Management of brinjal shoot and fruit borer, Leucinodes orbonalis (Guenee)(Lepidoptera: Crambidae) using Trichogramma sp.

Abstract

Brinjal (Solanum melongena L.) holds the status of most popular and affordable vegetable in India. The major constraint that hinders the crop from realization of yield potential is the infestation of brinjal shoot and fruit borer, Leucinodes orbonalis (Guenee). Farmers completely rely upon insecticides for immediate management of this pest. The irrational use of insecticides has led to the destruction of natural enemies, development of resistance in insect, health hazards to farmers and consumers, pesticide residue problems and environmental pollution. It is high time to adopt safe, eco-friendly and sustainable alternatives for the management of brinjal shoot and fruit borer. Biological control using Trichogramma egg parasitoids are considered to be the most viable and promising strategy. Many species of Trichogramma are reported to be having the ability to parasitise the eggs of L. orbonalis. However, wide variations have been reported in the relative success of each species. So far, no studies have been taken up for the evaluation of Trichogramma spp. against L. orbonalis in Kerala. Hence, the present study entitled “Management of brinjal shoot and fruit borer, Leucinodes orbonalis (Guenee) (Lepidoptera: Crambidae) using Trichogramma sp.” was carried out to identify an effective species of Trichogramma for the management of brinjal shoot and fruit borer, L. orbonalis. Efficacy of four different species of Trichogramma viz., T. chilonis, T. pretiosum. T. evanescens and T. embryophagum were evaluated in the laboratory. It was observed that T. pretiosum exhibited significantly higher parasitism (90.83%) followed by T. chilonis (76.67%). Adult emergence was comparable between T. chilonis (82.84%) and T. pretiosum (81.77%). The laboratory study revealed that T. pretiosum and T. chilonis are the two promising species with the highest parasitism and adult emergence. Hence, these promising species were selected for evaluating their efficacy under field condition. The effectiveness of T. pretiosum and T. chilonis against L. orbonalis on brinjal was evaluated in the field using the F1 hybrid, Neelima. The parasitoids were evaluated in comparison with neem seed kernel extract (5.00%) and an untreated control. Releases of Trichogramma were done @1,00,000 numbers per hectare at weekly interval for eight weeks. Among different treatments, T. pretiosum and T. chilonis recorded significantly lower mean shoot infestation with values of 0.53 and 0.79 per cent respectively, while the respective values were 2.14 per cent in NSKE and 3.44 per cent in control. The per cent reduction in shoot infestation over control was 48.97 and 44.33 respectively for T. pretiosum and T. chilonis. The supremacy of T. pretiosum and T. chilonis in lowering the mean fruit infestation on number basis was evident with infestation levels of 38.35 per cent and 40.02 per cent respectively compared to NSKE (47.52%) and control (63.65%). The per cent reduction in fruit infestation based on number over control was 27.90 and 25.96 respectively for T. pretiosum and T. chilonis. The results on fruit infestation on weight basis also revealed the potential of trichogrammatids over control. In plot released with T. pretiosum, the mean infestation was 34.76 per cent, which was comparable with the infestation (37.74 %) in plot released with T. chilonis. The per cent reduction over control was more pronounced in plots released with trichogrammatids and was 33.11 and 29.56 respectively for T. pretiosum and T. chilonis plots. Highest marketable yields were obtained from plot released with T. pretiosum (1178.06g plant-1 ) which was on par with plot released with T. chilonis (1078.41g plant-1 ). The study confirmed the significant role of T. pretiosum and T. chilonis in suppressing the population of L. orbonalis under Kerala condition.