numbers of eggs and punctures in treated grapes.
The estimated values of the deterrence index suggest
that oviposition was inhibited. The number
of eggs per puncture in the treated grapes and in
the control was not significantly different. Punctures
with fewer eggs (especially punctures having
between 0 and 5 eggs) were not more frequent
in treated grapes. This result contradicts the hypothesis
that the extract had a deterrent effect
on C. capitata oviposition. In other words, after
the introduction of the ovipositor, the presence of
the extract on the surface of the grape did not affect
the medfly’s oviposition behavior. The inhibition
of oviposition resulted from the interaction
or isolated action of the A. indica leaf extract as
repellent, locomotor stimulus and/or suppressor.
The negative stimulus may have facilitated one
or more of the following behavioral tendencies:
it may have induced the females to move away
from the treated grape (repellent), it may have
induced the females to move and disperse more
quickly in the presence of the neem extract (locomotor
stimulus) and it may have inhibited the
initial penetration of the ovipositor (suppressor
stimulus). The findings of this study can be extended
to other fruit fly species. Initially, Singh
& Srivastava (1983) demonstrated that neem
seed extract inhibits the oviposition of Bactrocera
cucurbitae (Coquillett) and Bactrocera dorsalis
(Hendel) when sprayed over Momordica charantia
L. and Psidium guajava L. fruits, respectively.
In another study (Chen et al. 1996) of B. dorsalis
on guava fruits treated with neem seed extracts,
the oviposition of the females was inhibited. In
addition, fewer females were found on fruits
treated with neem extracts. This last-mentioned
finding suggests that the A. indica extracts acted
as a repellent and/or as a locomotor stimulus. The
results reported by Valencia-Botín et al. (2004)
also suggest that the neem extract’s property of
repelling insects is the main factor responsible for
the smaller numbers of Anastrepha ludens (Loew)
eggs in oranges sprayed with neem aqueous extract
(5%) and neem oil (Neemix® 4.5%).