May 5, 2021Summer Sanitation Is Important as Ever
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Oxyfluorfen,(Goal and Galigan) has become a popular and effective herbicide for use on cole crops even though it was first registered in the 1980’s. Oxyfluorfen is a contact herbicide with the same mode of action as Chateau, Aim, Shark, Gramoxone, Paraquat , Sharpen and ET. They are all PPO Inhibitors that rupture cell membranes. Carfentrazone (Aim, Shark), ET and Paraquat (Gramoxone), are effective only as postemergence applications to small weeds, Sharpen and Goal are effective both preemergence and early postemergence and Chateau is used only preemergence but can cause severe crop injury if mixed with a surfactant. The only one of these that is registered for cole crops is Oxyfluorfen (Goal, GoalTender, Galigan). It does not make sense for a contact herbicide to be used on weeds that have not emerged. The way this works is that a barrier is created with the herbicide on the surface that kills the seedling weeds as they come in contact with it. It is important not to disturb this barrier or the weeds will not be affected. Oxyfluorfen (Goal) is an herbicide that defies reason in other ways as well. It normally adheres strongly to the soil and has very low water solubility. It is well known, however, that Goal can lift off of the surface and cause crop injury. When this happens, it is evaporating or going from a liquid to a gas and this is unaffected by its solubility or adsorption. It also works well when chemigated through a sprinkler system. You would think that it would wash off, but it works well with less crop injury when chemigated. Chemigation is registered for onions only but it works well with cole crops as well. It only takes half as much (4 ounces) and is safer to the crop when chemigated. It is best to apply it about 2/3 of the way through the sprinkler run to keep it in place and flush the system.
It is that time of the year! Every year, September starts with “Is it April yet?” If you did not say that, then you cannot sit with us!
This past growing season has been an interesting one. From wearing masks at 120 degree to maintaining social distancing; while producing same amount of produce, feeding same amount of people, and dealing with same amount of disease and pests. A big thank you to everyone involved in agriculture for your hard work and perseverance.
In regards to plant health, we had plenty of disease problems to deal with this year. Below is brief report of the major diseases observed in growing season 2020/2021 and the disease we should be keeping an eye on for next growing season.
We observed a lot of fields with fusarium wilt this year. We had a lot of infected watermelon fields from Winterhaven to Yuma, Wellton, and Mohawk Valley. Rain, and overwatering of fields when plants set fruits might have contributed to the disease development.
Disease management include planting clean seeds/transplants, use of resistant cultivars, crop rotation, soil fumigation, soil solarization, grafting, biological control. An integrated approach utilizing two or more methods is required for successful disease management.
Fusarium wilt of Lettuce
Though detected in a lot of fields and some new fields, the disease pressure in lettuce was relatively low. Please continue with proper management practice for next growing season. Avoid overwatering, add soil amendments/organic matter, practice crop rotation if possible.
Lettuce dieback associated virus
Lettuce dieback is a soil-borne disease caused by two closely related viruses from the family Tombusviridae Tomato Bushy Stunt Virus (TBSV) and Lettuce Necrotic Stunt Virus (LNSV) that has been reclassified as Moroccan Pepper Virus (MPV). The disease has been observed throughout the main lettuce producing areas of California and Arizona.
Sclerotinia rot (known as lettuce drop) is caused by fungi Sclerotinia sclerotiorum and Sclerotinia minor.The initial aboveground symptom is observed as wilting of outermost layer of leaves giving an impression of stress in plants. However, as infection progresses rapidly towards other leaf layers and the entire plant wilts including the head. The entire plant/planting can collapse within the matter of 2 days when the condition is favorable. Management practices include use of subsurface drip irrigation, keeping the top 5-8cm of soil on planting bed is crucial. Deep plowing, crop rotation with non-hosts like small grains and broccoli, removal of infected plant tissue from the field etc. help reduce the inoculum level. Soil fumigation is effective though may not be economical. In Florida growers flood fallow their lettuce field for 4-6 weeks in summer which has almost 100% control of S. sclerotiorum. This is something you might wan to consider doing this summer if you have had high disease pressure in your fields this growing season.
Downy mildew has been a problem for years in lettuce as well as spinach. One of the main reason that hinders the disease management is the complexity of the pathogen. Bremia lactucae (lettuce pathogen) consists of multiple races (pathotypes), and new races continue to occur as pathogen evolves. The pathogen is one of the fastest evolving plant pathogen. And each pathotypes have developed insensitivity to fungicides to different extent. Resistant cultivar, preventative application of fungicides are effective to some extent. Reducing leaf wetness and humidity by using drip or furrow irrigation can be helpful.
Impatiens necrotic spot virus (INSV)
INSV has been detected in a number in fields mostly in Tacna/Roll/Wellton area. It has been found in lower numbers in Gila Valley. If your field has been infected with INSV this growing season, be proactive next season in regards to clearing up the weeds, managing thrip population etc. If you see symptomatic plants please let me or Dr. Palumbo know.
This week in Clinic
If you haven’t submitted your entry for Melon powdery mildew fungicide trial for this spring please send it to Dr. Bindu Poudel-Ward (firstname.lastname@example.org)
Vol. 12, Issue 4, Published 2/22/2021
Keeping up to date with the latest developments in automated weeding machines is challenging. It’s a very fast-moving space with significant private and public investment. At the “Advances in Weed Control Technologies” breakout session at the 2021 Southwest Ag Summit, university experts and cutting-edge innovators will provide updates on the latest developments in automated weeding, autonomous ag robots and non-chemical weed control. The first presenter will be Tony Koselka, COO and Vice President of Engineering, Vision Robotics Corp. Tony will be giving a history on the evolution of automated thinning/weeding technologies and real-world examples of how vision systems and artificial intelligence (AI) is being used with automated weeding machines today. Following Tony will be Paul Nagel, Chief Revenue Officer, Stout Industrial Technology, Inc. Paul will be discussing AI technologies available today, their capabilities, and where the technology is headed. Jaime Eltit, Head of Commercial Farming Operations, FarmWise, Inc. will be also be discussing AI technology and how machine learning is used for robotic in-row weed control. Additionally, he will be presenting information on the latest developments in autonomous weeding robots and their application in Arizona vegetable production systems. Finally, Dr. Steve Fennimore, Weed Scientist, UC Davis will be presenting information on a novel technique for using steam heat to control sclerotinia lettuce drop, Fusarium wilt of lettuce and in-row weeds in vegetable crops.
The session will be held TOMMOROW Thursday, February 25th from 1:30-3:30. If you are unable to attend the live session, recordings of the presentations will be available on March 2 and March 3. For those interested in CEU’s, the session offers 2 AZ/CA PCA and CCA credits. One last thing, you must be registered for the 2021 Southwest Ag Summit in order to attend the session. To register or for more information about the Southwest Ag Summit, visit https://yumafreshveg.com/southwest-ag-summit/. Hope to see you there for what promises to be an enlightening and informative session.
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.
Beet armyworm: Moth activity has declined in most trap location and remains below average for this point in the season.
Cabbage looper: Cabbage looper activity remains unusually low for early November. Trap catches picked up a bit in Wellton and Gila Valley.
Whitefly: Adult movement has been about average for this time of year. Activity highest in Wellton near fall melons being harvested.
Thrips: Thrips activity picking up significantly in several trap locations; activity increased significantly in Bard and Dome and Gila Valleys.
Aphids: Aphid numbers peaked last week in many locations, particularly in the Gilas and Yuma Valleys.
Leafminers: Adult activity increased significantly last week, particularly in the Wellton area near melons.