Biopesticide from Luminescent Bacteria Safely Targets Common Agricultural Pests: Taiwanese Researchers

A papaya experimental field in Taiwan to test the effectiveness of mite killers. (Courtesy of Taiwan's Agricultural Chemicals and Toxic Substances Research Institute)

After years of research, Taiwan has created a microbial pesticide that uses a luminescent bacteria to target two common agricultural pests. The country will soon be the first in the world to mass produce this biopesticide, say researchers.

According to a press release issued on Nov. 1 by Taiwan’s Agricultural Chemicals and Toxic Substances Research Institute (TACTRI), the new biopesticide, made using a bacterial pathogen called Photorhabdus luminescens, can effectively eradicate carmine and two-spotted spider mites without negatively affecting consumers or the environment.

These small mites are notorious among Taiwanese farmers in papaya orchards, as they reproduce swiftly and acquire pesticide resistance easily.

Feng-chia Hsieh, director of TACTRI’s biopesticides division, told The Epoch Times on Nov. 4 that Taiwanese farmers have dozens of options when it comes to choosing mite killers. The low compound annual growth rate (CAGR) of 0.5 percent in mite pesticides for the past five years indicates that there’s a high demand for mite preventative treatment methods among Taiwanese farmers.

“In terms of killing mites, there are currently eight different mechanisms and 19 different chemical agents, at varying concentrations, available on the market for farmers to choose from, but farmers don’t know which one is the best,” he said.

In addition to chemical pesticides, which may harm consumers and the environment, farmers can also choose natural pesticides that employ horticultural oils, mineral oils, or citrus essential oils.  There are also mite-control solutions that use natural predators such as lacewings or insidious flower bugs.

However, natural pest control methods have encountered bottlenecks in terms of marketability and large-scale application.

A Luminescent Trojan horse

Photorhabdus luminscens, the active agent in the new biopesticide, is lethal to hosts such as mites, moths, and fungi, according to TACTRI.

Photorhabdus luminscens is a bacterium that lives in the gut of nematodes—small roundworms that kill insects. After a nematode invades an insect, bacteria are released from its gut and help kill the insect. The bacteria and the nematode then replicate inside the insect host. The luminescent bacterium is highly pathogenic to insects and can kill them rapidly at very low concentrations.

“It’s like the Trojan Horse. The nematodes don’t actually kill the host insects,“ said Hsieh. ”It’s the metabolites of the photobacterium that actually create holes in insects’ guts.”

Predacious mites in papaya, viewed under a microscope before the application of Taiwan's newly developed biopesticide. (Courtesy of Taiwan's Agricultural Chemicals and Toxic Substances Research Institute)

A papaya leaf, viewed under a microscope, after the application of Taiwan's newly developed biopesticide. (Courtesy of Taiwan's Agricultural Chemicals and Toxic Substances Research Institute)

The new biopesticide is the product of 18 years of research.

It was extremely difficult for the research team to obtain the Photorhabdus luminscens bacteria because of their microscopic size and their location inside the nematodes.

“The research team went to Baihe District in Tainan to obtain samples of dead host insects before crushing them in a lab to find the bacteria, and despite the bacteria’s ability to emit light, this process was still extremely difficult due to the tremendous amount of residual ingredients,” Hsieh said.

“It took TACTRI a year to isolate three subspecies of the bacteria, each with different levels of insecticidal activity.”

Taiwan will be the first country in the world to create a consumer product using Photorhabdus luminescens.

The metabolites extracted from the bacteria can be kept at room temperature for a year. Furthermore, the TACTRI field test demonstrates that the biopesticide is safe for all mammals and more effective than chemical pesticides, while maintaining a relatively similar price to chemical agents.

“With high activity, environmental friendliness, and no drug resistance properties, TACTRI has successfully developed a microbial mite killer pesticide at a cost comparable to chemical pesticides, and it’s anticipated to assist in lowering the use of chemical pesticides,” Hsieh said.