Can you Name the INSECT below?

When going into 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 yield potential, and 3) anticipate the next stage of development and what we need to do in terms of field crop management.  These considerations are commonly focused on aboveground crop evaluations.  The root system is also an important part of the crop condition to evaluate but we commonly do not evaluate roots because of the difficulty in doing so.
 
Root systems and early development were described in a basic manner in a recent article on 4 September (UA Vegetable IPM Newsletter Volume 15, No. 18).  
 
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 that about 70% of the moisture and nutrient uptake by plant roots takes place in the top 24 inches of the root zone; about 20% from the third quarter; and about 10% from the soil in the deepest quarter of the root zone (Figure 1).  
 
The small and very fine root hairs are the most physiologically active portion of a developing root system.  It is important that plants continue to develop and generate fresh young roots and an abundance of fine root hairs to maintain water and nutrient uptake.

Figure 1.  General pattern for plant-water and nutrient uptake from the soil profile.

Root development patterns are dependent on the nature of the soil profile in the field.  Soil profiles with compaction layers, as well as rock, clay, or caliche layers can limit and alter root development and the full exploration of the soil volume that the plants are capable of (Figure 2).  So, it is good to know what the soil profile looks like in the field and understand how that will impact plant root development.

Figure 2.  Generalized soil profile with major horizons.

Leafy green vegetable crops need to develop a marketable plant in a relatively short amount of time and a strong root system is essential.  Transplants are commonly being used in vegetable crop production systems and the transition of transplants to field conditions is a major step in the production process.  The transition is primarily experienced by the plant below ground.  
 
Transplanted crops will have altered root systems due to the constraints within the rooting cone.  Further root development beyond the original cone rooting mass is important for crop success.  Thus, it is important to monitor the root system transition and the relationship to overall plant development.
 
Checking root systems is a plant destructive process since we need to literally excavate the roots from the soil and it does take time and effort.  Accordingly, it is also important to be careful of where and how we sample plants and evaluate the root systems in a field.
 
Crop species can vary significantly in their patterns of root development, and it is important to know what is “normal” when evaluating crops in the field.  An excellent reference for vegetable crop root system development is a 1927 publication by Dr. John E. Weaver and William E. Bruner from the University of Nebraska (Root Development of Vegetable Crops).  This publication can be found at the following link:
 
https://soilandhealth.org/wp-content/uploads/01aglibrary/010137veg.roots/010137toc.html
 
A few basic examples from the Weaver and Bruner publication are provided in the following figures (Figures 3-10).

Figure 3.  Cauliflower, 3 weeks after transplanting


Figure 4.  Cabbage roots, 55 days after transplanting.


Figure 5.  Cabbage roots, 75 days after transplanting.


Figure 6.  Pepper roots, 24 days.


Figure 7.  Pepper roots, 45 days (6 weeks).


Figure 8.  Pepper roots, mature.


Figure 9.  Lettuce roots, 3 weeks.  The roots on the right were grown in compact
soil, the roots on the left were grown in loose/open soil.


Figure 10.  Lettuce roots, 60 days.

With melon season on full bloom, you will also start seeing diseases on melons. Cucurbit yellow stunting disorder is more of a problem on fall melons but they can also occur in summer melons. Cucurbit yellow stunting disorder is a cucurbit disease caused by a plant virus named Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus, family Closteroviridae). This virus was first detected in southern California and Arizona in 2006 and infects cantaloupe and honeydew melon, watermelon, and various types of squash. CYSDV is transmittedexclusively by the whitefly, Bemisia tabaci. Symptoms always start from the oldest leave which is a diagnostic feature of the virus. 
All biotypes of B. tabaci known to exist in North America can transmit the virus efficiently, including biotypes A, B and Q.  Whitefly transmission is responsible for virus spread over short distances (e.g., within and between fields). However, with high winds whiteflies can move long distances and transport the virus. The virus can stay infectious within whiteflies for up to 9 days. As virus infection is systemic (meaning they have to be circulated inside the plant system to show symptoms) it can take 3 to 4 weeks for disease symptoms to develop following infection. This gives a window for infected symptomless plants can be unknowingly transported and can lead to epidemics. The virus is not transmitted mechanically (by touch, mechanical damage, cuts etc) or via seed. However, the virus can be efficiently transmitted even if there is low whitefly pressure in the field. 
The best management approach is to monitor the whitefly population and be proactive with insecticides application. Rotate insecticides with different modes of action Group numbers to minimize development of insecticide resistance. Practice good weed management in and around fields to the extent feasible. Remove and destroy old crops/volunteers, enforce regional cucurbit -free period to eliminate the virus from the cropping system. 
Sweet Shield and Novira varieties seem to do well in Yuma area.

Last week, we initiated our first on-farm demonstration of soil steaming of the season with our self-propelled steam applicator. The machine is designed to inject steam into the soil and raise soil temperatures to levels sufficient to kill weed seed and soilborne pathogens (140°F for > 20 minutes). After the soil cools (< ½ day), the crop is planted into the disinfested soil.
In this trial, we are examining the viability of soil steaming for controlling weeds in organic carrot at the field scale level (plot size > ½ ac). The machine performed well in that it was able to reach target soil temperatures at reasonable travel speeds (> 0.4 mph), provide uniform temperature distribution across the bed and form nicely shaped beds suitable for subsequent planting. Stay tuned for reports of weed control efficacy, crop yield and overall profitability as compared to the grower standard. 
We are seeking collaborators to conduct similar field-scale trials/demos in Yuma, AZ. The primary objectives are to assess the viability of soil steaming at the field-scale level and obtain grower feedback on the device’s commercial potential. The machine can be adjusted to work with most bed configurations including narrow (40”, 42”) and wide (80”, 84”) beds, and is suitable for use in conventional or organic crops (soil steaming is organically compliant). To date, the device has been successfully trialed in iceberg lettuce, romaine lettuce, baby leaf spinach and carrot crops.
If you are interested in an on-farm demo of soil steaming, please let me know. I’d be happy to work with you.

Fig. 1. On-farm demonstration of a self-propelled steam applicator for weed and
disease control

Acknowledgements

This project is sponsored and funded in part by the Arizona Specialty Crop Block Grant Program and the Propane Education and Research Council (PERC). We greatly appreciate their support.

According to some authors "the human brain can process images up to 60,000 times faster than words"¹. So, I decided to share images of some of the onion herbicide tests we did at the Yuma Ag Center last season hoping you find them interesting as the season progresses. As you know the products tested could respond differently under different environments. Also some of these trials are done searching for new alternatives, therefore products are not registered.

1. https://www.linkedin.com/pulse/why-pictures-speak-louder-than-words-laura-nicole-brown#:~:text=According%20to%20Krista%20Neher%2C%20the,that%20really%20captures%20your%20attention.

Included below is a list of organic insecticides that you can consider for your organic IPM programs. Although there are few alternative organic insecticide options, it is important to rotate when possible. Like conventional insecticides, continuous exposure to the same biopesticides may pose some risk of further reducing their efficacy and leading to the development of resistance. 

A good organic insecticide rotation practice is to alternate selective organic insecticides with broad-spectrum organic insecticides. The use of selective organic insecticides favors the increase of beneficial arthropod populations which may help to keep the pest population in check and delay repeated application of insecticides. When the population of lepidopteran pests is low, spraying Bt-based insecticides first and pyrethrin or Spinosad-based products thereafter is a good strategy. Proper insecticide rotation is important because it can help reduce insecticide application frequency, resulting in reduced crop production costs. 

 Tank-mixing can help improve the efficacy of some organic insecticides against some target pests. Tank-mixing a Bt insecticide with pyrethrin, such as Xentari + Pyganic or Dipel + Pyganic, can be an effective combination for controlling lepidopteran larvae. Additionally, combining Pyganic and a neem-based insecticide like Aza-Direct can be a favorable combination for small lepidopteran larvae. Tank-mixing Entrust (spinosad) and M-Pede can help suppress flea beetles and bagrada bugs.

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.