Search

In the year 1993, a 100 tree plot in a 17 year old teak plantation at Nilambur in Kerala was experimentally protected from Hyblaea puera Cramer, a serious defoliator of teak plantations, using a naturally occurring baculovirus (HpNPV) reported earlier from this pecies. During the year, there were four major peaks of defoliator infestation from March to June. One-time foliar application of a crude preparation of HpNPV at the rate of 1x105 POB/ml of the spray fluid, at the earliest sign of each infestation, gave 70-76 per cent protection of foliage during the first two infestations. A reduced foliage protection of 33-43 per cent obtained during the third and fourth infestations was attributable to occurrence of rain soon after application of the spray. In protected trees, the basal area increment was enhanced by 41 per cent, indicating the efficacy of HpNPV as a biocontrol agent against the teak defoliator.

Natural control of the teak defoliator, Hyblaea puera Cramer by a large number of larval and pupal parasitoids has been reported (Chatterjee and Misra, ]974; Sudheendrakumar, 1985). However, only very very little information IS available on egg parasitoids of the teak defoliator (Beeson, 1941; Nair et al.. 1994).

Natural control of the teak defoliator, Hyblaea puera Cramer by a large number of larval and pupal parasitoids has been reported (Chatterjee and Misra, ]974; Sudheendrakumar, 1985). However, only very very little information IS available on egg parasitoids of the teak defoliator (Beeson, 1941; Nair et al.. 1994).

In the year 1993, a 100 tree plot in a 17 year old teak plantation at Nilambur in Kerala was experimentally protected from Hyblaea puera Cramer, a serious defoliator of teak plantations, using a naturally occurring baculovirus (HpNPV) reported earlier from this pecies. During the year, there were four major peaks of defoliator infestation from March to June. One-time foliar application of a crude preparation of HpNPV at the rate of 1x105 POB/ml of the spray fluid, at the earliest sign of each infestation, gave 70-76 per cent protection of foliage during the first two infestations. A reduced foliage protection of 33-43 per cent obtained during the third and fourth infestations was attributable to occurrence of rain soon after application of the spray. In protected trees, the basal area increment was enhanced by 41 per cent, indicating the efficacy of HpNPV as a biocontrol agent against the teak defoliator.

The nucleopolyhedrovirus of the teak defoliator, Hyblaea puera Cramer (Lepidoptera: Hyblaeidae) (HpNPV) is a potential biocontrol agent of the pest. This paper describes a method to mass multiply HpNPV in situ in the field population of H. puera. The method is based on application of the virus suspension on young teak plantation infested with H. puera. An average yield of 4.8816 x 10& Polyhedral Occlusion Bodies (POBs) per fifth instar larva was obtained with this method. The advantage of this method of HpNPV production is that it is less expensive as it does not depend on host larval culture maintained in the laboratory.

The nucleopolyhedrovirus of the teak defoliator, Hyblaea puera Cramer (Lepidoptera: Hyblaeidae) (HpNPV) is a potential biocontrol agent of the pest. This paper describes a method to mass multiply HpNPV in situ in the field population of H. puera. The method is based on application of the virus suspension on young teak plantation infested with H. puera. An average yield of 4.8816 x 10& Polyhedral Occlusion Bodies (POBs) per fifth instar larva was obtained with this method. The advantage of this method of HpNPV production is that it is less expensive as it does not depend on host larval culture maintained in the laboratory.

Effect of four entomopathogenic fungi, Beauveria bassiana, B. brongniartii, Paecilomyces fumosoroseus and Metarhizium anisopliae, isolated from different host insects, was tested in the laboratory against the teak defoliator, Hyblaea puera (Cramer) (Lepidoptera: Hyblaeidae) to assess their virulence and efficiency. Five different concentrations, 2x106, 4x106, 6x106, 8x106 and 1x107 conidia ml-1were directly and indirectly applied onto third instar larvae of H. puera. All the four fungi tested under both application methods were pathogenic to H. puera with higher efficiency in direct application than indirect application. At 9 days after exposure, the mean per cent mortality obtained was 100, 93.02, 93.02 and 66.74%, respectively, for B. bassiana, B. brongniartii, P. fumosoroseus and M. anisopliae at the highest concentration of 1 x 107 conidia ml-1 in direct application. Mortality of the larvae varied according to the concentration of conidia, method of application and fungi. The lowest LC50 (1.89 x 106 conidia ml-1) and LT50 (91.18 hr) values obtained for B. bassiana in direct application showed that B. bassiana was more pathogenic to H. puera than the other three fungi.

Effect of four entomopathogenic fungi, Beauveria bassiana, B. brongniartii, Paecilomyces fumosoroseus and Metarhizium anisopliae, isolated from different host insects, was tested in the laboratory against the teak defoliator, Hyblaea puera (Cramer) (Lepidoptera: Hyblaeidae) to assess their virulence and efficiency. Five different concentrations, 2x106, 4x106, 6x106, 8x106 and 1x107 conidia ml-1were directly and indirectly applied onto third instar larvae of H. puera. All the four fungi tested under both application methods were pathogenic to H. puera with higher efficiency in direct application than indirect application. At 9 days after exposure, the mean per cent mortality obtained was 100, 93.02, 93.02 and 66.74%, respectively, for B. bassiana, B. brongniartii, P. fumosoroseus and M. anisopliae at the highest concentration of 1 x 107 conidia ml-1 in direct application. Mortality of the larvae varied according to the concentration of conidia, method of application and fungi. The lowest LC50 (1.89 x 106 conidia ml-1) and LT50 (91.18 hr) values obtained for B. bassiana in direct application showed that B. bassiana was more pathogenic to H. puera than the other three fungi.

To overcome the problems in rearing the teak defoliator, Hyblaea puera on artificial diet in a two-piece rearing tube for HpNPV mass multiplication, a new three-piece tube was designed and evaluated. The two-piece tube (Tube A) consists of two parts - a cylindrical main body with one end open (55mm x 23mm) and a perforated cap. The three-piece tube (Tube B) consists of a main body with both ends open (55mm % 23mm), a diet cup (20mm % 22mm) and a perforated cap. Comparative evaluation of two types of tubes (main body of Tube A vs Diet cup of Tube B) was made in terms of their virus capture efficiency during inoculation and also easiness in diet dispensing and general handling. The short length of the diet cup of tube B favored highest virus capturing (added 30%) and efficient diet dispensing. Tube B could be an excellent option for rearing H. puera larvae for NPV mass production and laboratory culture maintenance and also for rearing of other lepidopteran larvae of similar behavior and size.

The economics of mass production of the nucleopolyhedrovirus of the teak defoliator, Hyblaea puera Cramer (Lepidoptera: Hyblaeidae) (HpNPV) using the laboratory-reared and field-collected (from teak plantations) host larvae was compared. The data were based on 7645 laboratory-reared (LR) larvae and 8925 field-collected (FC) larvae. The virus production was carried out using fifth instar larva inoculated with 1x106 OBs (Viral Occlusion Bodies)/larva. The virus yield/larva in LR and FC larvae was 4.8x108 and 3.6x108 OBs, respectively. The virus productivity ratio in LR and FC larvae was 241 ± 55 and 178 ± 100.85 OBs, respectively. The cost of production of HpNPV per larva was higher in the case of LR (Rs. 0.82/larva) in comparison with FC (Rs.0.72). However, the cost of HpNPV required for spraying in one hectare at the rate of 1.63 x 1011 OBs worked out to be Rs. 279 and Rs. 317 in the case of LR and FC, respectively. A marginal difference in the virus yield was found affecting the cost of the virus produced.

The economics of mass production of the nucleopolyhedrovirus of the teak defoliator, Hyblaea puera Cramer (Lepidoptera: Hyblaeidae) (HpNPV) using the laboratory-reared and field-collected (from teak plantations) host larvae was compared. The data were based on 7645 laboratory-reared (LR) larvae and 8925 field-collected (FC) larvae. The virus production was carried out using fifth instar larva inoculated with 1x106 OBs (Viral Occlusion Bodies)/larva. The virus yield/larva in LR and FC larvae was 4.8x108 and 3.6x108 OBs, respectively. The virus productivity ratio in LR and FC larvae was 241 ± 55 and 178 ± 100.85 OBs, respectively. The cost of production of HpNPV per larva was higher in the case of LR (Rs. 0.82/larva) in comparison with FC (Rs.0.72). However, the cost of HpNPV required for spraying in one hectare at the rate of 1.63 x 1011 OBs worked out to be Rs. 279 and Rs. 317 in the case of LR and FC, respectively. A marginal difference in the virus yield was found affecting the cost of the virus produced.

The biology, behaviour and seasonal dynamics of Sympiesis hyblaeae (Hymenoptera: Eulophidae) an ectoparasitoid of the teak defoliator, Hyblaea puera (Lepidoptera: Hyblaeidae) are discussed. S. hyblaeae prefers to lay eggs on first or second instar teak defoliator larvae. A single egg is deposited on each host larva. Each female lays an average of 5 eggs per day and an average of 15 eggs during its lifespan. The total developmental period is about 10-13 days. A high proportion (94%) of the pupae formed during the months, December to January are observed going through a diapause period ranging from 111-156 days, with an average of 13S days. The peak activity period of S. hyblaeae in the field is during September to December, which does not coincide with the peak incidence period (April-June) of its host (H. puera). The seasonal incidence pattern indicates that S. hyblaeae is not a potential natural biocontrol agent of the teak defoliator.

The biology, behaviour and seasonal dynamics of Sympiesis hyblaeae (Hymenoptera: Eulophidae) an ectoparasitoid of the teak defoliator, Hyblaea puera (Lepidoptera: Hyblaeidae) are discussed. S. hyblaeae prefers to lay eggs on first or second instar teak defoliator larvae. A single egg is deposited on each host larva. Each female lays an average of 5 eggs per day and an average of 15 eggs during its lifespan. The total developmental period is about 10-13 days. A high proportion (94%) of the pupae formed during the months, December to January are observed going through a diapause period ranging from 111-156 days, with an average of 13S days. The peak activity period of S. hyblaeae in the field is during September to December, which does not coincide with the peak incidence period (April-June) of its host (H. puera). The seasonal incidence pattern indicates that S. hyblaeae is not a potential natural biocontrol agent of the teak defoliator.