4. Essential characteristics of effective biocontrol agents
- Speed/Mobility to prevent pathogen to develop resistant structures.
- Longevity, enough to protect plant during its vulnerable period, whatever that may be
- Environmental tolerance, to sustain activity under different soil and climatic conditions.
- Mode of Action, varies from pathogen to pathogen, physical contact, chemical nature of killing component.
While using natural enemies, it is important to have fast growing biocontrol organism in the fields which can eventually make the conditions unfavourable for the pathogens proliferation
5. Technical consultancy for setting up of mass production of bioagents
Setting up of unit for mass production of bio agents especially those which are based on fungi, bacteria and virus is highly technical in nature. The skill required to handle the mass production process is also higher. For scientific and successful setting up of a unit, the entrepreneurs can take consultancy services from the following agencies:
- Project Directorate, Biological control, ICAR, Bangalore
- Indian Institute of Horticulture Research, Hesaragatta, Bangalore
- Central Integrated Pest Management Centre (CIPMC), White field, Bangalore
- Central Institute for Cotton Research (CICR), Nagpur
6. PRODUCTION TECHNOLOGIES
A. Trichogramma egg parasite
1. Introduction
1.1 Trichogramma spp. belongs to the category of egg parasitoid of biological agents. Trichogramma spp., the most widely used bio-control agent in the world and is effective against bollworms of cotton, stem borers of sugarcane, fruit borers of fruits and vegetables. It attacks the pest at the egg stage itself and hence damage done by larvae is avoided. It offers a lower cost but more effective plant protection option in comparison to insecticides. Two species i.e., T. chilonis and T. japonicum are predominantly used in India.
1.2 Trichogramma are dark coloured tiny wasps and the female wasp lays 20-40 eggs into the host's eggs. The entire cycle is completed within 8-12 days. The tiny adult wasps search for the host (pest) eggs in the field and lay their eggs into the eggs of the pests. The parasitised host's eggs turn uniformly black in 3-4 days. The Trichogramma eggs on hatching, feed the embronic contents of host's egg, completes its development and adult comes out of the host egg by chewing a circular hole. A single Trichogramma, while multiplying itself, can thus destroy over 100 eggs of the pest.
2. Major equipment needed
Equipments like semi-automatic corcera rearing cages, trays, iron racks, hot air oven, air conditioner, UV chamber, incubator, moth breeding tins, grinder, mating chambers, parasitization jars, refrigerator, wire mesh, netlon etc. are required for mass rearing of corcera and Trichogramma production.
3. Steps involved in production
3.1 Identification of host
The Trichogramma of multiplication starts with identification of a suitable host species, with the following characteristics :
- easily available.
- easy to culture with the locally available material.
- should yield maximum host egg/larvae/pupae per unit cost.
In India Corcera cephalonica, a stored grain pest has been used for mass multiplication of targetted species.
3.2 Rearing of host insect
The host rearing containers are made of materials which are non-toxic, cheap and optimum sized to permit mating and host searching and amenable to easy cleaning. Most commonly used cages are wooden cages, which are now replaced with semi automatic corcyra rearing cages. The nuclear culture, i.e. eggs of Corcyra cephalonica are introduced in rearing cages. In the model use of semiautomatic rearing cages of 30 no. is considered.
3.3 Preparation of feed material
Corcyra feed may be prepared from bold white sorghum grains without any insecticide residues. This can be tested by taking a sample of 100 g from each bag. The crushed sample is fed to 20 number of 1st/2nd instar Corcyra larvae for 2-3 days. Based on the mortality of the larvae, suitability of grains may be decided. The requisite quantum of sorghum is milled to make 3-4 pieces of each grain. Sorghum grains are heat sterilised in oven at 1000C for 30 minutes and the grains are sprayed with 0.1% formalin. This treatment helps in preventing the growth of moulds as well as to increase the grain moisture to the optimum (15-16%), which was lost due to heat sterilisation. Then grains are air dried.
3.4 Corcyra charging
In each rearing cage, 7.5 kg of sorghum grains are filled and charged with 0.5cc eggs (1cc = 20,000 eggs) of mother culture. Yeast, groundnut kernel and streptomycin is added to enhance egg laying capacity of the adult moths and for enriching the diet.
3.5 Collection of moths
After about 40 days of charging, moths start emerging and the emergence continues for two months. 10 to 75 moths emerge daily with the peak emergence being between 65th and 75th day.
Collect the moths daily and transfer to the specially designed oviposition cages for egg laying. Roughly 2000-3000 pairs of moth can be placed in one chamber. Moth emergence reduces after 100 days of initial infestation and cages are released for cleaning.
3.6 Collection of eggs
Eggs are collected by means of manual suction and are placed in tubes and counted with measuring cylinder. Approximately one cc of eggs of Corcyra counts about 20,000 at the fresh harvest. After that due to shrinkage of eggs the count may be increased. The present model assumes 20,000 eggs per one cc for calculation purpose. The final output of Corcyra eggs from one cage has been assumed at 7.5 cc.
4. Production of Trichocards
The demand for Trichocards will start from the onset of kharif season and extends to rabi season. The summer season vegetables offer an extra demand.
4.1 Egg preparation
The eggs of Corcyra thus collected are cleaned to make it free from insect scales etc. They are sieved thrice and then poured on a plain paper. By slowly tapping eggs come downward stick on to gummed card. Thus, the cleaned eggs are spread on the gummed cards (15 cm x 10 cm) with the help of screen. These eggs of Corcyra are exposed to UV rays of 15 watt UV tube for 45 minutes to prevent hatching. While UV exposure, egg card should be kept about 12-15 cm away from tube.
4.2 Introduction of Trichogramma
After the sterilisation the egg cards are placed in plastic bottles and are introduced with nucleus culture of Trichogramma species of egg or pupal stage. The ratio of host egg and parasite adult should be maintained at 1:5.
4.3 What is a tricho card ?
The parasitisation of Trichogramma spp., in laboratory condition on one cc eggs of Corcyra cephalonica, which are uniformly spread and pasted on a card measuring 15 cm x 10 cm is called as Tricho card. The card has 12 demarcations (stamps). About 12,000 Trichogramma adults emerge out from this card in 7-8 days after parasitisation. To delay the emergence of Trichogramma, these cards can be stored in refrigerator at 5-100C for 10-15 days. On removing the cards to room temperature, the parasitoids emerge normally. Trichocards have a shelf life of 2-3 days. However, these can be stored in a refrigerator for a period of 1 month without any spoilage.
Production technology in flow-chart form is presented in exhibit-I.
5. Dosage
5.1 For controlling sugarcane early shoot borer : Start releasing 6,000 parasites per week per acre area, for a period of 5 weeks, starting from 4th week of planting i.e., as soon as the adult male moths of early shoot borer are noticed in the field. Totally 30,000 parasites are to be released per acre. More parasites may also be released depending upon the crop and pest density.
5.2 In cotton- The Trichocards are released in the field at 45 days after sowing @ 5 cards / ha (one lakh eggs). In total three release are necessary.
6. How to use 'Tricho card'
The cards are to be used before the emergence of the adult parasite. Cut or tear each Tricho card into small pieces and distribute them all over the field. The pieces may be stapled to sugarcane leaf at 7-8 m distance. Care is to be taken to release the parasites either in morning or evening i.e., during cool hours, in windward direction and there should not be any pesticide spray. Before releasing the parasite, the infected shoots are to be cut to ground level and buried inside the soil so as to avoid secondary infestation.
7. Advantages of using Tricho cards
- Less cost, more effective.
- field application (releases) is very simple as compared to other methods.
- Records show higher yield in sugarcane (about 4-5 tonnes), as secondary infestation is avoided while using Tricho cards.
- Cost of pest control is very nominal.
- Added to all these, environmental pollution is avoided.
- 8. Precautions
The following precautions are required to be taken while using Trichocards :
- Trichocards should be packed in such a way that the parasitised surface is on the inner side.
- Emergence date should be specified on cards for the guidance of the users.
- Trichocards should be stapled on the inner-side of the leaf to avoid direct sunlight.
- Card should be stapled in morning hours and just before emergence to avoid predation.
- Farmers should refrain from using pesticides in the field where Trichogramma are released. If need arises selective / safer pesticides can be used and it is to be ensured that pesticides are used 15 days before or after release of Trichogramma
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