Now that the desert produce season is almost completed and the spring melon season is beginning, now is a good time to review the insecticide chemistries commonly used in your insect management programs. This is an important consideration as you make the transition from winter produce to alfalfa, spring melons and summer cotton where many of the same insecticide products are available in all these commodities.  Sustaining long-term insecticide efficacy that provides cost-effective crop protection requires a conscious effort on the part of PCAs and growers to use insecticides responsibly.  Over the past 35 years, Agrochemical Manufacturers have developed and brought to market over 20 new classes of chemistry that are highly effective, selective, and significantly safer than their chemical predecessors. These include the neonicotinoids, spinosyns, tetramic acid derivatives and anthranilic diamides to name a few.  Most recently, we have seen new feeding disruptor products, PQZ (pyrifluquinazon) and Versys/Sefina (afidopyropen) being applied to fall melons for virus management and in winter vegetables for aphid management. Although the development of new insecticide chemistries has been a bit slow over the past few years, we’re now seeing industry beginning to develop several new experimental insecticides for desert crops. You’ll be pleased to know that several compounds are being targeted for western flower thrips (i.e., Plinazolin). Of course, at best many of these products are a few years away from registration. But this is great news as many of the older products are slowly being phased out of the marketplace. It was just a couple of years ago that flubendiamide (Belt, Vetica) was removed from the market, chlorpyrifos (Lorsban) is now essentially gone, and EPA is currently proposing label changes to the neonicotinoids which could impact their use on many important crops. Thus, it is imperative to sustain the efficacy of the newer insecticide tools currently available and Insecticide Resistance Management (IRM) is now more important than ever. 
 
The most fundamental approach to IRM is to minimize the selection of resistance by a pest to any one type of insecticide chemistry. The key to sustaining insecticide susceptibility is to avoid exposure of successive generations of an insect pest population to the same MOA. Historically, alternating, or rotating compounds with different modes of action (MOA) each time you spray has provided sustainable and effective IRM in our desert cropping systems.  When it is comes to IRM; “rotation, rotation, rotation”. In other words, never expose a generation of insects to the same MOA more than twice.  The Insecticide Resistance Action Committee (IRAC), a coordinated crop protection industry group, was formed to develop guidelines to delay or prevent resistance. Using their most recent information we have produced a brief publication which provides the latest local information on the modes of actions, routes of activity and pest spectrum for important insecticide chemistries used in desert produce and melon crops - see the attached  Insecticide Modes of Action on Desert Produce Crops. This classification list will provide you with an additional set of guidelines for the selection of insecticides that can be used in desert IPM programs. 

In arid and semi-arid regions, water is our first limiting factor in a crop production system, followed closely by bio-available nitrogen (N).  Thus, our management of water and N are critically important to produce a healthy crop with good yields and quality.
 
Water and nutrient demands coincide with the fruiting cycle and efficient management of irrigation water and plant nutrients is enhanced by tracking crop development in the field.  The use of heat units (HUs) with 86/55 ^oF upper and lower thresholds can be applied to warm season crops in the desert Southwest in relation to the thermal environmental impacts on the development of all crop systems (Brown, 1989), including chiles, (Figures 1 and 2).
 
Crop Phenology Relationship to Water and Nitrogen Demand
 
Phenological guidelines have been developed for many crops, including New Mexico type chiles (Soto-Ortiz and Silvertooth, 2007 and Silvertooth, et al, 2010; Figure 1).  This phenological guideline can be used to identify or predict important stages of crop development that impact physiological requirements.  For example, a phenological guideline can help identify stages of growth in relation to crop water use (consumptive use) and nutrient uptake patterns (Figure 3).
 
This information allows growers to improve the timing of water and N inputs to improve production efficiency.  For some crops or production situations HU based phenological guidelines can be used to project critical dates such as harvest or crop termination.  Many other applications related to crop management (e.g., pest management) can be derived from a better understanding of crop growth and development patterns.

Figure 1.  Typical relationship between the rate of plant growth and development
and temperature.  Growth and development ceases when temperatures decline
below the lower temperature threshold (A) or increase above the upper
temperature threshold (C).  Growth and development increases rapidly when
temperatures fall between the lower and upper temperature thresholds (B).


Figure 2.  Basic phenological guideline for irrigated New Mexico-type chiles.

References
Brown, P. W.  1989.  Heat units.  Bull. 8915, Univ. of Arizona Cooperative Extension, College of Ag., Tucson, AZ.
Silvertooth, J.C., P.W. Brown, and S. Walker.  2010. Crop Growth and Development for Irrigated Chile (Capsicum annuum).  University of Arizona Cooperative Extension Bulletin No. AZ 1529
Soto-Ortiz, R. and J.C. Silvertooth.  2007. A Crop Phenology Model for Irrigated New Mexico Chile (Capsicum annuum L.) The 2007 Vegetable Report. Jan 08:104-122. 

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 UC Cooperative Extension 2024 Automated Technology Field Day in Salinas, CA a couple of weeks ago, 12 of the latest automated and robotic technologies were demonstrated in the field. Most were designed for weed control or thinning vegetable crops. Several of the technologies shown are relatively “new” for the 2024 season. These included laser weeders that also are capable of thinning lettuce (Fig. 1 & 2), a smart cultivator/side-dresser that cultivates between individual crop plants and simultaneously applies fertilizer at a variable rate depending on plant size (Fig. 3), a spot sprayer that utilizes superheated vegetable oil to kill weeds (Fig. 4), and a self-propelled machine that disinfests soil prior to planting using steam. Although the test runs were short, I was impressed with the possibilities for these machines. Company representatives said they will be in Arizona this upcoming season and are interested in meeting with growers. Company contact information can be found at their respective websites, or feel free to contact me if you would like additional information.

Fig. 1. Carbon Robotics’¹ (Seattle, WA) LaserWeeder^TM. The unit utilizes a vision
system to detect crop plants and weeds. A laser is used to kill unwanted plants.
The machine can be used for weeding or thinning lettuce crops (bottom).


Fig. 2. L&A¹ (Chico, WA) autonomous laser weeding/thinning robot. The unit is
equipped with a vision system to detect crop plants and weeds, and a laser to kill
unwanted plants. The machine can be used for crop thinning or weeding (weeded
carrot crop, bottom).


Fig. 3. Stout Industrial Technology’s¹ (Salinas, CA) smart cultivator/side
dresser. The unit is equipped with a vision system for detecting crop plants, and
blades that move in and out of the crop row to remove in-row weeds. Liquid
fertilizer (shown colored with blue dye) is applied at a variable rate depending on
plant size.


Fig. 4. Tensorfield Agriculture¹ (Union City, CA) precision spot spray weeding
machine. The unit has an 80” wide spray boom equipped with 232 individually
controllable spray nozzles to spot spray weeds with superheated vegetable oil
(bottom left, bottom right). A vision system is used to detect weeds and spot
spray resolution is ¼”.


Fig. 5. UA/UC Davis self-propelled band-steam applicator. Device injects steam
into the soil to kill weed seed and soilborne pathogens 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.

Boerhavia coulteri is a flowering plant that belongs to the Nyctaginaceae or Four O'clock family known by the common name Coulter's spiderling. Its native to the desert areas of the SW in the US and North of Mexico. It is a summer annual or perennial weed producing an erect or creeping stem up to 0.7-0.8 m in length. Grows in disturbed areas, ditch banks, and roadsides.

The cotyledons are oblong,1.0-2.5 cm.

Plants are slightly pubescent with sticky resin glands toward the bases. The leaves are lance-shaped, somewhat triangular, pointed, sometimes wavy or rippled along the edges, and 5 centimeters in maximum length¹.
We have this weed in our Yuma County AZ and very abundantly in the sandy soils of the Yuma Mesa.
I added a table from a weed control experiment conduced for Boheravia erecta.
 
The Research Paper called :” The effect of herbicide tank mix on the weed species diversity
in sugarcane (Saccharum officinarum)” mentions: “All the herbicide mixes significantly controlled Boheravia with Pendimethalin. Being Pendimethalin plus Atrazine the best treatment as shown in the table below.

1. Retrieved from: https://en.wikipedia.org/wiki/Nyctaginaceae
2. Retrieved from: https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=f6c87c4485da5772f26997828b5d4eaf9e856541

The push-pull strategy, a stimulo-deterrent diversionary strategy, combines behavior-modifying stimuli that manipulate the distribution and abundance of insect pests and/or natural enemies. When your main crop is intercropped with plant species that can mask the host (main crop) appearance or emit undesirable volatiles (smells) that divert the pests away from the main crop (push), on the other hand, other plants in your intercropping system can be extremely attractive using stimuli that are highly apparent and attractive to the pest, hence trapping the pest (pull) (Fig. 1). Insects use visual, chemical, or tactile cues. Thus, by intercropping the main crop with plants that emit more attractive smells, are more visually appealing, or release undesirable smells, one can cause the pest to be trapped and repelled from the main crops, resulting in effective control of the pests.

Figure 1. Pictorial representation of push-pull strategy. 

In Brazil, the push-pull strategy has been found effective in managing major kale pests. They found that using mustard as a preferred host pulled the pests away from the kale crops, while marigold plants increased the beneficial arthropod population which provided additional control of the pests (da Silva et al. 2022; https://www.sciencedirect.com/science/article/pii/S1049964421003029). My 

lab plans to evaluate the efficacy of similar systems for insect pest management in organic vegetable crops in Arizona. 

In Salinas, California, intercropping lettuce with sweet alysum has favored some measurable aphid control. Sweet alyssum attracts and feeds hoverflies, which then lay eggs in lettuce, producing hoverfly larvae that consume aphids. In this video, Dr. Brennan describes in detail how this system works. This research was conducted about a decade ago, but I believe this could be an important tactic to consider for aphid control in lettuce. We also plan to evaluate this system for aphid management in lettuce in Arizona lettuce growing regions. 

Figure 2. Graphical representation of Lettuce-Alyssum intercropping system for aphids control. (Image source: Brannan 2013). 

 Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 2, Jan 24, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:              
CEW moth counts are down areawide and average for this time of year. 
 
Beet armyworm:          
Trap counts decreased in most locations; about average compared to previous years.
 
Cabbage looper:         
Cabbage looper counts increased in most traps and about average for this time of season.
 
Diamondback moth:      
DBM moths continue to increase in all areas. Below average for this time of the year.
 
Whitefly:                      
Adult movement negligible, typical for early January. 
 
Thrips: 
Currently, numbers are about average compared with previous years.
 
Aphids:                        
Aphid movement increased significantly in the past two weeks, particularly in North Yuma and Gila Valleys. Well above average for early January.
 
Leafminers:                   
Adults decreased in most locations, but above average for January.