Each produce season is unique, and this fall was no different in terms of insect pressure. A quick look at both recent and historic data on pest abundance recorded from our University of Arizona research plots and areawide trapping and sampling suggests that insect pressure was unusual for several pests. For a look at the data see Pest Abundance on Desert Produce and Melon Cops in Fall 2021.  
 
Whitefly/CYSDV:   Whitefly populations in fall melons were similar to the past few seasons, and areawide, adult movement was below average. However, CYSDV incidence in cantaloupe fields was higher than we’ve seen in the past 8 years. The virus incidence at harvest in more than half of commercial blocks had very high incidence (>80%) of both CYSDV and CCYV, particularly in the Tacna Roll areas. Incidence had little to do with weather or poor insect management, rather these infected field were located 1-10 miles downwind of about 300 acres of abandoned watermelons which were highly infested with whiteflies and viruses. Given the monsoon activity occurring in these areas during stand establishment in Aug, it was the “perfect storm” for what occurred. Other melon fields far removed from the watermelons experienced much less virus. 
 
Beet armyworm (BAW), cabbage looper (CL), and corn earworm (CEW):  BAW and CL pressure in the early fall was very high, although not to the levels seen in 2020. BAW pressure subsided in early October associated with unusually below average temperatures. CL populations remined active throughout the fall, particularly when above average temperatures prevailed in November. Trap catches for both BAW and CL were below average. CEW trap catches peaked in early September and failed to be much of an issue at harvest in most locations. As always, CEW larvae seemed to be more abundant in Dome Valley. 
 
Diamondback moth (DBM):   DBM was not a problem again for local desert growers in 2021; about what we normally expect for the fall. PCAs began reporting the presence of larvae in late October but received no reports of difficulty in controlling populations.  Areawide pheromone trapping showed that DBM moth activity began later this fall but trended very similarly to previous years by late October consistent with the appearance of larvae in fields. At YAC, the larval populations were light compared to previous years, and field efficacy trials in cabbage and broccoli indicated that this population was very susceptible to all industry standard insecticides. Caution:  DBM are more active than other Leps during the cooler winter months and can increase quickly in the spring on those Feb-Apr Cole crops and late seed crops. 
 
Western Flower Thrips (WFT) / INSV:  WFT pressure on non-treated lettuce plants at YAC was comparable to recent seasons.  Areawide trapping indicated that adult activity was below average, but traps placed on edges of cantaloupe and lettuce fields showed that WFT activity was much higher. Movement peaked around melon at harvest and again following disking. In lettuce, trap catches peaked in mid-November coinciding with peaks in adult and larvae abundance on plants, and early harvest of fall lettuce. Although INSV infected plants have been detected at low levels in Tacna, Roll, Dome Valley, Gila Valley and Bard, to date virus incidence remains almost non-detectable in these areas.  Caution: If we experience a La Nina weather pattern as predicted, WFT populations may rapidly begin building in January. Be vigilant in your WFT management this winter/spring. 
 
Aphids:  Winged aphid immigration has been about average, slightly increasing throughout the fall.  There have recently been reports of aphids beginning to colonize broccoli and lettuce.  Note:  We’re beginning to pick up small numbers of individual Foxglove aphids on celery at YAC.
 
Have a Merry Christmas, and we’ll visit again next year!

The drought-related pressures on the Colorado River system that have been impacting the entire basin and region for 23 years have slackened briefly due to the wet winter in 2023 that included a good snowpack in the mountains, better rainfall throughout the basin, and improved flows into the river.  The current water level at Lake Mead on Hoover Dam is 1,068.25 ft. above sea level on 3 January 2024.  That level is 160.75 ft below full pool of 1,229.00 ft. (Figure 1).

In mid-December 2023 representatives from each of the seven Colorado River Basin states met in Las Vegas, NV during the annual Colorado River Water Users Association conference.  The focus of current discussions among the basin states is to negotiate a new compromise for the guidelines of use under conditions of water shortage.  These new guidelines will go into place at the end of 2026.  The immediate goal is to draft proposals by March 2024.
 
The negotiations are incentivized by having the opportunity for the post-2026 guidelines being developed by the basin states themselves as opposed to litigation or legislation.  A major concern driving this process among the basin states that basin state representatives should be able to do this better than turning the process over to people and entities that have less direct familiarity with the situation and no real “skin” in the game.  
 
The 1963 decision by the Supreme Court of the United States in of the Arizona v California case directed the federal authority on the management of the Colorado River to the Department of the Interior and the Bureau of Reclamation (BoR).  However, the basin states have the chance to negotiate their future management plans on the Colorado River.  If they fail to do so in the allotted time, the process will be managed by the federal government.  
 
The basic water budget challenge is based on the following basic statistics:
 

• The current water budget on Colorado River allocations is 16.5 million acre-feet (maf)/year.
• Average annual flow on the Colorado River from 1906-2017 was 14.8maf/year.
• The average annual flow between the years 2000 - 2018 has been approximately 12.4maf/year.
• That is 16% lower than the 20^th century average flow.
• It is estimated that 1.5 maf/year is lost due to evaporation and system loss.
• Thus, the 4 maf/year target reduction that has been identified by the BoR is basically the difference between the 16.5 maf/year allocated versus the 12.4 maf/year average flow in the first two decades of this century.

 
Some notable progress is being made for conservation of Colorado River water with agreements among lower basin states and tribes that will conserve more than 1.5maf/year through 2026.  For example, California water agencies have recently agreed to conserve up to 643,000 acre-feet/year through 2025.  The Quechan Indian Tribe has reached an agreement with federal water managers to save up to 39,000 acre-feet/year through 2025.  Arizona has agreed to conserve up to 348.00 acre-feet/year through 2026.  All these temporary agreements are being supported with federal funding.
 
With agriculture responsible for 70% of the diversions on the Colorado River, these negotiations are extremely important for the future of agriculture in this region and our capacity to support high population densities that are now common and rapidly growing.
 
These types of negotiations are certainly challenging in dealing with a limited water supply and a lot of demand.  There are many competing interests involved.  Yet, we are confident that the representatives we have will be able to work this out and come to a set of functional agreements.

Widely accepted definition of a living organism “A living organism has a cellular structure and is manifest by growth through metabolism, reproduction, and the power of adaptation to the environment through changes that originate internally”. Viruses are not cellular and do not metabolise, but they reproduce and adapt. 
 
A virus is a set of one or more nucleic acid template molecules, normally incased in a protective coats of protein or lipoprotein and is able to organize its own replication but only within a suitable host cells. Record of plant viruses do not go as far as human viruses, but plant viruses have caused considerable loss in agriculture system. 
 
 
One of the most common virus we see in agriculture system in todays world is Cucumber mosaic virus(CMV). CMV belongs to family Bromoviridae. The genome size of cucumber mosaic virus (see pic) is about 8000 to 9000 nucletotide bases (1 base=1 letter of AGTC). The genome size of Covid19 Coronivirus is about 30,000 bases and the genome size of human DNA is 6.4 billion bases. 
 
CMV has a very wide host range and is transmitted by aphids in nonpersistent manner (stylet borne). This means that the aphids acquire the virus particle in their stylet within seconds of feeding in infected plants, hop on to next plant and start feeding on next plant. The virus is transmitted to the next plant immediately. 
 
Next is incubation period. Viruses cause systemic infection. It can take anywhere from few days to few weeks from initial entry of the virus to symptom exhibition in your plants. The severity of symptoms varies depending on many factors. The age of plant (infection stage), the general plant vigor (health), varietal susceptibility, conducive environment (viruses express better in colder weather than hot weather), a plant that has already been infected with other viruses (preesisting condition) are to name a few.

1. Attachment – the virus attaches itself to the outside of a  new plant cell 
2. Penetration – the protein pushes the nucleic acid strand into the plant cell
3. Replication – the viruses’ nucleic acid uses the plant cell DNA to make many new nucleic acid strands and protein sheathes
4. Assembly – the nucleic acid and protein assembly into millions of new virus copies
5. Release – the viruses leave the cell – at this stage the cell is normally dead and bursts releasing the viruses
6. Transmission – the viruses move using a vector to new cells to infect.

When you see the symptoms in your plants, the first thing you have to understand is virus infection is systemic. The best you can do to manage the virus is to limit the transmission (flatten the curve). Some viruses need a vector for transmission like insects and nematodes. Some viruses are mechanically transmitted from one infected plant to another. Washing field tools between plants/field whenever possible limits the transmission of virus. Soap, bleach, and disinfectants reduce transmission by protein denaturalization of the virus.

Time flies. February is right around the corner and that means it is farm equipment/ag trade show season. Upcoming regional events include the World Ag Expo, Tulare, CA, February 13-15, the Southwest Ag Summit, Yuma, AZ, February 20-22, and AgroBaja, Mexicali, Mexico, March 7-10.  If you are interested in the latest ag tech and farm machinery, all are outstanding events and well worth attending. For more information, click on the links below.

Fig. 1. Upcoming farm equipment/ag trade show events: World Ag Expo, Tulare,
CA, February 13-15, 2024 theSouthwest Ag Summit, Yuma, AZ, February 20-
22,2024 and AgroBaja, Mexicali, Mexico, March 7-10, 2024.

Before making decisions for weed control it’s imperative to have a proper identification of the plant species. There are two names for plants:
The common name, which is a name that people come up with in a certain region to describe a particular weed and it varies by region and therefore can be confusing. Then we have an exact scientific name for each species that is based in the binomial nomenclature system started by Carl Linnaeus in 1753. This binomial (or two term) system includes the genus and the species, which is used worldwide¹.
 
Some very close species from the same family can be controlled by the same product but occasionally their herbicidal susceptibility varies. Such is the case of Chenopodium murale (goosefoot) and Chenopodium album (lambsquarter) two very close and similar species. A product like Pursuit (Imazethapyr) has good activity on goosefoot but can’t control lambsquarters. With accurate identification in a mixed population, you would be able to determine what strategy to use or select the herbicide that would control both species. 
 
There are about 75 weeds most common in Arizona and are included in the PCA² study guide, but many other species could be introduced to the State and complicate our crop production systems. Two great tools for weed identification are the books “An Illustrated Guide to Arizona Weeds” that lists 172 species, and “Weeds of California and Other Western States” which has at least one photograph of 735 weeds.
Another weed identification tool is the book “Weeds of the West”.
Additionally, there are many phone applications that can be used as identification tools such as “id weeds”, “PlantNet”, “PictureThis”, “iNaturalist”, “Seek”, “PlantSnap” and “LeafSnap”. When we have problems with weed ID we contact the UA herbarium.
Thank you for sending samples for Weed ID to the IPM Team it is always a learning experience.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 21, Oct 16, 2024

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts increased in most traps; about average for early October.

Beet armyworm: Trap counts increased in most areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts still most locations, below average for this time of the season.

Diamondback moth: Adult activity increasing, particularly in the Yuma and Dome Valleys.  Above average for this time of season.

Whitefly: Adult movement increasing Tacna, Dome Valley and Yuma Valley; overall about average for early October.

Thrips: Thrips adult movement picking up in all areas, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; about average for early October.