- Author: Ben Faber
Food safety:
Dung beetles and soil bacteria reduce risk of human pathogens
Food safety regulations increasingly pressure growers to remove hedgerows, ponds and other natural habitats from farms to keep out pathogen-carrying wildlife and livestock. Yet, this could come at the cost of biodiversity.
New research published today in the Journal of Applied Ecology encourages the presence of dung beetles and soil bacteria at farms as they naturally suppress E. coli and other harmful pathogens before spreading to humans.
Wild and domesticated pig faeces have been known to contaminate produce in the field, leading to foodborne illnesses. Wild, or feral, pigs especially pose a risk of moving around pathogens as farmers cannot control where or when these large animals might show up.
Matthew Jones, who led the research as part of his PhD project at Washington State University, said: "Farmers are more and more concerned with food safety. If someone gets sick from produce traced back to a particular farm it can be devastating for them."
"As a result, many remove natural habitats from their farm fields to discourage visits by livestock or wildlife, making the farmland less hospitable to pollinators and other beneficial insects or birds", he added.
Dung beetles bury faeces below ground and make it difficult for pathogens to survive. To study how this may aid food safety, the entomologist drove a van full of pig faeces along the US West Coast to follow the planting of broccoli at 70 farm fields during the growing season. Broccoli, much like leafy greens, is susceptible to faecal contamination due to its proximity to the ground and the likelihood of humans consuming it without cooking.
The pig faeces were used to attract dung beetles and see how quickly they would clean up. The experiment was carried out at conventional and organic farms, and farms with or without livestock.
The organic farms seemed to attract a diverse range of dung beetle species that were most effective at keeping foodborne pathogens at bay. At conventional fields or those surrounded by pastureland, a less effective and accidentally introduced species (Onthophagus nuchicornis) outweighed the number of native dung beetles.
"We found that organic farms generally fostered dung beetle species that removed the faeces more rapidly than was seen on conventional farms", said Professor William Snyder of Washington State University.
Dung beetles likely kill harmful bacteria when they consume and bury the faeces. Previous research also suggested that these beetles have antibiotic-like compounds on their body.
To validate these findings, the researchers exposed the three most common species found in the field survey to pig faeces contaminated with E. coli. A 7-day laboratory experiment revealed that Onthophagus taurus and Onthophagus nuchicornis, both of which bury faeces as part of their breeding behaviour, reduced E. coli numbers by > 90% and < 50% respectively.
They also found that organic farming encouraged higher biodiversity among soil bacteria, which decreased the survival of pathogens.
"Bacteria are known to poison and otherwise fight among themselves and the same may be happening here", said Snyder.
These results suggest dung beetles and soil bacteria may improve the natural suppression of human pathogens on farms, making a case for reduced insecticide use and the promotion of greater plant and insect diversity.
"Wildlife and livestock are often seen as something that endanger food safety, but our research shows that reducing on-farm biodiversity might be totally counterproductive", Jones concluded.
"Nature has a 'clean-up crew' of dung beetles and bacteria that quickly remove faeces and the pathogens within them, it appears. So, it might be better to encourage these beneficial insects and microbes."
https://phys.org/news/2019-03-food-safety-dung-beetles-soil.html#jCp
Jones MS, Fu Z, Reganold JP, et al. Organic farming promotes biotic resistance to foodborne human pathogens. J Appl Ecol. 2019;00:1-11.
Read more at: https://phys.org/news/2019-03-food-safety-dung-beetles-soil.html#jCp
Read more at: https://phys.org/news/2019-03-food-safety-dung-beetles-soil.html#jCp
Read more at: https://phys.org/news/2019-03-food-safety-dung-beetles-soil.html#jCp
- Author: Ben Faber
This is an intriguing article that popped up about how to improve blueberry production in alkaline soils. High pH soils are a major issues for many of our tree crops along the coast. pH is what controls the availability of most plant nutrients and what bacteria and fungi grow in the soil, creating the biosphere. So can growing a grass cover crop in our orchards improve lemon and avocado production?
A lawn is better than fertilizer growing healthy blueberries
Intercropping with grasses is an effective and sustainable alternative to chemical treatments for maximizing blueberry yield and antioxidant content in limey soils.
Blueberries are prone to iron deficiency - and correcting it increases their health-enhancing antioxidant content, researchers have discovered.
Published in Frontiers in Plant Science, their study shows that growing grasses alongside blueberry plants corrects signs of iron deficiency, with associated improvements in berry quantity and quality. The effects are comparable to those seen following standard chemical treatment - providing a simpler, safer, cheaper and more sustainable strategy for blueberry farming on sub-optimal soils.
What do superfruits eat?
All soils are rich in iron, but nearly all of it is insoluble.
"Most plants get enough iron by secreting chemicals that make it more soluble," explains senior study author Dr José Covarrubias, Assistant Professor of Agriculture Sciences at the University of Chile. "These iron 'chelators' can be released directly from the roots, or from microbes that grow among them, and allow the iron to be absorbed."
"Blueberries, however, lack these adaptations because they evolved in uncommonly wet, acid conditions which dissolve the iron for them."
As a result, most of the world's relatively dry or alkaline ('limey') cropland is unsuitable for optimal blueberry growth.
"Iron is essential for the formation and function of plant molecules like chlorophyll that allow them to use energy," Covarrubias continues. "That's why iron deficiency shows up as yellowing leaves - and drastically reduces plant growth and yield.
"And in blueberries, iron-dependent enzymes also produce the 'superfruit' antioxidants responsible for their celebrated blue skin and health-enhancing effects."
Strong blueberries must pump iron - but at what cost?
There are two approaches to correcting iron deficiency in blueberries: acidify the soil, or add synthetic iron chelators. Each has its drawbacks, says Covarrubias.
"The commonest industrial approach is soil acidification using sulfur, which is gradually converted by soil bacteria into sulfuric acid. The effects are slow and difficult to adjust - and in waterlogged soils, hydrogen sulfide might accumulate and inhibit root growth.
"Acids can also be added directly via irrigation systems for more rapid acidification - but these are hazardous to farmers, kill beneficial soil microbes, and generate carbon dioxide emissions.
"A commoner strategy among growers is application of iron bound to synthetic chelators - often sold as 'ericaceous fertilizer' - but these are very expensive and leach potentially toxic chemicals into the water table."
A cheaper, safer alternative is needed for efficient large-scale blueberry production. Thankfully, one already exists.
"Grasses - which are well-adapted to poor soils - can provide a sustainable, natural source of iron chelators via their roots when grown alongside fruiting plants. Intercropping with grass species has been shown to improve plant growth and fruit yield in olives, grapes, citrus varieties - and most recently, in blueberries."
A grassroots approach to sustainable blueberry farming
Now, Covarrubias and colleagues have brought intercropping a step closer to the mainstream of blueberry cultivation.
For the first time, they measured the effects of different methods of iron chelation on antioxidant content and other fruit qualities in blueberries.
"In an orchard of 'Emerald' blueberry bushes cultivated in alkaline (pH 8) soil, we compared the effects of five different iron chelation treatments: a 'gold-standard' synthetic iron chelator (Fe-EDDHA), intercropping with grass (common meadow grass or red fescue), cow's blood (Fe-heme), or no treatment (control)."
"We found the association with grasses increased not only the total weight and number of blueberries per plant, but also the concentration of anthocyanins and other antioxidant compounds in their skins, compared to control. The effect sizes were comparable with the proven synthetic chelator Fe-EDDHA, whereas applications of Fe-heme from cow's blood - a fertilizer commonly used in home gardens - had no significant effect."
The beneficial effects paralleled improvement in the plants' iron status (leaf color), which was also comparable between the grass-associated and the Fe-EDDHA-treated plants. None of the treatments had a significant effect on average berry weight
Turf is ready to roll out for healthier blueberries
A potential limitation of intercropping observed in the study was a decrease in berry firmness, since firmer berries are favored by consumers.
"The association with grasses decreased berry firmness compared with control plants, whereas the berries collected from plants treated with Fe-EDDHA reached intermediate values.
"However chemical analysis showed a non-significant trend towards increased ripeness in the berries collected from the intercropped plants, which could account for this small difference."
Intercropped plants also required an additional water supply to maintain a similar soil moisture to other treatments, but plant management was otherwise straightforward and the same across groups. The grasses were kept cropped between 5 and 15cm - a typical range for an attractive mown lawn.
"Our findings validate intercropping with grasses as a simple, effective, sustainable alternative to standard iron correction strategies in blueberries," concludes Covarrubias. "Both commercial and private growers can put this strategy to use right away to boost their blueberry crop and antioxidant content."
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Please link to the original research article in your reporting: https://www.frontiersin.org/articles/10.3389/fpls.2019.00255/full
Frontiers is an award-winning Open Science platform and leading Open Access scholarly publisher. Our mission is to make research results openly available to the world, thereby accelerating scientific and technological innovation, societal progress and economic growth. We empower scientists with innovative Open Science solutions that radically improve how science is published, evaluated and disseminated to researchers, innovators and the public. Access to research results and data is open, free and customized through Internet Technology, thereby enabling rapid solutions to the critical challenges we face as humanity. For more information, visit http://www.frontiersin.org and follow @FrontiersIn on Twitter.
- Author: Ben Faber
A local Ojai grower asks why there seems to be more citrus thrips damage to 'Pixie' mandarins this year. Was it because of the extended bloom due to warmer spring last year? The hotter summer up there that was more similar to climate in the Central Valley? Was it due to the Area-Wide Spraying for Asian Citrus Psyllid - ACP? Or is this a remnant of the Thomas Fire that dumped ash all over the county, disrupting biocontrol agents like lady bird beetles?
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26095
And what else does fire do to citrus?
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28315
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26510
This is classic thrips damage. In this area, it is not usually a problem. This year it seems to be more common. It's not always clear what is the main cause of and what all the interactions are that lead up to an outbreak like this. Just that there is damage now that occurred 10 months ago.
- Author: Phoebe Gordon
For those long drives when only a podcast will do. Have you listened to a Growing the Valley podcast? Here are a couple you might want to check out.
Old and New Perennial Weeds with Dr. Brad Hanson
In this short episode, Phoebe Gordon chats with Dr. Brad Hanson, Weed Specialist with UC Davis. They talk about perennial weed management, as well as two species that have recently become problematic in orchard crops: alkaliweed and threespike goosegrass. We don't know a lot about either, but Brad and other UC weed scientists are actively looking into management.
Herbicide Resistant Weeds with Kurt Hembree
Our first episode features an interview with Kurt Hembree, the Weed Management Advisor for Fresno County. We discuss herbicide resistance in weeds, and how to prevent herbicide resistance from emerging in your orchard, and more!
https://www.growingthevalleypodcast.com/podcastfeed/2018/6/1/orchard-floor-management
Original source: Growing the Valley Podcast website (https://www.growingthevalleypodcast.com/)
- Author: Ben Faber
The latest Topics in Subtropics quarterly is out. Check it out. And subscribe for further editions. And check out the archive of past editions.
http://ceventura.ucanr.edu/news/Topics_in_Subtropics/
Topics in Subtropics Winter Edition, Vol. 18, Number 1
TOPICS IN THIS ISSUE
- Distinguishing Between Symptoms of Drought And Root Rot in Avocado
- Avocado Trunk Cankers
- Viruses Are Our Friends – and Maybe for Citrus Too
- Ground Squirrel and Other Vertebrate Control
- Meet our new Citrus Specialist at UC Riverside/Lindcove
- Meet our new Extension Tree Crops Spray Application Engineer
- UC Ag Experts Talk
