“BT – understanding natural pest control?”

Researchers at the University of Oxford and Royal Holloway University of London have discovered that the commonly used and naturally occurring bacterial insecticide Bt works best if applied to young plants and is enhanced by the presence of the insect pests.

Spraying Bt – the bacterium Bacillus thuringiensis - is a common method for controlling a variety of insect pests.


BT -best natural pest controla variety of insect pests and is one of the main approaches to chemical-free pest control in agriculture.



Bacillus thuringiensis (or Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological alternative to a pesticide; alternatively, the Cry toxin may be extracted and used as a pesticide. Additionally , B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on the dark surface of plants.

Optimising sustainable farming techniques can help meet the challenge of feeding 9 billion people by 2050 using fewer resources and with minimum impact on the environment. Bt has been used commercially for about 40 years, but little  has been understood about the abundance of this or how it actually effected the plants it was sprayed on.

To use a natural environmental pesticide with both eyes open always checking to see what impact it is having is critical. Learning how it works; when to apply it for optimum results and when insects are becoming resistant to it is responsible pest control management.

Bt is found naturally in soils and on plants and exists as many different varieties that each have a preference for infecting different organisms.

Bt strains that are specific to certain insects rely on being able to infect those insects in order to reproduce. The researchers studied a strain called ST8, which infects the Diamondback Moth – a pest that attacks cabbages, broccoli and related crops – and they found that the population of bacteria (either existing or applied) establishes itself more readily when the insects are present. The team set up several cabbage plots in the field to examine what was happening when there were extra insects and/or extra bacteria added to what was already present. Then they took samples of soil and leaves.

Studying the genetics of the bacteria the scientists are developing a profile of the strains of Bt are present and in what numbers. The ST8 strain od BT is the most abundant naturally occurring  in the farm environment.  It grows on the seedlings so it gets the earliest possible opportunity to infect the moths. The more insects in the environment the more bacteria actually develop there.

Thus spraying young plants rather than the soil is the best way of using Bt to control insect pests.”

The research is published in the open-access journal PLoS Pathogens.

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