Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 4 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 15 areawide trap locations year-round. So why is this additional trapping data useful? For several reasons:
1) Understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops. Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests.
2) Trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally,
3) It gives me something to do in the summer other than write reports and papers.
So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to.
We are on the final section of virus transmission. Virus transmission by insects is one of the most efficient and economically important transmission in agriculture. When you have insects in your crops, not only you are losing your crops because of feeding/chewing by insects, a lot of insects also act as a vector of plant viruses.
Seven out of 29 orders of insect feeding on living green land plants are vectors of plant viruses.
Insect transmit viruses in 4 distinct modes:
Non persistent transmission: The insects can acquire the virus in a matter if seconds/minutes and they are immediately viruliferous. The virus in retained in the stylet of the insect and are transmitted to the next plant the insect feeds on. The virus is retained in the vector only for few minutes and is lost after insect molting. Most viruses transmitted by aphids are non persistent. So when you see few aphids in your melon field and see cucumber mosaic virus symptoms 1-2 weeks later in your field, don’t be surprised. Aphids are efficient vectors, and since viruses are systemic it takes anywhere from few days to 2-3 weeks for the plants to show symptoms. Thus it is very important to manage insects in the field even if you don’t think the ‘pressure’ is not as high.
Semi-persistent transmission: The insects can acquire the virus in minutes/hours and there is no latent (incubation) period in the insect. The virus can stay in the insects foregut for hours and is lost after insect molting. Some species of aphids and whiteflies fall in this category. Example: Cucurbit yellow stunting disorder virus in melons transmitted by whiteflies.
Persistent circulative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus for weeks. Virus can be present in the vectors hemolymph but there is no multiplication of virus in the insect body. Vectors in this transmission includes: Aphids, leafhopper, whiteflies, treehopper.
Example: Beet curly top virus transmission by beet leafhopper
Persistent propagative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus throughout its lifespan. The virus can multiply in the vector system and often times the virus particles are also passed on to the insect offspring. Tomato spotted wilt virus is transmitted on persistent propagative manner by 9 different species on thrips.
Save the Date : 2024 Plant Pathology Workshop
When: August 29th 8AM-12 PM ( breakfast and Lunch provided by Gowan Company and BASF)
Where: Yuma Ag Center, 6425 W 8th Street
What will covered: Plant Pathology program Updates, past season field trial results (we
have some exciting results to share), Q&A to help better Plant pathology program,
Industry panel discussion for all your industry related questions! See you in few weeks!
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.
Earning Continuing Education Units (CEU’s) Remotely
Faculty and staff at the Yuma Agriculture Center and Yuma Co. Extension office have been instructed to work from home when possible during this crisis. Fortunately, technology exists to continue most activities with little interruption. Some of our activities have been interrupted. One of these is conducting activities that offer Continuing Education Units. We are, however, exploring the opportunity to conduct meetings and workshops remotely that will qualify for CEU’s. Some opportunities already exist in which you can earn credits. Here are some sites that you can access to do this: