Natural alternatives to protect plants inspired by pharmaceutical research

The bacteria Streptomyces — which is commonly used in human antibiotics and found in the natural environments of wild plants as well as crops — could be used as an environmentally friendly alternative to pesticides, scientists in France write in an Opinion published December 1 in Trends in Plant Science. In addition to protecting plants from fungal and other threats, Streptomyces has been shown to keep roots healthy and promote plant growth. Streptomyces or their derived metabolites are already being used in six different agricultural products.

Streptomyces can really produce a wide diversity of molecules that have bioactive properties,” says lead author Thomas Rey, Biofungicide Research Program Manager at the De Sangosse Group in France. “This is a unique microbial genus that can do so many different things for plants, and it has the potential to be a cornerstone for how we could protect crops in a sustainable fashion.”

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This diagram shows the bacteria Streptomyces bioactivities that are beneficial to crops.

Credit: Rey and Dumas/Trends in Plant Science 2016

Streptomyces is most commonly found in the upper soil and inside plant roots, and it has primarily been used in antibiotics that treat serious infections such as tuberculosis. However, new advances in synthetic biology have allowed plant scientists to explore how they could rely on previous medical research to deploy Streptomyces strains for agriculture as well. Scientists know the microbe helps encourage the growth of plant roots and can control proliferation of plant pests in the soil. Additionally, Streptomyces can detoxify harmful mycotoxins, which are produced by certain fungi and can ruin large food yields from plants like grain or wheat.

“The soil around plants is rich in microbes that are amazingly diverse,” says Rey. “But we still have to find ways to accurately study how these microbes and the substances they release both interact with the environment and different parts of the plant so that we can transfer that knowledge to crops that would really benefit from exposure to Streptomyces.”

Rey and his team are aware of significant pitfalls to avoid when using the Streptomyces strains. Because Streptomyces is a source for antibiotics used in medicine, releasing antibiotics-producing strains into the environment must be avoided to prevent bacteria harmful to humans or animals from having more opportunities to adapt to these antibiotics. The status of mutagenized or genome-edited strains of Streptomyces in terms of environmental registration and deployment still need to be defined. But despite these potential challenges, Rey and his team believe that previous pharmaceutical and medical research involving Streptomyces lays the groundwork for its agricultural application.

“Using microbes to protect plants is a new trend, and Streptomyces is not the only type of microbe that can be used in biocontrol,” says Rey. “But Streptomyces is very unique in that it is one of the few microbes that can be studied in both pharmacology and agriculture, and we’re in a good position to use this new research to make it beneficial to agriculture.”

Source: Cell Press. www.cellpress.com




Pest control: Wicked weeds may be agricultural angels

Farmers looking to reduce reliance on pesticides, herbicides and other pest management tools may want to heed the advice of Cornell agricultural scientists: Let nature be nature — to a degree.

“Managing crop pests without fully understanding the impacts of tactics — related to resistance and nontarget plants or insects — costs producers money,” said Antonio DiTommaso, professor of soil and crop science and lead author of a new study, “Integrating Insect, Resistance and Floral Resource Management in Weed Control Decision-Making,” in the journal Weed Science (October-December 2016).

“We are taking a renewed look at a holistic, sustainable integrated pest management (IPM) approach,” DiTommaso said.

In corn production, for example, maintaining a few villainous milkweed plants in the middle of a cornfield may help minimize crop loss from the destructive European corn borer. The milkweed plants can harbor aphids (destructive sap-sucking flies) that produce a nectar food source for beneficial parasitic wasps Trichogramma. The wasps, in turn, lay eggs inside the eggs of the European corn borer, killing the corn borer eggs — reducing damage to the crop.

“Production management rarely considers the benefits of weeds in agricultural ecosystems,” said DiTommaso. “Let’s look at the big picture. If we open our eyes — even if it’s a weed growing in the cornfield — we show it could be beneficial. Integrating weed benefits will become increasingly important, as pest management is likely to move from total reliance on herbicides and transgenic crop traits for control, because of increasing resistance of weeds to these products.”

One additional side benefit for having a few milkweed plants in a field of corn is that it serves as a breeding place and food source for monarch butterflies. As of late, monarch numbers are down, and the U.S. Fish and Wildlife Service is evaluating a petition to have them protected under the Endangered Species Act.

While some growers elect not to use engineered crops, producers may see a return to IPM methods from two decades ago, as resistance could easily occur when relying on a single tactic.

With increasing no-till production, producers will inevitably see rebounds in perennial weeds — such as milkweed, the researchers said. Thus, some growers may be willing to tolerate a low milkweed population in favor of providing livable plant space for monarchs.

“Every organism in an agricultural system plays multiple roles,” said John Losey, professor of entomology. “If management decisions are based solely on the negative aspects, yield and profit can be lost in the short term and broader problems can arise in the longer term.”

Integration of the weed costs and advantages will become important. “The benefits of weeds have been neglected. They’re often seen as undesirable, unwanted. We’re now beginning to quantify their benefits,” said Kristine M. Averill ’05, M.S. ’09, weed research associate.

“It’s very important to recognize the benefits of all the species within the crop field — that includes both the crops and the weeds — not to mention cover crops. Weeds can offer ecosystem services, such as soil erosion protection and pollination services for the benefit of insects,” Averill said. “They can be part of a restorative cycle.”

Joining DiTommaso, Averill and Losey on the study were Michael Hoffmann, professor of entomology; and Jeffrey R. Fuchsberg, director of intellectual property at the Medical Center of the Americas Foundation.

Source: Cornell University. www.cornell.edu




Report provides options for organic soybean growers

Although soybeans are one of the most widely grown crops in the U.S., few soybean farmers are using organic practices. A new University of Illinois report details organic products and practices to combat pathogens and insect pests. New growers may be motivated by a strong profit margin for organically produced soybeans.

Soybeans were planted on nearly 84 million acres in the U.S. in 2016, but only a tiny fraction — less than 1 percent — were grown organically. This number has been increasing in recent years, and a group of University of Illinois researchers wants to give organic growers the tools they need to combat pathogens and insect pests.

“We wanted to give organic growers some opportunities. We summarized some practices to fight diseases and pests organically. It’s not an easy task, but it can be done,” says U of I and USDA ARS crop pathologist Glen Hartman.

Hartman, along with colleagues in the Department of Crop Sciences, produced a comprehensive report summarizing the disease and pest problems faced by soybean growers in the United States. For the first time, the report compiles specific organic management practices and products tailored for each scenario. By detailing the tools needed to successfully grow organic soybeans, the researchers hope more growers will give it a try.

“There is a movement for organic agriculture, but so far, soybeans haven’t been a major player,” Hartman notes.

The researchers want to encourage small-scale vegetable farmers that are already using organic practices to add soybeans to the mix. The expansion of the organic meat and dairy markets, combined with strong consumer interest in organic soy-based foods like tofu and edamame, are increasing the demand for organically grown soybeans. Over half of organic soybeans are imported, but several companies and entrepreneurs are working to increase the domestic supply.

Those who are selling organic soybeans today are getting almost twice as much per bushel compared to conventional soybeans. “Organic meat is probably double or triple the price compared with conventionally raised meat. And that’s partly from the cost of organic feed. Whoever’s producing this is going to make some money,” Hartman says. “Bags of frozen edamame sell for about $3 at the grocery store, and there might be 40-50 pods per bag. That’s equivalent to one or two plants. You can grow maybe 100,000 plants in an acre. You can do the math, and that’s a rough calculation, but there could be a lot of profit involved.”

Graduate student Theresa Herman also sees the potential for increased edamame production in the United States. “I have talked to school food service companies about incorporating edamame in school lunch programs. It’s a good source of protein, and kids eat the beans voraciously. They’re crazy about edamame,” she notes.

Soybeans grown for edamame appear to be more prone to insect and disease problems than grain soybean, and non-GMO grain varieties available to organic growers may not have the disease and pest resistance that is present in many elite conventional cultivars. However, there are organic solutions for both. In the report, the researchers lay out strategies in a number of categories, including biological control, cultural practices, breeding priorities, and organic pesticide products.

“Rotations to different crops are commonly used by organic growers,” Hartman says. “Organic producers have cover crops and alternative crops that are not used in most corn and soybean systems. They might have a four- to six- to eight-year rotation, which is one of the best ways to reduce diseases.”

Although the researchers point to the promise of longer rotations and cover crops, they would like to know more about the effectiveness of organic products and practices in real-world settings.

“We want to be able to experimentally test some of the products growers are using in organic soybean systems. We want to learn what their constraints are, and how we can help them,” Hartman says.

Herman adds, “A lot of people are happy with the way they do things, but they want to know more about why and how their system is working.”

Current and potential organic soybean growers can contact Hartman directly, and can read the new report, “Organically grown soybean production in the USA: Constraints and management of pathogens and insect pests,” published in Agronomy.

Source: University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES). aces.illinois.edu




Ornamental plants for conserving bees, beneficial insects

Insects play a vital role in ecosystem health, helping to aerate soil, keeping the natural system in balance, and preventing detrimental pests from taking over essential natural resources. Additionally, insects provide critical biological services such as pollination and biological controls. The authors of a study in the August 2106 issue of HortScience say that flowering ornamental plants have the potential to support beneficial insect communities, such as pollinating bees, wasps, and predatory plant bugs.

Bethany A. Harris, S. Kristine Braman, and Svoboda V. Pennisi from the University of Georgia conducted visual observations and sampled via sweep nets to assess the potential of flowering ornamentals to act as a conservation resource for pollinators. “By monitoring pollinator and beneficial insect occurrence within habitat management sites, ornamental plant species can be evaluated for their arthropod attractiveness and the provision of arthropod mediated ecosystem services,” said Bethany Harris, lead author of the study.

beneficial-insects
Observations showed that hoverflies, skippers, and parasitic wasps (such as the sphecid wasp shown here on Coreopsis ‘Cosmic Eye’) were frequent visitors to butterfly and conservation gardens.

Credit: Bethany A. Harris

The research included visual observations and sweep-net sampling in four research plots at the University of Georgia’s Griffin Campus. The plots, called the “Butterfly” and “Conservation” Gardens, included 74 commercially available annual and perennial herbaceous and shrub ornamentals, including exotic and native plant species.

“The gardens attracted a diverse population comprised of pollinators (30+ species and 16+ families) and beneficial insects (20+ species and 9+ families),” Harris noted. Hoverflies, skippers, predatory plant bugs, and parasitic wasps were frequent visitors to Butterfly and Conservation Gardens. “In addition, species of native bees were identified in the gardens, suggesting that pollinator habitats could be created in southeastern landscapes using these taxa.”

Celosia, Gaura, Lantana, and Nepeta xfaassenii were some of the most-visited plants by both pollinators and beneficial insects. “This could be due to the vibrant colors, rich nectar and pollen supply, and the variety of floral inflorescences these plants possess,” Harris said. Agastache and Celosia were the most frequently visited by pollinators among 74 plant taxa.

“To the best of our knowledge, this study is the first to document the response of pollinators and natural enemies to plantings of ornamental plants suitable for southeastern landscapes,” the authors noted. They said that determining which plants will provide adequate resources at different times in the growing season is one of the first steps toward conservation of bees and other beneficial insects. “Using these data, recommendations can be provided on the use of flowering ornamental plants for pollinator and beneficial insect conservation purposes as well as sampling methods that can be employed to effectively survey beneficial insect communities.”

Source: American Society for Horticultural Science. www.ashs.org




High number of pesticides within colonies linked to honey bee deaths

Honey bee colonies in the United States have been dying at high rates for over a decade, and agricultural pesticides — including fungicides, herbicides and insecticides — are often implicated as major culprits. Until now, most scientific studies have looked at pesticides one at a time, rather than investigating the effects of multiple real-world pesticide exposures within a colony.

A new study is the first to systematically assess multiple pesticides that accumulate within bee colonies. The researchers found that the number of different pesticides within a colony — regardless of dose — closely correlates with colony death. The results also suggest that some fungicides, often regarded as safe for bees, correlate with high rates of colony deaths. The study appeared online September 15, 2016, in the journal Nature Scientific Reports.

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A honey bee forager collecting nectar from a cleome flower. Bees make honey from nectar. They also collect pollen, which they convert into bee bread.

Credit: Kirsten S. Traynor

“Our results fly in the face of one of the basic tenets of toxicology: that the dose makes the poison,” said Dennis vanEngelsdorp, an assistant professor of entomology at UMD and senior author on the study. “We found that the number of different compounds was highly predictive of colony death, which suggests that the addition of more compounds somehow overwhelms the bees’ ability to detoxify themselves.”

The researchers followed 91 honey bee colonies, owned by three different migratory commercial beekeepers, for an entire agricultural season. The colonies began their journey in Florida and moved up the East Coast, providing pollination services for different crops along the way. They also spent time in locations meant for honey production, as well as “holding areas” where beekeepers prepare large numbers of colonies for upcoming pollination contracts.

A total of 93 different pesticide compounds found their way into the colonies over the course of the season, accumulating in the wax, in processed pollen known as bee bread and in the bodies of nurse bees. At every stop along the beekeepers’ itinerary, the researchers assessed three different parameters within each colony: the total number of pesticides; the total number of “relevant” pesticides (defined as those above a minimum threshold of toxicity); and each colony’s “hazard quotient,” a measure devised by other researchers to integrate the total hazard posed to each colony by the cumulative toxicity of all pesticides present.

All three measures correlated with a higher probability of colony death or queen failure. In addition, the researchers found between five and 20 different pesticide residues in every sample of bee bread that exceeded a hazard quotient’s safety threshold. The highest number of pesticides accumulated in the colonies early on, shortly after beekeepers placed colonies into early season flowering crops like apples and blueberries. Honey production stopovers and holding areas offered the bees some respite from further contamination.

The study results also suggest that some fungicides, which have led to the mortality of honey bee larvae in lab studies, could have toxic effects on colony survival in the field. In the current study, pesticides with a particular mode of action also corresponded to higher colony mortality. For example, the fungicides most closely linked to queen deaths and colony mortality disrupted sterols — compounds that are essential for fungal development and survival.

“We were surprised to find such an abundance of fungicides inside the hives, but it was even more surprising to find that fungicides are linked to imminent colony mortality,” said Kirsten Traynor, a postdoctoral researcher in entomology at UMD and lead author on the study. “These compounds have long been thought to be safe for bees. We’re seeing them at higher doses than the chemicals beekeepers apply directly to the colonies to control varroa mites. So that is particularly concerning.”

The current study borrows a concept from human cancer research: the “exposome,” or the sum total of chemicals an organism is exposed to over its lifetime. But instead of looking at individual bees, the researchers assessed each colony as a single “superorganism” that functions as a single, cohesive unit.

Within this framework, the researchers tracked the death of queen bees, which is a life-threatening event for the colony as a whole. In some cases, a colony is able to create a new queen, but if those efforts fail the entire colony will die. In the current study, colonies with very low pesticide contamination in the wax experienced no queen events, while all colonies with high pesticide contamination in the wax lost a queen during the beekeeping season.

“This is a huge problem for beekeepers currently. Not long ago, a queen would typically last up to two years. But now many commercial beekeepers replace the queens in at least half of their colonies every spring in the hopes that this will prevent premature queen deaths,” Traynor explained. “Even with such measures, many queens still don’t make it through one season.”

The research team did not find a significant contribution from neonicotinoid pesticides. These compounds, derived from nicotine, are currently some of the most common pesticides in use globally. Because of their ubiquitous use, neonicotinoids have received significant media attention for their potential role in honey bee declines.

“We just did not find neonicotinoids in the colonies,” vanEngelsdorp explained. “There were some trace residues of neonicotinoids in a few samples, but not nearly on par with other compounds. However, it’s possible we did not test the right matrix — we did not test nectar, for example — or that the product breaks down faster than others in the collection process or that neonicotinoids are simply not very prevalent when crops are flowering.”

Because industrial practices have changed since the researchers collected the data for this study, Traynor and vanEngelsdorp acknowledge that further research could reveal new patterns in the relationship between pesticides and honey bee health. But the current study nonetheless offers some important insights for beekeepers and farmers alike.

“We have to figure out ways to reduce the amount of products that bees are exposed to while still helping farmers produce their crops,” vanEngelsdorp said. “This will require careful examination of spray plans, to make sure we only use the products we need, when we need them, in order to reduce the number of products bees are exposed to while pollinating different crops.”

Source: University of Maryland. cmns.umd.edu




Genetically engineered crops are safe, review of studies finds

Genetically engineered (GE) crops are no different from conventional crops in terms of their risks to human health and the environment, according to a report published in May 2016 by the U.S. National Academies of Sciences, Engineering, and Medicine.

Leland Glenna, associate professor of rural sociology and science, technology and society in Penn State’s College of Agricultural Sciences, served on the committee that authored the report.

“The study committee found no substantiated evidence of a difference in risks to human health between currently commercialized GE crops — specifically soybean, maize and cotton — and conventionally bred crops, nor did it find conclusive cause-and-effect evidence of environmental problems from the GE crops,” said Glenna. “These findings should not be interpreted to mean that there are not still many challenges related to both conventional and GE crops, just that currently available GE crops and conventional crops are not different in terms of their risks to human health and the environment.”

Glenna, a sociologist who studies how social institutions influence scientific research agendas and who, for the past 15 years, has studied the social impacts of agricultural science and technology, noted that GE crops commonly are portrayed either as the solution to social and economic problems or as the cause of them.

“GE crops are also commonly presented as though there are only two sides to this debate: either you are for them or against them,” he said. “But new technologies bring both promises and perils; what seems promising to some might seem perilous to others.

“However, there is still insufficient research to make conclusive statements on the social and economic impacts of GE crop technologies. I hope that those who read and discuss this report do not shoehorn it into the existing paradigm but, instead, recognize the complexity and nuances of GE crops.”

The researchers used data published during the last two decades from more than 900 research and other publications to evaluate the positive and negative effects of GE crops — crops that have been engineered to resist insects or herbicides. The scientists also heard from 80 diverse speakers and read more than 700 comments from members of the public to expand their understanding of GE crop issues.

Nearly 180 million hectares of GE crops were planted globally in 2015, roughly 12 percent of the world’s planted cropland that year.

According to the report, Bt crops, those that contain an insect-resistant gene from the soil bacterium Bacillus thuringiensis, comprise a large segment of GE cropland. The researchers found that from 1996 to 2015, the use of Bt maize and cotton contributed to a reduction in synthetic insecticide use and in crop losses. Some pest-insect populations dropped; however, insect biodiversity increased overall. Insect resistance to Bt proteins was slow to develop only when the crops produced a dose of Bt protein that was large enough to kill insects. Damaging levels of resistance did evolve in some species when resistance-management strategies were not followed.

The team found that the use of herbicide-resistant (glyphosate-resistant) crops contributed to greater crop yield by reducing weed pressure. When such crops first were adopted, total kilograms of herbicide applied per hectare of crop per year declined, although the decreases generally have not been sustained. Some weed species have evolved resistance to glyphosate; however, the team noted that delaying such resistance is possible with integrated weed management.

To examine the human health effects of GE crops and foods, the team examined animal experimental studies and found a lack of evidence that animals are harmed by eating foods derived from GE crops.

“Many people are concerned that consuming GE foods may cause cancer, obesity and disorders such as autism spectrum and allergies,” Glenna said. “However, the committee examined epidemiological datasets over time from the United States and Canada, where GE food has been consumed since the late 1990s, and similar datasets from the United Kingdom and western Europe, where GE food is not widely consumed. We found no differences among countries in specific health problems.”

The team also found that economic outcomes of GE crops have been favorable for most producers who have adopted these crops. However, the cost of GE seed may limit the adoption of GE crops by smaller, resource-poor farm holders. Furthermore, economic benefits tend to accrue for early adopters. The team concluded that enduring and widespread use of GE crops will depend on institutional support and access to profitable local and global markets.

The report can be downloaded from the National Academies of Sciences, Engineering, and Medicine website: http://nas-sites.org/ge-crops/

Source: Penn State University. www.psu.edu