With fall produce now underway bagrada bugs have begun to show up on direct seeded and transplanted cole crops. Reports of bagrada in local cole crops are beginning to trickle in from PCAs and so far, the pressure does not appear to be as heavy as we’ve seen in the past few years. Populations of bagrada bugs at the Yuma Ag Center however, are as heavy as ever and are quickly causing damage to untreated broccoli plots. Based on research conducted over the past four growing seasons, peak abundance of bagrada bug has occurred from late September to early October. So, what should a PCA expect for this season? Can’t say for sure, but don’t be complacent just because you’re not finding a lot of bagrada adults on your first few fields. It would be wise to assume they will eventually show up in some intensity in some of your acreage, and you should prepare for them accordingly. Monitoring for bagrada at stand establishment should focus on fresh feeding signs on new plant tissue, and adults later in the day when they are most active. Research and anecdotal observations in fields conducted over the past 2 years suggests that direct-seeded and transplanted crops are susceptible to bagrada bug infestations during stand establishment and up to the 6 leaf stage. Furthermore, results suggests that it doesn’t take a large number of bagrada adults to cause significant stand losses or crop injury. In untreated plots, we have consistently observed significant damage (15-20% blind plants) to direct seeded plants during the first 7 days after emergence (cotyledon to 1-leaf Stage) with only finding an average of 1 bagrada adult / 6 row ft. If you readily find fresh feeding signs and/or adults during stand establishment, control should be initiated immediately. This can include chemigation or aerial applications with pyrethroids. Contact insecticides (such as pyrethroids, Lannate, and Lorsban) should be used once stands are lined out and pipe is pulled. After stands are established and plant size increases up to the 2 leaf stage, or on tagged transplants, consider alternating to dinotefuron (Venom/Scorpion) to protect plants from bagrada feeding. This neonicotinoid will also provide knockdown of adult whiteflies and nymphs. More information on bagrada bug management on fall cole crops can be found in these Veg Update briefs: Bagrada Bug Management Tips for the Low Desert and Knockdown and Residual Control of Bagrada Bug With Foliar Insecticides in Broccoli: 2013 Efficacy Report.
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 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.
Area wide Insect Trapping Network (November 13, 2024)
Results of pheromone and sticky trap catches can be viewed here.
Corn earworm:CEW moth counts down in most traps over the last 2 weeks; about average for early October
Beet armyworm: Moth Trap counts increased in several areas last week and appear to remain active in cooler temps, and well above average for early November.
Cabbage looper: Cabbage counts peaked last week in all locations, about average for this time of the season.
Diamondback moth: Adult activity declined in the past 2 weeks ago, Below average for this time of season.
Whitefly: Adult movement continues with the termination of melon harvests; overall about average for early November.
Thrips: Thrips adult movement still down, overall activity below average.
Aphids:Winged aphids movement peaked in the north Yuma and Gila Valleys; above average for early November.
Leafminers: Adult activity down in most locations, below average for this time of season.
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
