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
It’s October and planting season is well underway. When planting lettuce, uniform seed spacing is critical for efficient, economical crop thinning. Due to their lack of precision, automated lettuce thinning machines cannot eliminate lettuce plants that are spaced closer than about 1 1/8” apart. These closely spaced plants, commonly referred to as “doubles”, must be carefully removed by hand which is time consuming and expensive.
Several years ago, we conducted trials examining the influence of planter travel speed on seed spacing uniformity (Siemens and Gayler, 2016). In the study, two types of planters - a vacuum planter (Stanhay 785 Singulaire) and a belt planter (Stanhay 870) were tested with pelleted lettuce seed at travel speeds of 1.0, 1.5, 2.0 and 2.5 mph at the Yuma Agricultural Center. Vacuum planter test results showed that the percentage of “difficult to thin” spacings, defined seeds spaced less than 1.1” apart, increased from about 5% to 10% as speed increased from 1.0 mph to 2.5 mph (Fig. 1). Concomitantly, the percentage of seeds “precisely placed” within 0.5” of the target location (i.e., 2.0 ± 0.5”) decreased from 70% to less than 45%, and the percentage of skips increased from 7% to 30%. Variability of seed spacing uniformity as measured by the coefficient of variation (COV) of seed spacings also increased.
Similar declines in planter performance were found with the belt planter (Fig. 2). As travel speed increased from 1.0 to 2.5 mph, the percentage of difficult to thin spacings increased from 2% to 10%, precise spacings decreased from 93% to 65% and skips increased from 2% to 8%.
For both planter types, there was a significant decline in performance as speed increased from 1.5 mph to 2.0 mph, a difference in speed of only 0.5 mph. These results suggest that it is prudent to check planter performance at the chosen operating speed prior to establishing an entire block to ensure that seed spacing uniformity, not just the number of seeds per foot, is acceptable.
In short, the study showed that planter travel speed had a significant effect on seed spacing uniformity and difficult to thin, close spacings - the higher the speed, the poorer the performance.
You may be asking what is the reason for the phenomenon observed? A logical explanation is that seeds are traveling at the speed of the planter when they are released and tend to “bounce and roll” in the direction of travel when they hit the soil surface. Thus, the higher the travel speed, the further seeds bounce and roll resulting in increased seed spacing variability.
References
Siemens, M.C., & Gayler, R.R. (2016). Improving seed spacing uniformity of precision vegetable planters. Appl. Eng. Agric., 32(5), 579-587
Fig. 1. Seeding performance of a vacuum vegetable planter sowing lettuce when
operated at four travel speeds.
Fig. 2. Seeding performance of a belt vegetable planter sowing lettuce when operated at
four travel speeds
It is reported that the herbicidal activities of Plant Growth Regulators (PGRs) were discovered in the 1940’s. Then, investigators in England and in the United States started their research on this type of herbicides1.
Some of these substances are hormones produced naturally by the plants and other are synthetically produced. Examples of naturally occurring growth regulators are gibberellins, auxin, cytokinin. Some stimulate stem elongation and cell elongation. One of the first synthetic selective herbicides developed is 2, 4-D (2,4-dichlorophenoxiacetic acid).
PGRs are used extensively for broadleaf weed control in grass crops in this region such as grain production, bermudagrass, alfalfa, cole crops, sugarbeet, forages, and turf grasses. These herbicides upset the natural balance of the hormones that controls cell division, cell enlargement, protein synthesis, and respiration. That is why this group of herbicides is sometimes called the “hormone herbicides”2. In our area growers are very careful using these products due to volatility with our summer temperatures and the problems caused to sensitive crops.
According to a report from Texas A&M “phenoxy growth regulator herbicides are reported to have the least plant activity and soil residual activity; the carboxylic acids generally have the most. Broadleaf crops and turf grasses should not be planted into soils recently treated with these herbicides because they severely inhibit seedling emergence”2.
Some PGRs:
|
Family |
Common Name |
Trade Name |
|
phenoxy |
2,4-D |
Pasture pro, others |
|
2,4-DB |
Butyrac |
|
|
MCPA |
Rhonox |
|
|
MCPP |
Several names |
|
|
benzoic acid |
dicamba |
Banvel |
|
carboxylic acid |
Picloram |
Tordon 22K |
|
Clopyralid |
Stinger |
|
|
triclopyr |
Remedy |
|
|
quinclorac |
Facet |
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.
