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March 2nd 2014 Vegetable IPM Updates
Insect Management
Weed Science
Upcoming Events
Pheromone/Sticky Trap Monitoring Network
Insect Management:

Insecticide Modes of Action on Desert Produce and Melons

As the produce season winds down and the melon season in full swing, it is an important time to review the insecticide chemistries that you may have used this winter/spring on produce crops and those that you may consider using on spring melons. To sustain the insecticide efficacy that annually provides PCAs and growers with cost-effective crop protection requires a conscious effort to prevent insecticide resistance. Over the past 20 years, the Agrochemical Industry has developed and brought to the market an unprecedented number of new chemistries that are highly effective, selective and more safe than their chemical predecessors. These include the neonicotinoids, spinosyns, tetramic acid derivatives and diamides to name a few. Most recently, a couple of new chemistries have been added including the sulfoxamines (Closer, Transform) and a mitochondrial complex I electron transport inhibitor (Torac). The development of new chemistries has slowed a bit and older chemistries are continually being phased out of the marketplace. Thus, it is imperative to sustain the efficacy of these newer IPM tools currently available, and makes insecticide resistance management (IRM) more important than ever. The most fundamental approach to IRM is to minimize the selection of resistance to any one type of insecticide. Historically, alternating or rotating compounds with different modes of action (MOA) has provided sustainable and effective IRM in our desert cropping systems. The Insecticide Resistance Action Committee (IRAC), a coordinated crop protection industry group, was formed to develop guidelines to delay or prevent resistance. Using their most recent IRAC MOA Classification Brochure we have produced a table which provides Insecticide Modes of Action on Desert Produce and Melon Crops We also provide general information on the route of activity and pest spectrum for each chemistry. These classification lists will provide you with an additional set of guidelines for the selection of insecticides that can be used in desert IPM programs.

Remember: "When in Doubt...Scout"

Click picture to listen to John’s update video link

To contact John Palumbo go to:



Gray Mold

The disease gray mold does occur on lettuce and onion crops in the desert southwest. Botrytis cinerea, the fungus that causes this disease, produces an easily recognizable grayish fuzzy growth on affected plants when humidity levels are high. Although invisible without magnification, profuse amounts of spores are produced by the gray growth and dispersed in the air. When favorable temperature and humidity levels exist, spores landing on senescent or damaged lettuce or onion tissue will germinate and grow into healthy plant leaf and stem tissue, leading to potential plant collapse and death. This outcome on lettuce is similar to that caused by Sclerotinia minor and S. sclerotiorum, the causal agents of lettuce drop. Botrytis and Sclerotinia are related fungal pathogens; however, the visible mycelial growth of Sclerotinia on plants is white. Fungicides effective against Sclerotinia are usually active against Botrytis. As with Sclerotinia, fungicide applications for Botrytis management are beneficial when plants are treated before the appearance of fungal growth and disease symptoms. Due to scarcity of rainfall and periods of high humidity, gray mold occurrence has been limited during this vegetable production season.
Click picture to listen to Mike's update video link
To contact Mike Matheron go to:


Weed Science:

Postemergence Grass Herbicides

Postemergence grass herbicides have been available for the past 20 to 25 years. These include fluazifop (Fusilade-1985), sethoxydim (Poast-1986, Segment, Vantage and others), and clethodim (Select-1991, Select Max, Arrow, Envoy, Volunteer, and others). They only control grasses and are registered on numerous broadleaf vegetable and field crops as well as trees and vines. These herbicides are all classified as lipid biosynthesis inhibitors. They work by inhibiting the production of an enzyme (ACCase) used to produce fatty acids which are needed in the formation of cell walls and other plant membranes. They are slow acting and have no soil activity. There are some herbicides that use this same mode of action but are used safely on wheat and barley. These include Discover (clodinafop),Dakota, Puma (fenoxaprop), Axial (Pinoxaden) and Achieve (tralkoxydim) which are commonly used to control Canarygrass, wild oat and other grasses.

These herbicides are all fairly broad spectrum and control most grasses although there are differences between them on some grass species. Clethodim will control sprangletop while sethoxydim and fluazifop will not. The same is true for annual bluegrass which is controlled only by clethodim when it is small. All of these are weak on sandbur.

These herbicides have no soil activity and typically need to be applied 2 or 3 times to achieve season long weed control. They all require the use of a crop oil concentrate to help penetrate the leaf surface except for Select Max which requires either a non-ionic surfactant or crop oil.

These herbicides are normally very safe to the crops that they are registered on. There have been only a few instances over the past 25 years where crop injury has occurred. One was to melons where above labeled rates of Select Max was applied in overlaps or at the ends of fields. This was only from Select Max. Another instance was several years ago on onions where liquid fertilizer (AN20) was previously sprayed over the onions for weed control. The third instance was to some leafy vegetables, especially arugula, where the crop oil concentrate caused leaf burn.

Although these herbicides once seemed fool proof, each year more failures are being reported. Last year, for instance, Poast and Select did not control Rabbitfootgrass in a couple fields and Canarygrass was missed by Poast in others. The only documented case of herbicide resistance in this region has been the resistance of Canarygrass to sethoxydim, fluazifop and clethodim in the Imperial Valley. There are several potential causes for herbicide failures and resistance is only one of them and is rare in this region.

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To contact Barry Tickes go to:


Upcoming Events:


Upcoming Meeting 2AZ, 2CA CEU’s –Apr 24, 2014



Areawide Insect Trapping Network

Apr 2, 2014

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

Corn earworm/Tobacco budworm: Corn earworm activity peaked at its highest level so far this spring. Trap catches remain steady or increased in most trapping areas, and a particularly sharp increase in flight activity was observed in the south Yuma Valley.

Cabbage looper/Beet armyworm: Beet armyworm remain active in most areas, and cabbage looper moth activity remains steady in all locations this week, particularly in Wellton and the Gila Valley.

Whitefly: Adult activity remains negligible in all areas relative to fall activity.

Thrips: Thrips numbers are beginning decrease again as produce acreage declines.

Aphids: Winged aphid movement is beginning to decline in all areas.
To contact John Palumbo go to: jpalumbo@ag.arizona.eduvideo link



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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