In the past several weeks I’ve had a number of calls concerning spider mites on melons. Two spotted spider mites, Tetranychus spp, are widespread on melon crops throughout the southwestern U.S, and in general, outbreaks are more common on watermelons than other netted and mixed melon varieties. However, problems can certainly occur on all melon types. The hot dry weather we are now experiencing can be favorable for mite infestations. Mite populations can increase dramatically. For example, mites can go from egg to adult in about 37 days when temperatures average about 60° F, but at average temperature of 86° F, it only requires 7 or 8 days for them to complete their lifecycle. Several natural enemies (including predatory mites and thrips, minute pirate bugs and lacewings) play an important role in regulating mite populations below economically damaging levels. Predators can maintain mite populations in check by feeding on slowly developing mite populations. However, when temperatures become hot and dry, the mites can quickly out run the predator population due to their rapid reproduction. Good irrigation and fertilization management increases plant tolerance to mites. Although economic thresholds have not been adequately established for spider mites in the low desert, treatment with an acaricide is recommended when significant webbing can be found on leaves and predatory mites and thrips are absent. A number of effective miticides are available for melons including Agri-Mek, Oberon, Acramite, Fujimite, Zeal and sulfur. If leafminers are present in the field, Agri-Mek is a good option. If whiteflies nymphs are beginning to build on older leaves, Oberon may be an effective option. For more information on mites and their management please visit: Melon Insect Pest Management in Arizona

****Also wanted to Thank all of you who completed your Lettuce Crop Losses Surveys and Bagrada surveys. The information will be very useful. If you haven’t yet completed your surveys, please get those back to us as soon as possible.

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

Two years ago, Alphabet’s (Google) X-Labs initiated one of their infamous and far reaching “moonshot” projects focused on growing food sustainably on global scale. As you might expect, the project has been, and is kept pretty secret, but the company recently unveiled some details about the project through a company blog article (Grant, 2020) and their newly established website (https://x.company/projects/mineral/). The project is called “Mineral” and according to project lead Elliot Grant, the team has been working “alongside experts in the field – literally and figuratively…developing and testing a range of software and hardware prototypes based on breakthroughs in artificial intelligence, simulation, sensors, robotics and more”.

One of the tools the team has developed is a self-propelled “plant buggy” equipped with multiple cameras, sensors, GPS and other electronic equipment (Fig. 1). According to Mineral’s website, “Over the past few years, the plant buggy has trundled through strawberry fields in California and soybean fields in Illinois, gathering high quality images of each plant and counting and classifying every berry and every bean. To date, the team has analyzed a range of crops like melons, berries, lettuce, oilseeds, oats and barley—from sprout to harvest.” Stated objectives of Mineral’s software are to combine and analyze data collected from the field, soil health information and weather data to 1) predict how different varieties of plants respond to their environments, 2) allow growers to treat individual plants with fertilizers and pesticides to optimize production and reduce inputs and 3) help growers predict the size and yield of their crops.

It is exciting that a cutting-edge tech company like Alphabet is taking on an agricultural project like this. It will be fascinating to see what technical breakthroughs and solutions the company will be able to achieve for all crops, including vegetables.

References
Grant, E. 2020. Mineral: Bringing the era of computational agriculture to life. X Development LLC blog article. Mountain View, CA: X Development LLC. Available at https://blog.x.company/mineral-bringing-the-era-of-computational-agriculture-to-life-427bca6bd56a.

March is traditionally the time when winter annual weeds die and summer annual weeds start growing. Weed management would be much easier if this transition was clear cut. Like everything else, many factors can complicate this. Especially here in the low desert with mild winters and summer irrigation. Some summer annual weeds have survived all winter and some winter annual weeds will grow all summer. Sprangletop and sandbur are classified as summer annuals but they have survived all winter in a dormant state and will regrow from established crowns as it continues to warm up. Not all survive the winter and some new plants will come from seed this summer. Those coming from seed can be controlled with preemergence herbicides but those coming from crowns can not be. Other weeds that survive year round that are not normally classified as perennials are clovers, mallows and thistles. Many of these have become very widespread and difficult to control. White sweet clover and both green and Mexican sprangletop have become more widespread every year.

Area wide Insect Trapping Network   VegIPM Update, Vol. 13, No. 15, Jul 13, 2022
Results of pheromone and sticky trap catches can be viewed here.
 THE MOST RECENT RESULTS
Corn earworm:            
CEW moth counts increased slightly in the past 2 weeks and remains higher than the previous 2 summers.
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Tacna) but lower than last summer
 
Cabbage looper:          
Cabbage looper numbers remain low consistent with the lack of activity this fall compared to last season.
 
Diamondback moth:      
DBM moths were not caught in any trap in the past 2 weeks; average for this time of the year.
 
Whitefly:                     
Adult movement continuing to increase, particularly in Gila, Yuma and Dome Valleys consistent with melon harvest.
 
Thrips:                         
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                       
Aphid movement is absent consistent with what we typically see in the summer. 
 
Leafminers:                  
Adult activity has highest in Wellton and Dome Valley, and above average for early July.