Precision insecticide

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Precision insecticide

Fields full of crops are an all you can eat buffet for many insects. They eat the plants. Not something a farmer wishes, as it lowers the yield. The most effective method: killing all the insects with insecticides. Although, this is also not something we like to do. A dilemma for the farmer. How to only kill the harmful insects?

The ideal: only killing the insect that eats the plant, the ones that are harmful. With this idea, scientist went on searching. Searching for precision insecticide. They bumped into a method that organisms already use. The turning off genes using interference-RNA.

Interference-RNA are small pieces of RNA that match a gene. When a gene is turned on, the cell makes an RNA-copy of it, which the cell uses in the process of making the protein that the gene codes for. But when an RNA-copy comes across matching interference-RNA, then they bind together. A sign for the cell to cut the RNA-copy in small pieces, not making the protein. This can switch off a specific gene, as the small piece of RNA only binds RNA that precisely matches. If the small piece of RNA matches a gene that is essential for an organism, the organism dies. A perfect method to only kill those insects that harm the plants.

Lots of insects nibble on leaves. To kill these, using the interference-RNA method, just spraying the small pieces of RNA on the leaves is enough. A special challenge are the sap-sucking insects. These insects, like vampires, drink the sap from the veins in the plant. To kill the sap-sucking insects, the small pieces of RNA need end up in the veins, so the sap-sucking insects will drink them. Australian researchers took on this challenge.

First, they designed small pieces of RNA so that they would only kill the sap-sucking whitefly. This they tested by feeding the interference-RNA to whiteflies, aphids and bees. While the whiteflies died after eating these small pieces of RNA, the closely related aphids and bees stayed alive.

Next, the researchers attached the small pieces of RNA to so called BioClay particles, miniscule grains made of magnesium and iron. The effect of this was that the RNA stayed longer intact. The researchers sprayed the BioClay attached RNA pieces together with a helping substance on the leaves of cotton plants. The helping substance was needed so the RNA pieces could penetrate the water repelling layer on the surface of the leaves. This gives the RNA pieces a chance to get inside the leaf. This they did.

The researchers observed that the small pieces of RNA got into the leave and into the veins. Whiteflies that drank the sap of these plant died more often than whiteflies that drank sap of the control plants. But not only that also the eggs and nymphs of whiteflies on plants treated with the BioClay coupled RNA pieces died more often than those on control plants.

Interference-RNA does appear a precise way to deal with insects that eat our crops. With it you can precisely kill, not only nibbling insects, but also sap-sucking insects. A possible way out for a farmer that prefers to kill only the insects that eat his crops.

Literature

Ritesh G. Jain, Stephen J. Fletcher, Narelle Manzie , Karl E. Robinson, Peng Li, Elvin Lu, Christopher A. Brosnan, Zhi Ping Xuand Neena Mitter (2022) Foliar application of clay-delivered RNA interference for whitefly control. Nature Plants, VOL 8, 535–548