Cyromazine Induced Effects on Larvae and Adults of ... - Iresa

of the pre-adult life stages of insects, and
are effective against many insects (25).
<strong>Cyromazine</strong>, N-cyclopropyl-1,3,5-
triazine-2,4,6-triamine, is an atypically
substituted s-triazine, which acts as an
insect growth regulator used as a chitin
synthesis inhibitor for fly control in cattle
manure, field crops, vegetables and fruits
(7, 34). It is an effective larvicide against
a number of dipteran and lepidopteran
species (20, 29). <strong>Cyromazine</strong> has a good
activity against many dipteran species,
especially when it is orally administered
to larvae which usually exhibit a wide
range of different morphological
abnormalities (3, 15, 27, 35).
<strong>Cyromazine</strong> is characterized by a
rapid stiffening of the cuticle, affecting
mostly larvae of Diptera (9, 14, 18).
Reynolds and Blakey (29) have shown
that an early action of cyromazine leads
the cuticle to become less extensible
when subjected to simple constant load
extension tests. They have suggested that
the cyromazine-induced reduction in
cuticle extensibility may be responsible
for the other symptoms of poisoning and
hence may be the primary effect of the
insecticide. Moreover, cyromazine
induces gross deformities manifest in
larvae and pupae of dipteran insects (3,
9), and also reduces egg laying and egg
hatch when fed to Lucilia cuprina adult
(38). Moreover, Alam et al. (2) clearly
demonstrated that cyromazine, ingested
by female flies, is incorporated into eggs
and inhibits larval development in the
first generation.
<strong>Cyromazine</strong> is also effective as
foliar spray in horticultural crops against
leafminers (Liriomyza spp.) and various
other insects, including fleas, thrips, and
coleoptera (18, 32). It is reported to be a
main translaminar pesticide used to
control respectively the pea leafminer
Liriomyza huidobrensis and the
serpentine leaf miners (L. trifolii) (13, 17,
30, 37). <strong>Cyromazine</strong> was used because it
is harmless to parasitoids (6, 31).
Recently, there is an increasing trend
among onion growers in New York to
manage onion maggot using a
combination of cyromazine seed
treatment and chlorpyrifos (Lorsban 4E,
Dow AgroSciences LLC) in furrow
treatments (28). The Medfly, C. capitata
was reported among the susceptible
species to cyromazine applications (35).
Larvae when reared on an artificial diet
supplemented with different
concentrations of cyromazine, suffer from
severe developmental disruption
depending on larval age and duration of
exposure (11, 36). Symptoms of
poisoning include body malformations,
such as swelling of the integument and
elongation of the larvae, as well as
inhibition of larval growth, increase of
larval mortality and a lower pupation and
adult emergence rate. Furthermore, Budia
and Viňuela (10) reported that the
delivery of cyromazine could affect the
reproduction and larval development of
C. capitata.
The present work aims to assess
cyromazine effects on larvae and adults
of Tunisian Medfly strain reared under
laboratory controlled conditions.
MATERIALS AND METHODS
Insect. Larvae of C. capitata were
reared on an artificial diet based on wheat
bran, sucrose and yeast (Table 1). The
wheat bran was first sterilized at 120°C
for two hours. After that, all solid
ingredients were weighed and mixed until
a homogenous consistency was reached.
Liquid yeast and hydrochloric acid were
then added. To avoid bacterial and fungal
contaminations, sodium benzoate and
nipagin were added to the diet.
The rearing culture was kept in a rearing
room at 27 o C ± 1 o C, 75 ± 5% R.H and
under continuous light.
Tunisian Journal of Plant Protection 214 Vol. 5, No. 2, 2010