May 5, 2021Summer Sanitation Is Important as Ever
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Although it is not vigorous or vegetative, Shepardspurse is one of the most widespread and difficult to control broadleaf weeds worldwide. I used to think that it spread when there was more alfalfa here and because it is not controlled with 2,4-DB (Butyrate & Butoxone) but it has continued to spread in vegetable crops. It likely has become worse each year because of its growth habits more than its tolerance to herbicides. It germinates from on or just below the soil surface. Herbicides that move or are placed below the surface often miss it. It is difficult to control with Kerb, for instance, because it leaches easily with overhead sprinklers. The seed is less than 0.1 inch in diameter and moves easily in wind and water. It is very small, and the cotyledon leaves are hardly ever seen. By the time you see it, it is at the 3 or 4 leaf stage. It grows rapidly in a rosette that is low to the ground and often covered by the crop. Herbicide coverage is difficult. It soon puts up a thin seed stalk and several seed pods (“purses”). Unlike many annual broadleaf weeds, it can produce several generations in one season. It can grow year round in many regions but has a difficult time surviving the summers in the low desert.
Viruses vectored by insects
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:
Viruses transmitted in non-persistent manner:
Papaya ringspot virus
Zucchini yellow mosaic virus
Watermelon mosaic virus
Example: Beet curly top virus transmission by beet leafhopper
Vol. 12, Issue 7, Published 4/7/2021
Over the last several years, there has been a tremendous amount of research activity towards the development of autonomous agriculture vehicles. A quick internet search will reveal over 50 companies or university research groups working in this space. A question I get often from groups developing such platforms is “What is a good agricultural application for our lightweight “robot”?”. It’s a great question, and for Arizona vegetable production, it’s also one that I’m not sure I have a satisfying answer for.
The calls I get regarding autonomous robots are mostly related to automated weeding applications. Automated weeding machines are commercially available, but their adoption has been limited not because of labor costs for tractor operation, rather it is the lack of the development of a functional and cost-effective means for identifying and removing weeds.
For decades, researchers have been attempting to develop sensing systems that are able to reliably detect weeds. Techniques such as 2-D and 3-D color imaging, x-rays, hyperspectral sensing and artificial intelligence have been tried (Slaughter, 2014; Bender et al., 2020). The best performing systems provide about 96% accuracy, meaning that 4% of the crops plants are identified as weeds and would be destroyed by the weeder. For high value vegetable crops like lettuce with gross revenues of roughly $10,000 per acre, killing 4% of the crop equates to $400 per acre of losses. Economically, this does not make sense as hand weeding labor costs are typically $300 per acre or less. The other main issue is that current automated weeding technologies are not highly precise and provide only partial control. Our studies with these types of machines have shown that these systems remove only about 1/3rd of the in-row weeds (Lati, et al., 2016) and a follow up hand weeding operation is often necessary. To be highly cost effective, elimination of the hand weeding step is needed.
In short, my recommendation to research groups asking about applications for autonomous robots is that their time and technical skills would best be served developing reliable crop/weed differentiation systems and a technique to remove a very high percentage of weeds.
Bender, A., Whelan, B. & Sukkarieh, S. 2020. A high‐resolution, multimodal data set for agricultural robotics: A Ladybird's‐eye view of Brassica. J. Field Robotics. 37(1): 73-96.
Lati, R.N, Siemens, M.C., Rachuy, J.S. & Fennimore, S.A. (2016). Intrarow Weed Removal in Broccoli and Transplanted Lettuce with an Intelligent Cultivator. Weed Technology, 30(3), 655-663.
Slaughter, D.C. The biological engineer: Sensing the difference between crops and weeds. Autonomous robotic weed control systems: A review. Computers and Electronics in Agriculture 61(2008): 63-78.
The Yuma County Leaf Wetness Network remains in place for the 2018/19 vegetable season. Growers and PCAs may access information generated by the network by entering the following internet address: http://22.214.171.124:460
Upon entering the address above, you will be transferred to internet page that provides a series of tabs at the top of the page. Simply click on the tabs to access the information of interest.