Strawberry growers now have a free smart phone application tool to predict spray coverage to combat such pests as two-spotted spider mites, lygus bugs and leafrollers, thanks to a three-year collaborative project involving UC Davis agricultural entomologist Christian Nansen and several UC Davis computer science majors.

“Many variables are known to affect the actual spray coverage in crop fields,” said Nansen, an associate professor in the UC Davis Department of Entomology and Nematology said. “These include tractor speed, spray nozzles, spray volume, boom height, adjuvants, and weather conditions. But which ones are the most important ones? And are there possible interactions among some of these variables?”

Through Smart Spray, an app designed for both iOS and Android phones, growers can optimize and perform quality control of pesticide spray applications in their strawberry fields, Nansen said. 

Computer science major Krishna Chennapragada, now an alumnus, launched the programming and initial design, tallying some 500 hours before his graduation. Today's team, in addition to Nansen, is comprised of recruits Gabriel Del Villar, a 2019 computer science graduate, and Alexander Recalde, a senior majoring in computer science. Together they have amassed nearly 400 hours on the project.

“The project is truly multidisciplinary,” said Nansen, adding “One of the great things about UC Davis is that the barriers between colleges are very, very shallow.”

The computer scientists “have no experience in agriculture but they're really interested in the project and how they can contribute to sustainable food production,” said Nansen, adding “They're really, really good. We need people with their skills and the work they're doing also enriches their career.”

The Smart Spray app, they said, allows a user to predict spray coverage under different operational scenarios, including type of nozzles, spray volume, and tractor speed, as well as weather data, such as temperature, relative humidity and wind.  A key part of the process: the user places a water-sensitive card in the field prior to a spray application, photographs it, and uploads it into the app.

“If you're a grower, you might expect that when you go out to spray, that the more that comes out of nozzle, the better coverage you'll get,” Nansen said. “But, for example, if the wind is too strong, the relative humanity is too low, the pressure is too high, or you're going too fast--even when you're spraying large volumes--you can get very poor coverage and it's costly. Excessive spray can also reach other fields or nearby urban developments due to so-called “spray drift”.”

“Typically, a grower will spray 100 to 150 gallons per acre when he or she sprays,” Nansen explained. The water-sensitive card is yellow, but it codes blue when it interacts with moisture. “These cards have been around a long time,” he said. “They cost about $1 a card, not cheap. But it's inexpensive when you're spending thousands of dollars to control the pests. And the pesticide companies can pay for the cards.”

“Say you want to predict your coverage before you spray tonight or tomorrow,” Nansen explained. “Look at the weather conditions; what is the forecast? Then how are you going to do this? What if you spray 100 gallons and want to go two miles per hour. You enter the data—and all the other applicable data--on the Smart Spray app. It will predict the coverage you'll get with nine different nozzles. Those are the nozzles the typical strawberry grower uses, a number we based on almost 3000 experimental sprays over three years. So we did a lot of homework on this, for example—different spray rigs, different sizes of crops, different spacing of plants, and under different weather conditions. We covered all the ranges we could think of. We collected the water and operational data and we did the progression analysis (for the modeling).”

“Using this prediction, you can give it a name, say Field 6, and access it from the database,” Nansen said. “It's about quality control. It's a tool to predict and do quality control. It empowers the grower and also the sprayer to do a better job. For example, if the conditions are bad and the app shows the spraying will be only 20 percent effective, you shouldn't be spraying.”

Recalde said the user can also choose metric or imperial, as well as add the Global Positioning System or GPS.

“The Smart Spray is not just insecticides--it's fungicides, herbicides, and whatever you want to spray,” Nansen noted. “This app was developed for strawberries; if it were used for soybeans, onions and cabbage, it would still be useful but the accuracy would be off.” Pending apps: almond, pistachio and tomato.

The computer scientists enjoy working on the project. Recalde attended a Central Coast sprayers' meeting to talk about the app. “I heard ‘Oh, wow, you look so young!' he remembered. “Then we told them about this useful tool, different ways that technology can be applied to agriculture. They were really interested in how technology can improve what they're doing.”

Del Villar, whose computer interests also include teaching youth how to code, said he eagerly looks forward to making the Smart Spray app even better and more useful. Fluent in Spanish, as well as English, he plans to translate the app into Spanish. Other language translations are also in the works.

Now the team is seeking feedback to improve the app. “We're hoping growers will embrace it,” Nansen said, “and help us find ways to improve it.”

One feedback from Eric Flora, global field development and manager of Crop Enhancement, Inc., Paso Robles: “I think Smart Spray is a very helpful tool for growers and advisers as a guide to select spray tips, spray volumes, tractor speed, and other important factors to maximize sprayer coverage. Using spray cards is the best and simplest way to know, if you are penetrating everywhere in the canopy your pest target is a problem--placing cards where the specific pests attack the host gives the best information.”

State, federal and industry grants, including the California Strawberry Commission and the Floriculture and Nursery Research Initiative (FNRI) of the U.S. Department of Agriculture's Agricultural Research Service, help fund the project. 

California grows about 88 percent of the nation's strawberries on approximately 34,000 acres along the California coast, according to the Strawberry Commission. Strawberries are available year-around in California.

Statewide, fresh strawberry production averages 50,000 pounds per acre each season. The approximately 300 strawberry growers hail from five distinct areas of California: Watsonville/Salinas, Santa Maria, Oxnard, Orange County/San Diego, and the Central Valley. They include multi-generation farming families growing both organic and conventional strawberries.

For more information on the Smart Spray app, access the manual at https://bit.ly/2q3lsL3 or contact Nansen at chrnansen@ucdavis.edu or 530-752-2728.

UC Davis agricultural entomologist Christian Nansen, the newly selected guest editor of a special issue of the journal Remote Sensing, has issued a call for contributions.

Nansen, associate professor,  Department of Entomology and Nematology, is serving as the guest editor of the issue, "Remote Sensing to Detect and Diagnose Organismal Responses." The journal (impact factor 4.118) is a leading outlet for research articles and reviews on all aspects related to remote sensing.

"I'm inviting authors to submit studies that go beyond the detection of an optical reflectance response and tie a thorough analysis of remote sensing data to other types of data (physiological, molecular, genetic, biochemical)," Nansen said. "In other words, the special issue will embrace a phenomics approach, in which the overall goal is to, at least partially, explain why and how organisms exhibit an optical reflectance response to stressors and/or treatments."

As the guest editor, Nansen said he is seeking articles describing "exciting applications of remote sensing technologies to detect and diagnose differences and/or stress across all kingdoms."

Contributions are due by March 2020. For more information, access the website: https://www.mdpi.com/journal/remotesensing/special_issues/rs4organismal_response.

The UC Davis entomologist specializes in applied insect ecology, integrated pest management and remote sensing, including proximal (lab) and aerial (drone) applications of remote sensing in agriculture; and robustness and accuracy of optical classification algorithms.

Nansen, who joined the UC Davis faculty in 2014, completed his doctorate in zoology at the University of Copenhagen, Denmark.  He previously held faculty positions at Texas A&M, Texas Tech, and most recently, the University of Western Australia. He may be reached at chrnansen@ucdavis.edu.

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Imagine food production without waste…

Insects, such as darkling beetles and black soldier flies, can and should be bred to convert organic agricultural waste into usable products--like animal feed, pharmaceutical products, and biofuel, say UC Davis agricultural entomologist Christian Nansen, an associate professor in the Department of Entomology and Nematology and doctoral student Trevor M Fowles of the Nansen lab.

Fowles was recently awarded a grant from the California Department of Food and Agriculture (CDFA) to develop lines of insects for bioconversion of agricultural waste.

“In the 21st Century, we will be breeding insects for their ability to effectively convert agricultural organic waste, and researchers at UC Davis are leading the effort,” Nansen says.

Nansen will be among those speaking at a two-day workshop on “Aligning the Food System for Food Safety in Food Waste Systems,” set May 15-16 in the UC Davis Conference Center and the Walter A. Buehler Alumni Center.  Nansen will be part of a panel discussion from 1:30 to 3:35 p.m., Thursday in the Alumni Center on “Composing and Anaerobic Digestion for Nutrient Recycling.” He joins fellow panelists Jenny Stephenson, environmental protection specialist with the U.S. Environmental Protection Agency (EPA), Steve Zacari, director of engineering and research and development, California State Soil; and Robert Horowitz, supervisor, Organic Materials and Construction and Demolition Unit, CalRecycle.

Fowles and Nansen compare insect breeding to livestock breeding. “We are used to thinking of livestock breeding as producing dairy cows with higher milk production or chickens producing more and bigger eggs.”

As part of his PhD project, Fowles applies the concepts of livestock breeding to insects “so that specially adapted lines of insects can be developed and commercialized to manage economically important agricultural organic wastes, such as, skins and stems from wine production and from tomato processing. As the human population continues to grow, so, too, do the concerns regarding the sustainability of waste management from our food production systems. In the U.S. alone, we generate 145-602 gigatons of organic waste annually-- or about nine pounds per day per person! Disposal of these wastes in compost and landfilling operations generates greenhouse gases and other environmental pollutants.”

Fowles and Nansen noted that California law, effective Jan. 1, 2020 (Assembly Bill 1826) prohibits pre-consumer organic wastes from entering the landfills. “Therefore, developing innovative ways to use pre-consumer organic wastes is important, and an economic opportunity. When waste management is tied to the mass-cultivation of insects, we can get rid of agricultural waste and at the same time produce insects that can be turned into animal feed, biofuel, or used as input in pharmaceutical productions! And the leftover from insect mass-cultivation can be used to grow edible mushrooms.”

The Nansen lab research, funded by CDFA and the Western Sustainable Agriculture Research and Education, emphasizes economic feasibility, community engagement, and environmental stewardship.

Fowles and Nansen recently co-authored a paper, "Artificial Selection of Insects to Bioconvert Pre-Consumer Organic Wastes. A Review" in the journal, Agronomy for Sustainable Development (https://link.springer.com/article/10.1007/s13593-019-0577-z).

“The potential for using insects to consume organic waste materials and convert them into feed for animal, biofuels, and other valuable secondary products is gaining momentum as both a research discipline and as a business opportunity,” they wrote in their abstract. They described insects as the ideal bioconverters, as “insects uniquely equipped to convert wastes into biomass and other valuable secondary products, and we present the current knowledge and existing research gaps towards the development of such organisms. We conclude that (1) targeted breeding of insects and their gut microbes can produce tailored insect lineages for bioconversion of specific waste streams; (2) research is needed to take full advantage of the existing insect diversity to identify new candidate species for bioconversion; and (3) further research into insect-gut microbial complexes will likely provide important insight into ways insects can be used as sustainable bioconverters of highly specialized waste streams.”

Currently, only a few insect species are used for bioconversion of organic wastes. They include crickets, locusts, black soldier flies, green bottle flies an several species of mealworms.

In addition to funding from CDFA, Fowles has also secured an EPA grant for his research,  “Beetle Larvae as Biodegraders of Styrofoam and Organic Waste,” involving darkling beetles, Tenebrio molitor. In the wild, darkling beetles and larvae are general decomposers, eating decaying leaves, sticks, grasses, and carcasses, but the larvae are also known to eat polystyrene or plastic foam, commonly known as Styrofoam. They can decompose as much as three-fourths of a pound of Styrofoam within a three-week period, Fowles says. After biodegrading the Styrofoam, the beetles can be pelletized for animal feed, and the excrement or frass can be used as “high-value amendment to compost mixtures.”

(News media: you're invited to contact the Nansen lab to see the mass rearing processes and breeding. E-mail Christian Nansen at chrnansen@ucdavis.edu or call the lab at (530)-752-2954.)

When a wasp lays its eggs inside a caterpillar or parasitizes it, it's not always easy to tell what's going on without destroying both species.

But newly published research by UC Davis agricultural entomologist Christian Nansen and insect physiologist Michael Strand of the University of Georgia reveals a new, non-destructive and quite accurate method to characterize physiological responses to parasitism: proximal remote sensing or body reflectance response data.

They published their research, “Proximal Remote Sensing to Non-Destructive Detect and Diagnose Physiological Response by Host Insect Larvae to Parasitism,” Dec. 4 in the journal Frontiers in Physiology.

Nansen, first author of the paper and an associate professor in the UC Davis Department of Entomology and Nematology, specializes in insect ecology, integrated pest management and remote sensing. Strand, a professor of entomology at the University of Georgia, is an international authority on the physiology of insect parasitism.

The scientists studied two common parasitic wasps or parasitoids, Microplitis demolitor, and Copidosoma floridanum, which lay their eggs in the larval stages of the soybean looper moth, Chrysodeixis includens. The pest, found throughout much of North and South America and elsewhere, feeds on soybeans.

The Nansen-Strand project involved soybean loopers without parasitism (control group) and with parasitism, involving both wasp species.

“Based on reflectance data acquired three to five days post-parasitism, all three treatments (control larvae, and those parasitized by either M. demolitor or C. floridanum) could be classified with more than 85 percent accuracy,” they wrote.

Due to parasitism-induced inhibition of growth, “it's easy to differentiate soybean loopers parasitized by M. demolitor from non-parasitized larvae as long as the developmental stage of the host larva is known,” they said. In addition, a single M. demolitor offspring emerges from the host larva 7-9 days post-parasitism to pupate, while non-parasitized larvae continue to increase in size to the final instar.

Copidosoma floridanum minimally alters host growth until late in the final instar, when thousands of wasp progeny complete their development. This wasp is known for having the largest recorded brood—3,055 individuals--of any parasitoidal insect.

The researchers said that the accuracy rate of more than 85 percent holds promise. “The hyperspectral proximal imaging technologies represent an important frontier in insect physiology, as these technologies can be used non-invasively to characterize physiological response across a range of time scale factors, such as minutes of exposure or acclimation to abiotic factors, circadian rhythms, and seasonal effects. Although this study is based on data from a host-parasitoid system, results may be of broad relevance to insect physiologists.”

Parasitoids are often categorized as either idiobionts--whose hosts cease development after parasitism--or koinobionts--whose hosts continue to develop as the parasitoids offspring grow. “Parasitoids also are commonly divided into ectoparasitic species whose offspring grow by feeding externally on hosts or endoparsitoids, whose offspring grow by feeding internally,” the authors wrote. “Most known idiobionts are either ectoparasitoids that paralyze and lay eggs on the surface of larval stage hosts or are endoparasitoids that lay their eggs inside sessile host stages like eggs or pupae.”

Both of the wasps they studied are idiobionts and endoparasitoids.

Nansen noted that “many species of minute wasps are parasitoids of eggs and larvae of other insects, and parasitism represents one of the most extreme life strategies among animals”

“Living inside the body of another animal,” he said, “poses a series of non-trivial challenges, including how to overcome/suppress the defense response by the host; how to obtain oxygen; how to feed on the host without killing it--because once the host is dead, then microbial organisms and general decomposition will make the host body unsuitable--and how to manage waste.”

Nansen likened the developing parasitoids to astronauts flying in a space capsule. “A developing parasitoid faces a long list of serious practical challenges, so the evolutionary selection pressure has been immense and lead to some of the most extreme cases of co-evolution.”