- Author: Kathy Keatley Garvey
“Weather patterns associated with climate change may adversely affect the performance of some of the most important insecticides, systemic insecticides, against coleopteran and lepidopteran pests,” Nansen says.
“These insecticides depend on efficient water and nutrient uptake through the root system and on vascular flow – both mechanisms may be partially compromised under drought conditions,” Nansen points out. “This leads to lower uptake and non-uniform distribution of systemic insecticide in plant tissues – and therefore, higher risk of pests NOT acquiring a lethal dosage.”
In an opinion-based article published in the current edition of the Journal of Economic Entomology, Nansen and three lab researchers take it one step further, and argue that non-uniform distribution of systemic insecticide in plant tissues may also select for behavioral resistance in target pest populations.
The research, “Does Drought Increase the Risk of Insects Developing Behavioral Resistance to Systemic Insecticides?” is the work of Nansen, doctoral students Trevor Fowles and Emily Bick and researcher Haleh Khodaverdi. The researchers cite some 60 references.
“Increases in severity and frequency of drought periods, average global temperatures, and more erratic fluctuations in rainfall patterns due to climate change are predicted to have a dramatic impact on agricultural production systems,” they wrote in the abstract. “Insect pest populations in agricultural and horticultural systems are also expected to be impacted, both in terms of their spatial and temporal distributions and in their status as pest species.”
The UC Davis researchers discussed how indirect effects of drought may adversely affect the performance of systemic insecticides and also lead to increased risk of insect pests developing behavioral insecticide resistance. “We hypothesize that more pronounced drought will decrease uptake and increase the magnitude of nonuniform translocation of systemic insecticides within treated crop plants, and that may have two concurrent consequences: 1) reduced pesticide performance, and 2) increased likelihood of insect pests evolving behavioral insecticide resistance,” they wrote in the abstract.
“Under this scenario, pests that can sense and avoid acquisition of lethal dosages of systemic insecticides within crop plants will have a selective advantage. This may lead to selection for insect behavioral avoidance, so that insects predominantly feed and oviposit on portions of crop plants with low concentration of systemic insecticide.”
Nansen noted that limited research has been published on the effect of environmental variables, including drought, on pesticide performance. It's important to study the many ways environmental factors can affect, directly and indirectly, both the performance of insecticides and the risk of target insect pests developing resistance, Nansen says.
Potato beetles and diamondback moths are two of the pests mentioned in the research article. Potato beetle larvae attack potato crop foliage, while the larvae of the diamondback moths are major pests of cabbage.
- Author: Kathy Keatley Garvey
And that's grounds for concern, researchers say.
Agricultural entomologist Christian Nansen of the UC Davis Department of Entomology and Nematology and four colleagues analyzed 15 brands of roasted coffee beans, purchased at an area supermarket on two dates about six months apart, and using hyperspectral imaging technology, found “they were all over the board.”
“There was no consistency in the protein/sugar content and within the roasting classes of light, medium, medium dark, and dark or between sampling dates,” said Nansen, who specializes in insect ecology and remote sensing and uses imaging technology to quantify variability and identify trends and patterns in biological systems. “I thought this would be interesting to apply my hyperspectral imaging technology to a commercial system rather than a biological system.”
The research, “Using Hyperspectral Imaging to Characterize the Consistency of Coffee Brands and Their Respective Roasting Classes" is published in the current edition of the Journal of Food Engineering. Hyperspectral imaging involves collecting and processing information from across the electromagnetic spectrum.
Co-authors of the paper are postdoctoral research Keshav Singh of the Nansen lab; assistant professor Christopher Simmons and doctoral candidate Brittany Allison, both in the UC Davis Department of Food Science and Technology; and Ajmal Mian of the University of Western Australia's Computer Science and Software Engineering.
The study is not only relevant to the coffee industry and consumers but to a wide range of commercial food and beverage brands, Nansen said. Statistics show that Americans, the leading consumers of coffee in the world, consume 400 million cups of coffee per day. They spend an average of $21 per week on coffee.
Nansen, a coffee drinker, came by the topic naturally and also out of curiosity. “I got interested in this topic because I like coffee but also because I am certain that many food and beverage products vary markedly in quality. I thought this would be interesting to apply my hyperspectral imaging technology to a commercial system rather than a biological system.”
“The uniqueness and consistency of commercial food and beverage brands are critically important for their marketability,” the researchers wrote in the abstract. “Thus, it is important to develop quality control tools and measures, so that both companies and consumers can monitor whether a given food product or beverage meets certain quality expectations and/or is consistent when purchased at different times or at different locations.”
“We acquired hyperspectral imaging data (selected bands out of 220 narrow spectral bands from 408 nanometers to 1008 nanometers from ground samples of the roasted coffee beans, and reflectance-based classification of roasting classes was associated with fairly low accuracy.”
Their research provides evidence that the “combination of hyperspectral imaging and a general quality indicator (such as extractable protein content) can be used to monitor brand consistency and quality control,” the scientists wrote. “We demonstrated that a non-destructive method, potentially real-time and automated, and quantitative method can be used to monitor the consistence of a highly complex beverage product.”
The research was funded in part by Mian's ARC Fellowship.
- Author: Kathy Keatley Garvey
Yes, it does, says UC Davis agricultural entomologist Christian Nansen of the Department of Entomology and Nematology, who set out to investigate whether there's a relationship between the “physiological” and “behavioral” resistance in insects and found “some quite interesting patterns.”
In a first-of-its-kind research, published March 4 in the Public Library of Science (PLOS), Nansen and his colleagues discovered that “certainly there was an effect of level of physiological resistance or susceptibility of moth strains” – this they demonstrated by comparing two moth strains with high and low levels of insecticide resistance. But they also found intriguing differences in life stages. “We found that ovipositing females and developing larvae may not show the same levels of behavioral responses to insecticides.”
“This is all very interesting and clearly links theoretical evolutionary biology with applied pest management,” he said, concluding that “behavioral avoidance ought to be considered in evaluating the performance of an insecticide.”
The research, “Behavioral Avoidance—Will Physiological Insecticide Resistance Level of Insect Strains Affect their Oviposition and Movement Responses,” by Christian Nansen and fellow scientists Maria Nansen of UC Davis and Olivier Baissac, Kevin Powis and Greg Baker, all of Australia, targeted the Brassica pest, Plutella xylostella, commonly known as “the cabbage moth.” It is responsible for an estimated $4 to $5 billion loss annually in the United States, Nansen said. Cole crops are the moth's host plant. It lays its eggs only on the family Brassicaceae. Its larvae or caterpillars feed on the leaves, floral stalks and flower buds.
The main objective of the Christian Nansen-led study was to quantify two possible types of behavioral avoidance:
- under choice conditions with leaves having different levels of pesticide spray coverage (including an untreated control leaf), females oviposit predominantly on leaf surfaces without insecticides, and
- larvae avoiding insecticide-treated leaf surfaces.
“As a model system, we studied movement and oviposition responses by two strains of DBM denoted ‘single resistance' and ‘double resistance' based on their levels of physiological resistance to two insecticides: gamma-cyhalothrin and spinetoram,” they wrote.
The researchers compared behavioral responses by these two strains as part of characterizing the relative effect of levels of physiological resistance on the likelihood of insects showing signs of behavioral avoidance.
“Although we are unaware of any theoretical framework providing clear predictions of expected behavioral responses by phenotypes with different of physiological resistance," Nansen said, "we predicted that: (1) DBM individuals with confirmed physiological resistance to a given combination of dosage and insecticide show similar movement and oviposition responses to host plant surfaces with/without insecticides, and (2) DBM individuals should avoid insecticide treated surfaces and show significant changes in movement and oviposition behavior, if they are exposed to a combination of dosage and insecticide to which they are susceptible.”
Nansen said the study “highlights the possibility of associations between physiological resistance and avoidance responses by ovipositing females. In addition, larvae from the single resistance strain moved significant faster than those from the double resistance strain, when the entire arena was treated with either gamma-cyhalothrin or spinetoram.”
"Our study highlights the importance of conducting behavioral studies as part of characterizing effects of selective pressures by insecticides and as part of performance evaluations of insecticides.”
The diamondback moth, thought to be of European origin, is found throughout the Americas and in Europe, Asia, Africa, Australia, New Zealand and the Hawaiian Islands. It was first observed in North America in 1854 in Illinois and by 1883 had spread to Florida and the Rocky Mountains, data shows.
The diamondback moth was the first insect found to have become resistant to biological control by the Bt toxin (from Bacillus thuringiensis) in the field. In the 1980s, the moth developed resistance to pyrethroids, and today, virtually all insecticides are ineffective, entomologists say.
Cold winters help to kill off overwintering pests. In California, natural enemies can often effectively control the diamondback moth, according to the UC Integrated Pest Management (UC IPM) Program website. “In southern California, the ichneumonid wasp, Diadegma insularis, has been identified as the most common parasite. Trichogramma pretiosum may also attack diamondback eggs," IPM says. "Various predators such as ground beetles, true bugs, syrphid fly larvae, and spiders can be important factors in controlling populations.”
- Author: Kathy Keatley Garvey
The review, co-authored by Nansen and Norman Elliott of the U.S. Department of Food and Agriculture's Agricultural Research Service, Stillwater, Okla., explains remote sensing and highlights how it influences entomological research by “enabling scientists to nondestructively monitor how individual insects respond to treatments and ambient conditions. Furthermore, novel remote sensing technologies are creating intriguing interdisciplinary bridges between entomology and disciplines such as informatics and electrical engineering.”
“To most people, remote sensing refers to imaging-and reflectance-based surveying mounted on airborne devices and vehicles such as airplanes or satellites,” they pointed out. They rely on a broader definition: “The measurement or acquisition of information of some property of an object or phenomenon by a recording device that is not in physical or intimate contact with the object or phenomenon under study.”
“Consequently, even imaging through a microscope may be considered a type of remote sensing,” they wrote. “In many remote sensing applications, the data are collected in parts of the radiometric spectrum that are not detectable by the human eye…We wish to emphasize that entomological remote sensing is expanding in many directions and creating intriguing opportunities for collaborative research between entomology and disciplines such as informatics and electrical engineering. “
Remote sensing has been an established research discipline for more than four decades, Nansen related. “It was Isaac Newton who discovered that light could be separated into a spectrum of colors, and approximately 100 years later, James Clerk Maxwell discovered that light as we see it is part of a very wide radiometric spectrum.”
(See the Nansen/Elliott review at http://www.annualreviews.org/doi/abs/10.1146/annurev-ento-010715-023834)
The Annual Review of Entomology, launched in 1956, reviews significant developments in the field of entomology, including biochemistry and physiology, morphology and development, behavior and neuroscience, ecology, agricultural entomology and pest management, biological control, forest entomology, acarines and other arthropods, medical and veterinary entomology, pathology, vectors of plant disease, genetics, genomics, and systematics, evolution, and biogeography.
Nansen, who joined the UC Davis Department of Entomology and Nematology in 2015, is focusing on four major themes: host plant stress detection, host selection by arthropods, pesticide performance, and use of reflectance-based imaging in a wide range of research applications.
He is using his international expertise to zero in on more sustainable farming systems, better food production and fewer pesticides.
“The agricultural sector in California is so exciting, because of its diversity and economic importance,” said Nansen, whose agricultural entomology expertise encompasses seven countries including his native Denmark. “Secondly, there is a strong spirit of innovation in this region, and I hope to contribute to the development of highly advanced crop monitoring systems and decision support tools, so that farming practices can become less reliant on pesticides.”
Born and educated in Denmark, Nansen received his master's degree in biology from the University of Copenhagen in 1995 and his doctorate in zoology from the Royal Veterinary and Agricultural University in Denmark in 2000. He accepted positions in Portugal, Benin, United States, UK and Australia before joining the UC Davis Department of Entomology and Nematology in January as an assistant professor. Nansen previously held faculty positions at Texas A&M, Texas Tech, and most recently at the University of Western Australia.
His international experience also includes being an international exchange student at the University of Lisbon, Portugal and a visiting professor at Northwest A&F University, Yangling, China.
Related Link:
Christian Nansen's Website
- Author: Kathy Keatley Garvey
But non-healthy insects, just like sick humans, can also show changes in body reflectance.
Newly published research led by a University of California, Davis agricultural entomologist shows that radiometric energy reflected by pesticide-exposed adult beetles indicates when they become “terminally ill.”
Christian Nansen, lead author of “Detection of Temporal Changes in Insect Body Reflectance in Responses to Killing Agents,” published in PLOS ONE, said the first-of-its-kind research is “completely non-destructive and completely non-invasive.”
“The results may be of considerable relevance to insect physiologists and toxicologists studying responses to treatments and/or to behavioral entomologists studying adaptations and behavioral responses,” he said.
Nansen and colleagues Leandro Prado Ribeiro of the University of São Paulo,Brazil, and Ian Dadour and John Dale Roberts of the University of Western Australia researched the effects of two species of beetles exposed to killing agents (an insecticidal plant extract and entomopathogenic nematodes).
Their subjects were maize weevils (Sitophilus zeamais), and larger black flour beetles (Cynaus angustus). The maize weevil is a major pest of corn and also feeds on standing crops and stored cereal products, including wheat, rice, sorghum, oats, barley, rye, buckwheat, peas and cottonseed, as well as pasta.
“The larger black flour beetle thrives in cotton gin trash piles on the Southern High Plains of Texas,” Nansen said, “and sometimes becomes a nuisance after invading public and private structures.”
In their study, they addressed two questions: 1) Will exposure to known killing agents cause a detectable change in body reflectance? And 2) And if so, after what exposure time?
“It is common to use infra-red thermometers to measure skin reflectance of radiometric energy in specific wavelengths as part of determining our body temperature, and body temperature is one of the key diagnostics in detection of human illnesses,” said Nansen, a specialist in integrated pest management (IPM), insect ecology and remote sensing. “In our study, we analyzed radiometric energy reflection by adult beetles (in particular wavelengths in the visible and infra-red spectrum) and showed that reflectance features change when beetles are starting to become terminally ill!”
“By following their body reflectance over time, we demonstrated that, compared to healthy /untreated individuals, there was a significant change in the body reflectance at the time point when killing agents are known to cause lethal symptoms.”
“Specific spectral bands were used to develop reflectance-based classification models for each species, and independent validation of classification algorithms showed sensitivity (ability to positively detect terminal stress in beetles) and specificity (ability to positively detect healthy beetles) of about 90 percent,” the authors wrote. “Significant changes in body reflectance occurred at exposure times, which coincided with published exposure times and known physiological responses to each killing agent. The results from this study underscore the potential of hyperspectral imaging as an approach to non-destructively and non-invasively quantify stress detection in insects and other animals.”
Nansen, a native of Denmark, received his master's degree in biology from the University of Copenhagen in 1995 and his doctorate in zoology from the Royal Veterinary and Agricultural University in Denmark in 2000. He accepted positions in Portugal, Benin, United States, UK and Australia before joining the UC Davis Department of Entomology and Nematology in January as an assistant professor. His international experience also includes being an international exchange student at the University of Lisbon, Portugal and a visiting professor at Northwest A&F University, Yangling, China. As part of his undergraduate studies, Nansen traveled to Brazil to write a book about sustainable agriculture in rainforest areas.