The persistence of chromafenozide and methoxyfenozide in and on tomato
fruits under filed conditions during 2006 season was studied. Chromafenozide (Virtu
5% SC) and methoxyfenozide (Runner 24% SC) were sprayed on tomato fruits at
their recommended rates of application, 400 ml and 150 mUfed, respectively. The
most suitable method for extracting chromafanozide and methoxyfenozide was the
use of methylene chloride. The percent recoveries were 92 and 89 for
chromafenozide and methoxyfenozide, respectively. The initial deposit of
methoxyfenozide on the tomato fruits (0.559 ppm) was higher than that of
chromafenozide (0.123 ppm). The data show that washing tomato fruits at zero time and at different intervals
after application of methoxyfenozide removed a reasonable quantity of residues, from
42.1 to 51.2% of the initial total amount. The corresponding values for
chromafenozide ranged from 8.2 to 44.5%. This clearly demonstrated that after
application of chromafenozide to tomato, it is either absorbed or bound to the surface
or due to the solubility in waxy layer so tightly that it can not be removed by simple
washing, whereas, in the case of methoxyfenozide its absorption or binding to the
tomato surface was lower than chromafenozide. Methoxyfenozide was more persistent than chromafenozide when exposed to
sunlight. However, methoxyfenozide degraded more rapidly than chromafenozide
during the first five hours. The half-life times of chromafenozide and methoxyfenozide
were 14.3 and 26.2 hours, respectively after exposure to sunlight. The results also
indicated that the photodecomposition rate of methoxyfenozide was more rapid than
chromafenozide in the first 6 hours after exposure to UV-light with 14.1, 28.5 and
44.8% loss after 1, 3 and 6 hours. while the corresponding amounts for
chromafenozide were 8.0, 19.4 and 44.6% loss, respectively. Statistically, the half-life
of chromafenozide and methoxyfenozide as dry thin films exposed to UV light were
6.8 and 8.0 hours, respectively.