Creating a Test to Measure Bug-Killing Substances on Soybean Leaves

Greg Howard
1st February, 2024

Creating a Test to Measure Bug-Killing Substances on Soybean Leaves

Image Source: Natural Science News, 2024

Insect pests are a major problem for farmers worldwide, often wreaking havoc on crops and significantly reducing yield. Traditionally, chemicals known as small molecule insecticides have been the go-to solution for controlling these pests, but they come with a host of problems. Not only do these substances sometimes cause unintended harm to other wildlife, such as honeybees, but pests can also develop resistance to them. This means that over time, the insecticides become less effective, and new solutions are constantly needed. One alternative to traditional insecticides is bioinsecticides. They are biological materials (like microbes and their derivatives) that are generally considered more environmentally friendly. A well-known example is the toxin produced by a bacterium called Bacillus thuringiensis, or Bt for short. It has been used successfully in pest control for some time and is the basis for many genetically modified crops that resist insect damage. Another promising source of bioinsecticides comes from an unexpected place: arachnid venom. Arachnids, such as spiders and scorpions, produce venoms that are rich in compounds capable of killing insects selectively and efficiently. These natural venoms could provide the blueprint for new, potent bioinsecticides. Despite the potential of these natural compounds, there has been a challenge in testing their effectiveness under laboratory conditions that mimic real-world situations on the farm. In order to address this issue, researchers developed a new method using a simple setup called the leaf disk assay (LDA). This method tests how different insecticidal agents affect pests when they are applied to leaves, which the insect then eats. To do this, researchers used very young larvae of a common pest called the cotton bollworm and fed them soybean leaves treated with different insect-killing agents. They evaluated both Bt toxin and a traditional small molecule insecticide called imidacloprid. Imidacloprid acted more quickly, but both had effects that increased with the amount applied. The researchers also tested various arachnid venoms and found some that were effective against the cotton bollworm larvae, especially when used in combination with sub-lethal doses of Bt toxin. A sub-lethal dose is an amount that is not enough to kill the insect on its own but can still affect its health or behavior. Their findings suggest that the leaf disk assay, when used with the cotton bollworm, can be an effective way to assess potential new insecticides, including environmentally friendlier options like those derived from Bt and arachnid venom, under controlled laboratory conditions that reflect the challenges faced in the field. This sort of testing is an important step toward developing new tools for farmers to protect their crops without the environmental and health concerns associated with traditional chemical insecticides.

AgricultureBiotechPlant Science


Main Study

1) Development of a soybean leaf disc assay for determining oral insecticidal activity in the lepidopteran agricultural pest Helicoverpa armigera.

Published 1st February, 2024

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