July 12, 2012 | Minda Berbeco

In 1904, Louis Henderson, one of the first botanists to explore the Western States, was called out to a farm in the Boise valley to solve an unusual mystery. He was taken to an apple orchard where he found a patch of blackened, wilting trees surrounding a bee hive. The farmer was stumped: were the bees killing the trees?

Henderson quickly identified the problem. The disease was fire blight, a necrotic wilt disorder caused by bacteria, and it was being spread by the busy, little pollinators (1).

In those days, there were few options for battling disease and pestilence outbreaks like fire blight. The treatment was to cut back the diseased trees and burn the cuttings. Today there are many options available that save the trees while eliminating the pests. However, as consumer interest and government regulations have shifted towards more environmentally friendly management, many farmers are being encouraged to look beyond conventional pesticides to more biologically-based management schemes.

Dating back to ancient times, people have attempted to take advantage of pre-existing biological relationships in nature to manage pests on their farms. In ancient China, farmers placed carnivorous ants in orange groves to protect their fruit from other insects (2). As understanding of these relationships has gotten better, industry advocates and farmers alike are developing new biologically-based pesticides to manage disease and insect outbreaks on farms.

Biopesticides are organisms or naturally-derived toxins developed and utilized for non-synthetic pest control. They include everything from viruses that liquefy caterpillar’s internal organs to predatory nematodes that ambush their insect prey. Though this is not a novel concept, as a new industry biopesticides are already a $1.3 billion dollar enterprise with a projected 16% growth over the next 5 years (3).

Unlike conventional pest management practices, which distribute toxins indiscriminately, biopesticides are advertised as being more targeted, only affecting the pest they are designed to eliminate, and not harming humans or other animals. The challenge, though, is determining what is targeted enough. Sure, you’ve tackled all the aphids and mites, but did you mean to take out the flies and termites too?

Famously, the biopesticide bacteria Bacillus thuringiensis was so successful in managing caterpillar pest populations that its toxic component was engineered into genetically modified Bt-crops. This was touted at the time as more effective than a spray-on biopesticide, as it would not get washed or blown away by bad weather (4). Much to the chagrin of both farmers and industry advocates, though, the Bt-crops landed themselves in PR hot water when it was suggested that in addition to targeting pests, they also killed migrating monarch butterflies (5). The research has since moved on to suggest that this is not the case (6), but the crops themselves have not overcome this negative publicity.

Not all biopesticides have suffered the same fate and many have been found to be highly effective. The fungus Beauveria bassiana has been used for years now to control insect outbreaks. This microbe kills aphids, mites and caterpillars, with no known negative impacts on mammals or birds. It is reportedly safer for honeybees as well, compared to more conventional pesticides (7). In fact, it is targeted enough that it has been used to kill parasitic mites attached to bees while leaving the bees themselves unharmed (8). Recent research has even suggested that it may be successful in combating the bed bug infestation that has been sweeping the United States (9). If research continues to support this, the B. bassiana might end up the most revered fungus of all time.

Some biopesticides are more effective as part of a larger management plan. An example of this is the benign bacteria, Pantoea agglomerans, which has been developed to fight the aforementioned fire blight. In the 1950’s, farmers started successfully treating fire blight with antibiotic streptomycin. Over the years, though, the disease adapted to streptomycin, creating resistant strains and making the antibiotic less effective. Researchers found that adding P. agglomerans during flowering reduced the risk of disease outbreak by 55%, as these beneficial bacteria out-competed the fire blight bacteria (10). Unfortunately, this was still not as effective as using streptomycin alone. As a result, as with many other biopesticides, manufacturers started recommending the use of P. agglomerans as part of a larger integrated pest management plan to reduce, not eliminate, streptomycin use (11).

This recommendation was echoed by Travis Glare, Professor of Applied Entomology at the Bioprotection Research Centre in Christchurch New Zealand. “Mixing biopesticides with low doses of chemical pesticides has achieved excellent results in some situations.”

But he warned that caution was needed when utilizing biopesticides with more conventional pesticides.

“Mixing a biopesticide that uses a live fungus with a chemical fungicide will obviously not work. It may sound simple, but it happens (often by accident).”

Glare also recommended that farmers consider the environmental conditions of their farm before applying biopesticides.

“Applying in the cool of the evening rather than midday, avoiding applying in heavy rain, targeted application to the  underside of leaves (for example) to avoid excessive UV exposure, will all improve activity of most biopesticides.”

In this new world of biopesticides that takes advantage of pre-existing warfare between biological organisms, farmers are being given the opportunity to think about their farms from a holistic perspective in which even the pesticides are living beings.

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Further reading:

1. Biopesticides by US EPA http://www.epa.gov/oecaagct/tbio.html
2. Startup Profile: Pest Busting Ag Entrepreneur Offers Farmers a Natural Solution  http://seedstock.com/2011/07/25/pest-busting-ag-entrepreneur-offers-farmers-a-natural-solution/

Citations:

(1) Henderson LF (1904) Fire Blight Disease of the Pear and Apple, Deseret Evening News, June 17^th, page 11 http://news.google.com/newspapers?id=DVYwAAAAIBAJ&sjid=C1QDAAAAIBAJ&pg=5688,3407347&dq=fire+blight&hl=en

(2) Woods MW & MB Woods (2000) Ancient Agriculture: From Foraging to Farming, Lerner Publications.

(3) Markets and Markets: Global Biopesticides Market Worth $3.2 Billion by 2017.  Press Release. June 15^th 2012.  http://www.marketwatch.com/story/marketsandmarkets-global-biopesticides-market-worth-32-billion-by-2017-2012-06-15

(4) Sanahuja1 G, Banakar1 R, Twyman, RM, Capell T & P Christou (2011)  Bacillus thuringiensis: a century of research, development and commercial. Plant Biotechnology Journal, 9:283–300.   http://onlinelibrary.wiley.com/doi/10.1111/j.1467-7652.2011.00595.x/pdf

(5) Losey JE, Rayor LS & ME Carter (1999) Transgenic pollen harms monarch larvae.  Nature 399: 219.  http://www.nature.com/nature/journal/v399/n6733/abs/399214a0.html

(6) Shelton AM & MK Sears (2001) The monarch butterfly controversy: scientific interpretations of a phenomenon.  The Plant Journal, 27(6):483-488.  http://onlinelibrary.wiley.com/doi/10.1046/j.1365-313X.2001.01118.x/pdf

(7) Krupke CH, Hunt GJ, Eitzer BD, Andino G & K Given (2012) Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields. PLoS ONE 7(1). http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029268

(8) Meikle WG, Mercadier G, Holst N, Nansen C &V Girod (2008) Impact of a treatment of Beauveria bassiana (Deuteromycota: Hyphomycetes) on honeybee (Apis mellifera) colony health and on Varroa destructor mites (Acari: Varroidae).  Apidologie, 39(2):247-259.  http://www.springerlink.com/content/t3351k01001j2301/

(9) Barbarin AM, Jenkins NE, Rajotte EG, Thomas MB (2012) A preliminary evaluation of the potential of Beauveria bassiana for bed bug control.  Journal of Invertebrate Pathology. In Press.  http://www.sciencedirect.com/science/article/pii/S0022201112001152

(10)  Stockwell VO, Johnson KB, Sugar D & JE Loper (2002) Antibiosis Contributes to Biological Control of Fire Blight.  Phytopathology, 1202-1209.  http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.2002.92.11.1202

(11) Northwest Agri Products, Bloomtime FD. http://www.nap-chem.com/Products/Bloomtime.html