SIMULATED FIELD EVALUATION
OF THE EFFICACY OF TWO FORMULATIONS OF DIFLUBENZURON, A CHITIN SYNTHESIS
INHIBITOR AGAINST LARVAE OF AEDES AEGYPTI (L.) (DIPTERA:CULICIDAE)
IN WATER-STORAGE CONTAINERS
Usavadee Thavara 1
Apiwat Tawatsin 1
Chitti Chansang 1
Preecha Asavadachanukorn 2
Morteza Zaim 3
Mir S Mulla 4
Affiliations :
1 National Institute of Health,
Department of Medical Sciences, Ministry of Public Health, Nonthaburi
2 Departmant of Statistics, Faculty
of Commerce and Accountancy Chulalongkorn University, Bangkok, Thailand
3 WHO Pesticide Evaluation Scheme,
World Health Organization, Geneva, Switzerland
4 Department of Entomology, University
of California, Riverside, California, USA
Source :
Southeast Asian J Trop Med Public
Health Vol 38 No.2 March 2007 : 269-275
Language :
English
Abstract
Tablet (40 mg a.i./tablet) and
granular (2% a.i.) formulations of diflubenzuron, a chitin synthesis
inhibitor, inhibitor, insect growth regulator, were evaluated for
larvicidal efficacy against the larvae of Aedes aegypti
(L.) in water-storage containers under field conditions in Thailand.
Each formulation was applied to 200-l clay jars at 5 different dosages
(0.02, 0.05, 0.1, 0.5 and 1 mg/l a.i.). The jars were covered with
solid celocrete sheets and placed in the shade under a roof. Another
experiment was also carried out using 3 different dosages (0.1, 0.5
and 1 mg/l) where half the water in each treated jar and the control
was removed and refilled weekly. Each treatment was replicated four
times. The treatments were challenged by adding 25 3rd
instar larvae/jar weekly. Assessments were made of each treatment
through emergence inhibition (%El) by removing and counting pupal
skins one week after larval addition. Using these assessment techniques,
a high degree of larvicidal efficacy (96-100%El) was achieved with
4 dosages (0.05, 0.1, 0.5 and 1 mg/l) of both (tablet and granular)
formulations for a period of 23 weeks post-treatment. The efficacy
of the lowest dosage (0.02 mg/l) of tablet and granular formulations
lasted for 21 and 22 weeks post-treatment, respectively. Under the
conditions of water removal and weekly refilling, a high degree of
larvicidal efficacy (96-100%El) at the 3 dosages was obtained with
the tablet formulation 18 to 21 weeks post-treatment, whereas the
efficacy of the granular formulation persisted 15 to 23 weeks post-treatment
depending on the dosage. This study clearly demonstrates a high level
of residual activity with both formulations of diflubenzuron against
larvae of Ae. aegypti in water -storage containers.
Considering environmental factors and water-use conditions, it is
likely that dosages of 0.05 to 0.1 mg a.i/l are effective dosages
providing long-lasting control for 3 to 4 months in the field.
Full Text