In response to the recent outbreaks of Diamondback moth (DBM) , Plutella xylostella in Yuma, we have established a pheromone trap network designed to monitor the activity and movement of adult populations of DBM. PCAs have had difficulty controlling DBM in cabbage, broccoli and cauliflower since October. Wing Traps with DBM pheromone lures have been placed in Roll, Wellton, Dome Valley, Gila Valley and Yuma Valley in locations where Cole crops are presently being grown, or in areas where infestations were known to occur this fall. The data we collect is not intended to indicate field infestations, as trap data is largely a reflection of adult movement. The data may reflect emergence/ activity of adults in adjacent fields with known infestations, or provide an indication that DBM may be moving into fields not previously infested. If nothing else, the data may make PCAs aware of increased pest activity in some areas and encourage intensified scouting in susceptible produce fields. DBM are still active in many fields, and most recently we’ve observed that populations are beginning to spread into direct-seeded crops that were not previously effected by DBM. For this reason, we are tracking moth activity to monitor their activity relative weather conditions and crops sources. We have a historical perspective of DBM activity in Yuma. From 1998-2000, we established a pheromone trap network during the winter and spring in Yuma which included DBM. Not surprisingly during that 2-year trapping period DBM counts never exceed 6 moths/trap/day at any time during the spring season. DBM have historically been a secondary pest, that may cause issues in spring cabbage crops. However, in just the few weeks we’ve been trapping DBM since Dec 20, we’ve had four trap locations where DBM counts have exceeded 10 moths/trap/day and in one location (Co. 9th and Ave F) over 25 moths /day were recorded. These traps were all located in the Yuma Valley, stretching from Co. 21st up to Co. 9th street. We will continue to monitor DBM trap activity throughout the season, as well as trap population activity throughout the summer to determine whether DBM is active when brassica crops are not available. This may give us an indication of the potential for more problems going into next season. From a historical perspective, trap counts during the summer of 1999 in the Yuma Valley occasionally caught DBM moths in traps at low levels (0.2-1.2 moths/trap/night from July-August). We concluded at that time that many of the DBM captured may have come in with transplants, as we were uncertain whether DBM was capable of over summering in the desert in the absence of brassica crops. We hope to gain more insight into the pest’s activity during summer months in Yuma this year by actively trapping throughout the area. For access to DBM trap counts please visit Areawide Diamondback Moth Trapping Network.

Whenever we go to the field to evaluate a crop, there are typically three fundamental points we need to take into consideration that include: 1) stage of growth, 2) general crop vigor and condition, and 3) anticipate the next stage of development and what we need to do in managerial response.  These considerations are commonly focused on aboveground crop evaluations.  However, the root system, completely belowground, is an extremely important part of the crop condition to evaluate.
 
Root systems are responsible for all water and nutrient uptake by the plant and provides the physical anchoring and support of the plant structure.  Each plant and crop species has its own “personality” and growth habits and the nature of the root systems also vary among plants species.  Many plant species can have root systems that constitute ~ 50% of the total plant dry matter and we generally consider plants to have at least 30% of total plant dry matter allocated to the root systems.
 
Young plants will often develop some basic aboveground tissue to perform sufficient photosynthesis for establishment and then devote a high amount of the energy, carbohydrates produced, along with the nutrients and water from the soil to root system growth and development. Sometimes it can appear that plants are not growing rapidly while investing energy and resources into root system development.  The depth of the roots will vary according to the soil physical conditions and effective soil depth, soil fertility and salinity management, plant-available water, and of course the natural rooting characteristics of the plant.  
 
The effective root zone depth is the depth of soil used by the bulk of the plant root system to explore a soil volume and obtain plant-available moisture and plant nutrients.  Effective root depth is not the same as the maximum root zone depth. As a rule of thumb, we commonly consider about 70% of the moisture that is taken up by the root is obtained in the top half of the root zone; about 20% from the third quarter; and about 10% from the soil in the deepest quarter of the root zone.  The small and very fine root hairs are the most physiologically active portion of a developing root system.  It is important that the plants continue to develop and generate fresh young roots and an abundance of fine root hairs to maintain water and nutrient uptake.
 
Therefore, in scouting fields and making crop evaluations, examining the root systems is an important part of the process.  Leafy green vegetable crops need to develop a marketable plant in a relatively short amount of time and a strong root system is essential.  It does take more time and effort to check root systems and it is a plant destructive process since we need to literally excavate the roots.  So, it is also important be careful of where and how we sample plants and the root systems in a field.

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%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles. 
 

Month	Max	Min	Average	Rainfall
January	68	42	54	1.14 in
February	73	47	59	0.50 in
March	77	50	63	0.31 in

 
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19  and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results.   Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft² areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft² area of bed was approximately 144. 

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that  provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.

Mark C. Siemens Vol. 12, Issue 20, Published 10/06/2021 Plans are shaping up for the 2nd Automated Weeding Technologies Field Demo Day. The event will be held Thursday, October 21st at the Yuma Agricultural Center. Registration begins at 7:00 am and the program starts at 7:30 am. We have eight presentations/field demos scheduled (details below). The focus this year is on the latest automated weeding technologies that are “new” since our 2018 event. We would love to showcase as many innovations as possible and it’s not too late to be added to the program. It’s an open invitation - private companies, university and government researchers are all welcome to show their technology. Please contact me if you are interested or know someone that is.

Because there are so few selective herbicides registered for use in lettuce, it is necessary to kill as many weeds as possible prior to planting. Fumigants, flooding and solarization will kill weed seeds but it will be necessary to germinate them first for most herbicides to be effective. Almost any herbicide can be used preplant that is registered for “fallow” conditions as long as the preplant and preharvest intervals are observed. The following table summarizes the most commonly used herbicides for ground preparation in lettuce.

Area wide Insect Trapping Network   VegIPM Update, Vol. 13, No. 17, Aug 24, 2022
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts increased slightly in the past 2 weeks, about average for late summer
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Wellton) particularly near alfalfa.
 
Cabbage looper:          
Cabbage looper numbers remained low consistent previous years.
 
Diamondback moth:     
DBM moths not active in any trap since June; average for this time of the year.
 
Whitefly:                       
Adult movement decreased in past 2 weeks consistent with previous years
 
Thrips:                          
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                        
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                   
Adult activity tending downward, average for early late August