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Mothra (Photo by Hulton Archive/Getty Images)

Mothra may not exist, but genetically engineered pest-limiting moths now do

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Feb 12, 2020, 8:40 PM EST (Updated)

Mothra had her own gargantuan pest to face off against — Godzilla. She may not have been able to take him down, but a new strain of genetically altered moths are now hoping to right that wrong.

Plutella xylostella or the diamondback moth is an epic agricultural pest. Swarms of them sabotage crops of cruciferous vegetables like broccoli, cabbage, cauliflower, and brussels sprouts (everyone’s favorite), and something not involving pesticides needed to be done. What do you do to bring down the population of a harmful species that’s chewing up the human food supply? As a group of scientists found out, you screw around with their DNA.

“Alternative, biologically-based approaches for pest management are sorely needed and one approach is to use genetically engineered insects,” said Anthony M. Shelton, who recently published a study in Frontiers in Bioengineering and Biotechnology. “This species is a particularly damaging pest because of its high reproduction rate and its ability to develop resistance to most insecticides.”

Insecticides are usually the go-to for this sort of thing, but the problem, besides deleterious effects on our planet, is that pests like the diamondback moth are becoming more and more resistant to them. You know how the flu virus has kept mutating to keep up with the advances in vaccines? If things went that way with pesticides, we would have to keep upping the strength until crops and people ended up poisoned along with the pests.

Instead of messing with chemicals, Shelton and his team created what they call a “self-limiting strain” of male moths, identified as the OX4319L strain. This strain of males was designed to limit the diamondback moth population by mating with females that would produce viable male but sterile female spawn. They raised two OX4319L strains of P. xylostella in separate environmental chambers. Self-limiting moths were coated in fluorescent powder to distinguish them from the actual pests, and in case the powder wore off, only a small amount of DNA would need testing to identify their uniquely altered genes.

The OX4319L moths were released in cabbage fields, about a thousand at a time, where they would mate with wild females. Most OX4319Ls stayed in the area of the field where they were released. Later, both males and females were taken back to the lab to see what would happen to the resulting eggs and larvae. Some of those larvae were fluorescent. This was a sign that the transgene, which is an artificial gene introduced into the moth’s genome, had been passed on to them. This particular transgene was supposed to result in the sterility of female offspring. Sure enough, any fluorescent females that spawned were infertile.

Infertility is a positive thing when it comes to pests that devour four to five billion bucks in crops each year, and are pretty much unaffected by insecticides.

Shelton and colleagues said that the study showed “promise for application of OX4319L for crop protection programs against P. xylostella” and that “this self-limiting strain may provide an effective management tool by itself on [cruciferous] crops and improve the efficacy of chemical or plant-based insecticidal methods.”

At least this time, Mothra wins.

(via Frontiers in Bioengineering and Biotechnology)