May 5, 2021Summer Sanitation Is Important as Ever
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Contact herbicides are those that only affect the part of the weed that they “contact” They don’t move into or affect any other part of a plant. They were the first herbicides used and surprisingly, they still are better at controlling some weeds than any other products that have been developed. They usually control only small weeds with good coverage although some of them will kill large malva , Purslane and some other difficult to kill weeds. Goal, Sharpen, Treevix and Gramoxone, which are all contacts, will kill malva and purslane while systemic herbicides like Glyphosate and 2,4-D, misses them. Maestro or Bucril (Bromoxynil), also an old contact, will kill swinecress while many systemics like the growth regulators ,miss it. Glufosinate( Liberty, Rely) is a contact that is very broad spectrum and kills more grasses and broadleaves than many systemic herbicides. These all work very fast and in this age of immediate gratification ,you don’t have to wait long. Most have little soil residual activity (except Goal, Chateau and a couple others) Goal and Chateau are contacts but used mostly preemergence to the weeds. They “ contact” the weeds when they emerge at the surface. which is a benefit where double or triple cropping is common. Most( again except Goal) are not volatile but will cause pretty clear contact injury when the spray moves to sensitive crops. Paraquat was registered in 1959 and is still a very useful tool for desiccating plants. Many restrictions have been put on its use because of its toxicity to humans. Most contact herbicides are non-selective and will injure most living plant tissue. They are used selectively with directed spray or timing. Adjuvants are often required to increase absorption, spreading and sticking.
Last year we had a lot of watermelon fields infected with Fusarium from Winterhaven to Yuma, Wellton, and Mohawk Valley. Rain, and overwatering of fields when plants set fruits might have contributed to the disease development.
Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum, is one of the oldest described Fusarium wilt diseases and the most economically important disease of watermelon worldwide. It occurs on every continent except Antarctica and new races of the pathogen continue to impact production in many areas around the world. Long-term survival of the pathogen in the soil and the evolution of new races make management of Fusarium wilt difficult.
Symptoms of Fusarium can sometimes be confused with water deficiency, even though there is plenty of water in the field. In Yuma valley we have seen fusarium problem in some overwatered fields.
Initial symptoms often include a dull, gray green appearance of leaves that precedes a loss of turgor pressure and wilting. Wilting is followed by a yellowing of the leaves and finally necrosis. The wilting generally starts with the older leaves and progresses to the younger foliage. Under conditions of high inoculum density or a very susceptible host, the entire plant may wilt and die within a short time. Affected plants that do not die are often stunted and have considerably reduced yields. Under high inoculum pressure, seedlings may damp off as they emerge from the soil.
Initial infection of seedlings usually occurs from chlamydospores (resting structure) that have overwintered in the soil. Chlamydospores germinate and produce infection hyphae that penetrate the root cortex, often where the lateral roots emerge. Infection may be enhanced by wounds or damage to the roots. The fungus colonizes the root cortex and soon invades the xylem tissue, where it produces more mycelia and microconidia. Consequently, the fungus becomes systemic and often can be isolated from tissue well away from the roots. The vascular damage we see in the roots is the defense mechanism of the plant to impede the movement of pathogen.
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.
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.
Growers and PCAs can monitor data from the Yuma Leaf Wetness Network through the AZMET website located at the following URL: http://22.214.171.124:460
The website updates information on leaf wetness and near-surface air temperature every 15 minutes. Wetness data are provided in graphical format (see figure below). Output from the leaf wetness sensors increase from the grey (dry) zone of the graph to the blue (wet) zone when wetness (dew or rain) is detected by the sensors.
Area wide Insect Trapping Network VegIPM Update, Vol. 11, No. 22, October 28, 2020
Results of pheromone and sticky trap catches can be viewed here.
Corn earworm: Moth activity is about average for mid-October, particularly in Dome Valley and south Yuma Valley.
Beet armyworm: Moths remain active throughout the desert, especially active in Tacna and Dome Valley.
Cabbage looper: Cabbage looper activity remains unusually low for early October, likely a result of unusually hot weather. Larvae are yet to show up in many fields.
Whitefly: Adult movement has been about average for this time of year. Activity highest in Tacna near fall melons.
Thrips: To date, thrips activity has been seasonably low at all trap locations; activity increased significantly in Roll.
Aphids: Aphids beginning to show in most traps along the Colorado River (Bard, Gila, Yuma) which is normal for this time of year. Recent high winds may begin to disperse them throughout the area.
Leafminers: Adult activity below normal for September, but high numbers caught in Wellton in areas where melon harvest has commenced.