Temperatures are still warm and worm pressure remains steady in most growing areas.   Here at the Ag Center, beet armyworm pressure is about average for early October, and still troublesome on new stands. Cabbage looper eggs are beginning to now show up. Pheromone trap counts for armyworm and loopers remain below average in most areas. However, diamondback moth larvae are present on broccoli and transplants at the Ag Center.  I’ve had several PCA reports of diamondback pressure in transplanted brassica crops in Wellton and Roll, and in the Yuma Valley. Trap catches have begun to increase also. So far, all insecticide products we’ve tested are providing good Lep control and no complaints from the field.  
 
Fortunately for local PCAs, several insecticide alternatives are available that provide excellent residual activity on Lep pests.   Perhaps equally important, many of the products have unique modes of action (MOA) that can be alternated throughout the growing season. This is important because the most fundamental way to reduce the risk of insecticide resistance is to eliminate exposure of multiple generations of Leps to the same MOA.   By using a different MOA on each subsequent spray application, you can minimize the risk of resistance by Lep larvae to these insecticide compounds. In contrast, repeatedly applying insecticide products with the same MOA for Lep control in the same area will significantly increase the risk of resistance.  This is particularly important with the Diamide group of insecticides (IRAC group 28). These products can be applied as both foliar sprays and soil systemic treatments, and currently 7 Diamide products are labeled for use in leafy vegetables - all with the same MOA (Coragen, Durivo, Besiege, Minecto Pro, Verimark, Exirel and Harvanta).  To avoid confusion among the Diamides, the IRAC group number (28) is placed on each label, adjacent to the product name.  Furthermore, applying a Diamide product (i.e., Coragen/Verimark) to the soil at planting or as a tray drench, and then subsequently applying Diamide foliar sprays (i.e., Harvanta/Besiege) on the same field is not a good idea as it can expose multiple generations of Leps to the same MOA.  For example, under ideal weather conditions, one could potentially expose 5-6 generations of BAW or DBM to the same MOA given the residual efficacy of the diamides.  That’s not a good way to use these products if you want them to remain effective.   Since the Diamides, as well as the other key products currently available (e.g., Radiant, Proclaim, Intrepid, Avaunt, Bts), are critical to effective management of Leps in leafy vegetables, PCAs should consciously avoid the overuse of any of these compounds. The most effective way to delay the onset of resistance by Leps in leafy vegetables is to consider the recommendations provided in the guidelines entitled Insecticide Resistance Management for Beet Armyworm, Cabbage Looper and Diamondback Moth in Desert Produce Crops.

John Wesley Powell, the Civil War veteran who lost most of his right arm at the Battle of Shiloh, led his first expedition down the Green and Colorado Rivers, including the Grand Canyon in 1869.  This provided the first exploration of the Colorado River basin by Americans of European descent and it began the process of understanding the nature of western territories of the United States, including Arizona (Figure 1).
 
The degree of aridity of this region was very strongly impressed upon Powell and he spent much of his life working to educate law and policy makers of the conditions prevalent in the western U.S.  He worked diligently with lawmakers, government experts, and citizens to communicate the fact that the development of the western territories, which the nation was rapidly embarking on after the Civil War, would be limited due to the lack of water.  His comments to the Montana Constitutional Convention in 1889 “All the great values of this territory have ultimately to be measured to you in acre feet” is a good example of his basic message and it has proven to be quite prophetic in our experiences of living and working in the desert Southwest in the 20^th and 21st centuries.
 
Powell became the second director of the U.S. Geological Survey (USGS) from 1881 to 1894.  In this and similar capacities, he constantly advocated for policies for the development of the arid West that were consistent with the prevailing arid conditions.  As the lands in the western U.S. were being developed, the need for land “reclamation” was recognized.  It was 120 years ago this week, on 17 June 1902 that Theodore Roosevelt signed the Reclamation Act and the U.S. Reclamation Service (USRS) was formed within the USGS under the Secretary of the Interior Ethan Allen Hitchcock.  The new USRS was given the responsibility of studying potential water development projects in each western state with federal lands.  Revenue from the sale of federal lands was the initial source of the USRS funding.
 
Thus began the process of the USRS in the development of about 30 western water projects between 1902 to 1907.  In 1907, the Secretary of the Interior separated the USRS from the USGS and created the Bureau of Reclamation (BoR) as a distinct entity within the Department of the Interior.  The Boulder Canyon (Hoover Dam) project was authorized in Congress in 1928 and funded by general funds appropriated by Congress to the BoR, and from that the development of Lake Mead began.  Lake Mead is the main storage reservoir for the lower basin of the Colorado River.
 
In the late 19^th and early 20^th centuries, efforts in the western U.S. to develop lands for agriculture encountered problems with lands and soils that were found to be unsuitable for irrigation, often due to salinity, sodicity, and drainage problems.  The “reclamation” of these lands became an important part of the BoR objectives and operations.  All this development was dependent on the availability of water and good land and water management capacities.
 
During the 20^th century, the BoR was responsible for some tremendously large and ambitious projects, including Boulder Dam, Grand Coulee Dam, Glen Canyon Dam, and many others.  Today, the BoR operates in 17 western states with water and electrical power projects with more than 600 dams, reservoirs, powerplants, and canals.  The BoR is the largest wholesaler of water in the U.S. and supports irrigation water storage and conveyance throughout the west on farmlands that produce more than 60% of the nation’s vegetables and 25% of the fruit and nut production in the country. The BoR is the second largest producer of hydroelectric power in the U.S. with 53 powerplants.  The western U.S. development and population is heavily dependent on the BoR water and power works.
 
In Arizona and the desert Southwest, the lands and people here today have a very close relationship to the BoR for water and electrical power.  All the lands along the mainstem of the Colorado River and the Central Arizona Project (CAP) are intimately connected to the BoR.  Our efforts to deal with the water shortages on the entire Colorado River system are some of the greatest challenges this region and the BoR have faced since the early days of development in the 19^th century.  
 
Thus, there are many participants in the process of dealing with the current water shortage on the Colorado River system, including the U.S. Department of the Interior, the BoR, and all the basin states.  An accentuating feature of the current water shortage on the Colorado River is due to the fact that for the past 22 years, the average annual flow in the Colorado River has been ~ 12.4 million acre-feet (maf) while the Colorado River water is budgeted for a total of 16.5 maf of allocations between U.S. states and Mexico. 
 
Essentially, all of us living in the desert Southwest are in this together; including agricultural, urban, and tribal entities.  All parties involved must work together to resolve this disparity between the water that the river is providing and the greater amount that is desired and allocated.  The issues and general situation that we are facing has an urgency that requires immediate attention.  I remain hopeful that we can meet the challenges of our time as our predecessors did in the past.

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. 

Diagnosis can be done at Yuma Plant Health Clinic at Yuma Ag Center or at Dr. William Wintermantel’s USDA lab in Salinas, CA (samples have to be shipped overnight). Molecular diagnosis is required as symptoms sometimes can be misleading. Dr. Wintermantel’s (bill.wintermantel@usda.gov)  team is working on looking at virus titer (amount of virus) in single and mixed infections  and also looking at source of resistance. If your plants have the symptoms and like them to be tested please contact me (bpoudel@email.arizona.edu, 928-920-1110). You will get your molecular diagnosis for free, and we will be contributing towards a research in mitigating the problem. 
Sweet Shield and Novira varieties seem to do well in Yuma area. 

New kid in the block! Please welcome Rebecca Ramirez! She is a recent addition to our Plant Pathology Program. Rebecca started working as a volunteer at the Plant Clinic since April, 2019 and started working full time this week. Rebecca will be working mainly on the diagnostic clinic and the Fusarium bioassay project. We are delighted to have her on board. Rebecca can be reached as rebeccaramirez@email.arizona.edu. Send her warm welcome, stop by and say hello, send best wishes, tell her she has the best boss and all that ;) 

Interested in staying up to date on the latest international robotic ag technologies? FIRA (International Forum for Agricultural Robotics) held an “Open Day” May 13th and posted recorded presentations on their website. In addition to technical panel discussions with industry experts, the event included live field demos of weeding, scouting and general farming robots. The FIRA Connect website also has replays of presentations given at the 2021 FIRA Conference held last December. In total, there are thirty short presentations and field demos of ag robots freely available. About 1/3^rd of the presentations/demos are weeding machines from Europe that utilize various methods for in-row weed removal – lasers, precision spot sprayers, concentrated light beams, and mechanical devices including knife blades, rotating heads, and weed pulling mechanisms. The site also provides links to a “Robot Wall” and a “R&D Wall” where companies have posted information about their commercially available and in-development ag robots. It is a quality website and worth checking out to learn more about the latest automated agricultural technology innovations being developed around the world. 

To connect to the FIRA website, click here

Overreliance in glyphosate could increase the risk of reduced efficacy of this herbicide. Some the weeds difficult to control with glyphosate in our area are: Hairy fleabane (Coniza bonariensis), Horseweed (Coniza canadiensis), White sweet clover (Melilotus albus). Pig weed (Amaranthus palmeri), and Cheeseweed (Malva parviflora). We are conducting experiments in the Yuma area to identify effective herbicide control options for Hairy fleabane. Some research done in Australia has shown that Fleabane cannot be controlled with a single herbicide treatment even with knockdown herbicides such as paraquat + diquat, and researchers suggest the need of combinations of different modes of action to achieve control effectively¹. In one fleabane evaluation started May 6, 2022, we included the following treatments: 1. Embed Extra 2pt/A+5%NIS 2. Rely 82 floz+5%NIS 3. Chateau+ Treevix+MSO (12oz+1oz/A+1%)

We noticed treatments including Glufosinate (Rely) showed best burndown activity, but regrowth was observed in two weeks (13-14 plants per ft²). So, a second application was performed on three weeks after first on the Rely plots.
The grower and PCA informs us that Sulfenacil (Sharpen) has worked effectively for them with sequential applications. Additionally, we are evaluating Suppress and Clopyralid in the same location.

You are always welcomed to send your comments, suggestions to the IPM Team. Let us know what you are doing and your findings. We know there is a researcher in every grower and PCA and your input is greatly appreciated.

1. Hanwen Wu, Steve Walker and Geoff Robinson (2008). Chemical control of flaxleaf fleaeabane (Conyza bonariensis (L.) Cronquist) in winter fallows. Plant Protection Quarterly Vol.23(4) 2008
2. Travlos, I., & Chachalis, D. (2010). Glyphosate-Resistant Hairy Fleabane (Conyza bonariensis) Is Reported in Greece. Weed Technology, 24(4), 569-573. doi:10.1614/WT-D-09-00080.1

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 17, Aug 21, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased areawide; about average to previous years.
 
Beet armyworm:         
BAW moth counts are up in south Yuma valley and Dome valley; about average for August

Cabbage looper:           
Cabbage looper numbers are low consistent with previous years and higher temperatures.
 
Diamondback moth:      
DBM moths were not caught in any trap; average for this time of the year.
 
Whitefly:                      
Adult movement continues to decrease, average for this time of the year.
 
Thrips:                          
Thrips adult activity continues to decline, average for August.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity declining and average for August.