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University of Arizona
March 2nd 2014 Vegetable IPM Updates
Insect Management
Weed Science
Some Videos to Check Out
Insect Management:

Management Guidelines for Whiteflies and CYSDV on Fall Melons

Growers are beginning to prepare local fields for fall melons, and with that comes the threat of cucurbit yellow stunting disorder virus (CYSDV). The virus was first identified in desert melons in the fall of 2006 where widespread infection on cantaloupes, honeydews and other melons cost growers a significant portion of their crops. Without question, yields and quality in desert melon crops can be seriously affected by CYSDV infection. Additionally, melon pest management has been affected by CYSDV as insecticide usage on fall melons has increased significantly since 2006. Over the past six years we have been studying the virus and trying to understand its epidemiology and impact on fall melon production. In addition, we continue to develop new information on control of the vector of CYSDV (Bemisia whitefly adults). Whitefly numbers this spring and summer have been very heavy and the incidence of CYSDV on spring melons was higher than I’ve ever observed it. However, how this translates into virus incidence this fall is unknown, but I would anticipate the risk from CYSDV to be as high as previous years. 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 melons were produced the previous spring are at a high 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 the status of CYSDV in Yuma County and guidelines for whitefly/CYSDV management visit Management of Whiteflies and CYSDV on Fall Melons.
Whitefly Adult Sampling
Remember: "When in Doubt...Scout"

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Summer Preplant Soil Flooding as a Management Tool for Sclerotinia Lettuce Drop

Lettuce disease management is probably the last thing on a Pest Control Advisor’s or grower’s mind as we now enter the hottest part of the year in the desert southwest region of Arizona, where the mean daily high/low temperature is now 108/83°F. However, this is the perfect time to perform preplant soil flooding in fields that had high levels of Sclerotinia drop this past season. You might wonder how a soil flooding treatment in the summer can help manage a disease that will not be a problem for several more months. 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 of these sclerotia will 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 virtually all 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 a 3-week period of flooding in the summer destroyed virtually all sclerotia of S. minor and S. sclerotiorum present in soil. Some growers in the Yuma area have used this soil treatment technique to successfully manage Sclerotinia lettuce drop in fields chronically affected by this disease.
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Weed Science:

Nutsedge Control with EPTC(Eptam) and Summer Fallow

Nutsedge is one of the most difficult to control weeds in Arizona and worldwide. It is a perennial that spreads vegetatively with below ground tubers that can stay viable for many years. Both yellow and purple nutsedge are common throughout Arizona. Most of it is purple which is the more difficult to control of the two. There are few herbicides that will completely control nutsedge and it is so prolific that even fairly high levels of control last only one season. Most herbicides need to be used for several consecutive years to keep this weed in check.

When nutsedge infestations get worse every year it can become beneficial to combine summer fallow with chemical treatment to break the cycle and get the problem under control. One of the most effective and economical treatments for nutsedge control is Eptam (EPTC) combined with summer fallow. This technique can be highly effective but it can also completely fail if proper application and cultural practices are not followed. It was developed 25 years ago but is still often misunderstood. The following six principals are important for this technique to be effective:

1) Both above ground shoots and below ground tubers must be destroyed. Emerged shoots will provide nutrients for the production of new below ground tubers. Viable below ground tubers will produce new rhizomes, basal bulbs and above ground shoots. Tillage and some herbicides such as glyphosate can be used to destroy above ground shoots. The Eptam fallow treatment will destroy rhizomes as they attempt to reach the surface.

2) Eptam is one of the most volatile herbicides available. It is lost in several ways including microbiological and photochemical decomposition but the most common means of losing EPTC in the irrigated southwest is by contact with water. It volatizes from irrigation water, off of wet soil and is leached deep into the soil. It should be incorporated into dry soil where it will remain active for a much longer period of time. It should not be irrigated after application unless the objective is to move it down to contact deep tubers or to remove it in preparation for the planting of a susceptible crop.

Red sprangletop is, in general, a lighter green color and has a finer seed head than does Mexican sprangletop which is darker green or gray and has a visibly coarser seedhead. Both form clumps or crowns that often survive through the winter months. Both are fairly tolerant to Poast (sethoxydim) and Fusilade (fluaziflop) but are controlled with high rates of Select (clethodim).

3) Eptam works on those parts of the nutsedge plant that are trying to grow (rhizomes and shoots). It works best on stressed plants but will have no effect on nutlets that are dormant. Enough moisture should be made available to stimulate nutsedge growth but under stressed conditions. An irrigation may be necessary. Once the top 6 inches is dry the Eptam should be applied and incorporated.

4) A chemical tarp is created with the surface application of Eptam that will prevent shoots and rhizomes from reaching the surface. The surface should, therefore, be left as smooth as possible. Any untreated areas or breaks in the surface from implements, wheels or even footprints will allow shoots to emerge.

5) Eptam should not be applied too early (April or May) because of possible degradation prior to the period of rapid nutsedge growth or too late (August or September) because of decreasing growth and potential injury to fall planted crops.

6) To avoid injury to following crops, irrigate at least 30 days prior to planting. The Eptam label specifies "Do not plant cotton or crops not listed on the Eptam label for 90 days after application."

Real IPM
(Photo by Barry Tickes)
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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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