New Horizons in Insect Science Towards Sustainable Pest Management

328 T. Venkatesan and S. K. Jalali

sucking pests and borers, DBM/bollworms pests.
Trichogramma are released to suppress differ-
ent caterpillar pests attacking maize, rice, sugar-
cane, cotton, vegetables, fruits, etc. (Singh and
Jalali 1994 ). However, their use in crops where
insecticides are most frequently used is diminish-
ing due to high insecticidal usage and hot weath-
er conditions found in some part of our country.
Release of trichogrammatids in crops like cotton,
tomato, cabbage, etc. are not giving satisfactory
results due to high application of insecticides.
Jalali et al. ( 2002 ) reported that the enemies were
absent on cotton throughout India in sprayed
fields and recorded trichogrammatids parasit-
izing only in four states, viz., Punjab, Andhra
Pradesh, Tamil Nadu, and Madhya Pradesh, out
of nine cotton-growing states in India. Jalali and
Singh ( 1993 ) observed trichogrammatids to be
highly susceptible to all insecticides and even
residues were found to effect parasitizing abil-
ity up to 21 days on cotton. Adult Trichogramma
are quickly killed by broad-spectrum insecti-
cides applied to cotton (Jalali and Singh 1993 ).
The trichogrammatids are susceptible to a broad
spectrum of insecticides and reduced parasitism
had been reported in T. exiguum and T. pretiosum
and H. zea and Manduca sp. in plots treated with
pyrethroids (Campbell et al. 1991 ). Similarly, the
drift of pesticide even a mile away and single ap-
plication of pesticides in cotton reduced the ef-
ficacy of trichogrammatids (Stinner et al. 1974 ;
Bull and House 1983 ; Bull and Coleman 1985 ).
Realizing the need of integrated pest man-
agement (IPM) approach to minimize the use
of insecticide, biological control, and other en-
vironmental friendly approaches has gained mo-
mentum. However, the use of chemical insecti-
cides continues to be widely adopted and remains
mainstay of insect pest control. In such a crop
scenario where insecticides are frequently used,
releases of susceptible strain of T. chilonis will
not give any appreciable supression.
Preliminary results revealed that multiple
insecticides tolerant strain of T. chilonis gave
63 % more parasitism against cotton bollworms
compared to susceptible laboratory strain in five
places in three states. Again 11.2 % higher yield
against existing IPM practice and 63.4 % higher
yield was obtained to untreated check (Anony-

mous 2003 ). The efficacy of trichogrammatids

is largely dependent on temperature conditions.

Earlier studies have suggested that temperature

> 35 °C prevents adult emergence (López and

Morrison 1980 ; Singh and Jalali 1994 ; Scholler

and Hassan 2001 ), thereby reducing efficacy of

trichogrammatids drastically at higher tempera-

tures. In India, most of the crops are grown dur-

ing March–November when the temperature is

high and much of insecticides are used frequent-

ly during the period. Therefore, the strain of T.

chilonis having insecticide and high temperature

tolerance could be utilized against lepidopterous

pests of crops in different parts of the country.

Material and Methods

Working out Initial LC 50 Values for Field

and Laboratory Collected Population of

T. chilonis

The parasitoid, Trichogramma chilonis was col-

lected from tomato fields in and around Banga-

lore where several rounds of insecticides were

sprayed during crop period. This provided initial

stock culture for work on genetic improvement.

The experiment was carried out by serial dilution

of three insecticides, viz., endosulfan, monocro-

tophos, and fenvalerate by 1/2 seven times from

field recommended dosages to work out LC 50

values. The testing was carried out with labora-

tory and field collected parasitoids, after raising

parasitoids in sufficient numbers in F 2 generation.

The data obtained on mortality were subjected to

probit analysis by statistical program SPSS ver-

sion 8.0. The data were transformed to log base

10 before probit analysis and antilog of calculat-

ed values gave actual LC 50 and LC 90. The fiducial

limits slope and χ^2 values were also calculated.

Working out Initial Temperature

Response for Field Collected and

Laboratory Populations of T. chilonis

The experiment was carried out in growth cham-

bers set at 32, 36, 40 and 45 °C, and at variable

range of 32–38 °C. About 100 parasitized eggs

T. Venkatesan and S. K. Jalali