New Insecticide Chemistry on Desert Produce and Melons
Over the past 20 years, there has been an unprecedented development of insecticide chemistry that has had a major impact on how PCAs manage insects on leafy vegetables and melons. Among these were several breakthrough chemistries including the neonicotinoids, spinosyns, ketoenols and diamides. Without question these products (along with other recently registered compounds) are more effective and safer to use than compounds used prior to 1993. It appears that the AgriChemical Industry is beginning a new cycle of insecticide discovery and development where several new products are nearing registration. In 2014, it is anticipated that several new insecticide products will be available for management of the key pest found on desert crops. Closer (Sulfoxaflor) is currently registered for use in leafy vegetables and melons in Arizona and should have an excellent fit for aphid management in leafy vegetables. Although it has a similar target site as the neonicotinoid chemistry, it is not considered a neonicotinoid by IRAC because of differences in how insects metabolize the toxin. Rather, it is classified as a sulfoximine and the first of the chemical class to be registered. Exirel/Verimark (Cyazypyr) are anticipated to be registered in Arizona/California in early 2014. Cyazypyr is not a new chemistry, but rather a 2nd generation Anthanilic diamide. What sets Cyazypyr apart from the other diamides is its unique cross-spectrum activity against major chewing and sucking pests via soil systemic or foliar applications. Two other compounds, Sivanto (flupyradifurone) and Torac (tolfenpyrad) are anticipated to be available in late 2014-early 2015. Sivanto, like Closer, is not a neonicotinoid, but rather is considered a Butenolide. It has good activity against whiteflies as both a foliar spray and as a soil-applied systemic treatment. As a soil systemic in fall melons, it has shown to be very effective against adult whitefly and CYSDV suppression similar to Venom. Finally, Torac is a pyrazole; a mitochondrial complex I electron transport inhibitor. In essence, it is a metabolic toxin that inhibits energy metabolism when the insect comes in contact with the compound. It has shown good thrips activity when used in combination with Radiant or Lannate, and may be an alternative to pyrethroids in tank mixtures. More detailed information on these compounds can be found in the following publications: New Insecticides for Desert Produce and Melons.
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%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches 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. 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.
Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.
Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.
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. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any 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:
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
