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March 2nd 2014 Vegetable IPM Updates
Insect Management
Weed Science
Insect Management:

Management Guidelines for CYSDV on Fall Melons

Planting of fall melons is rapidly approaching and as growers begin to prepare local fields for fall planting they should be considering the threat of cucurbit yellow stunting disorder virus (CYSDV). This whitefly transmitted crinivirus was first identified in desert melons in the fall of 2006 where widespread infection on cantaloupes, honeydews and other melons occurred. CYSDV can cause significant losses in melon fruit yield and quality, and without question, desert melon crops have been seriously affected by this virus. Melon IPM has also been impacted by CYSDV where insecticide usage on fall melons has increased significantly. Over the past ten years we have been studying the epidemiology of CYSDV and trying to understand the complex relationships between the virus, vector and our local cropping system. Our ultimate goal is to develop practical approaches for reducing CYSDV impact on fall melon production. In addition, we continue to develop new information on chemical control of the whitefly vector (Bemisia whitefly adults). Last fall, whitefly populations were light and CYSDV incidence on fall melons was at an all-time low. Thus far, whitefly numbers this spring and summer have been relatively light compared to previous years and the incidence of CYSDV was low on spring melons. How the low numbers translate into virus incidence on the fall melon crop is unknown. However, our experience suggests that growers should anticipate CYSDV to be present. Further, given the aggressive management programs that PCAs and growers are now using, it will be interesting to see how CYSDV impacts melon production this fall. Our research to date suggests that fall melons produced near cotton or near areas where spring melons were recently produced are at the highest risk of infection. When possible, growers should attempt to isolate fall plantings as far away as possible from these sources of whiteflies and CYSDV. Growers forced to plant fall melons near these crops should be vigilant in minimizing adult whitefly infestation levels with insecticides during pre-bloom growth stages. To view a summary of the status of CYSDV in Yuma County and guidelines for management visit 2016 Guidelines for Whitefly and CYSDV Management on Melons.


Name this Insect Pest. - Swede Midge
Cartoonist: Juan Pena
Hey John, did you paint your truck? No Bill . . . it’s the whitefly!

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

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Summer Soil Flooding as a Management Tool for Sclerotinia Lettuce Drop

We are now in the hottest part of the year in the desert southwest region of Arizona, with respective average high and low temperatures of 108 and 83°F. Lettuce disease management is probably the last thing on a Pest Control Advisor’s or grower’s mind at this time. However, this is the perfect time to perform preplant soil flooding in fields that had high levels of Sclerotinia drop this past season. How can a soil flooding treatment in the summer help manage a disease that will not be a problem for several more months in a yet to be planted lettuce crop? The two fungi that cause lettuce drop, Sclerotinia minor and Sclerotinia sclerotiorum, carry over in fields between crops of lettuce as small black structures called sclerotia. These fungal propagules function like seeds, remaining dormant until they germinate in cool moist soil and infect lettuce plants. Many sclerotia decay naturally over time; however, sufficient numbers can remain in a field after one or more years to cause lettuce drop when a planting is established. If sclerotia in a field could be destroyed, then this field would no longer be a source of the Sclerotinia lettuce drop pathogens. This is where summer preplant soil flooding comes in. Past research conducted at The University of Arizona Yuma Agricultural Center demonstrated that virtually all sclerotia of S. minor and S. sclerotiorum present in soil were not able to germinate after a 3-week period of flooding in the summer. This soil treatment technique has been used successfully by growers in the Yuma area to successfully manage Sclerotinia lettuce drop in fields chronically affected by this disease.

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Weed Science:

Time Required After Herbicide Application Before Lettuce Can Be Planted

The time required before lettuce can safely be planted after herbicides have been applied to a previous crop is dependent upon several variables and can difficult to predict. It can vary from year to year and field to field depending on soil type, stress, irrigation technique and schedule, rate, climatic conditions and several other variables. A general guideline is needed, however, to base management decisions on. The following table is intended to be a general guideline and if all else fails, read and follow the label.

VIPM_Update_Vol_7_Num_15_004.png “Soil Temps Yuma AZ”

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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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