On farm production of entomopathogenic fungi

Kennedy Ningthoujam, Mareena Sorokhaibam, K Mamocha Singh, Yanglem Herojit Singh, Rojeet Thangjam *

Entomopathogenic fungi are often reported as causing high levels of epizootics in nature and are the most versatile biological control agents, and are environmentally safe. An attractive feature of these fungi is that the virulence cause by contact and the action is through penetration. These fungi subsume a heterogeneous group of over 100 genera with approximately 750 species, notified from different insects.

Many of these are proved to be highly potential in pest management. The most considerable fungal species are Metarhizium spp., Beauveria spp., Nomuraearileyi, Verticillium lecanii and Hirsutellaspp. Among them, Metarhizium spp. and Beauveria spp. were the most widely exploited entomopathogenic fungus in biocontrol. It is known to attack over 200 species of insect belonging to order Coleoptera, Homoptera, Lepidoptera, Dermaptera and Orthoptera.

Mode of Action and Host Reaction

The mode of action of insect pathogenic fungi varies and kills the insect by different ways such as causing starvation to toxin production. These insect pathogenic fungi produce many toxins and extracellular enzymes such as proteases and chitinase which aid penetration of the host physical defenses.

Cuticle is the main hurdle to infection in insects as it is the main path of fungus penetration. Hence, it needs some physical or enzymatic means to pierce the hard cuticle. The infective unit in most fungi is a spore, usually a conidium. In many cases, the conidia are adhesive to the cuticle, or secrete adhesive mucus as the conidium swells during pre-germination.

In favourable conditions, the conidium, germinates into a short germ tube which gives out small swellings called appressoria, the appressorium attaches itself to the cuticle and sends out an infection peg which provides a firm attachment that the fungus needs to physically force its way into the host.

The hyphae then penetrate the layers of the integument by enzymatic dissolution of chitin and protein, ramify first in the cuticle and then reach the haemocoel and internal organs. The invasion by the fungal mycelium continues until the insect is virtually filled with the fungus and becomes quite firm to touch.

Conidiophores are then produced which erupt through the cuticle and produce spores on the outside of the insect, infecting nearby healthy insects also. Death of the host is by obliteration (choking) of the tissues and also by the toxins produced by the fungus.

Symptoms

Loss of appetite followed by decreased irritability, general or partial paralysis, discolored patches on integument and increased acidity in the blood. The body hardens and the insect in upright on its legs at the time of death. Death occurs within a week or even within 24 hours.

The causes of death may be as follows: hyphae may force apart muscles, blood cells may stop circulating due to increased hyphae, blockage of the gut and by the toxin produced by the fungus.

Commercial Production of EPF

Most of the commercially produced fungi are species of Beauveria, Metarhizium and Lecanicillium that are relatively easy to mass produce. Attention has focused predominantly on the technical aspects of biopesticide development, such as mass production and formulation, and the selection of strains with rapid kill.

Production requirements include reasonable cost, long-term stability, and, most importantly, consist-ent efficacy under field conditions. The on-farm production of EPF by using grains is simple and cost effective.

The production methods are given below: On-farm Production of Entomopathogenic Fungi on Grains Material required (a) EPF mother culture (b) Sorghum grains (or any cereals) (c) Polypropylene bags (Autoclavable) (d) PVC pipe (e) Cotton plugs (f) Pressure cooker (g) Wooden chamber (h) Spirit lamp (i) Plastic trays

Production technology

Sterilization of grains

1. Take 100 g of grains (sorghum or any cereals) in an autoclavable polypropylene bag and add 100 ml of water (1:1 ratio)
2. Fix a 1.5" PVC pipe at the top of the bag with a rubber band
3. Close the PVC pipe using a cotton plug
4. Keep the bags in a pressure cooker in an upright position and cook for 40 minutes
5. Take out the sterilized bags from the pressure cooker and keep them to cool down to reach room temperature

Inoculation with EPF mother culture

1. Before the inoculation sterilize the wooden chamber using spirit
2. Lit a spirit lamp in the wooden chamber
3. Take the sterilized grains into the wooden chamber and open the cotton plug in front of spirit lamp
4. Transfer the mother culture into the bags from the PVC pipe
5. After inoculation close the PVC pipe with cotton plug

Incubation

1. After inoculation take the bags from the wooden chamber and shake the bags for a proper mixing of EPF mother culture with grains
2. Keep the bags in a dry place outreach of sunlight at room temperature
3. Shake the bags at least three times a day
4. After three days of inoculation white mycelial growth will be observed
5. And after seven days of inoculation we can observe the sporulation of inoculated mother culture

Drying

1. After the incubation take the grains in a plastic tray (sterilized with spirit)
2. Close the tray using a newspaper and tie a rubber band
3. When the grains get dried up take the grains in a mixture grinder and make them a fine powder

Use of EPF in Pest Management

EPF are a major component of integrated pest management techniques as biological control agents against insect pests and other arthropods and are an integral part of mycoinsecticides in horticulture, forestry and agriculture.

Some of the commonly used EPF are as follows.

1. Beauveria bassiana —These enter the host insects body through food or in contact with the host cuticle and reproduce inside the insect body. It produces toxins namely beauvericin, bassianocide etc. inside the host body causes paralysis of the host insects and ultimately kills the insects within four or five days. They are used particularly to control sucking pests and caterpillars infesting crop plants.

These fungi are used to control the caterpillars of yellow stem borer and leaf folder of rice, white grub of groundnut, sugarcane pyrilla, coconut rhinoceros beetle, caterpillars of pulses, tomato and cotton, diamond back moth, leaf eating caterpillars of tobacco and sunflower etc.


2. Lecaniceliumlecanii —This beneficial fungus is mainly used to control whiteflies, aphids, thrips, brown plant hopper, scale insects, mealy bugs and other sucking insect pests of crop plants.

3 Metarrhiziumanisopliae —This pathogenic fungus is used to control mainly coconut rhinoceros beetle, groundnut cut worm, rice brown plant hopper, diamond back moth and early shoot borer, top shoot borer and intemode borer of sugarcane.

4. Nomuraearileyi — It is used tocontrol pod borers, cut worms, cabbage borers etc.

5. Hirsutellathompsonii —These fungi are used to control different hoppers and bug pest, whiteflies, red mites etc.

6 Paecelomycesfumosoroseus — This fungus is used to control yellow and red mite, whiteflies etc.

Field Dosage

Soil application of Metarrhiziumanisopliae @ 5 x 1013 conidia ha1 for soil pests. Foliar application of Beauveria bassiana @ 1 x 107 spores m1-1 + 0.05% teepol for foliar pests.


For further details contact: -
Public Relations& Media Management Cell,
CAU, Imphal.
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