To date, whitefly numbers on fall melons have varied from very low (1-2 / leaf) in the Yuma Valley to extremely high (> 100 / leaf) in the Dome Valley/Wellton area. These differences in whitefly abundance can be attributed largely to the crop landscape in these areas. Melon fields near or adjacent to cotton and alfalfa clearly are the most heavily infested. In fact, last week I observed very high numbers of adults steadily moving out of a cotton field in Dome Valley that reminded me of the "whitefly clouds" of the early 1990's. Does this mean fall crops in 2010 will experience heavy whitefly pressure? Don't know, but PCAs should start thinking about whiteflies and talking with their growers concerning control strategies. Remember, the key to effective whitefly management in fall crops is to prevent adult and immature populations from colonizing small plants. Thus, it is recommended that growers apply a soil neonicotinoid on early lettuce and cole crops that are planted near cotton, alfalfa or in areas that historically have high whitefly numbers. Local research suggests that imidacloprid (Alias, 16 oz/ac; or 0.25 lbs AI/ac) applied at planting provides less residual control of nymphs today than it did 10 years ago. This is not surprising considering the heavy neonicotinoid usage on fall and spring crops over the past 17 years. The insecticide still provides short-term control (21-28 days), but will likely require additional foliar treatments to prevent damage, particularly on cole crops. Growers may consider using higher rates of imidacloprid (0.375 lb AI/ac), or switching to an alternative soil-applied product such as Venom or Durivo. Also, several foliar insecticides are available that can provide effective control of both adult and immature whiteflies. (See the following documents for more information on whitefly biology, management and insecticide alternatives).

Insect Management on Desert Vegetables and Melons: Whiteflies

Whitefly Management in Leafy Vegetables, Cole Crops and Melons

Bacterial soft rot is caused by several types of bacteria, but primarily subspecies and pathovars of Erwinia caro-tovora and E. chrysanthemi. Other bacterial species that cause soft rot include Pseudomonas cichorii, P. marginalis, and P. viridiflava. They have a wide host range host range and includes genera from nearly all plant families

In lettuce fields, the symptoms are observed close to the harvest time. The tissue, mostly around inside the head of head lettuce softens and becomes mushy or watery. Slimy masses of bacteria and cellular debris frequently ooze out from cracks in the tissues. Decaying tissue, which may be opaque, white,

cream-colored, gray, brown, or black frequently gives off a characteristically putrid odor. The odor is caused by secondary invading bacteria that are growing in the decomposing tissues. The bacteria overwinter in infected fleshy tissues in storage, in the field, garden or greenhouse, in the soil (especially in the rhizosphere around the roots of many plants), and on contaminated tools, equipment, containers, and in certain insects. The bacteria enter primarily through wounds made during planting, cultivating, harvesting, grading, and packing and through freezing injuries, insect and hail wounds, growth cracks, and sunscald. They may also follow other disease-producing organisms. Uninjured tissues may become infected when the humidity approaches 100 percent or when free moisture is present. Rains, poorly drained or waterlogged soils, and warm temperatures favor infection in the field, as does high humidity in storage or transit.

The bacteria multiply rapidly by dividing in half every 20 to 60 minutes under ideal conditions at temperatures between 65° and 95° (18° and 35°C). Minimum temperatures for development is between 35° and 46°F (2° and 6°C); and maximum between 95° and 105°F (35° and 41°C. The bacteria are spread by direct contact, hands, tools and farm machinery, insects, running or splashing water, contaminated, water in washing vats, clothing, and decayed bits of tissue.

Management

Promptly and carefully destroy infected plants. Maintain well aerated field, avoid close planting and overhead irrigation. To minimize post-harvest losses, avoid mechanical injury after harvest, packing and shipping. Do not pack produce when wet. Store and ship produce at temperatures near 4°C (39°F).

Source: IPM.Illinois.edu

In several previous articles (Vol. 11 (13), Vol. 11 (20), Vol. 11 (24), Vol. 12 (5), Vol 12 (12)), I’ve discussed using band-steam to control pests. Band-steam is where steam is used to heat narrow strips of soil to levels sufficient to kill soilborne pathogens and weeds (>140 °F for > 20 minutes). The concept has shown promise (see previous articles) and we are continuing to examine the technique to confirm previous results and assess its efficacy for controlling additional pests.

Over the course of the last several weeks, we established five trials, two in in Yuma, AZ and three in Salinas, CA. In Yuma, AZ, we are assessing control of weeds and Fusarium oxysporum f. sp. Lactucae, the pathogen which causes Fusarium wilt of lettuce in romaine and iceberg lettuce. In Salinas, CA, we are examining control of weeds and cavity spot (Pythium spp.) in carrot, lettuce drop (Sclerotinia spp.) in romaine lettuce, and fusarium wilt of lettuce in iceberg lettuce (Fig.1).

Consistent with previous studies, early results from Yuma, AZ are showing treatment with steam heat is effective at controlling weeds (Fig. 2). Stay tuned for final trial results.
The band-steam applicator will be back in Yuma, AZ this fall for additional testing. If you are interested in evaluating band-steam on your farm, please contact me. We are seeking additional sites, particularly those with a known history of Fusarium wilt of lettuce disease incidence to test the efficacy and performance of the device.
As always, if you are interested in seeing the machine operate or would like more information, please feel free to contact me.

Acknowledgements
This work is supported by Crop Protection and Pest Management grant no. 2017-70006-27273/project accession no. 1014065 from the USDA National Institute of Food and Agriculture, the Arizona Specialty Crop Block Grant Program, and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
A special thank you is extended to Christensen & Giannini, LLC for allowing us to conduct research trials on their farm.

Fig. 1. Establishing band-steam trials in Salinas, CA to determine the efficacy of
using steam heat for controlling weeds and fusarium wilt of lettuce.



Fig. 2. Band-steam and untreated plots planted to lettuce (12 days after planting).

Weeds are a problem year after year even where they have been diligently controlled. A major reason for this is that weed seeds continually move into fields by irrigation water, wind, equipment, contaminated seed and other means. Controlling weeds on irrigation ditch banks can greatly help to reduce weed seed movement into fields.
The EPA regards non-crop areas as those that are not dedicated to crop production. Although crops are not normally grown on irrigation ditch banks, these areas should not be managed as non-crop. Several very broad spectrum and long lasting herbicides are registered for non-crop areas which include roadsides, industrial sites, fence rows, around structures, railroads etc.. Irrigation ditch banks should be considered separately because of their proximity to crop fields and irrigation water and the potential for herbicide movement into sensitive areas.
It is important to read the label carefully and only use those products that are specifically allowed for use on ditch banks. Some products are restricted to drainage ditch banks or dry ditches. Some can be used only above the water line and some can only be used for non-irrigation ditch banks Because most ditches here are used for irrigation, this can be confusing. The definition of a ditch however, can include an open trench or natural channel. It can also include ditches that are not in use for long periods of time. Some labels specify how long this non-use period should be. Some herbicides that have been used on ditch banks in the past are now restricted from this use because of groundwater contamination or off target movement that has occasionally occurred. Do not assume that products that were used for ditch banks in the past can still be used. Even very old products like MSMA can no longer be used for irrigation or drainage ditches. The following summarizes how some of the more common products that have been used on ditches can be used although the product labels should be read for more complete directions. There are several broad spectrum herbicides that are registered for “Non-Crop” sites but that are retricted from use on irrigation ditches. These include Bromacil,Triclopyr,Imazapyr,Thiazapyr Flumioxyzin,Imazomox,Topamezone,Valpar and others.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 3, Feb 7, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts increased in the Rol and Dome Vallley areas, above average for this time of year. 
 
Beet armyworm:         
Trap counts low; lower than 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 counts increased in most areas. About average for this time of the year.
 
Whitefly:                       
Adult movement negligible, typical for mid-winter. 
 
Thrips:                          
Thrips adult counts remain low, likely in response to rainfall in late December. Currently, numbers are below average compared with previous years.
 
Aphids:                        
Aphid movement increased significantly in the past two weeks, particularly in North Yuma and Gila Valleys. Highest numbers we’ve seen in 11 years.
 
Leafminers:                   
Adults remain low in most locations, average for January.