Hi, I’m Chris, and I’m thrilled to be stepping into the role of extension associate for plant pathology through The University of Arizona Cooperative Extension in Yuma County. I recently earned my Ph.D. in plant pathology from Purdue University in Indiana where my research focused on soybean seedling disease caused by Fusarium and Pythium. There, I discovered and characterized some of the first genetic resources available for improving innate host resistance and genetic control to two major pathogens causing this disease in soybean across the Midwest.
I was originally born and raised in Phoenix, so coming back to Arizona and getting the chance to apply my education while helping the community I was shaped by is a dream come true. I have a passion for plant disease research, especially when it comes to exploring how plant-pathogen interactions and genetics can be used to develop practical, empirically based disease control strategies. Let’s face it, fungicide resistance continues to emerge, yesterday’s resistant varieties grow more vulnerable every season, and the battle against plant pathogens in our fields is ongoing. But I firmly believe that when the enemy evolves, so can we.
To that end I am proud to be establishing my research program in Yuma where I will remain dedicated to improving the agricultural community’s disease management options and tackling crop health challenges. I am based out of the Yuma Agricultural Center and will continue to run the plant health diagnostic clinic located there.
Please drop off or send disease samples for diagnosis to:
Yuma Plant Health Clinic
6425 W 8th Street
Yuma, AZ 85364
If you are shipping samples, please remember to include the USDA APHIS permit for moving plant samples.
You can contact me at:
Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
Office: 928-782-5879
In a prior article (Vol. 14, Issue 19), I discussed the initiation of a fall 2023 trial examining the use of band steam for controlling Fusarium wilt of lettuce. Again, the premise behind the research is to use steam heat to raise soil temperatures to levels sufficient to kill soilborne pathogens. For Fusarium oxysporum f. sp. lactucae (FOL) the pathogen which causes Fusarium wilt of lettuce, the required temperature for control is generally taken to be > 140°F for 20 minutes. Soil solarization, where clear plastic is placed over the crop bed during the summer, exploits this concept. The technique raises soil surface temperatures to 150-155˚F, effectively killing the pathogen and reducing FOL disease incidence by 45-98% (Matheron and Porchas, 2010).
In our trials, we used steam heat to raise soil temperatures. Steam was delivered by a 35 BHP steam generator mounted on a custom designed elongated bed shaper (Fig. 1). As the device traveled through the field, steam was injected into the soil in narrow bands centered on the seedline. Four band sizes ranging from 4” wide x 2” deep to 6” wide by 4” deep were examined to determine the optimal width and depth of the band of soil that needs to be disinfested to prevent disease. Travel speed was 0.2 mph and soil temperatures were raised to about 190°F. After cooling (< ½ a day), the crop (FOL susceptible iceberg lettuce variety El Guapo) was planted into the disinfested soil.
Preliminary results are very encouraging (Table 1, Fig. 2). The percentage of diseased plants was roughly four times lower in steam treated plots as compared to the untreated plots at the first evaluation date, 39 days after planting (DAP) (19% vs ~ 5%), and about two times lower at the second evaluation date, 60 DAP (32% vs ~17%). These results are consistent with our previous studies which showed that in soils that have moderate FOL inoculum levels, steam treatment reduced disease incidence at maturity by more than 40%. A surprising result was that the width and depth of soil steam treatment did not have a significant effect on disease incidence. A logical explanation for this result could not be formulated as one would expect disease incidence to be reduced if a larger volume of soil is disinfested.
Stay tuned for final trial results!
On a slightly different note, if you are interested in seeing the plots, I will be at the field site Field Day this Wednesday, November 30th from 8:00 am-12:00 pm. The location is the JV Farms Fusarium Trial site, located off of Hwy 95 and Ave 5E (32.6920898, -114.5395051).
Hope to see you there!
References
Matheron, M. E., & Porchas, M. 2010. Evaluation of soil solarization and flooding as management tools for Fusarium wilt of lettuce. Plant Dis. 94:1323-1328.
Acknowledgements
This project is sponsored by USDA-NIFA, the Arizona Specialty Crop Block Grant Program and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support.
A special thank you is extended to Fatima Corona, Pablo Delgado, Chad VanMatre, Matt McGuire and JV Farms for their generous assistance and allowing us to conduct this research on their farm.
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Table 1. Effect of band-steam on Fusarium wilt of lettuce disease incidence in a trial conducted with iceberg lettuce in Yuma, AZ in 2023. |
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----------------- Disease Incidence, % ----------------- |
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Treatment1 |
39 DAP2 |
60 DAP |
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Band-steam: 4”x2” |
2.4 |
17.5 |
|
Band-steam: 4”x4” |
5.0 |
15.0 |
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Band-steam: 6”x2” |
8.5 |
22.4 |
|
Band-steam: 6”x4” |
3.8 |
16.4 |
|
Untreated |
19.2 |
32.1 |
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1Dimensions for band-steam treatments indicate the width and depth of the band of soil that was treated with steam. |
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Fig. 1. Band-steam applicator principally comprising a 35 BHP steam generator
mounted on a bed-shaper applicator sled. The device injects steam into the soil
as beds are formed.
Fig. 2. Fusarium wilt of lettuce control with band-steam in iceberg
lettuce. Steam was applied in a narrow band (4” wide x 4” deep)
centered on the seedline prior to planting. After the soil cooled (< 1/2
day), the crop was planted into the disinfested soil.
In the absence of Dacthal (DCPA) growers are looking for different herbicide options for Broccoli and Onions.
The following is data from a broccoli trial done in 2010 by Tickes/Pena, which compares Prowl, Goal Tender, Prefar, Treflan, Devrinol and Dacthal at different application timings. Plots were visually evaluated for weed control of Goosefoot (Chenopodium murale), Malva (Malva parviflora), and Yellow Sweet Clover (Melilotus oficinalis). The label recommendations for Devrinol are “Use the lower rate on light soil (coarse textured-sandy), and the higher rate on heavy soil (fine textured-clay)”. The rate goes from 1-2 lbs on the DF-XT 50% formulation.
We hope this information is useful in our decision making for broccoli herbicide programs.
This time of year, John would often highlight Lepidopteran pests in the field and remind us of the importance of rotating insecticide modes of action. With worm pressure present in local crops, it’s a good time to revisit resistance management practices and ensure we’re protecting the effectiveness of these tools for seasons to come. For detailed guidelines, see Insecticide Resistance Management for Beet Armyworm, Cabbage Looper, and Diamondback Moth in Desert Produce Crops .
VegIPM Update Vol. 16, Num. 20
Oct. 1, 2025
Results of pheromone and sticky trap catches below!!
Corn earworm: CEW moth counts declined across all traps from last collection; average for this time of year.
Beet armyworm: BAW moth increased over the last two weeks; below average for this early produce season.
Cabbage looper: Cabbage looper counts increased in the last two collections; below average for mid-late September.
Diamondback moth: a few DBM moths were caught in the traps; consistent with previous years.
Whitefly: Adult movement decreased in most locations over the last two weeks, about average for this time of year.
Thrips: Thrips adult activity increased over the last two collections, typical for late September.
Aphids: Aphid movement absent so far; anticipate activity to pick up when winds begin blowing from N-NW.
Leafminers: Adult activity increased over the last two weeks, about average for this time of year.
