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


Invasive Species Workshop

We will be holding an Invasive Species Workshop at the Yuma Ag Center on July 24 beginning at noon with a yummy lunch, and followed up with speakers from the University of Florida and Georgia who will inform us on a couple of potential invasive insect pests that we should be on the lookout for. It should be very informative meeting. Invasive species are nothing new to the Yuma vegetable industry. In fact, in the past 30 years a number of exotic insect pests have become established in Yuma beginning with the american serpentine leafminer, Liriomyza trifolii . As some may recall, damaging levels of this pest were first found infesting lettuce in 1987. A section 18 was obtained two years later for Agri-Mek and the problem soon subsided. That was followed by the sweet potato whitefly, Bemisia tabaci-biotype B in 1991-1992. Of course, the Section 18 registration of Admire, and subsequent registrations of a variety of new chemistries (IGRs) resulted in area-wide suppression of whitefly populations and since have allowed the industry to effectively manage the pest. Then a few years later (1999) the lettuce aphid showed up in the Yuma Valley, a transplant from Europe, where it had first been found in Salinas the previous year. Along with it came the foxglove aphid which was not previously thought to occur in Arizona. Both aphid species are found sporadically infesting lettuce throughout the area every season. With the registration of Movento (2008) growers can now effectively manage these aphids in leafy vegetables. Finally in the past few years we’ve had two important invasive species invade the desert. The first was a whitefly-transmitted virus, cucurbit yellow stunting disorder virus (CYSDV), on melon crops in 2006, and more recently, the bagrada bug on cole crops in 2010. Both crept into the desert unexpectedly and are causing economic losses to our local vegetable industry. Hopefully, as we continue to learn more about these 2 important pests, cost-effective management programs will be developed. So, I encourage you to attend the Invasive Species Workshop on the 24th and learn about a couple of potential invaders.
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Winged Lactucae Aphid
Remember: "When in Doubt...Scout"

Click picture to listen to John’s update video link

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

 

Diseases:


Soil Solarization

It is now officially summer and constant triple-digit daytime temperatures will be the norm until at least the beginning of autumn in southwest Arizona. Although we may not personally appreciate the summer heat, it is the perfect time for soil solarization. Briefly, solarization of soil is accomplished by covering moist soil with clear plastic, then 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 as well as weed seeds. The plastic serves to both 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°F at a depth of 2 inches during a 1-month summer solarization period, compared to 102°F for nonsolarized soil. The average peak afternoon temperature in solarized soil during these trials was 128°F. In these yearly solarization trials, conducted in soil naturally infested with the lettuce Fusarium wilt pathogen, disease incidence in a subsequent planting of lettuce was reduced from 42 to 91%, depending on the trial, compared to disease levels in nonsolarized 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 as well as numbers of viable weed seeds. Drawbacks include the cost of buying, laying, maintaining, and removing the plastic film.
Click picture to listen to Mike's update video link
To contact Mike Matheron go to: matheron@ag.arizona.edu.

 

Weed Science:


Distinguishing Characteristics of Similar Summer Annual Grasses

Two closely related but different species of several summer annual grasses are common in the low deserts. In general, these are all easy to distinguish from each other in the field and they respond similarly to herbicides. Some of these and their distinguishing characteristics are:

• Watergrass (Echinochloa colonum) and Barnyardgrass (Echinochloa crusgalli)

These are very similar but watergrass has purple bands or chevrons on the leaves and barnyardgrass often has awns or bristles at the end of the spikelets. Both respond the same to herbicides.

• Red Sprangletop (Leptochloa filiformis) and Mexican Sprangletop (Leptochloa uninervia)

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).

• Field Sandbur (Cenchrus pauciflorus) and Southern Sandbur (Cenchrus echinatus)

Both of these equally miserable weeds are only found in sandy soils and fairly easy to distinguish. Field sandbur has thinner, gray colored leaves and yellowish burs that are longer than broad. Southern sandbur has darker and broader leaves and fatter red colored burs. Southern sandbur has a more compact seed head with distinctly more burs than does southern sandbur. Both of these are fairly tolerant to Poast (sethoxydim), Select (clethodim) and Fusilade (fluaziflop).

• Southwestern Cupgrass (Eriochloa gracilis) and Prairie Cupgrass (Eriochloa contracta)

These similar grasses are fairly easy to distinguish in the field. Southwestern Cupgrass is one of the wider leafed grasses in the deserts. Prairie Cupgrass leaves are not as wide and are hairy. Southwestern is more branched than prairie and the ligule is shorter and less prominent. The branches are longer and fewer on prairie than on southwestern Cupgrass. Both respond the same to most herbicides.

• Green Foxtail (Setaria viridis) and Yellow Foxtail (Setaria glauca)

Both green and yellow foxtail typically form clumps, produce lots of seed and stand more upright than many other summer annual grasses. They are not difficult to distinguish in the field. Green has a darker greenish or brown seedhead compared to the yellow. The leaves of yellow are generally longer and have more bristles (5-20) per spikelet than green, which typically has 3 or less darker colored bristles. Both respond the same to most herbicides.

• Purple Nutgrass (Cyperus rotundus) and Yellow Nutgrass (Cyperus esculentus)

Right! These are not grasses. They are sedges which are much different. Sedges all have solid triangular stems. They are perennial and reproduce primarily by below ground tubers. Purple has bigger( 1/8” to 3/4” ) irregular shaped tubers that are connected by rhizomes and have an almond -like odor. Yellow are smaller pea size and round. They are not connected and don’t smell. Yellow is often taller and has pointed leaves while purple has blunt shaped leaves.

Real IPM
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(Photo by Barry Tickes)
Click picture to listen to Barry video link
To contact Barry Tickes go to: .

 

Check Out These Videos!
Links:

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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