Dr. John Palumbo’s contributions shaped our vegetable IPM program and supported countless growers and PCAs across the region. While no one can truly take John’s place, we want to reassure you that we remain committed to continuing the vital work he championed. With care and respect for the foundation he built, we are working to carry his efforts forward.

A dedicated team is in place to ensure that the needs of growers and industry partners are met for the quickly approaching 2025–26 growing season. While a permanent replacement will be hired through a formal search and selection process, the team remains fully committed and ready to maintain John’s high priority projects in the meantime.

Moving forward, members of the John Palumbo transition team will be present at future Extension and industry meetings to share trial results, program updates, and to ensure ongoing support for stakeholders. The Vegetable IPM Newsletter will remain a key outlet for sharing trial results and updates on ongoing research, as well as providing the biweekly insect trapping network results that so many rely on for timely, informed decisions. John’s information will continue to hold the top spot in the newsletter, in recognition of his leadership and as a way to keep his work front and center for our community. We also want to share that the Name the Pest competition will continue, and John’s beloved (and often legendary) hats will still be awarded as prizes. Though John’s presence can never be replaced, we can carry his spirit forward by advancing his research, keeping his traditions alive, and continuing to serve our vegetable IPM community with the same dedication he inspired in all of us.

John built this program to serve you — the growers, PCAs, and industry partners who shape and sustain it. Your letters and statements supporting a timely search and strong candidate recruitment will help keep it strong and aligned with your needs. Thank you for your dedication, your voice, and for honoring John’s legacy by continuing to move forward together.

The water shortage on the Colorado River that we are dealing with today has been accelerated by the extensive drought that began more than 20 years ago.  Climatologists have recognized this drought, extending more than 22 years, as the most extensive drought this region has experienced in more 1,200 years.  However, there are many factors that have been in operation for more than 100 years that are contributing significantly to our current water shortage dilemma.
 
To effectively address a problem, it is important to understand the situation leading to the problem in question and that includes understanding the derivation and historical background leading to the current condition.  Accordingly, I am offering a few points of historical importance in my view that have contributed to the development of the challenges we are dealing with on the Colorado River system today.
 
The Colorado River watershed and system (Figure 1) is one of the largest in the U.S.  The main channel of the Colorado River extends over 1,450 miles, covers 244,000 square miles in the drainage basin, and it has the greatest elevation fall of any watershed in North America. The Colorado River supports more than 40M people, nearly 6M acres of cropland, 30 native American tribes, and provides large amounts of electrical power generation for southwestern U.S.

Figure 1. The Colorado River watershed.  Source: USGS.

Average annual flow in the Colorado River between 1906-2017 was 14.8 million acre-feet (maf), Figure 2.  Between 2000 and 2018, the average annual flow has been ~ 12.4 maf, Figure 3.  The allocated water for diversion on the Colorado River has been 16.5 maf (15 maf in the U.S. + 1.5 maf to Mexico).  Thus, there has been a structural deficit of at least 2.0 maf for many years and during this megadrought of the early 21^st century we have been operating on a deficit of ~ 4.0 maf.  
 
Actual water use estimates for the past 30-40 years are shown in Table 1, including evaporation and actual diversions, so that the total use of the Colorado River has been estimated at ~ 16.0-17.5 maf. Collectively, as a result over the past 22 years, the great reservoirs of Lakes Mead and Powell have been significantly diminished.

Figure 2.  Colorado River Annual Flow, 1905-2010 with an overall average and 10-year
average. Source: Bureau of Reclamation.


Figure 3.  Colorado River Annual Flow, 1905-2020 with an overall average and 2-year
average. Source: Bureau of Reclamation.

Colorado River Basin Section	MAF	MAF
	Min	Max
Upper Basin mainstream uses (includes evaporation)	4.0	4.5
Lower Basin mainstream uses	7.5	7.5
Lower Basin reservoir evaporation	1.0	1.5
Lower Basin tributaries	2.0	2.5
Total Lower Basin	10.5	11.5
Subtotal (U.S.)	14.5	16.0
Mexico	1.5	1.5
TOTAL	16.0	17.5

Table 1. Colorado River Use Estimates. Source: Bureau of Reclamation.
MAF = million acre-feet per year.
 
One observation that can be drawn from a review of Figures 2-4 is that annual flow in the Colorado River is highly variable.  Secondly, the past 20 years indicates a distinct decline in annual flow in the river.  Comparatively, the first 20 years of the 20^th century had relatively high annual flows, particularly in contrast to the first 20 years of the 21^stcentury.  This has contributed to the difficulties being experienced today.
 
Governance of the Colorado River is commonly referenced to the “Law of the River”, which is based on the Colorado River Compact of 1922 (CRC of 1922) and a collection of laws, contracts, agreements, and definitions.  Thus, the Law of the River is not one distinct entity but rather an amalgam of various components.  Key components include the CRC of 1922 which was formally negotiated among the basin states to define how much water from the Colorado River can be used by each state on an annual basis. Other agreements contribute to the aggregate Law of the River, including a 1944 Treaty, that agreed to Colorado River water allocations to Mexico.  In 2007, basin states negotiated interim guidelines to deal with Colorado River water shortages and determine the reductions for each state depending on the elevation of water in Lake Mead.  The reductions associated with a shortage of Colorado River water was further augmented in 2019 by the Drought Contingency Plan (DCP) among the basin states, with specific guidelines for both the upper and lower-basin states.
 
The CRC of 1922 is a foundation to the “Law of the River” and was developed following a period of relatively high annual flows, Figure 4.  Based on the records associated with the transactions leading to the signing of the CRC of 1922, the hydrologists and other scientists were providing data and interpretations to the commission that was working on the CRC of 1922.  Even though these hydrologists and scientists did not have the technological capabilities that are available today, they did an amazingly good job.  There is evidence that the data was presented to commission negotiators showing that allocating 16 maf (plus the future allocation to Mexico for delivery) was more than the 10 year-average for much of the timespan of the available data.  Nevertheless, the operational base of Colorado River water allocation was defined in the CRC of 1922 with 15 maf allocated among the basin states and they have been able to make it work for 100 years.  However, as we can see from review of Figures 2-4 and considering the annual average flow of the past 20 years being ~ 12.4 maf, the original CRC of 1922 allocation budget is not sustainable.

Figure 4.  Natural annual Colorado River flow data from 1878-2013 with a running average
(gray line) and 10-year moving average (orange line) and indicating the point of CRC of 1922 signing. 

The good news is that we do have ~ 12 maf of annual flow currently to work with.  That represents about 27% less annual flow than the budgeted amount of 16.5 maf.  If all states receiving Colorado River water allocations were proportionately reduced by 27%, each state would then need to determine how that water would be allocated within their boundaries.  Arizona’s allocation would change from 2.8 to ~ 2 maf.
 
One of the good things about common attitudes for people in agriculture is the tendency to appreciate and deal with reality and the basic facts that we are faced with.  Whatever we do, we must deal with the reality of this situation on the Colorado River and come to terms with the facts of the matter the best we can.  Agriculture is responsible for ~ 70% of the total water diversions in Arizona which supports an industry worth more than $23B annually and provides food and fiber to the state, region, nation, and global exports.  
 
Some experts are advocating a review and re-negotiation of the CRC of 1922 and the basic budget of water allocations.  That is a reasonable suggestion considering the facts of the case.
 
The climate is bearing down upon us, conditions on the Colorado River are increasingly dire, and we do not have much time to act.  In agriculture, we need to be part of the process of dealing with the Colorado River water shortage and be part of the solution in a manner that is sustainable for all of Arizona and the productive agricultural systems of this state and region.

Bacterial leaf spot is caused by the bacterium, Pseudomonas syringae pv. Aptata. Hosts of the pathogen include Table beet, Sugar beet, Spinach, Swiss chard, Snap bean, Dry bean, Cantaloupe, Pumpkin, Squash, Lettuce, and Pepper.

Significance

Bacterial leaf spot is most commonly found affecting table beet at early stages of growth. This may be because younger plants are more susceptible. It may also be related to the prevalence of cool, wet conditions at the beginning of the cropping season. These conditions are most conducive to infection and disease development. The disease may affect green leaf area in developing seedlings and in severe cases can lead to plant death. Diseased leaves will lead to weakened seedlings which may affect transplant success. Bacterial leaf spot does not directly affect root quality.

Figure 1. Bacterial leaf spot caused by Pseudomonas syringae pv. aptata of table
beet:(left) Small focus of the disease, and (right) 2-6 true leaf stage of plants
affected by the epidemic.

Symptoms

Bacterial leaf spot symptoms are irregular in shape and black to brown in color. The spots may occur across the leaf surface but have a tendency to occur on the leaf edges. Lesions are water-soaked not often accompanied by chlorosis (yellowing). Lesions may initially be small (up to ¼ inch in diameter) but if conditions are conducive may rapidly expand and coalesce but do not cross major veins. The leaf is usually puckered and deformed around the lesions, especially if they occur on the margins (Fig. 2). When the disease is severe, the affected the tissue may also tear giving the appearance of abiotic damage such as hail.

Figure 2. Symptoms of bacterial leaf spot on table beet (cv. Merlin). Note the black
color of the lesions and puckering and deformation of the leaves around the
symptoms.

Bacterial leaf spot symptoms maybe confused with other fungal foliar diseases (e.g. Cercospora and Phoma leaf spots; see complementary fact sheets for these diseases) and insect damage (e.g. thrips). Bacterial leaf spot lesions do not have black pin-head, fungal structures across the lesions as found in Cercospora leaf spot. Phoma leaf spot lesions also have small, black structures within the lesions but found in rings and usually accompanied by an ooze of spores.

Disease Cycle

Figure 3. Schematic diagram of the potential sources of Pseudomonas syringae pv. aptata inoculum which may contribute to Bacterial leaf spot epidemics in table beet. 

P. syringae pv. aptata may be introduced to the table beet crop through several ways (Fig. 3). P. syringae pv. aptata is seedborne and infested seed is a common means of pathogen introduction into table beet fields. The pathogen can also be present in the infested crop residues from the previous season as well as the alternative hosts. Alternative crop hosts include typical Chenopods (e.g. spinach, sugar beet, and Swiss chard) but also other non-related species including beans, cucurbits, and lettuce. Cool temperatures between 45-60°F and wet conditions typical of those that occur in early spring in upstate New York are conducive for pathogen infection and disease development. These conditions are similar to those that predispose table beet also to Phoma leaf spot. The pathogen can spread within the field through infested seed and irrigation water.

Disease Management

One of the most critical factors to achieve management of bacterial leaf spot is the use of certified seeds (Fig. 4). Other factors that will also contribute to reducing the initial inoculum and hence risk of disease include: (i) tillage to bury plant residues to promote breakdown, (ii) rotation between host crop species of at least three years; and (iii) drip or furrow irrigation to avoid dispersal of the pathogen through water splash. Currently, little is known of differences in cultivar susceptibility to bacterial leaf spot. Anecdotal reports have described severe epidemics in cvs. Merlin, Boro, and Pablo.

Figure 4. Complementary practices towards the management of Bacterial leaf spot of table beet.

In-season control.
If bacterial leaf spot is severe, applications of copper-based products should be considered to prevent disease spread. There are a range of conventional and OMRI-listed copper-based products available, including: Cueva (copper octanoate; FRAC M1), Badge X2 (copper oxychloride + copper hydroxide; FRAC M1), and Kocide 3000-O (copper hydroxide; FRAC M1). Remember to check the label for rates, re-entry intervals, and pre-harvest intervals applicable to your state and crop. Avoid applying copper-based products on transplants before hardening off, and in high temperatures due to the risk of phytotoxicity.

Source:
https://www.vegetables.cornell.edu/pest-management/disease-factsheets/bacterial-leaf-spot-of-table-beet/

Vol. 13, Issue 05, Published 3/09/2022
A couple of weeks ago, I presented summarized results of our multi-year trials examining the use of band-steam to control sclerotinia lettuce drop, Fusarium wilt of lettuce and in-row weeds at the 2022 Southwest Ag Summit. Band-steam has been described in previous UA Veg IPM articles (Vol. 12 (5), Vol. 11 (15). Briefly, the concept behind band-steam is to disinfest narrow bands of soil centered on the seedline using high temperature steam prior to planting.
Results varied as you might expect depending on field conditions, but in general, injecting steam pre-plant was found to provide very good on weed control (85-100%), and reasonable control of sclerotinia (up to 70%) and Fusarium (>40% when initial inoculum levels were moderate). Crop yield increases of 24% to more 40% were found in trials (5) conducted in fields with varying levels of disease history. Energy requirements and fuel costs were high (~$900/acre) when initial soil temperatures were low (50°F, winter), but much more reasonable (~178/acre) when initial soil temperatures were high (110°F, winter).
We concluded that band-steam may be a viable technique for controlling soilborne pests in high value conventional and organic vegetable crops, particularly if steam is applied when initial soil temperatures are high and the significant yield increases found in our studies can be realized at the field scale level. The presentation was uploaded to YouTube where you can find more specific details and to see the band-steam applicator in action. To see the presentation, click here or on the link below.
Acknowledgements
This work is partially funded by the Arizona Iceberg Lettuce Research Council, Arizona Specialty Crop Block Grant Program and USDA-NIFA Crop Protection and Pest Management Program.

Dacthal was first registered in 1959 but like most older products that are still used, we are constantly adapting it to our changing cultural practices. Dacthal is a mitotic inhibitor and kills germinating weeds by stopping cell division. This is the same mode of action as many other preemergence herbicides such as Trifluralin, Prowl, Balan, Kerb and others but its chemistry and how it moves in the soil and plant are different. Dacthal is absorbed by both shoots and roots of germinating seedlings although most of the activity is from shoot absorption. When absorbed by the shoots, it will move upward into the plant. It is not absorbed by foliage and can be safely applied over the crop. Dacthal has a strong affinity for soil and adsorbs strongly to soil particles. If Dacthal is applied to dry soil, it sometimes will not work because the herbicide it stuck on the soil and not available to kill weeds. Conversely, if the soil is saturated, it may not be adequately incorporated. The best time to apply Dacthal is when the soil is moist but not saturated. When Dacthal was first being developed it was tested for use on lettuce.If it is sprayed on or chemigated it will cause severe injury to lettuce. If it is mechanically incorporated it is surprisingly safe to lettuce. It is fairly broad spectrum but weak on mustards.

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

 

Corn earworm: CEW moth counts remain at low levels in all areas, well below average for this time of year.

Beet armyworm: Trap increased areawide; above average compared to previous years.

Cabbage looper:  Cabbage looper counts decreased in all areas; below average for this time of season.

Diamondback moth: DBM moth counts decreased in most areas. About average for this time of the year.

Whitefly: Adult movement beginning at low levels, average for early spring.

Thrips: Thrips adult counts reached their peak for the season. Above average compared with previous years.

Aphids:  Aphid movement decreased in all areas; below average for late-March.

Leafminers: Adults remain low in most locations, below average for March.