MSc.

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.