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Bio control:: Mass production::Parasitoids

Mass production of some important parasitoids

1. Mass production of Corcyra cephalonica
2. Mass production of Brachymeria spp
3. Mass production of Bracon brevicornis
4. Mass production of Bracon hebetor
5. Mass production of Chelonus blackburnii
6. Mass production of Goniozus nephantidis
7. Mass production of Trichogramma sp

1. Mass Production of Corcyra cephalonica

Introduction
Corcyra cephalonica commonly called as rice meal moth or rice moth is a pest of stored foods, viz., cereals, cereal products, oilseeds, pulses, dried fruits, nuts and spices.  Many of the natural enemies mass-bred in the laboratory for use in field against crop pests are dependent on either egg or larval stages of Corcyra due to the simple reason that it is easier and cheaper to produce natural enemies on different stages of Corcyra(Fig.1) than on their original hosts. 

Morphology and Biology of Corcyra
The eggs are oval and measure 0.5 x 0.3 mm.  The white surface is sculptured and has a short nipple-like process at one end.  The larvae are generally creamish – white except for the head capsule and the prothoracic tergite, which are brown.  There are well-developed prolegs on abdominal segments 3-6 and 10. A fully matured larva measures 15 mm.  The last-instar larva spins a closely woven, very tough, double-layered cocoon in which it develops into a dark-brown pupa.  The anterior portion of the cocoon has a line of weakness through which the adult emerges.  The adults are small.  The hind-wings are pale-buff, and the fore-wings are mid-brown or greyish-brown with thin vague lines of darker brown colour along the wing veins.  The males are smaller than the females.
Sexual activity usually begins shortly after adult emergence.  There is a pre-oviposition period of about 2 days.  Egg-laying mainly occurs during the night.  The greatest numbers are laid on the second and third days after emergence, although oviposition may continue throughout life.  Eggs take about 2-3 days to hatch.  Optimum conditions for larval development of C. cephalonica are 30 – 32.50C and 70 per cent RH, at which, the period from egg hatch to adult emergence is only 26-27 days.  There is considerable variation in the number of larval instars; however, males generally have 7 and females have 8.  The last-instar larvae pupate within the food.  The adults emerge through the anterior end of the cocoon, where there is a line of weakness.  The sex ratio is 1:1.  The adult moth is nocturnal and is most active at nightfall.

Mass production of Corcyrain the laboratory
Materials required

Absorbent cotton 

Storage racks

Blotting paper

Streptomycin sulphate

Broken cumbu grain

Rubber band

Camel hair brush

Measuring cylinder

Enamel Tray

Oven

Honey

Home milling machine

Khada cloth

Sieves

Mosquito net

Formaldehyde 40%

Moth aspirator (collector)

Filter paper

Oviposition drums

Moth scale egg separator

Plastic basin

Face masks

Shoe brush

Storing drums

Soap

Ground nut kernel

Specimen tube

Sulphur (WP)

Yeast

Coarse weighing balance

Procedure
1. Preparation of rearing basins
The basins (16” dia) used for Corcyra multiplication are thoroughly cleaned with 0.5% detergent wash and rinsing in tap water followed by wiping with dry, clean – used towel and shade drying. Whenever the trays are emptied after a cycle of rearing, they have to be cleaned preferably to 2 per cent formaldehyde and returned to storage until further use. On reuse the cleaning steps are repeated (Fig 2).

2. Preparation of bajra medium for Corcyra

a.

The required quantities of bajra grains are coarsely milled and broken into 2-3 pieces in a milling machine. The broken grains are heat sterilized at 1000C for 1 hour to eliminate the residual population of stored product insects viz., Rhizopertha dominicaSitotroga cerealellaTribolium castaneum and fungal contaminants.  Upon sterilization the grains are cooled under fan in a clean area.  The grains are then transferred to plastic basins @ 2.5 kg/basin.

b.

Groundnut kernel in required quantity is broken using a pounding machine or a mechanical blender (domestic mixer). Then 100 g of the broken kernel is transferred to each basin and the contents are hand mixed thoroughly.

c.

Dry yeast (Bakers) and wettable sulfur is added @ 5g/ basin and the contents are mixed thoroughly.  A spray of 10 ml of 0.01-0.05% streptomycin sulfate and mixing of the contents follows this.  This medium is used for rearing Corcyralarvae.

d.

The number of basins required for egg infestation is calculated and the medium is prepared accordingly.

3. Preparation of Corcyraeggs
The primary source of Corcyraeggs is reputed laboratories, commercial producers for bulk preparation. If it is intended to begin the production with nucleus colony, the adult moths can be collected from warehouses where the food materials are stored (Fig 3).

a.

The eggs used for building up the colony of Corcyrahave to be free from contaminants like the moth scales and broken limbs and not exposed to UV light.

b.

The collections of overnight laid eggs are measured volumetrically to ascertain the number of trays that can be infested with eggs.  A cc of eggs is known to contain approximately 16000 – 18000 eggs.

4. Infestation of medium with eggs
The overall production scheme (Fig. 4) involves initial infestation of the cumbu medium with Corcyraeggs in desired quantities.  This is accomplished by sprinkling the freely flowing eggs on the surface of the medium in individual basins. Per basin 0.5 cc eggs of Corcyrais infested. The basins are then covered with clean khada cloth and held tightly with rubber fasteners. The basins are carefully transferred to the racks. At a time 84 such basins are stacked in the rack designed at TNAU.

5. Handling the trays during larval development
The larvae that hatch out in 3-4 days begin to feed the fortified Bajra medium. At this stage, light webbings are noticed on the surface. As the larvae grow up they move down.  During this period the larvae are allowed to grow undisturbed in the trays.

Handling of adults
The adults begin to emerge in 28-30 days after infestation of the eggs. The adults can be seen on the inner side of thekhada cloth.  They are either aspirated with mechanical moth collector or collected with specimen tubes.  The whole operation is carried out in a tent of mosquito net.  This prevents the large-scale escape of the moths, which if uncontrolled can migrate to the storage area and spoil the grains stored by laying eggs.  Workers involved in the collection of moths should wear face moths continuously to avoid inhalation of scales.  The moths collected are transferred to the oviposition drum @ 1000 pairs per drum at a time (Fig 4).  The oviposition drums of size 30 x 20 cm are made of galvanized iron.  The drums rest on tripod frames with legs of height 5cm.  The bottoms of the drums are provided with wire meshes that enable collection of eggs.  The walls of the drums have two vents (ventilation holes) opposed to each other.  The vents are again covered with wire mesh.  The lids of the drums have handles besides slots for introducing the moths and adult feed.  The oviposition drums filled in a day are maintained for four to seven successive days for egg collection after which are emptied and cleaned for next cycle of use.  

The adults are provided feed containing honey solution. The adult feed is prepared by mixing 50 ml honey with 50 ml water and 5 capsules of vitamin E (Evion). The feed is stored in refrigerator and used as and when required.  Piece of cotton wool tied with a thread is soaked in the solution and inserted into the drum through the slot at the top.  From a basin, moths can be collected upto 90 days after which the number of moths emerging dwindles down and keeping the basins is not economical for the producer (Fig 4).

6. Handling of eggs
The moths lay the eggs in large numbers loosely.  The scales and broken limbs are also found in larger quantities along with the eggs.  They cause potential hazard to the workers after years of working in Corcyralaboratory. To minimize the risk of scales freely floating in the air, the oviposition drums are placed on sheets of filter paper in enamel trays which trap effectively the scales.  Sets of several oviposition drums are kept in ventilated place near an exhaust fan to enable the workers comfort.  Daily morning the oviposition drums are lifted up and the wire-mesh bottoms are cleaned gently with a shoe brush so that the eggs and remnants of scales and limbs settled on the mesh are collected along with those on the filter paper.  The collections are cleaned by gently rolling the eggs on filter paper to another container.  Then they are passed to sieves in series and finally clean eggs are collected.  The eggs are quantified in measuring cylinders and used for building up the stocks and natural enemy production.
About 100 pairs of adults produce 1.5 cc of eggs in 4 days laying period inside the oviposition drums.  From each basin an average of 2500 moths are collected.  Hence from each basin 18.00 – 20.00 cc of eggs can be obtained in 90 days.

7. Maintenance of history sheet

Accurate information is needed on the history of individual basins. 

The following information is furnished.

  1. Date of egg infestation
  2. Date of preparation of feed
  3. Source of egg
  4. Expected date of adult emergence
  5. Daily collection of moths
  6. Problems encountered with the basin during production
  7. Personnel handling the basin
 
Egg of Corcyra cephalonica
2. Mass production of Brachymeria spp.           

Introduction
Brachymeria are important parasitoids of coconut black headed caterpillar, Opisina arenosella.  Out of the six important species of Brachymeria, B. nosatoiB.nephantidis B. lasusB. excarinataB. hime attevae and B. euploeae recorded onO.arenosella recorded on O. arensella, B. nosatoi is the dominant species followed by B. nephantidisB. nephantidis is widely distributed, but it is more effective in southern districts of Kerala where the parasitism reaches 25 per cent.  B. excarinata is a dominant species in Mahua; Gujarat.  Significant parasitism by B. hime attevae has been observed in Salem, Tamil Nadu. B. nosatoi is a solitary endoparasitoid, posses the essential attributes and great potential in suppression of O. arenosella.  It adheres to rigid selection of masses and elaborate courtship, provides higher percentage of parasitism, breeds well in summer months and prolonged drought conditions and disperse uniformly in pest-infested coconut gardens.  The pupae parasitized byBrachymeria show one or more black dots, which are the characteristic  oviposition punctures made by the females.

Production procedure

  • About 50 adults of B. nosatoi comprising both sexes are released in a clean, dry cylindrical jar of 17.5x6.75 cm. A 12 cm long and 6.25 cm wide cardboard piece is inserted to facilitate the parasitoids to move and rest. 
  • The mouth of the jar is secured with a piece of muslin cloth tightened with rubber bands.  The jar is kept horizontally. 
  • The parasitoids are transferred to fresh clean jar every 4 to 5 days. 
  • For adult parasitoids, undiluted honey is provided daily in minute droplets on wax coated paper.
  • The jar containing parasitoid is kept in diffused sunlight for 10-15 minutes daily for about 3-4 days after which only the host pupae are to be offered for parasitization. 
  • Exposure to sunlight stimulates mating.
  • Pupae of O. arenosella reared in the laboratory are carefully removed with cocoons and silken galleries intact or leaf-bits containing pupae within cocoons and silken galleries and placed on a piece of card board, 12 x 6 cm in such a way that they are accessible to the parasitoid from all the three sides. 
  • The card board piece containing several pupae is inserted into the horizontally placed glass jar containing the mated parasitoids for parasitization.
  • The parasitoids partially disorganize the pupal tissues standing on the galleries with their ovipositors by repeated thrusts and oviposit in the pupae. 
  • The pupae without cocoons and silken galleries are placed on the card board and covered with silken galleries as the parasitoid will not parasitize naked pupae. 
  • Depending on the activity of female parasitoids, the host pupae can be exposed for a period of 4-6 hours for parasitization. 
  • To avoid super parasitism the parasitized host pupae are to be removed immediately after oviposition by the parasitoids (holes chewed in the cocoons indicate oviposition). 
  • The card board piece containing parasitized pupae is transferred to a similar glass jar or the parasitized pupae alone to a conical flask and kept for emergence of the parasitoid.
  • Normally the emergence of parasitoid commences 12 days after oviposition and continues up to 20 days in the laboratory at temperature and RH ranging between   22-30oC and 45-80% respectively.  The parasitoids are aspirated into field release container.
3Mass production of Bracon brevicornis
  • B. brrvicornis is an important gregarious larval ecto-parasitoid of many lepidopterans.
  • It is widely distributed and recorded from Antigastra catalaunalisAdisura atkinsoniEarias sp., Helicoverpa armigera,Noorda moringaeOpisina arenosellaPectinophora gossypiellaChilo partellus etc.,
  • Its natural parasitism is not very high. 
  • However, it paralyses many lepidopteran larvae and some of them never revive.  This contributes to indirect control.
Production procedure
  • B. brevicornis is amenable for mass rearing in the laboratory on the alternate host, Corcyra cephalonica.  For small scale culture, glass chimney and the ‘Sandwich’ technique are adequate. 
  • About 20 mated females are confined in a glass chimney, covering both sides of the chimney with muslin sheet held in place with rubber bands.
  • A cotton swab soaked in 50% honey water solution is stuck to the side of the chimney to serve as food.  With many hymenoptera, adult nutrition is of great importance as it influences sex-ratio. 
  • High protein diet at times improves the sex ratio so that more female progeny are produced.  ‘Proteinex’ can be used to produce the desired results. 
  • Replacing honey with laevulose or fructose also is beneficial in some cases.  Exposure to sunlight frequently stimulates mating, oogenesis and fertilization of eggs.
  • About 10 full grown larvae of Corcyra are placed between two sheets of facial tissue paper and placed over the muslin sheet covering the wider mouth of the chimney. 
  • The tissue is again covered with a sheet of muslin and fastened with a pair of rubber bands. 
  • The chimney is then placed with the host larvae facing a window or light source.  Females of B. brevicornis are attracted to the host larvae, probe through the muslin and paralyze the larvae on each of which they lay about 25 eggs per day. 
  • At the end of 24 hours, the tissue sheets bearing parasitized larvae are removed and held in flat plastic containers until the parasitoid grubs hatch, complete development and spin cocoons. 
  • The egg, larval pupal and adult stages are completed in 28-36 hours, 4-7, 3-6 and 15-40 days respectively. 
  • The female parasitoid is capable of depositing 150-200 eggs in its life time. Emerging adults are again collected for mating and egg laying. 
  • Adults survive up to 15-40 days but egg laying usually tapers off after the first ten days.  Two day old adults of B. brevicorniscould be stored for 30 days at 50C and 50-60% RH.
4. Mass production of Bracon hebetor

 

  • B. hebetor is a common gregarious ecto – larval parasitoid.  There appears to be two strains of the parasitoid, one attacking field pests and the other stored product pests.
  • Among the hosts recorded are Corcyra cephalanicaDichocracis punctiferalis,Eublemma olivaceaHellula undalisOstriniaicius kashmiricaHelicoverpa armigera and Opisina arenosella of which the O. arenosella is the important host. 
  • Parasitism is observed throughout the year, it ranged from 26.2 to 26.7% during the peak period of O. arenosella infestation.

Production procedure

  • B. hebetor is reared on C. cephalonica at wide ranging temperature and fluctuating relative humidity. 
  • Pairs sorted out from freshly emerged brood are caged in specimen tubes (8 x 2.5 cm). Under laboratory conditions it is easy to rear. 
  • Fifth instar caterpillars of C. cephalonica of similar size are provided for oviposition and the parasitized larva removed daily from the tubes and maintained separately. 
  • The parasitoids are fed with 50% honey provided as tiny droplets on wax-coated paper strips.
  • B. hebetor completes its total developmental period in 7-12 days.  The egg, larval and pupal period are completed in 1-2, 2-4 and 3-7 days respectively. 
  • The females start laying eggs 2-5 days after emergence on partially paralyzed host caterpillars. 
  • The paralyzed larvae (not receiving the eggs) die within 3-5 days.  Female parasitoids feed on host’s haemolymph.
  • The eggs are laid singly or in groups of two to eight.  A female is capable of laying 229 eggs (142-345) on 14-32 host caterpillars during its life span of 20-63 days, the daily average being 2-27, and laid maximum number of eggs during the first ten days of oviposition period.
  • A single host larva supports the development of 11 eggs and 9 larvae of the parasitoid.  The preoviposition period is 3 days, oviposition period 22-55 days and post oviposition period 1-8 days. 
  • The fertile female lives for 20-63 days.  B. hebetor complete its developmental period on larvae of Corcyra cephalonica in 8.6 (7-10) days. 
  • Oviposition period lasts for 13 (5-22) days.  The mean fecundity is 72 (13 – 148).  Females live for 24-53 days.  Egg viability is 92% and adult emergence 81%.  Male to female ratio is 5:1.
Precautions
  • To avoid wastage, the surplus parasitoids could be stored in the cocoon stage for one month in the refrigerator. 
  • The coccons are kept in a clear plastic jar (19x9 cm) for emergence and provided with raisins as food. 
  • Segregate the mite (Pediculoides ventricosus) infested cultures of the host insect immediately.
5. Mass production of Chelonus blackburnii

Introduction         

  • C. blackburnii is introduced from Hawaii.  A parthenogenetic egg-larval parasitoid, C. blackburnii has a fairly wide host range but in India the common meal moth Corcyra cephalonica and potato tuber mothPhthorimaea operculella have often been used for multiplication of this parasitoid. 
  • It could also be multiplied successfully on Spodoptera exigua.  C. blackburnii has been used for the biological suppression of P. operculellaEarias vitellaPectinophora gossypiella and Helicoverpa armigera on cotton and other host plants in many states. 
  • It is becoming an important component of IPM systems on potato, cotton, etc.,

Production procedure

  • A set of 100, 0-24 hr old eggs of Corcyra (not exposed to UV) are pasted to 5 x 5 cm card.  This card containing eggs is exposed to 30 C. blackburnii adults in a 1.5 l container. 
  • The plastic container has windows with plastic mesh for aeration.  Two cotton swabs, one soaked in 10% honey solution and the other in drinking water are also placed inside from the side opening which is closed tightly with a cloth covered cotton plug. 
  • The egg card after exposing to C. blackburnii for 24 hrs is removed and placed on 500 g sterilized cumbu medium.  In 30 days time, adults start emerging from the cocoons formed in the cumbu medium after completing development on Corcyra larvae.  The adults live for 25 days and their fecundity is about 400 eggs.
  • The parasitoid could also be reared on potato tuber moth (PTM).  A set of 1500 egg of laid on a cloth are stapled to a card.
  • This card containing 0-24 hr old eggs is exposed to 30 C. blackburnii adults. The plastic container (14 cm x 11 cm) is converted into C. blackburnii rearing unit by cutting windows and fixing plastic mesh aeration. 
  • Two cotton swabs, one soaked in 50% honey solution and the other in drinking water are also placed inside from the side opening which is closed tightly with a cloth covered cotton plug. 
  • The PTM egg card after exposing to C. blackburnii for 24 hrs is removed and placed on punctured potatoes. This provides more entry points for PTM larvae and kept in a similar plastic container as described for exposure to C. blackburnii
  • The bottom of this container is lined with sterilized sand.  In 25-27 days time, adults start emerging from the cocoons formed in sand at the bottom of the cage or sometimes inside potatoes after completing development on potatoes. 
  • The adults live for 23-31 days and their fecundity is about 288-390. Parasitoid host ratio of 1:50 should be maintained and the fresh lot of eggs provided every day.
6. Mass production of Goniozus nephantidis

Introduction

  • Goniozus nephantidis is the most widely used parasitoid of Opisina arenosella.  It is a sturdy gregarious larval or prepupal ectoparasitoid. 
  • The female practices maternal care of eggs and larvae.  The host larvae are parasitized and the parasitoid even feeds on host body fluid. 
  • The parasitoid is also capable of suppressing the population by merely stinging and paralyzing 1st – 2nd instar larvae.  G. nephantidis is the most common and effective parasitoid of late instars caterpillars of O. arenosella in several parts of the country. 
  • The parasitoid is being mass multiplied and released in Karnataka, Kerala and several other states.
Production procedure
  • The parasitoid is multiplied on Corcyra cephalonica larvae in diffused light.  A pair of parasitoid is introduced in tube (7.5 x 2.5 cm). 
  • The adults are provided honey in the form of small droplets on wax coated paper.  After a pre-oviposition period of six days one healthy last instar larva is provided in a vial. 
  • The larvae parasitized and containing eggs of G. nephantidis are removed regularly from the vials till the death of the female.  Such larvae are kept in accordion type strips of paper in plastic boxes which are covered by muslin cloth.
  • Considering the fecundity as 20-50, the female is capable of parasitizing 6-7 larvae in three oviposition spells each separated by 4-5 days. 
  • The life cycle of the parasitoid is completed in 10-14 days (incubation 24-36 hrs, larval feeding 36-48 hrs, prepupal stage 48-60 hrs and cocoon period 48 to 56 hrs + resting adult inside the cocoon 108-128 hrs).
7. Mass production of Trichogramma sp.

Introduction 

  • The genus Trichogramma is cosmopolitan in distribution and present in all terrestrial habitats and is one of 80 genera in the family Trichogrammatidae.  Trichogramma are primary parasitoids eggs of Lepidoptera, but parasitism also occurs in eggs of other orders such as Coleoptera, Diptera, Hemiptera, Hymenoptera and Neuroptera.
  • It is important for plant protection because of its wide spread natural occurrence and its success as biological control agent by mass releasing. 
  • Since this parasitoid kills the pest in the egg stage itself before the pest could cause any damage to the crop and also that it is quite amenable to mass production in the laboratories, it has the distinction of being the highest produced and most utilized biological control agent in the world Trichogrammatidae includes the smallest of insects, ranging in size from 0.2 to 1.5 mm. 
  • Trichogramma are difficult to identify because they are so small and have generally uniform morphological characters.  Also, certain physical characteristics such as body color and the number and length of body hairs can vary with body size, season, rearing temperature and the host on which the adult was reared. 
  • A major advance in the systematics of Trichogramma was the discovery that characteristics of male genitalia can be used to identify species.  This is the primary means of identification today, but body color, wing venation and features of the antennae serve as supporting characteristics. 
  • Females cannot be identified with the same level of confidence, so collections submitted for identification must include males in addition to physical characteristics; studies of reproductive compatibility and mode of reproduction also have been especially valuable in identifying species.

Biology of Trichogramma

  • The development of all Trichogramma spp. is very similar.  Being an egg parasite, the female drills a hole through the chorion and deposits its eggs within the egg of the host. 
  • The internal pressure of the egg forces a small drop of yolk out of the oviposition hole.  Females feed on this yolk, which increases their longevity and under laboratory conditions a female parasitizes from one to ten eggs per day or from ten to 190 during her life. 
  • Large females parasitize more eggs than smaller females.  The number of eggs laid per host egg may vary from 1 to 20 or more depending upon the size of the host egg.  However in sugarcane, in which moth borer eggs are small, generally 1 or 2 parasites develop per egg. 
  • A female parasitoid can distinguish already parasitised eggs, thereby avoiding superparasitism or multiple-parasitism under natural conditions. Fecundity varies from 20 to 200 eggs per female according to the species, the host, and the longevity of the adult. 
  • Eggs in the early stages of development are more suitable for parasite development.  Older eggs, especially those in which the head capsule of the larva is visible, are not usually parasitized and if they are, parasite survival is much lower.  Venom injected by the female at the time of oviposition is believed to cause this predigestion of the egg’s contents. 
  • During the 3rd instar (3 to 4 days after the host egg was parasitized) dark melanin granules are deposited on the inner surface of the egg chorion, causing the host egg to turn black.  This is an invaluable diagnostic character for distinguishing them from unparasitised eggs.  Larvae then transform to the inactive pupal stage. 
  • The adult wasps emerge from the pupae and escape the host egg by chewing a circular hole in the egg shell.  The black layer inside the chorion and the exit hole are evidence of parasitism by Trichogramma. The egg, larval and pupal stages of Trichogramma at 28 ± 20C are completed in about 1 day, 3 to 4 days, and 4 to 5 days respectively. 
  • Thus, the life cycle is completed in 8 to 10 days, but it may be prolonged at lower temperatures or hampered at very high temperatures.  The adults are short lived (6-8 days).  Mating and oviposition take place immediately after emergence.  The sex ratio is generally 1:1.

Mass production

  • Different species and strains of Trichogramma typically prefer different host eggs and crop habitats and have different searching abilities and tolerance to weather conditions.
  • Efficacy is improved by selecting the most effective and adapted species or strain for the specific crop / pest situation. 
  • In the laboratory the parasitoids are multiplied on Corcyra eggs.  The eggs laid by the Corcyra moths are collected and sieved to remove the moth scales etc.
  • The pure eggs thus obtained are exposed to ultra-violet light in UV chamber to kill the host embryo but at the same time permit parasitization.
  • The quantity of the sterilized eggs is assessed in a measuring cylinder volumetrically. The eggs in volume of six cc are then sprinkled uniformly over a 144 gsm (chart paper) card of 30 x 18 cm size (Fig.1). 
  Trichogramma parasitized on egg
  • The card is divided into two halves of 30 x 9 cm (LxB).  Lengthwise it is subdivided into 15 grids (G1 to G15) of size 2cm.  The dimension of each grid is 7x2 cm.  Each grid can accommodate 0.2 cc of the eggs. 
  • Label information on the manufacturer, species of the parasitoid, date of parasitization and expected date of emergence are given in the left over spaces of size 30 x 1 cm on the top and bottom of each half of the card.
Fig.1. Trichogramma Card

1 cm

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

G1          7x2 cm

G2

G3

G4

G5

G6

G7

G8

G9

G10

G11

G12

G13

G14

G15

1 cm

Trichogramma chilonis

Date of parasitisation :

Date of emergence expected :

1 cm

Trichogramma chilonis

Date of parasitisation :

Date of emergence expected :

G16

G17

G18

G19

G20

G21

G22

G23

G24

G25

G26

G27

G28

G29

G30

1 cm

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

TNAU

  • A coat of 10% gum arabic is applied on the grids (G1-30) and the eggs are sprinkled uniformly in a single layer with the aid of a tea strainer. 
  • The excess eggs pasted are removed by gently passing a shoe brush over the card after sufficient air drying under fan. 
  • The egg cards are placed into polythene bags of suitable size and the nucleus card of Trichogramma are introduced in it.  The easiest way to accomplish this is to place a piece of ‘Tricho egg card’ containing parasitized eggs (i.e. pharate adults) that are ready to yield the adults and to hold them in subdued light for 2 to 3 days. 
  • The emerging parasites readily parasitize the fresh eggs.  The parasitoid - host ratio is adjusted accordingly to 1:6 get effective parasitism. 
  • The parasitized eggs in the Tricho Card turn back in 3 or 4 days and the adult parasitoids emerge in 8 to 10 days from the date of parasitization. 
  • The parasitized eggs in which the parasitoids in the larval or pupal stage (i.e. before or after turning black) can be stored in the refrigerator (at 50C) for about 3 weeks without any loss in emergence.

Precautions
Poor quality of mass reared Trichogramma can result in control failures.  The artificial conditions of mass rearing can select for genetic changes that reduce the effectiveness of the Trichogramma in the field.  Such rearing conditions include rearing multiple generations on unnatural host eggs, the absence of plants, crowding and interference, rapid generation time, and failure to rejuvenate genetic stock.  Except for obvious problems such as lack of adult emergence or wing deformities, growers and pest consultants cannot detect poor quality Trichogramma prior to release.  Commercial suppliers are responsible for maintaining desirable characteristics necessary for good performance in the field.  Production colonies should be periodically replaced with individuals from a stock culture maintained on the natural or target host.  Suppliers also should assess the per cent host egg parasitization, adult emergence, and the sex ratio of emerged adults to be sure they are within acceptable standards.  Standards for established cultures on Corcyraare 95±5 per cent egg parasitization, 90±5 per cent adult emergence, and a sex ratio of 1 to 1.5 females per male.

Delivery          
Tricho cards are delivered for use in the field. The cards in volumes of 6 cc as per TNAU method of production are assembled in aerated polythene bags and packed in paper cartons for transport. The cards have to be transported by the most rapid method of transport to reach the destination. During transport and holding the cartons should not be exposed to extreme conditions like toxic fumes, open sunlight, high temperature areas as the consignment could be damaged leading to mortality of the Trichogrammastages.

Field release
The parasitoids are released in the pharate stage or when few adults begin to emerge from the host egg during the evening hours. The cards are cut into bits neatly along the grids with least damage to the eggs and stapled beneath the foliage in the upper canopy level. To maximize the field parasitization it is recommended to release the parasitoids is as many locations as possible. Recently scientists are beginning to advocate the release of cards @ 1/5m row length.



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