Microbial Pest Control Agents (MPCA) include microorganisms including bacteria, fungi and
viruses, or their bioactive agents that can be utilized as active substances. MPCA are employed
as alternative strategies to chemical insecticides preventing resistance development and
minimizing negative environmental and human health consequences (Deshayes et al., 2017).
Bacillus thuringiensis (Bt) is the world’s most frequently used bioinsecticide in integrated pest
management (IPM) programs, being primarily responsible for producing crystal delta-endotoxins
and secretory toxins. The Bt toxins, however, are unstable for extended periods of time and are
extremely vulnerable to solar UV. As a result, genetically modified plants in which toxins are
expressed have been produced accounting for a significant part of the phytosanitary biological
products (Abbas, 2018). Furthermore, Beauveria bassiana and Metarhizium anisopliae are
entomopathogenic fungi that have also been used due to their insecticidal properties
(Mohammadbeigi & Port, 2015). Lastly, the only viruses that are used as MPCA are
baculoviruses which are utilized as biological control agents since they are the safest. They infect
insects and possess a limited range of hosts (Rohrmann, 2019). Most of the research on MPCA’s
to humans, non-target organisms, and the environment have only found acute toxicity, whereas
chronic toxicity has not been discovered. The purpose of this essay is to outline how bacteria,
fungi and viruses can be used to assist with pest management.
Bacillus thuringiensis is a spore-forming, aerobic, gram-positive soil bacteria with a unique
capacity to manufacture endogenous crystalline protein inclusions during sporulation (Argôlo-
Filho & Loguercio, 2014). Over a hundred BT-based bioinsecticides have been created since its
discovery in 1901, with most of them being employed against lepidopterans (butterflies and
moths), dipterans (blackflies and mosquito larvae), and coleopterans larvae (beetles) (Ibrahim et
al., 2010) Powders comprising dried spores and toxin crystals are used in commercial Bt
products. They are sprayed on plants and other places where insect larvae feed requiring
ingestion to be effective. Bt creates a protein that binds to gastrointestinal receptor, resulting in
starvation of insect larvae. Proteolytic enzymes in the alkaline gastrointestinal juice (pH 8-10)
activate the Cry toxin. The active toxin crosses through the peritrophic membrane and attaches to
receptors on the apical microvillar brush border membrane of the midgut epithelial cells, forming
pores through which the toxin penetrates to enlarged cells. The swelling will persist until the
cells lyse and split from the midgut epithelium’s basement membrane. The alkaline gut contents
flow into the hemocoel, causing the hemolymph pH to increase, resulting in the insect’s paralysis
and death within 1-3 days (Abbas, 2018). Cry proteins have been commercially produced to
target the primary pests of corn, cotton, maize, potato, rice, tobacco, and tomato, allowing for
higher coverage by reaching areas of the plant that foliar sprays cannot reach. There are many
different Bt strains, each with its own set of Cry proteins, and over 60 Cry proteins have been
found (Usta, 2013). For instance, some modern maize hybrids contain the Cry3Bb1 protein
designed to fight the corn rootworm complex, Diabrotica species (Order Coleoptera) which is a
major maize pest, particularly in North America (Moar et al., 2017).
Entomopathogenic fungi are key natural regulator of insect populations and could be used as
mycoinsecticides against a variety of agricultural pests. Beauveria bassiana and Metarhizium
anisopliae are naturally occurring mosquito pathogens that have been employed to manage insect
pests including caterpillars (Usta, 2013). Conidia or spores of fungi germinate on the surface of
