Next week the UA Vegetable IPM Team will be holding the 2017 Lettuce Insect, Disease and Weed Losses Workshop on Wednesday, April 12 beginning at 12:00 noon at the Yuma Agricultural Center (lunch is provided at no cost). Since 2004, we have annually surveyed PCAs and growers to document local pest activity and pesticide usage in Arizona lettuce through this interactive workshop. In my opinion, this is one of the more important meetings we hold each year. Not only do we gather your input on pest activity and pesticide use from this past produce season, but we also provide information on last year’s results and new information on vegetable IPM. This year we will discuss the light bagrada bug activity you experienced last fall and the local Diamondback moth outbreaks. The survey information provided by PCAs and growers during these workshops is very useful to the local produce industry. First, the data can be extremely helpful in addressing state and federal regulatory issues by providing “real world" information on insect pest status and insecticides usage. In the past data generated from the surveys has been used to support registrations of key insecticide products (i.e., Movento and Lannate) and is currently being used to support the re-registration of pyrethroids and imidacloprid. Secondly, from an academic perspective, the results of these surveys provide us with a historic record of pest occurrences and allows us to prioritize some of our research and educational activities. The insecticide usage data has also provided valuable support for many of the grant programs we request funding from. Finally, and perhaps most importantly for PCAs, it translates your efforts into economic terms for growers and shippers, and confirms the PCAs value to the lettuce industry by showing the importance of key pests and their cost-effective management in desert lettuce production. For example, survey results from the over the past 12 years show that on average, 1) costs associated with pest management fees have increased steadily where the cost of scouting and making management decisions by PCAs are well over $20/acre, 2) Leps, aphids and thrips are the most important economic pests in fall and spring lettuce, and 3) the use of older, broadly toxic insecticides (OP/Carbamates/Endosulfan) has dropped significantly, whereas use of the newer, softer reduced-risk chemistries (e.g., Radiant, imidacloprid, and diamides) continues to increase. Results from last year’s Crop loss surveys can be found in these two reports: 2015-16 Insecticide Usage on Desert Lettuce, 2015-16 and Insect Losses and Management on Desert Lettuce: 2004‐2016 For the most part PCAs already know this, but these surveys document this information for those less involved with the day-to-day activities of IPM in desert lettuce. Hopefully PCAs and growers see the value in this process and will join us next week. The agenda for the meeting can be found here: 2017 Lettuce Insect, Disease and Weed Losses Workshop. Will be quizzing the audience – correct answers get a UA Veg IPM cap. See you there!
In response to the recent outbreaks of Diamondback moth (DBM) , Plutella xylostella in Yuma, we have established a pheromone trap network designed to monitor the activity and movement of adult populations of DBM. PCAs have had difficulty controlling DBM in cabbage, broccoli and cauliflower since October. Traps have been placed in Roll, Wellton, Dome Valley, Gila Valley and Yuma Valley in locations where cole crops are presently being grown or in areas where infestations were known to occur this fall.
This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed. All irrigation water was supplied by sprinkler irrigation. Treatments were replicated four times in a randomized complete block design. Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed. Treatments were applied with a CO2backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.
Month
Max
Min
Average
Rainfall
January
68
42
54
1.14 in
February
73
47
59
0.50 in
March
77
50
63
0.31 in
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19 and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results. Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft2 areas within each of the four replicate plots per treatment. The number of spinach leaves in a 1-ft2 area of bed was approximately 144.
The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.
Controlling Fusarium Wilt of Lettuce Using Steam Heat – Trial Initiated
Earlier this week, we initiated a trial examining the use of band steam for controlling Fusarium wilt of lettuce. The premise behind this research is to use steam heat to raise soil temperatures to levels sufficient to kill soilborne pathogens. For Fusarium oxysporum f. sp. lactucae, 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 disease incidence by 45-98% (Matheron and Porchas, 2010).
In our trials, we are using steam heat to raise soil temperatures. Steam is delivered by a 35 BHP steam generator mounted on a custom designed elongated bed shaper (Fig. 1). Preliminary results were encouraging. The device was able to increase the temperature of the top 3” of soil to over 180°F at a travel speed of 0.5 mph as shown in this video of the machine in action (shown below). These temperatures exceed that of those known to control pathogens responsible for causing Fusarium wilt of lettuce (> 140°F for 20 minutes).
Stay tuned for final trial results and reports on the efficacy of using steam heat to control Fusarium wilt of lettuce.
If you are interested in evaluating the technique on your farm, please contact me. We are seeking additional sites with a known history of Fusarium wilt of lettuce disease incidence to test the efficacy and performance of the device.
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 Cory Mellon and Mellon Farms for allowing us to conduct this research on their farm.
Weeds are one of the most visible of all agricultural pests. They can’t move or hide and once established often stick up over the crop. Just one weed in a 10 acre field is annoying to look at. With insects and diseases, the damage is often more visible than the pest. That is not the case with weeds. A moderate weed infestation is approximately 10 weeds per square foot. If a herbicide produces 90% control, that leaves 1 weed per square foot or 43 weeds per acre. Without an untreated check, this can look like the herbicide failed! It is easy to leave an untreated spot in a field and it is well worth doing. Many applicators do so unintentionally because of skips, powerlines and other causes. They help determine crop injury and weed control. Here are some examples of what various levels of control looked like from one of our cole crop trials:
Corn earworm:
CEW moth increased in Tacna/Roll/Dome last week, and areawide about average for mid-October.
Beet armyworm:
Trap counts highest in Tacna, Wellton and Dome, but below average for October.
Cabbage looper:
Cabbage looper numbers increased in Tacna/Roll/Wellton but still below average.
Diamondback moth:
DBM moths are beginning to appear in traps in Yuma Valley, trending below average for early October.
Whitefly:
Adult movement increased in the past 2 weeks and above average for mid-October.
Thrips:
Thrips adult activity down over the past week, and trending below average in October.
Aphids:
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Can expect aphid flights to increase in the coming weeks.
Leafminers:
Adult activity increased significantly in Tacna associated with maturing melons. Trending above average for mid-October.
In response to the recent outbreaks of Diamondback moth (DBM) , Plutella xylostella in Yuma, we have established a pheromone trap network designed to monitor the activity and movement of adult populations of DBM. PCAs have had difficulty controlling DBM in cabbage, broccoli and cauliflower since October. Traps have been placed in Roll, Wellton, Dome Valley, Gila Valley and Yuma Valley in locations where cole crops are presently being grown or in areas where infestations were known to occur this fall.To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
