May 5, 2021Summer Sanitation Is Important as Ever
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Herbicide resistant weeds have received a lot of attention in recent years. It is often misunderstood. Three of the most misunderstood concepts regarding herbicide resistance are: 1- Weed tolerance and weed selection are not resistance,2- Weed resistance is not universal and does not affect every weed of a certain species from field to field or within a field and weed resistance often takes much longer than insect resistance that is more common and occurs faster.
No Herbicide controls all weeds. Those weeds that are not controlled are tolerant. They never were controlled by that particular herbicide and they are often selected for and become more prevalent over time if the same herbicide is used. Resistant weeds, on the other hand, were controlled at one time by a particular herbicide and have naturally developed a trait that stops the herbicide from working. These resistant weeds survive from generation to generation and become more prevalent over time.
Weed resistance does not occur in all weeds in a field at the same time. It can be just one plant of trillions in a field. As this plant survives the herbicide and goes to seed it becomes more widespread in the field and in other fields. We conducted a trial in Parker last year where sprangletop survived Glyphosate in one field and was killed by the same treatment down the road. If your neighbor has resistant weeds it doesn’t mean that you do too.
Lastly, insect resistance to insecticides has occurred in this region for many years and was the first exposure that many pest control advisers and growers had to pesticide resistance. The principals are the same although insects generally produce multiple generations per season and mutations that facilitate resistance occur faster than for weeds. Annual weeds often produce only one or two generations per season and resistance takes much longer.
In the past couple of weeks, the reports of INSV in fields has increased dramatically. INSV has been found in fields in Yuma/Gila Valley, Wellton, Tacna, Roll, and Imperial Valley.
PCAs have reported thrips pressure as low this year and most fields have infection less than 1% but some fields have been reported to have higher incidence. The virus has been detected in direct seeded field as well as transplants imported from Salinas, CA.
Impatiens necrotic spot virus, also known as INSV is a tospovirus closely related to Tomato spotted wilt virus. Infected plants usually have leaves with brown to dark brown necrotic areas. Sometimes the symptoms may be confused with “chemical burn”. As necrosis progresses the leaf browns or die out. Plants infected in early stage may become stunted and die, or become unmarketable.
What makes this virus of high economic importance?
The plants become unmarketable which is the ultimate economic loss. But there are factors that facilitate the virus outbreak.
The first one is efficient transmission by its vector (s). The virus is transmitted by western flower thrips, Frankliniella occidentalis.
If you remember our virus transmission series in past newsletters, thrips transmit viruses in persistent propagative manner. 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. Adult thrips can transmit these viruses only if acquired in the larval stage of development. Larval thrips will feed on a virus-infected plant, pupate, and emerge as a winged adult capable of transmitting the virus. The thrips then will carry the virus for life.
The next contributing factor is host range. INSV infects large number of ornamental and vegetable plants. We are talking 600 species of plants that are susceptible to INSV and thrips love flowers.
While it may not be practical to remove all your ornamentals in fear of INSV, it is definitely practical to monitor thrips population in your field. As the legend says “When in doubt, scout”.
And if you need diagnosis, drop the samples in the clinic! But then if you have immunostrips, you don’t have to make the drive to the Ag Center!
DIY testing: Impatiens necrotic spot virus (INSV)
As visual diagnosis of the virus is confusing and could even be misleading at times, it is very important to confirm a symptomatology via clinical diagnosis.
The good news is there are tools available for quick and easy diagnosis of INSV. You can order the immunostrips from Agdia (https://orders.agdia.com/agdia-immunostrip-for-insv-isk-20501)
The immunostrips cost anywhere from $5-20 depending on how much you buy. They perform better when they stay refrigerated until just before use.
Immunostrips are quick and easy tool to use. The kit comes with a buffer bag and immunostrip.
One band means that the positive control worked which means the system worked. Sometimes you see no bands at all. This means the system did not work and you have to repeat the test.
If you are seeing symptoms in your field please let Bindu Poudel-Ward know via email (email@example.com or text (928-920-1110). Please keep a note of weed species you are consistently seeing in your fields and keep the thrips population under check.
The autonomous agricultural robot industry is an incredibly fast-moving space. Startups, established companies and academic researchers are continuously putting forth new ideas and products. It’s hard to keep up with. In November of 2020, Future Farming (Misset Publisher, BV, Doetinchem, Netherlands) published a Field Robots Catalogue that provides a comprehensive overview of the state of autonomous ag robots. The article provides brief summaries of 35 autonomous ag robots that are currently commercially available. Along with a brief paragraph about what each robot does, the article presents information about how many robots from a particular manufacturer are actively being used, the cost of the machine, and links to a video of the device in action. Most of the robots are for weed management in vegetable crops. Kill mechanisms range from spot spraying to mechanical weed removal to electrocution. Several of the robots featured are applicable and relevant to Arizona vegetable production, and some are currently operating in the U.S. If you’re interested in ag robots and want to get up to date, this article is an excellent resource and quick read. The article can be found at the link provided below.
Title: Future Farming Field Robots Catalogue
Publisher: Misset Publisher, BV, Doetinchem, Netherlands.
Growers and PCAs can monitor data from the Yuma Leaf Wetness Network through the AZMET website located at the following URL: http://220.127.116.11:460
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.
Results of pheromone and sticky trap catches can be viewed here.
We have started our Areawide Insect and DBM Trapping Network for the 2019-20 season.
We have added another trapping location in Bard, CA.
Area wide Insect Trapping Network VegIPM Update, Vol. 11, No. 20, Sep 30, 2020
Results of pheromone and sticky trap catches can be viewed here.
Corn earworm: Moth activity about normal for September but beginning to increase, particularly in Dome Valley and south Yuma Valley.
Beet armyworm: Moths remain active throughout the desert, especially in Texas Hill and Tacna growing areas- Staring to pick up in the south Yuma Valley.
Cabbage looper: Cabbage looper activity unusually low for mid-late September. Larvae just starting to show up in some fields.
Whitefly: Adult movement has been relatively light and about average for this time of year. Activity highest in Dome Valley.
Thrips: To date, thrips activity has been seasonably low at all trap locations; most activity found in Bard. Numbers beginning to slowly trend upward
Aphids: No aphids have been caught on traps thus far. Normal for this time of year. Still early, anticipate they will begin to show up in October.
Leafminers: Adult activity below normal for September, but moderate numbers caught in Wellton and south Gila Valley in areas where cotton was recently harvested and disked under.