The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz. released June 26, 2012.

Alternatives to endosulfan for whitefly-CYSDV management in fall melons

By John Palumbo, UA Research Scientist and Extension Specialist

With the impending loss of the endosulfan registration on melons in July 2012, pest control advisers are faced with a difficult challenge to manage whiteflies and CYSDV on fall melons.

Since the early 1990s, the synergized pyrethroids (e.g., Brigade+Thionex) have been the most efficacious insecticide treatments for control of adult whiteflies. Either insecticide product applied alone often provides only marginal adult activity, but when combined the mixture consistently provides enhanced efficacy.

This activity is a result of one insecticide active ingredient (endosulfan) interfering with the metabolic detoxification of another insecticide (bifenthrin) at its site of action in the insect’s nervous system.

These pyrethroid tank mixtures are effective due to the synergistic effects of certain organophosphate, carbamate, and organochlorine insecticides which bind to the active site associated with esterase enzymes responsible for the detoxification of pyrethroid insecticides.

Over the past several years, the UA has evaluated OPs and carbamates as tank mix partners used as synergists for pyrethroids for adult whitefly control.

A study recently completed at the Yuma Agricultural Center compared several OPs, carbamates, and other chemistries as synergists with pyrethroids in spring melons. The results were consistent with previous studies and showed that among the OP/Carbamate + Brigade mixtures, only Diazinon (labeled for use on honeydew only) provided consistent adult efficacy, often comparable to Thionex+Brigade.

The other OP/Carbamate mixtures evaluated in the trial were less consistent and rarely provided activity comparable to Thionex. A new formulation of Agri-Mek SC was also evaluated, but did not consistently provide efficacy comparable to Diazinon or Thionex.

Assail 30SG - applied at the high label rate - provided consistent knockdown and residual control of adults comparable to Thionex following each application.

The complete results of this study can be found at: Evaluation of Insecticide Tank-Mixtures as Alternatives to Endosulfan for Control of Sweetpotato Whiteflies in Spring Melons, 2012.

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Remember, when in doubt – scout.

Contact Palumbo: (928) 782-3836 or jpalumbo@ag.arizona.edu.

Soil solarization

By Mike Matheron, UA Extension Plant Pathologist

According to 2012 weather records, the Yuma area has had more than 35 days of triple-digit temperatures as of June 23. Now that it is officially summer, constant triple-digit daytime temperatures will be the norm until at least the beginning of autumn.

Although we may not personally appreciate the daily exposure to the summer heat, it is the perfect time for soil solarization. The solarization of soil is accomplished by covering moist soil with clear plastic and allowing the sun’s energy to heat the soil over a period of time.

A great deal of research in diverse geographical regions has demonstrated that soil solarization can raise temperatures to levels lethal to many different types of plant pathogenic fungi. The plastic conserves soil moisture and retards heat loss.

In field solarization trials conducted a few years ago in Yuma, the average temperature of soil at a depth of two inches during a one-month summer solarization period was 113 degrees Fahrenheit, compared to 102 degrees in non-solarized soil. The average peak afternoon temperature in solarized soil during the trials was 128 degrees.

In these multi-year solarization trials conducted in soil naturally infested with the lettuce Fusarium wilt pathogen, the disease incidence in a subsequent planting of lettuce was reduced from 42 percent to 91 percent compared to disease levels in non-solarized plots.

Soil solarization, similar to other cultural practices, has its benefits and drawbacks. Documented benefits include significant population reductions of different soil-borne plant pathogens plus numbers of viable weed seeds.

The drawbacks include the costs to buy, lay, maintain, and remove the plastic film.

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Contact Matheron: (928) 726-6856 or matheron@ag.arizona.edu.

Maximizing glyphosate use

By Barry Tickes, UA Area Agriculture Agent

Glyphosate is the most widely used herbicide in the U.S. It was discovered in the late 1960’s, patented by Monsanto in 1974, and came off patent in 2000.

Glyphosate kills a broad spectrum of plants and was initially limited to non-crop and fallow use and was expensive. The use of Glyphosate increased significantly around 2000 when it came off of patent and genetically-engineered crops with a resistance to Glyphosate developed.

The popularity of Glyphosate is based on its broad spectrum weed control, lack of soil residual activity which does not limit what can be planted following use, low mammalian toxicity, and its current affordable price.

Unfortunately, the heavy reliance on Glyphosate has led to an alarming increase in resistant weeds and shifts to tolerant weeds. Although no weeds in this area have yet to be documented as resistant, weed shifts have occurred.

Glyphosate is a very broad spectrum, foliar-applied, and highly-systemic herbicide. It is absorbed by the foliage and moves throughout the plant. It inhibits the production of the EPSP enzyme needed for many phases of plant growth and development. It uses the same general mode of action as many other herbicides which inhibit amino acid synthesis.

Most of these are ALS inhibitors including Pursuit, Raptor, Express, Affinity, Sandea, Osprey, and others. Glyphosate and Sulfosate (Touchdown) are the only ones that inhibit EPSP. It can persist in the soil but is so tightly bound that it has no soil activity.

Although it kills many weeds, its performance can be greatly affected by many factors. These include application variables and environmental factors plus weed characteristics.

The factors which impact Glyphosate have been intensively studied, are interrelated, and can be complex.

A brief and simplified review of the most important factors follows. Click this link to read full article: "Maximizing the Use of Glyphosate"

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Contact Tickes: (928) 580-9902 or btickes@ag.arizona.edu.

Future meetings

“Melon Insect Losses Workshop and CYSDV Control Update” workshop – July 19, 2012 at noon, University of Arizona Yuma Agricultural Center, 6425 W. 8th St., Yuma, Ariz. 85364.

Click this link to view the Melon Workshop Agenda