The search for novel strains of Bacillus thuringiensis with different spectra of activities for diversifying its use against insect pests

The fact that Bt (Bacillus thuringiensis) has been used for over 30 years in commercial bio pesticides, in transgenic plants expressing Cry proteins since 1996 and also over 400 of Bt based formulations that has been registered being available on the market to-date for insect pest management says a lot about its viability in terms of standing the test of time. Yet there’s more and more spectra of activities against various pests yet to be discovered and tested.

What is this Bt the general public may wonder? Well Bacillus thuringiensis(Bt) is a ubiquitous, Gram-positive and sporulating bacterium that synthesizes insecticidal proteins with specificity against a wide range of insects during sporulation (Cry and Cyt) and vegetative growth (Vip and Sip). These proteins have portrayed Bt as an environmentally-friendly alternative to chemical insecticides. However, the intensive use of this resource has promoted the evolution of insect resistance to some of the most used Bt strains to date. This emphasizes the need for continuous efforts to obtain novel strains exhibiting new specificities in order to overcome insect resistance and maintaining the insecticidal potential of this bacterium.

Bt culturing

The main reasons why I am carrying out a project on the search of novel strains is that Bt can be isolated in different regions all over the world even in my own locality that is in Zimbabwe so why not take a leap for such a great possibility. Also on a higher note, the world statistics on population and pests are raising an alarm on the need for is environmentally friendly crop protection means.

The spread of pests and pathogens that damage plant life could cost global agriculture $540 billion a year. This is will continue to be worsened by global warming which brings with it an increase in agricultural pests, which will lead to significant crop loss across the globe. The current world population of 7.6 billion is expected to reach 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion in 2100, according to a United Nations report, this means more souls to feed! But already we are facing food shortages, in 2017 an estimated 124 million people faced crisis-level food insecurity or worse, up from 108 million in 2016. This rise in food insecurity has been driven by ongoing conflict and persistent drought, two trends that are expected to continue in 2018. This means that the number of people facing acute food crises will likely continue to rise and this will be worsened by insect pest so the need of crop protection.

So currently I am isolating the Bt bacteria from soils from different habitats but the initial experiments are focused on obtaining pure cultures of the bacteria. I am also collecting various pest (insects) from affected farmlands with great focus on the army worm and nematodes. After capture follows multiplication of these insect pests and nematodes in a controlled and safe environment. The next stage is preparing a bio-assay for testing the efficacy of the Bt isolates on the different pests. The final stage of my project is molecular analysis by PCR-RFLP of the BT strains.

Despite Bt seeming like a cliché project in combating pest, its potential in helping us in plant protection has not yet been fully unraveled, so more and more should be done to promote its use and further development.

Tawanda Zimba, Zimbabwe


  1. Brilliant work Zimba! You have shown great initiative in doing research on combating pests especially considering the current pest problem mainly with fall army worm with our main cereal crop


  2. Wow. Very relevent and much needed research work especially given the devastating effects of the Fall Army Worm on maize production, weevil infestation in sweet potato and aphids on leafy vegetable production in Zimbabwe. Well done. Will be closely following your research and subsequent findings.


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