Since the bagrada bug became established in the desert in 2010, growers and PCAs quickly found that preventing excessive feeding damage on newly-established crops is critical to economic broccoli production. Local surveys have estimated that the invasive stink bug annually infests more than 80% of the acreage in Arizona and southern California, resulting on average in more than 10% stand losses and plant injury to direct-seeded broccoli crops. The potential for the pest to cause significant crop losses coupled with the lack of biological control alternatives has left little alternative but to control outbreak populations with foliar applied insecticides. Furthermore, because bagrada bug can quickly cause significant feeding damage to seedling plants, effective insecticide treatments applied in the field need to be quick acting. Currently, vegetable growers in Arizona and California rely heavily on frequent applications of pyrethroid insecticides to control adult infestations on seedling cole crops. Given the magnitude of pyrethroid usage historically applied to desert vegetable crops, alternative insecticides will be needed to protect desert cole crops from bagrada bugs and conserve the pyrethroid chemistry. Among the newer classes of chemistry, foliar-applied neonicotinoids such as Venom/Scorpion have been shown to effectively control bagrada bug adults, but at-planting, soil systemic applications of neonicotinoids such as Admire Pro, Belay and Venom do not prevent bagrada bug from damaging seedling broccoli plants. However, in other parts of the world neonicotinoid seed treatments have been shown to provide protection against bagrada bug. For example, in India, field trials showed that planting mustard seeds treated with imidacloprid resulted in significantly lower plant damage due to bagrada bug. Recently, Valent U.S.A. registered clothianidin as a seed treatment on broccoli under the name of Nipsit®. Based on our research, this technology provides another tool for broccoli growers to use in their annual battle against bagrada bugs in the desert. The results of field trials conducted at the Yuma Ag Center from 2012-2014 that evaluated the effectiveness of Nipsit (clothianidin) seed treatments for preventing bagrada bug feeding damage and yield loss in broccoli can be found in Evaluation of Clothianidin Seed Treatments for Bagrada Bug Control in Broccoli.

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%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on Nov 28, 2023 on double rows 12 in. apart on beds with 42 in. 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, which contained two 25 ft rows of lettuce. Plants were thinned Jan 17, 2024  at the 3-4 leaf stage to a 12-inch spacing. 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.

Month	Max Temp (°F)	Min Temp (°F)	Average Temp (°F)	Rainfall
November	80	51	65	0.08 in
December	71	44	57	0.82 in
January	68	42	54	1.14 in
February	73	47	59	0.50 in

 
Powdery mildew (caused by Golovinomyces cichoracearum) efficacy trial treatments were made on February 15,2024, February 23, 2024, March 4, 2024, and March 12, 2024and .Disease was first seen on February  26,2024. Disease rating was done on March 15, 2024.   Disease severity was determined  by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 0.5 = one to a few very small powdery mildew colonies on bottom leaves; 1 = powdery mildew present on bottom leaves of plant; 2 = powdery mildew present on bottom leaves and lower wrapper leaves; 3 = powdery mildew present on bottom leaves and all wrapper leaves; 4 = powdery mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = powdery mildew present on entire plant. These ratings were transformed to percentage of leaves infected values before being statistically analyzed. Yield loss due to rejected lettuce heads would likely begin to occur on plants with a powdery mildew rating above 2.0 (percentage of leaves infected value of 40).         
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. The most effective fungicides were Rhyme, Merivon, Quintec, Cevya, Luna Sensation, Luna Experience, and Elisys. 

Over the last 5 years, there has been a tremendous amount of investment, research and advancement in technologies for robotic/automated in-row weed control. This surge in recent activity is due in part to the advent of low-cost computing systems that utilize artificial intelligence and on-board imaging systems that identify and locate crop and weed plants in real-time. Entities developing these innovations are quite varied, ranging from small start-ups to well established companies to university and government researchers.  A quick internet search will reveal over 50 companies or university research groups working in this space. Many are domestically based, but the majority are from Europe where labor costs are very high and there is more resistance to and restrictions on herbicide use.

As you might expect, the diversity of approaches to the in-row weeding problem is wide. Methods for controlling in-row weeds include traditional methods such as mechanical hoeing and spot spraying, as well as alternative techniques such as spot spraying hot oil, flaming, lasers, high voltage electricity and microwaves. The use of fleets of small (1-row to 4-row) autonomous robots is a common theme, but there are also pulled implements equipped with actuators for automated weed removal.

I discussed some of these technologies at a technical breakout session at the 2020 Southwest Ag Summit. A link to the presentation is given below. It provides an overview of some of the latest developments, technologies and concepts for in-row weeding being worked on around the world. The presentation should be self-explanatory as it includes audio clips and company source information, but feel free to contact me for further information or if you have any questions. In future articles, I will discuss these technologies and concepts in more detail and how they might best fit into Arizona vegetable production systems.

Click on the video below to view the presentation on Technologies for
Robotic/Automated In-Row Weeding in Vegetable Crops:

Marestail and Fleabane have become increasingly widespread in recent years. This has occurred mostly in areas around field edges, roads, ditchbanks citrus groves and alfalfa fields. Marestail (Conyza candensis, also called horseweed), has been here for many years while Flaxleaf Fleabane (Conyza bonariensisis) is more recent. Both are in the Conyza genus and the sunflower family. Both are described as summer annuals, but they grow year round in the low desert. Although these two weeds are easy to distinguish once they are established and have several leaves, the seedlings look very similar. They form a rosette like shepardspurse, soon after emerging. After they bolt Marestail puts up a tall central stem that is dark green with long thin leaves. Fleabane, on the other hand, does not have a central stem but has several branches with smaller, grey thin leaves. Marestail can get 10 foot tall while fleabane rarely gets taller than 3 to 4 feet.(See picture below)

Controlling both of these weeds can be difficult because they grow rapidly, and plant populations have developed resistance to Glyphosate in many areas. Glyphosate still works well on Marestail in many areas here but there have been increasing misses. This is a characteristic of resistance, but it has not been tested or confirmed here. It has been confirmed throughout California. We did not have these weeds in many of our older herbicide trials and are now working to update our information on herbicides in alfalfa and citrus, specifically for these weeds and with some of the newer herbicides. In a few of our older trials where we had some marestail we did have good control with 2,4-DB but only partial control with trifluralin. These weeds can germinate any time of the year and trash on the surface will reduce control in citrus. We did not have fleabane in these early trials. We have had good control with Sharpen (Treevix, Kixor) postemergence and Chateau preemergence on many broadleaf weeds but do not have enough data on fleabane or marestail yet. It is on the labels for both herbicides and we will have current data later this season.

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