Vol.18_No.2 - Pesticide Alternatives Lab - Michigan State University

Spring 2009 Resistant Pest Management Newsletter Vol. 18, No. 2
T.tabaci population was insignificant; hence inference
could not be made.
Effect on A. devastans
The population level of leafhoppers per 30
leaves before application of quinalphos varied from
20.3 to 26.5. The mean percent reduction affected by
quinalphos was 21.6 - 23.9 (RD), 31.0 – 37.6 (10X
RD), 10.6 – 12.3 (1/3 RD) and 7.4 – 7.6 (1/10 RD).
Effect on B. tabaci
The population level of whiteflies per 30
leaves before first application of quinalphos ranged
between 11.3 and 14.8. At recommended dose the
mean percent reduction varied from 38.0 – 39.9.
Increase in dose effected increased per cent reduction
of 45.7 – 47.6 (3X RD) and 55.0 - 55.3 (10X RD). At
lower doses the mean percent reduction was 23.3 –
27.8 (1/3 RD) and 15.3 – 18.2 (1/10 RD) (Table 6).
Yield
Application of quinalphos during winter, 2001
resulted in kapas yield of 1642.3 kg/ha. Increasing dose
by 3X and 10X resulted 1781.3 and 1985.5 kg/ha. At
lower doses the yield was 1421 (1/3 rd RD) and 1218.3
kg/ha (1/10 th RD).
The reduction over control reported by earlier
workers was 60.6 percent on boll basis and 56.0
percent on locule basis at Ludhiana in 1991 (Dhawan
and Simwat, 1997), 41.9 on boll basis, 39.8 on locule
basis, 54.6 on inter locular basis and 14.4 on bad kapas
basis during winter 1995-96 at 500 g ai/ha dose, 27.1
on boll basis, 38.7 on locule basis, 48.2 on inter locular
basis and 33.1 on bad kapas basis during summer 1996
(Valarmathi,1997), 51.1 percent on boll basis, 56.0 on
locule basis in 1995 (Dhawan and Simwat, 1997), 26.3
percent on boll basis and 34.2 on locule basis in 1996
in Surat (Vadodaria et al., 2000). 47.4 percent in 1998
in Guntur (Gopalaswamy, 2000), 53.1 on boll basis,
46.3 on locule basis, 26.5 on inter locular basis and 35.4 on
bad kapas basis in 1994 (Kumar, 1995). and Valarmathi
and Regupathy, 2004, 2007).
The results obtained in the present study due
to application of quinalphos when compared to that of
earlier reports (26.9 – 60.6) indicates that development
of resistance to quinalphos is significant, but low when
compared to synthetic pyrethroids as also indicated
from laboratory measured resistance. Application of
quinalphos effected moderate levels of check on
sucking pests A. gossypii, A. devastans and B. tabaci
unlike cypermetrin which caused resurgence of A.
gossypii and B. tabaci ( Niranjankumar et.
al.,2002)The measured resistance level in the
laboratory is almost reflected in the field control for
quinalphos as also observed endosulfan (Niranjan
Kumar and Regupathy, 2008), profenofos (Niranjan
Kumar and Regupathy ,2007), thiodicarb
(Ramasubramanian, and Regupathy. 2003) and
spinosad (Ramasubramanian and Regupathy,
2003). However in the case of cypermethrin the
relationship between laboratory measured resistance
and field control is not corroborating when
discriminating dose of 0.1 µg/ larva was used (
Niranjankumar et. al , 2003) indicating the need to
relate the level of resistance detected in the laboratory
and level of control achieved in field. In the present
study the quinalphos DD of 0.75 µg/ larva for
resistance monitoring could be used.
26