With the desert produce season almost completed and the spring melon season beginning, now is a good time to review the insecticide chemistries commonly used in your insect management programs. This is an important consideration as you make the transition from winter produce to alfalfa, spring melons and summer cotton where many of the same insecticide products are available in all these commodities. Sustaining long-term insecticide efficacy that provides cost-effective crop protection requires a conscious effort on the part of PCAs and growers to use insecticides responsibly. Over the past 30 years, Agrochemical Manufacturers have developed and brought to market over 20 new classes of chemistry that are highly effective, selective, and significantly safer than their chemical predecessors. These include the neonicotinoids, spinosyns, tetramic acid derivatives and anthranilic diamides to name a few. Most recently, we have seen new feeding disruptor products, PQZ (pyrifluquinazon) and Versys/Sefina (afidopyropen) being applied to fall melons for virus management and in winter vegetables for aphid management. Although, the development of new insecticide chemistries has been a bit slow over the past few years, we’re now seeing industry beginning to develop several new experimental insecticides for desert crops. You’ll be pleased to know that several compounds are being targeted for western flower thrips. Of course, at best many of these products are a few years away from registration. But this is great news as many of the older products are slowly being phased out of the marketplace. It was just a couple of years ago that flubendiamide (Belt, Vetica) was removed from the market, chlorpyrifos (Lorsban) is now gone, and EPA is currently proposing label changes to the neonicotinoids which could impact their use on many important crops. Thus, it is imperative to sustain the efficacy of the newer insecticide tools currently available and Insecticide Resistance Management (IRM) is now more important than ever. The most fundamental approach to IRM is to minimize the selection of resistance by a pest to any one type of insecticide chemistry. The key to sustaining insecticide susceptibility is to avoid exposure of successive generations of an insect pest population to the same MOA. Historically, alternating, or rotating compounds with different modes of action (MOA) each time you spray has provided sustainable and effective IRM in our desert cropping systems. When it is comes to IRM; “rotation, rotation, rotation”. In other words, never expose a generation of insects to the same MOA more than twice. The Insecticide Resistance Action Committee (IRAC), a coordinated crop protection industry group, was formed to develop guidelines to delay or prevent resistance. Using their most recent information we have produced a brief publication which provides the latest local information on the modes of actions, routes of activity and pest spectrum for important insecticide chemistries used in desert produce and melon crops - see the attached Insecticide Modes of Action on Desert Produce Crops. This classification list will provide you with an additional set of guidelines for the selection of insecticides that can be used in desert IPM programs.
Bindu Poudel, Martin Porchas, Jason Furr and Neeraja Singh Yuma Agricultural Center, University of Arizona, Yuma, AZ
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 15, 2022 on 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.
Month
Max Air temp0F
Min air temp0F
Avg air temp0F
Max Relative humidity
Min relative humidity
Rainfall (inches)
March 2022
81
48
65
66
12
0
April 2022
88
54
72
66
11
0
May 2022
95
60
78
64
11
0
June 2022
104
69
88
68
13
0
Spray treatments were done on 5-18-2022, 5-26-2022, 6-02-2022 and 6-10-22. Powdery mildew was first seen on 5/24/22.
Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-16-2022 an d 6-17-2022 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. Phytotoxicity symptoms were not noted for any treatments in this trial.
Controlling Disease and Weeds with Band-Steam – Yuma Trials Show Good Promise
In previous articles (Vol. 11 (13), Vol. 11 (20), Vol. 11(24)), I’ve discussed using band-steam to control plant diseases and weeds. Band-steaming is where steam is used to heat narrow strips of soil to temperature levels sufficient to kill soilborne pathogens and weed seed (>140 °F for > 20 minutes). The concept is showing good promise. This past season, three trials were conducted examining the efficacy of using steam for disease and weed control in Yuma, AZ. In the studies, steam was applied in a 4-inch-wide by 2-inch-deep band of soil centered on the seedline using a prototype band-steam applicator (Fig.1). The band-steam applicator is principally comprised of a 35 BHP steam generator mounted on top of an elongated bed shaper. The apparatus applies steam via shank injection and from cone shaped ports on top of the bed shaper.
Trial results were very encouraging as the prototype applicator was able to raise soil temperatures to target levels (140°F for >20 minutes) at viable travels speeds of 0.75 mph. Steam provided better than 80% weed control and significantly lowered hand weeding time by more than 2 hours per acre (Table 1). Results also showed that Fusarium colony forming units (CFU) were reduced from 2,600 in the control to 155 in the 0.75 mph and 53 in the 0.5 mph treatments, respectively (a more than 15-fold reduction). A significant difference in Fusarium wilt of lettuce disease incidence was not found, however disease infection at the field site was low (< 2%) and differences were not expected. At 0.5 mph, fuel costs were calculated to be $238/acre which was considered reasonable and consistent with the values reported by Fennimore et al. (2014).
An unexpected finding was that plants in steam treated plots appeared to be healthier and more vigorous than untreated plots (Fig. 2). This trial is still in progress and it will be interesting to see if this improved early growth translates into increases in crop yield.
In summary, early trial results are showing good promise for use of band-steam as a non-herbicidal method of pest control. We plan on conducting further trials in this multi-year study. If you are interested in evaluating the device on your farm and being part of the study please contact me. We are particularly interested in fields with a known history of Fusarium wilt of lettuce and/or Sclerotinia lettuce drop that will be planted to iceberg or romaine lettuce.
As always, if you are interested in seeing the machine operate or would like more information, please feel free to contact me.
Acknowledgements
This work is supported by Crop Protection and Pest Management grant no. 2017-70006-27273/project accession no. 1014065 from the USDA National Institute of Food and Agriculture, the Arizona Specialty Crop Block Grant Program and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
A special thank you is extended to Mellon Farms for allowing us to conduct this research on their farm.
References
Fennimore, S.A., Martin, F.N., Miller, T.C., Broome, J.C., Dorn, N. and Greene, I. 2014. Evaluation of a mobile steam applicator for soil disinfestation in California strawberry. HortScience 49(12):1542-1549.
Click link below or picture to see the band-steam and co-product applicator in action!
Carryover of Vegetable Herbicides to Wheat Grown in Rotation
Almost all the herbicides used on lettuce, cole crops and melons have restrictions on how soon wheat can be planted in rotation after they have been used. Experience has demonstrated, however, that safe intervals can vary considerably based upon many factors and are almost always much longer than they need to be. The most important factors are rate applied, irrigation practices and tillage. For example, when Kerb used to be banded at 2 to 4 lbs. per acre after planting and incorporated with furrow irrigation, it was common to see treated strips across wheat fields which followed. This is uncommon now that lower rates are Chemigated. We still see some Balan injury at ends of fields or in overlaps especially when sudan is planted. Wheat it not very sensitive to Prefar and carryover injury is uncommon.
