106 W. Q. Zheng et al.
trol, snail control and herbicide (Shi et al. 2009 ;
Auchmoody and Wendel 1973 ; Lu et al. 2006 ; Xu
et al. 2010 ). The larvicidal activity of CC against
housefly maggots was significantly higher in 2 %
concentration than in 1 %. The optimum killing
activity concentration for CC was 2 %. The opti-
mum length of exposure to determine the effec-
tiveness of treatment was 2 days. The test showed
that CC had great effect on killing housefly mag-
gots. In the study of effect of CC on killing eggs
of Schistosoma japonicum and maggots, all death
of maggots from liquid homogenized excreta 3
days after 1 % (W/V) CC exposure was found
and the effect lasted for 15 days (Wei et al. 2009 ).
This finding is in agreement with the observa-
tion by Wei et al. The present data indicated that
CC could be suitable as a promising alternative
housefly larvicide for medical use.
CC is soluble in water and is hydrolyzed
forming a soluble acidic salt Ca(HCN 2 ) 2 and cal-
cium hydroxide. Continuous carbonation of CC
in water results in calcium hydroxide and forma-
tion of hydrogen cyanamide (H 2 NCN) referred
to as cyanamide (Miller and Bann 1956 ). When
applied to moist soil, CC undergoes hydrolysis
as a result of which calcium hydroxide and urea
(CO(NH 2 ) 2 ) are formed, inducing pH value in-
crease in soil environment. Soil pH value directly
affects nutrient availability for plant growth and
development. The common practice of making
soils less acidic is to apply a material that con-
tain some form of lime or CC to adjust the soil
pH value. CC not only raises soil pH value, but
also provides abundant nitrogenous fertilizer (Oh
et al. 2006 ). Similarly, when CC is in contact
with water in larval rearing medium, it decom-Table 2 Relationship between CC concentrations and pH value of larval rearing medium after CC dissolved in the
complex
Concentration Time pH value
1 % Day 1 7.00
Day 2 7.00
Day 3 7.00
Mean ± SD 7.00 ± 0
2 % Day 1 7.50
Day 2 7.50
Day 3 7.50
Mean ± SD 7.50 ± 0
Blank control Day 1 6.50
Day 2 6.80
Day 3 6.60
Mean ± SD 6.63 ± 0.15
Table 1 Killing efficacy of different concentrations of CC against housefly maggots in larval rearing medium 72 h
after each touch
Contents Time 1 2 3 Mean
T N M (%) T N M (%) T N M (%) T N M (%)
1 % Day 1 71 13 18.31 78 22 28.21 106 53 50 255 88 34.51
Day 2 67 94.37 62 79.49 100 94.34 229 89.80
Day 3 71 100 78 100 106 100 255 100
2 % Day 1 69 28 40.58 100 44 44 46 9 19.57 215 81 37.67
Day 2 69 100 100 100 46 100 215 100
Day 3 69 100 100 100 46 100 215 100
Control Day 1 55 0 0 35 0 0 43 0 0 133 0 0
Day 2 0 0 0 0 0 0 0 0
Day 3 0 0 0 0 0 0 0 0
T is the total number of tested maggots, N is the cumulative number of the dead maggots, M is the cumulative mortality
rate of the dead maggots