out These Videos!

The Vegetable IPM Updates Archive page provides links to updates from previous weeks.

The Vegetable IPM Video Archive page contains a collection of educational videos from current research work in vegetable crops by University of Arizona Researchers.


For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.

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