Effective control of western flower thrips (WFT) to prevent cosmetic scarring and contamination is important in spring lettuce crops, and now that INSV has been found infecting plants in Yuma lettuce, management becomes even more important.  For most of the growing season, WFT numbers have been below average based on sticky trap counts, field reports and population densities here at YAC. However, in the past few weeks WFT populations have increased in most growing areas. This is not surprising as we typically observe “bioconcentration" of WFT during March and April on late lettuce as surrounding produce acreage declines. Each time a lettuce field is harvested, and disked, adult thrips disperse from these areas into the next available lettuce field.  As the number of lettuce acres becomes reduced near the end of the season, this creates a bottleneck effect that concentrates high numbers of thrips adults on the remaining fields under production. This can often make chemical control of WFT very difficult, particularly in March, as adults can continually re-infest fields following spray applications.   So, what management approaches can you take to manage thrips and hopefully reduce the potential incidence of INSV.  The first line of defense should be sanitation. Growers should disc under produce crops immediately following harvest. The longer a harvested crop remains above ground, the more insects that can build up and move to adjacent lettuce fields, especially with the dry, windy, and warm weather we typically have in March.   If only light INSV incidence is present in pre-harvest fields, PCAs should consider rogueing and removing suspect plants from the field.  Ultimately, this may curb secondary infection within the field. 
Controlling WFT with insecticides is the best approach to minimizing cosmetic feeding damage and may reduce spread of INSV within fields. For adults, which can easily be found on the leaf surface, your best choices of insecticide are methomyl (Lannate) or acephate at a high label rate.  They are the most efficacious products against adult WFT. Radiant is not as consistently efficacious against adults, but a 7 oz or higher rate will provide the best knockdown and residual control of WFT larvae.  Remember, the key to preventing cosmetic damage by WFT is to maintain larval populations at low levels.  The cryptic or thigmotactic behavior of thrips often makes them difficult to find on lettuce plants. Research has shown that if you can see a few adults and larvae on the plant, it means that there are likely 10-fold more thrips actually on the plant (hiding near the base of the plant between midribs).  This behavior also means that spray coverage is important, particularly with contact insecticides like Lannate. There are other insecticides such as Torac, Minecto Pro, Exirel, Movento and Assail that can provide suppression (50% control or less) against WFT larvae, but don’t expect much activity against adults. For more information on the identification, biology, ecology, and management of thrips on desert produce please visit Western Flower Thrips Management on Desert Produce.

 

Name pest contest: 

What caused this damage to this small watermelon fruit?

Improvements of irrigation and crop water management are always central to any discussions in the agricultural communities of the desert Southwest regarding higher crop production efficiencies.  That is particularly true in these days of water shortages.
In any crop production setting the crop (plant)-soil-water relationships are essential to producing a healthy and productive crop.  In desert agriculture, water is our first limiting agronomic (crop and soil) factor and there is no substitute for that.
Amid all the discussions about improvements in irrigation efficiency, the focus on plant-soil-water relations needs to be continually emphasized.  The objective of any irrigation system is to provide adequate irrigation water to the soil for the benefit of the crop.  Thus, it is important to understand the soil conditions and the actual crop-water needs for each irrigation event.

Every combination of a soil and a specific crop is unique, and that delicate relationship is compounded by the above ground environment the plant is growing in, the meteorological conditions.  The dynamics of crop-water demand change with each plant species and it will vary daily within a given crop in response to soil conditions, stage of growth, and meteorological conditions, i.e., temperature, humidity, wind speed, solar radiation, etc.   These meteorological factors must be appropriately considered for efficient irrigation management, irrespective of any type of irrigation system, i.e., flood, sprinkler, drip, etc.
In Arizona we are fortunate to have the Arizona Meteorological Network (AZMET) in place and fully operational with high quality data being collected from agricultural areas across the state on an hourly basis.  At present, this data is summarized daily from 25 agricultural sites and seven urban sites across the state.  https://ag.arizona.edu/azmet/

Dr. Paul Brown, Extension Specialist in Biometeorology (retired) began the development of the AZMET system in 1985 and the full operation of the system began in January 1986.  Prior to his retirement a few years ago, Dr. Brown managed and directed the AZMET system along with a robust research and Extension education program to provide numerous crop production tools that this system supports.  Together, Paul Brown and Bruce Russell developed an excellent weather system that is available to us all.   Dr. Jeremy Weiss now directs the AZMET program.

The meteorological data collected by AZMET include temperature (air and soil), humidity, solar radiation, wind (speed and direction), and precipitation.  AZMET also provides a variety of computed variables, including heat units (degree-days), chill hours, dew point, and reference crop evapotranspiration (ETo).  AZMET data are summarized in a variety of formats, including several ready-to-use summaries and comma-delimited (raw) ASCII text files that can be imported into most database and spreadsheet programs (Russell, 2011).
I have participated in numerous discussions recently regarding efforts to manage water resources in a broad sense, such as within an area or district, as well as in individual crop fields where the use of satellite-based evaporation (ET) estimates are being considered for application.  In Arizona, that should not be necessary since we have AZMET stations on the ground that are well-placed in agricultural areas with high quality data available daily.  The AZMET system provides direct measurements of daily atmospheric conditions that our crops are dealing with in each of the 25 locations.

With AZMET and the information directly available and accessible, in my view we should be using this system for our weather-based needs for crop management and not a remote satellite system.  Even if someone insists on using satellite-based systems, it will need ground truthing and AZMET data would be essential for that.
We should be using the AZMET data and related crop management tools.  This system has been developed by the University of Arizona Cooperative Extension System and it is openly available for direct access and use.

References:
Russell, B. 2011.  AZMET.  The Arizona Meteorological Network : A Brief Overview.  University of Arizona Cooperative Extension.  https://ag.arizona.edu/azmet/azmet04.htm

Plant viruses cannot penetrate the intact plant cuticle and cellulose cell wall that acts as barrier to infection. The virus overcomes the problem by either avoiding the need to penetrate (example seed transmission) or by using the wound in plants as infection site, or transmission by insects, nematodes or fungi as a vector.  
 
Mechanical transmission involves the introduction of infective virus or viral RNA into the wounds of plants. Viruses such as Tobacco mosaic virus (TMV), Potato virus X are highly stable, and reach high concentration in plants.  As you all know TMV can readily contaminate hands, clothings, and implements and can be spread by worker. TMV can even spread mechanically by tobacco smokers as the virus is present in cured tobacco leaves. 
Mechanical transmission is of great importance.  In field and greenhouse, great amount of caution has to be implemented to not transmit the infection. Field sanitation, tool sanitation is very important to avoid the spread of virus. 
However, in experimental world mechanical transmission is a very useful tool to study viruses. Mechanical inoculation of virus to a heathy host plant is done for assays, to produce local lesions, in the propagation to of viruses for purification, in host range study, diagnosis, and to understand the interaction between virus and susceptible cells. 
 
 
Seed transmission:  About 1/7 th of the known plant viruses are transmitted through seeds. Different viruses have different host ranges (the plants that they can infect). Tobacco mosaic virus, Cucumber mosaic virus are some viruses with a very wide host range and they may not be seed transmissible in all plants they infect. Seed transmission plays a huge role in virus epidemiology. Not only they can be a primary source of infection, leading to an epidemic in the field upon conducible environment, seed transmission is an effective way for long distance travel of the virus, thus introducing the virus to new places. You have heard of USDA regulations/restrictions on different crops, from certain foreign countries to avoid introduction of infected seeds/plant materials. 
 
Seed transmission can occur simply by contamination of seeds, as in tomato seeds by Tobacco mosaic virus. This can be readily inactivated by seed treatments. 
The second type of seed transmission occurs when the virus is present in the embryo tissue that can happen prior to fertilization or takes place at pollination. Pea seed-borne mosaic virus is a well studied plant virus in this category. 
 
 
Pollen Transmisison:  Some viruses are transmitted from plant to plant via pollen. As in seed transmission, pollen transmission has two mechanisms, gametic infection of embryo and direct infection of mother plant. 
 
Vegetative propagation: An important horticultural practice, and unfortunately a very effective method for perpetuating and spreading viruses. In clonally propagated plants, an infected mother plant which could be asymptomatic could be used to make hundreds and thousands of daughter plants, which will all have the virus. Any vegetative parts  such as bulbs, corms, runners, and cutting will be infected. 
 
Grafting: Essentially a form of vegetative propagation, once the organic union has been established and plants (Scion and Stock) function as a single plant. In experimental front, grafting is used as a virus transmission methods, when all other methods fail.

At the 2024 Southwest Ag Summit Field Demo a couple of weeks ago, many of the latest technologies were demonstrated in the field. Most were related to pest control. Several of the technologies demonstrated or on display at the event are brand new to the Yuma, AZ area. The new technologies presented included an implement designed for cultivating high density crops (Fig. 1a), a field scale drone sprayer (10.6 gal) (Fig. 1b), a high precision spot sprayer (Fig. 1c) and a self-propelled machine that disinfests soil prior to planting using steam. Updated versions of laser weeders, camera-guided cultivators and smart, automated in-row weeding machines (mechanical) were also demonstrated. Over the next several years, it will be interesting to watch the technologies in this space evolve further and become integrated into our cropping systems.

Fig. 1. New pest control technologies demonstrated/on display at the 2024
Southwest Ag Summit Field Demo included a) Oliver¹ high density cultivator b)
DJI Agrospray T40 drone sprayer c) Ecorobotix ARA high precision spot sprayer
and d) UC Davis/University of Arizona self-propelled steam applicator for
disinfesting soil prior to planting.

[1] Reference to a product or company is for specific information only and does not endorse or recommend that product or company to the exclusion of others that may be suitable.

The Southwest Agricultural Summit that recently took place in Yuma included a breakout session on Thursday, 21 February 2024 titled “New Developments in Weed Control”.
In this session Jose Antonio Cabrera representing BASF technical services for Coastal CA and Arizona provided a review of the new technologies being developed by his company in the Weed Control area. This includes new active ingredients as well as novel encapsulation technologies. The breakout session also included the lecture “Registration Support for Pest Management Tools in Specialty Crops, The IR-4 Project: Purpose and Process” by Roger B. Batts. “The IR-4 Project was established in 1963 by the U.S. Department of Agriculture to ensure that specialty crop farmers have legal access to safe and effective crop protection products. Helps growers address pest management concerns, develops data necessary for the registration of safe and effective pest management solutions with the U.S. Environmental Protection Agency¹.
Roger is the Weed Science biologist from the NC State University IR-4 headquarters. If you have questions such as: What is the IR-4 Mission? Why is IR-4 Needed? What are the programs within the IR-4 project? you will find some answers in the IR-4 Presentation Slides here.
We are currently conducting trials in Yuma in coordination with this project that could result in the addition of new labels and weed control tools for our Arizona vegetable growers.
Thank you for attending the SW Ag Summit Weed Science breakout session.
 
 
Reference:

1. https://www.ir4project.org/

 

Get your free copy of the Weed Seedling Identification Pocket Guide at the Yuma
Agricultural Center.

 

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.

Leaf miners: Adult activity light in all areas, about average for this time of season