Insecticide Pre-mixtures and Insect Management 2011
There are a number of insecticide pre-mixed products currently available for management of insect pests on desert vegetable and melon crops. These products offer growers and PCAs the convenience of having two different active ingredients in the same formulated product. Examples of pre-mixtures include Durivo, Vetica and Brigadier. These pre-mix products contain combinations of active ingredients that PCAs have been using for many years (e.g., thiamethoxam, bifenthrin), as well as active ingredients recently registered (e.g., chlorantraniliprole and flubendiamide). In some cases, the pre-mixed products are available at reduced prices relative to tank-mixing two individual products. However, it is important that users consider which active ingredients are included in the "in-can" mixtures, and at what rates these active ingredients are applied relative to the pre-mixed formulation. This is important. First, the rates used for the pre-mixture should be within the recommended rates of the individual active ingredients necessary to control a particular insect(s). This may force PCAs to use high rates of the pre-mixture in order to achieve adequate control of multiple pests. Traditionally, this has been achieved through tank-mixtures of 2 or more products, each at their recommended rates. Secondly, although the active ingredients found in these pre-mixes are of different chemical classes, one or both of these active ingredients may be the same as other products currently being used in the same field. PCAs should be careful not to inadvertently expose insect populations to the same chemical class (mode of action) by making repeated applications with products with the same mode of action. This is how insecticide resistance quickly develops. To avoid this, be aware of the active ingredients in all the products you apply. For example, the pre-mixtures Durivo, Voliam Xpress, Voliam Flexi, and Vetica all contain active ingredients with the same mode of action as Coragen and Synapse. More information on these pre-mixtures, their active ingredients and rate equivalencies can be found in the document: Insecticide Pre-Mixtures for AZ Vegetables and Melons.
2023-2024 Powdery Mildew of Lettuce Fungicide Trial
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%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on Nov 28, 2023 on double rows 12 in. apart on beds with 42 in. between bed centers. All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed, which contained two 25 ft rows of lettuce. Plants were thinned Jan 17, 2024 at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.
Month
Max Temp (°F)
Min Temp (°F)
Average Temp (°F)
Rainfall
November
80
51
65
0.08 in
December
71
44
57
0.82 in
January
68
42
54
1.14 in
February
73
47
59
0.50 in
Powdery mildew (caused by Golovinomyces cichoracearum) efficacy trial treatments were made on February 15,2024, February 23, 2024, March 4, 2024, and March 12, 2024and .Disease was first seen on February 26,2024. Disease rating was done on March 15, 2024. Disease severity was determined by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 0.5 = one to a few very small powdery mildew colonies on bottom leaves; 1 = powdery mildew present on bottom leaves of plant; 2 = powdery mildew present on bottom leaves and lower wrapper leaves; 3 = powdery mildew present on bottom leaves and all wrapper leaves; 4 = powdery mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = powdery mildew present on entire plant. These ratings were transformed to percentage of leaves infected values before being statistically analyzed. Yield loss due to rejected lettuce heads would likely begin to occur on plants with a powdery mildew rating above 2.0 (percentage of leaves infected value of 40).
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. The most effective fungicides were Rhyme, Merivon, Quintec, Cevya, Luna Sensation, Luna Experience, and Elisys.
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 counts remain low across all locations; average for this time of the season.
Beet armyworm:
Trap counts decreased in all locations, and below average for late-January.
Cabbage looper:
Cabbage looper trap counts remained low in all locations; below average for early February.
Diamondback moth:
Adult activity increased slightly in some locations, particularly fields where trap is adjacent to with nearby brassica seed crops. Overall, activity is below average for this time of year.
Whitefly:
Adult movement remained low in all locations consistent with previous seasons.
Thrips:
Thrips adult movement beginning to increase slightly in most locations. Activity a about average for mid-February.
Aphids:
Aphid movement increased in many locations, particularly in Yuma Valley. Trap captures about average for this time of year.
Leafminers:
Adult activity increased in most areas, below average for this time of season.
