Aug 10, 2022Insect Pests Important at Stand Establishment
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Figure 1. The Colorado River watershed that includes seven western U.S. states and 2
Mexican states, supports >40M people, >5.5M acres of farmland, and 22 Native American
tribes. Source: USGS.
Table 1. Drought Contingency Plan reductions in Arizona’s allocation from the Colorado River.
FAS = feet above sea level; KAF = thousand acre-feet; MAF = million acre-feet
Figure 2. General outline of reductions in water allocations by general source associated
with the Drought Contingency Plan.
So, this translates to nearly 480KAF less water moving through the Grand Canyon and into Lake Mead in FY22 and it puts the lower basin (the region below Lake Powell, Figure 1) one step closer to Tier 2 reductions.
The BoR periodically runs a series of model projections regarding the water levels at the dams for both Lakes Mead and Powell. Results from these models recently projected future water levels at the dams for the end of calendar year (CY) 2022 and 2023. For Lake Mead the end of CY 2022 projections include a most probable level of 1,049.37 FAS and the lowest probable level at 1,047.10 FAS. These results project the need for a Tier 2a level declaration by the end of CY 2022.
For the end of 2023, Lake Mead projections include a most probable level 1,035.63 FAS, which would trigger Tier 2b reductions in Colorado River water allocations to Arizona and a most probable minimum level of 1,020.63 FAS, which would necessitate Tier 3 reductions.
Due to the recent changes in river management plans that have been announced by the BoR associated with Lake Powell, these model projections for the end of CY 2022 and 2023 are probably high and probably project an overly optimistic condition. But we can see that the probability of moving into the Tier 2a, 2b, and Tier 3 reductions are very likely to occur by the end of 2023, if not sooner.
The warnings of John Wesley Powell, the famous one-armed Civil War Veteran who first directed an expedition down the Colorado River and the Grand Canyon in 1869, are certainly very prescient in the face of the circumstances we are dealing with today. In an address to the Montana Congressional Convention in 1889 he offered the following statement: “All the great values of this territory have ultimately to be measured to you in acre feet”. That is incredibly prophetic and certainly true in the reality of conditions that we are dealing with on the Colorado River today.
Essentially what we have today on the Colorado River is a supply and demand problem. Very simply, our demand and extractions from the Colorado River have been greater than the supply and what the river can provide. As a result, the great reservoirs on the river system, the savings accounts so to speak, have been depleted. We must come to grips with that reality and decide how the allocations of Colorado River water must be adjusted to bring them into an appropriate balance with the water we do have in the river.
The overall situation with the Colorado River offers some good news and some bad news for all of us depending on this water to live, work, and survive in this desert. The average annual flow of the Colorado River between 2000 and 2018 has been approximately 12.4MAF, which is 16 % lower than the 1906-2017 average of 14.8MAF/year. So, the good news is with the recognition that we have ~ 12MAF average annual flow in the Colorado River under these megadrought conditions. The bad news is that the Colorado River system is budgeted for 16.5MAF of allocated water between the U.S. and Mexico. Thus, there is a functional difference of >4MAF and the fact is that we must reconcile that difference and fast action is needed, much faster than our water governance systems normally operate.
Arizona agricultural is responsible for ~ 70% of the water diversions on the Colorado River and agriculture is taking the reductions now with Tier 1 and will carry much of the responsibility for the Tier 2 reductions. How agriculture fares in this process of Colorado River management in response to the water shortages is critical for the future of Arizona agriculture and the overall complexion of life in the desert Southwest.
I believe agriculture will prevail, but a lot of hard work, difficult decisions, and changes are ahead of us in the near future. Agriculture has some strong and effective groups working in this decision-making arena for water governance on the Colorado River and we need to be sure that practical agricultural considerations are being made in the process with both short and long-term implications.
With melon season on full bloom, you will also start seeing diseases on melons. Cucurbit yellow stunting disorder is more of a problem on fall melons but they can also occur in summer melons. And it is always a good idea to be prepared for the next crop. Cucurbit yellow stunting disorder is a cucurbit disease caused by a plant virus named Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus, family Closteroviridae). This virus was first detected in southern California and Arizona in 2006 and infects cantaloupe and honeydew melon, watermelon, and various types of squash. CYSDV is transmitted exclusively by the whitefly, Bemisia tabaci. Symptoms always start from the oldest leave which is a diagnostic feature of the virus.
All biotypes of B. tabaci known to exist in North America can transmit the virus efficiently, including biotypes A, B and Q. Whitefly transmission is responsible for virus spread over short distances (e.g., within and between fields). However, with high winds whiteflies can move long distances and transport the virus. The virus can stay infectious within whiteflies for up to 9 days. As virus infection is systemic (meaning they have to be circulated inside the plant system to show symptoms) it can take 3 to 4 weeks for disease symptoms to develop following infection. This gives a window for infected symptomless plants can be unknowingly transported and can lead to epidemics. The virus is not transmitted mechanically (by touch, mechanical damage, cuts etc) or via seed. However, the virus can be efficiently transmitted even if there is low whitefly pressure in the field.
The best management approach is to monitor the whitefly population and be proactive with insecticides application. Rotate insecticides with different modes of action Group numbers to minimize development of insecticide resistance. Practice good weed management in and around fields to the extent feasible.
Remove and destroy old crops/volunteers, enforce regional cucurbit -free period to eliminate the virus from the cropping system.
Sweet Shield and Novira varieties seem to do well in Yuma area.
Hairy fleabane grows about 4 feet, branches from the bottom and leaves are pubescent also stems are covered with stiff hairs. The growth habits of horseweed (marestail) are different in that they grow up to 10 feet tall and branches from the upper half of the plant.
You can find Fleabane flowering right now in the Yuma area especially the Yuma Mesa. The IPM Team has received calls from our friends PCAs and growers stating that the Fleabane survives the application of Glyphosate, which has been reported for both conyzas. So, we got some trials in progress looking for options to control Fleabane as well as other weeds that have shown tolerance to Roundup such as White sweet clover or malva in different crops.
The results from the evaluations will be shared in this newsletter.
1. UC/IPM Retrieved from http://ipm.ucanr.edu/PMG/WEEDS/hairy_fleabane.html
Results of pheromone and sticky trap catches can be viewed HERE.
Results of pheromone and sticky trap catches can be viewed HERE.
Corn earworm: CEW moth activity increased a bit in the past 2 weeks but remains well below average for late spring.
Beet armyworm: Moth counts increased slightly, but remain very low consistent with seasonal temperatures, and below average for this point in the season.
Cabbage looper: Significant increase in activity in Dome Valley, Gila Valley and Tacna, but moth counts remain unusually low for this time of year, as they have all season.
Whitefly: No adult movement recorded across all locations and overall low numbers consistent with temperatures.
Thrips: Thrips adult movement beginning to pick up considerably, particularly in Yuma and Dome Valleys. Movement is below average for late March.
Aphids: Seasonal aphid counts down considerably compared with the Feb and Jan. Counts highest in Bard and Gila Valley. Below average movement for this time of year. Majority of species found on traps were green peach aphid.
Leafminers: Adult activity up slightly in some locations, but well below average for late season.