Research at UAF - Refinement Of Rearing/ Release Technique Of Bracon Hebetor (Say) As A Bio-Control Agent For The Integrated Management Of Armyworm (Spodoptera Litura (Noctuidae: Lepidoptera))
Principal Investigator: Prof. Dr. Muhammad Ashfaq (T.I), Department of Agri. Entomology, University of Agriculture, Faisalabad, Pakistan.
Area Code Telephone :9200161 Ext. 2903
Tele-fax:9201083
E-mail:drashfaqti@yahoo.com
Co- Principal Investigator: Dr. Rashad Rasool Khan, Assistant Professor, Department of Agri. Entomology, University of Agriculture, Faisalabad, Pakistan.
Telephone: 9200161 Ext. 2903
Tele-fax: 9201083
E-mail:rashad_khan1@yahoo.com
Duration: 3 years (July 2007- June2010)
Cost: 2.002 Million Rupees
Funding Agency: Pakistan Academy of Sciences

Progress Reports

Adults (Male & female)

Abstract:
Armyworm Spodoptera litura (Fab) (Noctuidae: Lepidoptera) is a polyphagous and sporadic insect pest of many crops including cotton. Its larvae feed on the lower surface of the leaves. Damage mostly, appears in patches. The larvae feed on the green leafy material and, in case of severe attacks, the veins are only left behind. Under favourable conditions, its population increases, in large numbers, and moves across the fields, from one to another, like an army, hence it is called “armyworm.” Pest control is an acceptable and necessary part of the modern agriculture. Different control measures are in practice to control this pest. Excessive use of insecticides has not only developed the resistance in pest against not only the different insecticide groups but has also yielded a series of unbearable problems, on the radiative aspects of human health like residues in the food chain, contamination of water, elimination of natural enemies and loss of pollinators etc. Bracon hebetor (Say) is an important bio-control agent especially for the Lepidopteran insect pests of various crops. The use of bio-control agents for the control of insect pest has shown promise and provides efficacy and safety which can be demonstrated adequately with appropriate manipulation of environmental factors.

Problem Statement:
Armyworm Spodoptera litura (Fab) (Noctuidae: Lepidoptera) is a polyphagous and sporadic insect pest of many crops including cotton (Seema et al., 2002). Young larvae feed gregariously on the lower leaf surface and in severe cases tender fruiting parts are also attacked. Sometimes the damage in the infected crop is so high that field has to be ploughed up with out any harvest. Pest control is an acceptable and necessary part of modern agriculture and is required for the protection of public health and welfare. However, some of the methods used during the past few decades have produced undesirable side effects. Excessive use of insecticides has not only developed resistance against organophosphates, carbamates, pyrethroids and even new chemistry insecticides like lufenuron (Byrne and Toscano, 2001; Babu and Santharam, 2002; Karanthi et al., 2002; Sudhakaran, 2002; Vijayaraghavan and Chitra, 2002), but has also yielded a series of unbearable problems, on the radiative aspects of human health concerns like residues in food chain, environmental pollution, soil degradation, extinction of friendly fauna etc. Future needs for pest control is expected to increase, in the days to come. Prevailing conditions and attitudes are likely to dictate an increase emphasis on pest management systems which include the use of alternative methods such as exploitation of bio-control agents, cultural practices and mechanical means etc.
The bio-control agents include vertebrates, invertebrates and a great variety of microbial organisms which can be successfully applied in IPM, of which insect parasites and parasitoids are of immense significance. Bracon hebetor (Say) is an important bio-control agent especially for the Lepidopteran insect pests of various crops. Unfortunately, their efficient management and manipulation has not been demonstrated and exploited as per their potential on commercial scale.
The use of bio-control agents for the control of insect pest has shown promise and provides efficacy and safety which can be demonstrated adequately with appropriate manipulation of environmental factors. Therefore, to work out the practical feasibility of using bio-control agent, chiefly Bracon hebetor (Say) (One of the most voracious and potent larval parasitiod) in IPM and basic principles relevant to the operational aspects for the use of this bio-control agent for the management of many Lepidopteran insect pests in general and Spodoptera litura in particular, the proposed studies are invisible.

Egg


Objectives:
I.     Refinement of rearing technique for efficient mass production and field delivery of the parasitoid (Bracon hebetor and various hosts).
II.    Evaluation of the field release techniques and efficacy of augmentative releases of Bracon hebetor to control the armyworm.
III.   Studies on the effect of various interventions viz. chemical and cultural practices, on population dynamics of Bracon hebetor on various crops.

Methodology:

  • Pest scouting and monitoring in the field
    The pest activity will be monitored in various crops by conducting the extensive pest surveys in different localities of various agro-ecological zones of Punjab.
  • Studies on bio-systematics of the parasitoid
    The parasitoid will be collected from the field and brought to the laboratory for rearing. The parasitoid will be first identified on the basis of morphological characters and will be compared with available literature.
  • Refinement of mass rearing techniques for field release at local level
    The experiment will be conducted to modify the techniques for mass rearing of Bracon hebetor as wel as the hostGalleria mellonella.
  • Evaluation of release techniques and efficacy of parasitoid under semi-natural condition
    The experiments will be conducted to evaluate the different techniques for the release of Bracon hebetor in the field against various pests and the parasitizing ability of the parasitoid will also be cheked against different pest.
  • Studies on effects of various control tactics/ methods
    The parasitoid will be tested in the semi-field conditions for its compatibility with various insecticides of new chemistry groups.

Results and Discussions:

  • Improvement of diet for the rearing of the host Galleria mellonella
    The larvae of G. mellonella, collected from the field as well as those hatched from the eggs, laid by the adults, on folded sheets, are reared on a semi-natural diet. Different diets were tested to maintain the culture of the host. crushed maize, 500gms; honey-bee wax, 200gms; date-syrup, 100 gms; honey, 50 gms; glycerine, 100 ml and yeast, 50 gms  and crushed-wheat, 250 gms; crushed-maize, 250 gms; honey-bee wax 200gms; date-syrup, 100 gms; honey, 50 gms; glycerine, 100 ml and yeast, 50 gms were found best as good number of larvae and pupae, with a comparatively short, larval and pupal durations were obtained, when the insect were reared on these two diets
  • The searching and parasitizing abilities of the Bracon hebetor.
    For this purpose, iron wire-cages of different sizes (1 ft3, 2 ft3, 3 ft3, 4 ft3and 5 ft3), were used. A number of thirty larvae (3rd instar) of S. litura, were released in the cages. Ten fertilized females, were also released, in the same cage to search and parasitize these larvae. The results, reveal that the complete parasitism (100.00±0.00%) by the B. hebetor, occurred, in 36 hours, in the cages of 1ft3 size, and it took 2.5 days in the cage of 2, 3 and 4ft3, size. So, the capsules, in the field, must be placed at a distance of 20-40ft2, as the dose-rate of the parasitoid, increases ten folds, in the field.
  • Potential of the Bracon hebetor, at different Temperatures.
    The parasitism of B. hebetor, was studied, at different temperatures, i.e., 25 oC, 30 oC, 35 oC and 40 oC. The newly emerged females, of the parasitoid, B. hebetor, were placed in the vials, alongwith the host-larvae, under the given set of environmental conditions, maintained in the incubator. Larvae were completely parasitized, by the parasitoid, at 25±2 °C and 30±2 °C. However, at higher temperatures, the parasitism as well as the growth of the parasitoid, were negatively affected.
  • Monitoring of the Pest (Spodoptera litura), on Various Field-Crops and Vegetables as well as the Development of its Life Tables, in Each Case.
    The experiment was conducted on consumption and utilization of different food plants offered to Army worm, Spodoptera litura, in the Laboratory. The experiment was conducted on consumption and utilization of different food plants offered to Army worm, Spodoptera litura, in the Laboratory. The experiment started on the commencement of the 3rd instar. The result revealed that the larvae of Spodoptera litura, have accepted a variety of food plant, served during the experiment, and confirmed that the armyworm has a great adaptability for its host plants.
  • Influence of Two Type of Diets on the Fecundity of B. hebetor.
    To improve the colony of the parasitoid, B. hebetor (Say), for the mass rearing, two types of diets of 20% honey and 10% sugar, were tested, in order to evaluate their impact on the fecundity of the females, and to choose the best out of them, for the mass rearing of the parasitoid, under laboratory conditions, maintained at 29±1°C and 65±5% RH, with 16.8 LD hours. The average number of eggs, laid per female, ranged from 53.76 to 56.96 for the females, fed on sugar solution, at 25 ± 1 °C, respectively, whereas, those fed on honey solution, it ranged from 75.2 to 84.10, under the same conditions. The incubation-period of the parasitoids, B. hebetor (Say) did not show any significant difference, in both the diets.
  • Studies on the Selective Insecticide-Applications, in Relation to the B. Hebetor, Efficiency
    The recommended insecticides, against Spodoptera litura,, on the cotton crop, in Pakistan, were selected for this purpose. The efficacy of insecticides was checked, under lab conditions, on Bracon hebetor and the data were collected, 12, 24, 36 and 48 hours, after the insecticide treatments.

C. Conclusions:
1.     Crushed maize, 500gms; honey-bee wax, 200gms; date-syrup, 100   gms; honey, 50 gms; glycerine, 100 ml and yeast, 50 gms and       crushed-wheat, 250 gms; crushed-maize, 250 gms; honey-bee wax 200gms; date-syrup, 100 gms; honey, 50 gms; glycerine, 100 ml and yeast, 50                      gms are best for the rearing of Galleria mellonella..
2.   Complete parasitism (100.00±0.00%) by the B. hebetor, occurred, in 36 hours, in the cages of 1ft3 size, and it took 2.5 days in the cage of 2, 3 and 4ft3, size. So, the capsules, in the field, must be placed at a distance of 20-40ft2, as the dose-rate of the parasitoid, increases ten folds, in the field.
3.   The best ecological conditions, for the mass-rearing of parasitoid as well as for its performance, are 30±2 °C temperature, 65±10% R.H and 16:8 LDHS.
4.  Maize was the most preferred followed by the sugarcane and wheat by armyworm.
5.   Using the honey solution for feeding the females of B. hebetor, caused, an increase not only in the number of eggs laid but also in the larvae, as well as the pupae and adult numbers developed vis-a-vis increasing the longevity of the adults over two generations. the longevity of the adults, was extended upto 27.8 ± 1.3 days, when the insects were fed on honey solution.
6.  Under laboratory conditions insecticides like, indoxacarb, spinosad and lambda-cyhalothrin were least toxic to the adults of the Bracon     hebetor.

Recommendations:
1.  Crushed-wheat, 250 gms; crushed-maize, 250 gms; honey-bee wax 200gms; date-syrup, 100 gms; honey, 50 gms; glycerine, 100 ml and yeast, 50 gms is the best for the rearing of Galleria mellonella..
2.  20% honey solution for feeding the females of B. hebetor, caused, an increase not only in the number of eggs laid but also in the larvae, as well as the pupae and adult numbers developed.
3.  The best ecological conditions, for the mass-rearing of parasitoid as well as for its performance, are 30±2 °C temperature, 65±10% R.H.
4.  Releasing of Bracon hebetor pupae in field via plastic capsule attached to the plants, give best results. So, the capsules, in the field, must be placed at a distance of 20-40ft2, as the dose-rate of the parasitoid, increases ten folds, in the field.

Pupae

Larvae