May 5, 2021Summer Sanitation Is Important as Ever
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
The volatility of herbicides, or the change from a solid or liquid to a gas, is dependent on several environmental factors and is extremely variable. We have been working on finding a replacement for Glyphosate for non-crop weed control and have tried to determine the stability of the potential herbicide alternatives. There are various methods used to measure herbicide volatility. All herbicides are initially tested in the laboratory to determine volatility and other properties. Volatility is specifically measured by placing a given volume of herbicide in a container, exposing it to various temperatures and humidity’s and then weighing how much is left. This is done under very controlled conditions. Another technique that is often the next step is to conduct bioassay studies in a greenhouse. This usually involves placing a container with the herbicide spray solution in a closed environment with sensitive plants. Injury to the bioassay plants are measured visually or by some other means. Field Studies are often conducted to measure herbicide volatility. This technique is the most applied, but the results are often imprecise and variable depending on environmental conditions. This commonly involves spraying an isolated area in the field and after the spray has settled placing sensitive plants at variable distances and directions away. Injury is observed or measured at variable time periods. We used this technique on June 10 to June 15 this year at the Yuma Valley Agriculture Center to measure volatility of 13 herbicides we are evaluating as alternatives to Glyphosate. Seven X 10 Ft. plots were sprayed, and tomato plants were placed 25Ft. away from each sprayed area on the north, south, east and west corners 1 hours after application A 50 Ft. buffer separated each sprayed plot. Visual injury was measured to the tomato plants at 24 and 48 hours after they were placed in the field. The 13 herbicides were used in this trial included 5 modes of action and are listed below.
The temperature reached above 100 F, the humidity was 10 to 20% and wind was 5 to 10 MPH during the trial. No injury symptoms were observed to any of the tomato plants from any of the herbicide treatments. The trial included low volatility formulations of the plant growth regulators, 2-4-D (Embed) and Dicamba (Enginia) which are often volatile under these hot and dry conditions. Neither of these two, or any of the other included herbicides, moved 25 ft or more in this one trial. We know, however, that in other trials the results have sometimes been different. Volatility is variable and difficult to measure in field trials.
It is about that time of the year/growing season when you start seeing bacterial diseases. With the rain we got last week and as plants get more vegetative growth bacterial issues become more prevalent. Cilantro and parsley are two crops grown in desert southwest that often suffer from bacterial leaf spots. Most times, the disease incidence is also high because of sprinkler irrigation used in these cropS. On both crops, initial symptoms of bacterial leaf spot are water-soaked lesions on leaves. The lesions develop into spots that are varying shades of tan or brown (see picture ‘B’ on parsley whereas advanced spots on cilantro can be black (see picture ‘A’ on cilantro). The lesions are usually limited by leaf veins and thus have an angular, square, or rectangular appearance, a typical feature of bacterial infection. Lesions tend to be relatively small about 1/8 to 1/4 inch (3–6 mm) in diameter and are visible from both the top and bottom of leaves. Under favorable conditions, free moisture from rain or sprinkler irrigation, leaf spots may coalesce and cause considerable blighting of the entire foliage.
Pseudomonas syringae pv. apii (Psa) and P. syringae pv. coriandricola (Psc). cause bacterial leaf spot on parsley and cilantro. Pseudomonas syringae pv. apii (Psa) can cause leaf blight in celery and fennel as well. Though the problem is documented as more of a problem in cilantro and less in celery, in severe condition the disease can result in unmarketable produce in any host. The bacteria are likely seedborne in both crops. However, water from rain, sprinkler irrigation, and heavy dews and fogs will splash bacteria from infected plants onto adjacent healthy foliage resulting in heavy infestation.
To manage the disease, always use tested/treated seeds, rotate crop with non-host to reduce inoculum level, switch from sprinkler to furrow irrigation to limit secondary spread, avoid excessive use of nitrogen fertilizer. Copper spray/copper based fungicide provide limited control against the pathogens.
Two years ago, Alphabet’s (Google) X-Labs initiated one of their infamous and far reaching “moonshot” projects focused on growing food sustainably on global scale. As you might expect, the project has been, and is kept pretty secret, but the company recently unveiled some details about the project through a company blog article (Grant, 2020) and their newly established website (https://x.company/projects/mineral/). The project is called “Mineral” and according to project lead Elliot Grant, the team has been working “alongside experts in the field – literally and figuratively…developing and testing a range of software and hardware prototypes based on breakthroughs in artificial intelligence, simulation, sensors, robotics and more”.
One of the tools the team has developed is a self-propelled “plant buggy” equipped with multiple cameras, sensors, GPS and other electronic equipment (Fig. 1). According to Mineral’s website, “Over the past few years, the plant buggy has trundled through strawberry fields in California and soybean fields in Illinois, gathering high quality images of each plant and counting and classifying every berry and every bean. To date, the team has analyzed a range of crops like melons, berries, lettuce, oilseeds, oats and barley—from sprout to harvest.” Stated objectives of Mineral’s software are to combine and analyze data collected from the field, soil health information and weather data to 1) predict how different varieties of plants respond to their environments, 2) allow growers to treat individual plants with fertilizers and pesticides to optimize production and reduce inputs and 3) help growers predict the size and yield of their crops.
It is exciting that a cutting-edge tech company like Alphabet is taking on an agricultural project like this. It will be fascinating to see what technical breakthroughs and solutions the company will be able to achieve for all crops, including vegetables.
Grant, E. 2020. Mineral: Bringing the era of computational agriculture to life. X Development LLC blog article. Mountain View, CA: X Development LLC. Available at https://blog.x.company/mineral-bringing-the-era-of-computational-agriculture-to-life-427bca6bd56a.
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://184.108.40.206:460
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.