In agricultural countries like Pakistan, the loss of crop productivity due to insect pests is a serious issue. The yield of cereal crops such as wheat, rice and maize etc. is lost due to attacks of pests in either fields or in storehouses.
Farmers are using large amounts of chemical pesticides to control them. These chemicals are not only hazardous for the health of farmers and consumers but also killing the natural enemies released in the field. Due to the frequent use of pesticides the insects are developing resistance against the chemicals making it difficult to control them.
Apart from the Bio-control method (using natural enemies to kill the pests) using entomophagous fungi to control the pest is an environmentally friendly and useful way of controlling the pest population.
An entomophagous fungus is the one that inoculates its spores in an insect’s body and either kills them or disables them. The spores of the fungi reside on the external surface of the insect body and the hyphae grow inside the body of the insect when the temperature and humidity of the environment become favorable. The hyphae of the fungi proliferates the body cavity of the insect and thus kills them.
Most common entomopathogenic fungi are:
- Metarhizium anisopilae
- Beauvaria bassiana
Metarhizium anispilae is also known as Entomophthora anisopilae. It infects the population of Red imported fire ants, thrips, termites, Sweet potato weevil, Rice black bug and spittlebugs (Mahanarva fimbriolata). The disease is known as Green muscardine disease because of the green color of the spores. These cause the death of insects by inserting their hyphae inside the exoskeleton of the pests and thus killing them.
There are two methods to apply Metarhzium anispilae in the field:
- Spray Method
- Irrigation Method
- Mix all-purpose detergent and water to prepare a solution.
- Add fungal spores in the solution.
- Add the suspension in the spray tank and apply in the field early in the morning or late afternoon.
- The results will appear 4-7 days after the spray.
- Mix all-purpose detergent in water along with fungal spores to make the suspension.
- Drain the field before application.
- Mix the suspension in the water stored for irrigation or add it in the water inlets.
- Bring the water level up to 6cm.
- Allow it to evaporate and try to maintain the normal water level up to 2cm
No harm to human health is seen till now due to the Metarhizium anispilae. It was tested in a laboratory on the animals and luckily no toxic effects appear on them.
Beauvaria bassiana is the most common fungi throughout the world. It kills the pests by invading its hyphae in the body of the insect pest thus causing their death. The disease caused by Beauvaria bassiana is known as white muscardine disease due to its whitish mould that appears from the body of the insect. As the residues of this Bio pesticide are not harmful to consumers it can be used up till the harvest and this is considered as the main advantage of Beauvaria bassiana. It enters the exoskeleton and then in the hemolymph and in turn kills the insect. It kills the small insects in 3 to 5 days and large insects in 7 to 10 days.
Mainly it is used to target foliar pests because the soil pests have developed resistance against it.
The target pests of this fungus are:
- Many kinds of caterpillars
Its role in the control of Malaria-transmitting mosquitoes is under investigation.
Application of Beauvaria bassiana:
- Weigh the required dose of Beauvaria bassiana.
- Transfer it into the container. The container must be hermetically sealed.
- Add cold water in the dose. Avoid mixing hot water in the fungus.
- Mix it for 30 to 45 seconds.
- Pour this premix in the water tank.
- Rinse the container and add the water again in the water tank. Repeat this 2 to 3 times.
- Make new premixes for each application.
The optimum temperature for the application of Beauvaria bassiana is 66.2F to 84.2F. It became inactive at the temperature higher than 89.6F.
Apply it in the afternoon or early morning or on rainy days because it could not withstand UV rays.
It is found to cause disease in a person with a weak immune system. It may also cause respiratory problems in some people. However it is not a cause of major health issues for humans and animals.
To sum up the whole article it is found that in the world with increasing global warming due to excessive use of chemicals, using fungi as an alternative to chemical pesticides could be very beneficial. In an agricultural country like Pakistan, using these kinds of biopesticides can lower pollution and also result in promotion of sustainable agriculture.
Developing resistance in plants to insect pests has now great importance in entomology and agriculture. Plant resistance to insect pests has advantages over other direct control tactics. It should be encouraged for betterment of future modern agriculture.
Lamia Masood B.Sc. (7th Semester) Entomology Department of Entomology, University of the Punjab, Lahore