The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz. released June 26, 2013.

Whitefly management on fall produce, melons

By John Palumbo, UA research scientist and Extension specialist

As the spring melon harvest winds down, it is important to think about whitefly management in fall produce and melons crops.

The first line of defense to avoid whitefly issues in fall vegetable plantings is for pest control advisers and growers to be vigilant in whitefly management program on cotton. In the Yuma, Ariz. area, cotton is the primary host crop for whiteflies during the summer. Alfalfa and sudangrass may serve as alternate hosts in some areas.

Before whitefly management begins in cotton, whitefly populations should be prevented from building up in large numbers in spring melons in recently harvested fields, or field to be harvested in the next week or so.

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In surveying melon crops for cucurbit yellow stunting disorder virus (CYSDV) this spring, it was readily apparent that a large proportion of the spring melon acreage throughout the area was grown near cotton.

In fact, UA surveys suggest that on an area-wide basis almost 75 percent of the melon acreage this spring were grown adjacent to or within one-half mile of cotton.

Although whitefly numbers have been relatively light thus far, increased whitefly numbers have been observed over the last week in cotton, coinciding with higher temperatures and area-wide melon harvests.

Proper sanitation in spring melons is critical for preventing unnecessary whitefly buildups in cotton. It is highly recommended that melon growers quickly destroy plant residue as soon as possible following harvest.

A delay in disking under melon fields following harvest can provide a large source of adult whiteflies which can readily disperse into cotton, especially when the insects do not need to fly very far. These whiteflies may also move into nearby weeds many of which (e.g., common mallow and silverleaf nightshade) are hosts for CYSDV.

Another source of whiteflies and CYSDV during July and August can be volunteer melons in fields where spring melons were previously grown. These plants also potentially extend the host acquisition transmission period for CYSDV. This may be important since CYSDV incidence in spring melons, albeit at non-economic levels, was quite evident this year.

Our experience to date suggests that the incidence of CYSDV in fall melons is generally much higher in fall plantings growing in proximity to where melons were produced the previous spring.

For more information on sanitation practices see Whitefly Management on Desert Vegetable and Melons.

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 “Remember, when in doubt - scout.”

Contact Palumbo: (928) 782-3836 or [email protected].

Soil solarization

By Mike Matheron, UA Extension Plant Pathologist

With summer officially here, constant triple-digit daytime temperatures will be the norm until at least the beginning of autumn.

Summer is the perfect time for soil solarization. The solarization of soil is accomplished by covering moist soil with clear plastic, allowing the sun’s energy to heat the soil over a period of time.

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 serves to conserve soil moisture and retard heat loss.

In field solarization trials conducted a few years ago in Yuma, the average temperature of soil was 113 degrees F. at a depth of two inches during a one-month summer solarization period, compared to 102 degrees for 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, disease incidence in a subsequent planting of lettuce was reduced from 91 percent to 42 percent, compared to disease levels in non-solarized plots.

Soil solarization, like any other cultural practice, has its benefits as well as drawbacks.

Documented benefits include significant population reductions of different soil-borne plant pathogens plus viable weed seeds. The drawbacks include the cost of buying, laying, maintaining, and removing the plastic film.

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Contact Matheron: (928) 726-6856 or [email protected].

FIFRA pesticide registrations

By Barry Tickes, UA area agriculture agent

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was first passed by Congress in 1947. The law required all pesticides sold in the U.S. be registered by the Environmental Protection Act (EPA). The law focused on protecting consumers from ineffective products and did not regulate pesticide use.

FIFRA was rewritten in 1972 and mandates that the EPA regulate product use to protect human health and the environment. The EPA can also approve the use of unregistered pesticides to address emergencies or special local needs.

There are three basic types of registrations defined under sections of FIFRA:

Section 3 - Federal Registration

This registration is for product use on labeled sites throughout the U.S. Approved products have passed a complete EPA review and met all registration requirements. States can apply for certain restrictions within the state.

Section 24(c) - Special Local Need (SLN)

This registration allows states to register products already with federal registrations to use the product on additional sites or for other uses to address special local needs.

There are two types of SLN’s: first, the first party SLN where the applicant is the registrant of the product; and second, a third-party SLN where the applicant is someone other than the registrant, including a grower, PCA, university, and others.

Section 18 - Emergency Exemption

This registration allows states to approve the use of un-registered products for emergency pest conditions in a specific region for a limited time. Other options are normally not available. It is rare to obtain this type of registration for weeds present for many years.

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Contact Tickes: (928) 580-9902 or [email protected].

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