Beet Armyworm and Cabbage Loopers in Fall Produce 2012
Beet armyworms and cabbage loopers have been very active in desert crops over the past week or so and are historically the most important pests of produce during September and October. Worm pressure has been light the past few fall growing seasons, but this year’s populations overall appears to be above normal. Armyworms have been heavy on produce crops for a couple of weeks. At the Yuma Ag Center they are presently averaging more than 1 larvae per plant in untreated lettuce. Similarly, cabbage loopers were fairly abundant on our fall melons this year, and egg lays and small larvae are beginning to show up on all produce crops in fairly large numbers. Remember, temperatures drive larval development and adult activity, particularly when night time temps remain high (in the mid-70s or higher). The higher temperatures we’ve been experiencing the past week or so is ideal for worm development and moth activity. As long as the average temperature remains around 85°F, worms should be active at damaging levels. Fortunately, there are a number of very effective insecticides that can be applied as stand-alone foliar products that provide effective residual control of both of these lepidopterous species. Radiant, Proclaim, Intrepid, Avaunt and any one of the Diamide products (Coragen, Belt, Voliam Xpress and Vetica) can provide good knockdown and extended residual control of armyworms and loopers. Research trials have showed that these products provide comparable control on lettuce and cole crops during September and October. Of course, residual control will often depend on the rate applied. In general, the higher the rate, the longer the residual, but this will also depend on how fast the plant is growing and plant size. Before selecting a product for Lep control, be conscious of products (chemistries) previously used on the crop. Avoid using products with the same mode of action more than twice on any given field. More information on the insecticides available for effective control of beet armyworm and cabbage looper can be found in this document: Lepidopterous Larvae Management in Desert Produce Crops.
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.
Evaluation of Automated Autonomous Weeding Machines in Lettuce – UC Davis Trial Results
Over the last couple of years, there has been tremendous investment and research and development in autonomous weeding machines. At least 40 such robots have been promoted all over the world. Two of these available in the Yuma area are Naio Technologies’ Dino1 and FarmWise’s Titan. If you are not familiar with these technologies, the Naio Dino is a four wheeled, self-driving platform (Fig. 1). The robot is equipped with an imaging system that detects crop rows and an actuator that automatically adjusts the position of cultivating tools relative to the crop row allowing for close cultivation. The FarmWise Titan is an autonomous power unit coupled with an automated weeding machine (Fig. 2). It utilizes an imaging system to detect crop plants. Pairs of knife blades are automatically controlled to open and close around the crop plant to control in-row weeds.
Mosqueda et al. (2021) evaluated the two autonomous weeders in trials with lettuce last summer in Salinas, CA. The results were published in a UC Davis ANR blog article and the highlights are summarized here. In the study, the Naio Dino was equipped with finger weeders, a ground driven rubber fingered wheel designed for in-row weeding. Performance was compared to that of a standard cultivator which left an uncultivated band of 4-5 inches around the crop row. Assessments included stand and weed density counts before and after cultivation, hand weeding time and crop head weight. Weed counts were made in a 6 inches wide band centered on the seedline. The robot is equipped with finger weeders, a ground driven rubber fingered wheel designed to remove in-row weeds.
Trial results showed the finger weeder equipped Naio Dino controlled more than 1/3rd of the in-row weeds and reduced hand weeding time by about 2 hours per acre. This result is consistent with our findings in trials conducted in cotton crops where finger weeders controlled about 40% of the in-row weeds. Crop stand and head weight were not significantly reduced as compared to standard cultivation.
Similar results were found with the FarmWise Titan. The automatically controlled paired knife-blade weeding tool generally provided 40-50% in-row weed control and crop stand or yield was not significantly affected. As you might expect, reductions in hand weeding time were highly dependent on weed pressure. When weed density was low (<0.2 weeds/ft2) labor savings were negligible (< 0.1 hours/acre). At moderate weed (1.7 weeds/ft2) and high densities (>7 weeds/ft2), labor savings were more substantial at 1.7 hours/acre and > 7 hours/acre, respectively.
In summary, the trials showed that use of automated weeding machines were effective at controlling in-row weeds, reducing hand weeding time and that crop yield as measured by head weight was not negatively affected. Use of these machines is best suited for fields where weed pressure is high and significant labor savings can be obtained. I want to acknowledge Mosqueda et al. (2021) again for conducting these studies and sharing this information that helps growers make more informative decisions.
References
Mosqueda, E., Smith, R. & Fennimore, S. 2021. 2020 Evaluations of automated weeders in lettuce production. ANR Blogs. Davis, Calif.: University of California Davis. Available at: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=45566. 1Reference to a product or company is for specific information only and does not endorse or recommend that product or company to the exclusion of others that may be suitable.
Table 1. Weed control, crop stand, and yield of trials conducted in lettuce with autonomous automated weeding machines in Salinas, CA in 20201.
Trial
Treatment
Weed
Density
Pre-Cult
Weeds
Density
Post-Cult
Weed
Control
Total
Weed
Control
In-Row2
Weeding
Time
Stand
Reduction
Head
Weight
(no. ft-2)
(no. ft-2)
(%)
(%)
(hr acre-1)
(%)
(lbs)
Naio Dino
1
Naio
1.0
0.6
34.9
33.2
NA
0.0
1.9
Standard
1.3
1.2
1.7
NA
0.0
2.1
2
Naio
1.7
0.4
73.7
40.4
6.5
NA
1.4
Standard
2.3
1.5
33.3
8.4
NA
1.4
FarmWise Titan
1
FarmWise
1.0
0.4
58.4
13.9
9.4
0.3
2.8
Standard
1.3
0.7
44.5
11.1
0.0
2.8
2
FarmWise
0.3
0.1
69.8
39.1
0.3
1.4
Standard
0.4
0.2
30.7
0.0
1.3
3
FarmWise
0.2
0.0
85.9
42.4
3.8
0.4
2.2
Standard
0.1
0.1
43.5
3.9
0.0
2.1
4
FarmWise
3.9
0.8
80.1
47.3
9.9
4.5
1.5
Standard
3.4
2.3
32.8
16.9
0.3
1.4
5
FarmWise
3.0
0.5
81.7
47.6
6.7
2.2
1.7
Standard
3.4
2.2
34.1
14.7
0.3
1.7
1Data adapted from Mosqueda et al. (2021).
2In-row weed control results are estimates calculated from differences between automated and standard cultivator weed control data.
In November the EPA announced new requirements for handling Paraquat (Gramoxone, Cyclone, Helmquat, Parazone, Firestorm). Paraquat was first registered in 1959 by ICI Ltd. It is used on more than 100 crops in more than 100 countries but is the most toxic herbicide that has been used for many years. The new regulations involve labelling, applicator certifications and the use of closed system packaging. New containers are required to include supplemental warnings and stickers attached to the containers that state “one sip can kill.” Retailers can continue to sell old labeled products until supplies are exhausted. Paraquat has been a restricted use pesticide, meaning that applicators have had to be licensed and certified to apply it, but new additional regulations now apply. Two certifications are now required and anyone handling the product needs to be certified. Working under the supervision of someone who is certified does not count. In addition to a Pesticide applicators license, handlers now have to have a paraquat specific training certificate. This can be obtained by on-line training at www.usparaquattraining.com. This has been developed by the National Pesticide Safety Education Center (NPSEC).
