A significant decline in insect pest activity has occurred over the past 2 weeks. These changes are consistent with cooler, seasonal temperatures. We all know that weather influences produce crop growth and ultimately can create wide fluctuations in markets. Similarly, our local weather can significantly impact pest activity on desert produce crops.    For insects, their activity and abundance are closely aligned with weather. The reason for this is that temperature is the driving force behind insect development, growth and behavior. Unlike many animals, insects are poikilothermic (“cold-blooded”); that is, they are unable to regulate their body temperature. Their internal temperature varies along with that of the ambient environmental temperature. Consequently, insect pests such as whiteflies, beet armyworms, cabbage loopers, diamondback moths, and leafminers are more active and develop rapidly when temperatures average ~85° F; in contrast, they are less active and develop much slower under cool, winter conditions.  That is one of the primary reasons these insect pests can be so abundant on produce crops in Sep-Nov.  Behavioral activities such as flight, movement, reproduction, feeding and oviposition are similarly influenced by seasonal temperatures. But temperature requirements for insects vary with species (see table below).  For example, the optimal temperature for growth and development of beet armyworms and diamondback moths is the same (86 °F), but diamondback moth can complete a generation quicker and can develop over a much broader range of temperature. Thus, they can be more problematic season long if not adequately controlled.  Then you have Bagrada bug which tend to prefer warmer weather for development.  Its lower developmental threshold of 62°F is the main reason the pest is generally hard to find during the winter months.  In contrast, green peach aphids, which we annually find on winter produce crops, thrive in cooler weather (optimal temperature for growth is 55°F.  That’s the main reason we don’t find them on summer crops; it is just too hot for them.  In general, extreme hot (> 120°F) or cold temperatures (<32 °F), can be lethal or greatly restrict insect growth and behavior.  Consequently, temperature and other weather factor such as rainfall, humidity, sunlight and wind play a major role in determining insect activity and abundance on local desert crops; but they can also suppress insect abundance under extreme conditions. For a more detailed explanation on the impact of weather on insects visit Weather Influences Desert Insect Pests.
 
 

	Developmental Threshold(°F)		Optimal Temp.(°F)for Development	Immature development (days)
	Lower	Upper
Beet armyworm	54	100	86	16.5
Diamondback moth	39	107	86	11.1
Bagrada bug	62	108	95	14.5
Green peach aphid	36	82	55	8.5

 

I have recently provided some articles for this newsletter addressing the increasing fertilizer prices that U.S. agricultural communities have been experiencing (1 December 2021 and 8 February 2022).  The situation continues to change following the Russian invasion of Ukraine, which is making things even more difficult and driving fertilizer prices even higher.
 
Fertilizer prices have more than doubled in the past year for most materials commonly used in production agriculture.  Fertilizer prices have been increasing primarily as a function of higher natural gas prices, high global demand, and low inventories.  In addition, supply chain disruptions have served to further complicate the situation.  In response, the USDA has announced plans for a $250M investment to support innovative American-made fertilizer to give US farmers more choices in the marketplace (USDA Press Release No. 0060.22).  That will be an interesting program to watch.
 
Now, with the war in Ukraine, the resultant sanctions, and global disruptions; the Russian government has restricted fertilizer exports.  This is a major problem since Russia is a major low-cost exporter of every type of crop nutrient, particularly of nitrogen (N), phosphorus (P), and potassium (K).  Russia is the second-largest producer of ammonia, urea, and potash and it is the fifth-largest producer of processed phosphates. Russia provides 23% of the global ammonia for the export market, 14% of urea, 21% for potash, and 10% of the processed phosphates (The Fertilizer Institute; TFI, https://www.tfi.org/).
 
Currently, Belarus and Russia account for about 15% of all world fertilizer. Europe, including Ukraine, are heavily dependent on both countries for fertilizer inputs. Due to Russia’s large fertilizer production and footprint as a global fertilizer supplier, Russian products being removed from the global marketplace will have an impact on supply.
 
Large amounts of natural gas are required in the industrial process of N fixation by the Haber-Bosch process that provides the base for most N fertilizers.  Russia supplies about one-third of Europe's natural gas supply and many of the globally important N fertilizer plants are in Europe.
 
Potassium fertilizers are mined from deposits of potassium chloride (KCl, muriate of potash), potassium sulfate (K2SO4), and potassium nitrate (KNO3).  Canada is by far the largest producer of K fertilizer worldwide.  Russia also has huge deposits of K minerals that are mined for fertilizer production and it ranks second in production and #3 globally in K fertilizer exports (Table 1).  In 2020, the U.S. was just below Spain and produced ~ 350,000 metric tons of K fertilizer (The Fertilizer Institute; TFI, https://www.tfi.org/; Potash Investing News, https://investingnews.com/daily/resource-investing/agriculture-investing/potash-investing/top-potash-countries-by-production/).
 

Nation	Metric Tons of K fertilizer
Canada	14M
Russia	7.6M
Belarus	7.3M
China	5M
Germany	3M
Israel	2M
Jordan	1.5M
Chile	900K
Spain	470K

Table 1.  Top countries in K fertilizer production, 2020.  U.S. Geological Survey

 
The U.S. has a robust fertilizer industry but prices for our products are driven by global supply and demand factors, and it is important to note that more than 90% of all fertilizer is consumed outside of the U.S.  North America imports ~ 20% of its urea N fertilizer (46-0-0) from Russia.  Some nations have a much larger exposure to these global fertilizer problems and Brazil tops the list with the importation of 47% of their K fertilizer supply coming from Russia along with ~ 20% of their urea and 30% of their mono-ammonium phosphate.
 
Russian exports ~ 14% of the global urea supply and China makes up about 20%.  Many experts in the international fertilizer industry are anticipating that China will increase global urea fertilizer exports in 2022 due to the current circumstances but that is not certain at this point.
 
The fertilizer supply and price situation does not seem likely to improve soon.  So, we are going to have to deal with it.  Fortunately, we have good methods for managing our crop nutrient needs and the use of fertilizers in our crop production systems.  This makes the value of soil testing more important and the use of the various tools we have at our disposal to improve fertilizer use efficiency. 
 
Developing a sound fertilization program begins with a good understanding of actual soil conditions. The collection and analyses of a good (representative) set of soil samples and then relating that information to established guidelines are the first steps toward developing a strong soil fertility and plant nutritional management program for any crop. This is important for the overall agronomic, economic, and environmental efficiency of a crop production system.
 
To maximize nutrient management efficiency, it is always important to include and consider the 4R concept of plant nutrient management and application, consisting of:
 1.   The Right fertilizer source at the
 2.   Right rate, at the
 3.   Right time and in the
 4.   Right place
 
The 4R nutrient stewardship approach utilizes the implementation of best management practices (BMPs) that optimize the fertilizer use efficiency by the crop. The primary objective of the 4R approach and BMPs is to match nutrient supply with crop requirements and to minimize nutrient losses from fields.  Each case can vary among farms and fields, dependent on local soil and climatic conditions, crop, management conditions, and other site-specific factors.  Field level management is always important and it will be increasingly critical with high fertilizer prices.
 
References:
The Fertilizer Institute https://www.tfi.org/
 
Potash Investing News https://investingnews.com/daily/resource-investing/agriculture-investing/potash-investing/top-potash-countries-by-production/
 
U.S. Geological Survey, Mineral Commodity Summaries, January 2021 https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-potash.pdf
 
USDA. 11 March 2020. USDA Announces Plans for $250 Million Investment to Support Innovative American-made Fertilizer to give US Farmers more choices in the Marketplace. Press Release No. 0060.22.  https://www.usda.gov/media/press-releases/2022/03/11/usda-announces-plans-250-million-investment-support-innovative

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches between bed centers. All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart. 

Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.  

Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves  ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any treatments in this trial.

ANR Webinar 10/17 click link for details.

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.

London Rocket (Sisymbrium irio)
If you drive through the Valley of Yuma Arizona this week you will see a significant amount of London rocket, a winter annual broadleaf weed from the family of the Brassicaceae. We can see it in already harvested lettuce fields, edges of alfalfa fields, on roadsides, orchards, and gardens.
Why London Rocket? According to some sources the common name "London rocket" allegedly comes from its abundance after the Great Fire of London in 1666 even though years later Dr E J Salisbury failed to find specimens in a study in 1940 ^[1].
The seed leaves (cotyledons) are oval, around 2–6 mm long, without pubescence. True leaves are a bit larger than the cotyledon, has smooth edges or a few weak teeth, and is on a long stalk. Leaves are alternate on the stem.
The mature plant grows approximately 24-36” tall in our area. It grows erect and ranches are mostly close to the base of the plant. The leaves have very little pubescence and have opposite lobes. Right now, we can see its abundant yellow flowers in our area and grow in clusters at the top of the stems (pic below). The fruits are 1-1.5” seedpods that are straight or a little curved and about 1mm wide.
Here in the “Lettuce capital of the world” this weed can be a problem because of it is highly competitive. 
In lettuce production the application of Kerb (Pronamide) has shown good London rocket control when applied properly. This means not too early or with too much sprinkler irrigation to avoid leaching. Delayed application is often needed, and the location of the herbicide is critical for best performance. Approximately 1-3 days after starting sprinklers for early plantings (Aug-Sep) and from 3-6 days for mid-season plantings (Oct-Nov) ^[3].

Interestingly, medical researchers tested some extracts of seeds and found it showed significant antipyretic and analgesic effects and antibacterial action ^[2]. Other medicinal properties have been reported such as the reduction of swelling and use for cleaning of wounds, rheumatism relief, chest congestion, cough, detoxify the liver and spleen ^[1]. 
When weeds like London Rocket are infesting our lettuce or alfalfa fields, they can be such a nuisance. But it's possible that in other parts of the world people are looking for them as beneficial herbs.

London rocket seedling and mature plant in alfalfa field.

References:
1. Retrieved from: https://en.wikipedia.org/wiki/Sisymbrium_irio
2. Antipyretic, Analgesic and Antimicrobial Studies on Sisymbrium irioS. B. Vohora, S. A. H. Naqvi, I. Kumar (1980) Institute of History of Medicine & Medical Research, Tughlaqabad, New Delhi (India).
3. Retrieved from: https://www.farmprogress.com/timing-critical-kerb-herbicide

MOST RECENT Area wide Insect Trapping Network Report   VegIPM Update, Vol. 14, No. 14, Jul 12, 2023
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased in the past 2 weeks and about average for this time of summer.
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Valley and Wellton) but about average for July.
 
Cabbage looper:          
Cabbage looper numbers remain low consistent with the lack of activity this fall compared to last season.
 
Diamondback moth:       
DBM moths were not caught in any trap in the past 2 weeks; average for this time of the year.
 
Whitefly:                       
Adult movement continuing to increase, particularly in Gila and Yuma Valleys consistent with melon harvest.
 
Thrips:                           
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                        
Aphid movement is absent consistent with what we typically see in the summer. 
 
Leafminers:                  
Adult activity has highest in Yuma and Dome Valley, and above average for early July.