Abstract:
Waxy scales (Ceroplastes spp.) are sap-sucking insects that cause a vast damage to horticultural crops. At present there is an increasing trend of spreading the infestation of waxy scales
on cultivated mango plants. They suck plant sap thus severe infestation may result die back
of shoots, branches and occasionally death of the host plant. The insecticides recommended
for control scales are not effective due to its hard waxy cover. The study was carried out to
investigate the efficacy of different locally available insecticides against waxy scales on mango
under laboratory and greenhouse conditions at Fruit Research and Development Institute, Horana. Eight treatments including different concentrations of selected insecticides, 10 ml/10 L
and 8 ml/10 L of Phrifluquinazon. 10 ml/10 L and 8 ml/10 L of Fluphyradifurone, 5 ml/10 L of
Spirodiclofen, 5 g/10 L of Sulfoxaflor, and 1 g/1 L of Thiamethoxam (treated) with untreated
control were tested under laboratory conditions.Both adults and nymphs were bio assayed separately. All treatments were arranged in Completely Randomized Design with 5 replicates. The
number of dead scales was taken from 15 number sample at 3, 7and 9 days after the treatments.
Mortality percentages were calculated. Results indicated that significantly higher mortality percentage of adults in Sulfoxaflor and Thiamethoxam treatments compared to other treatments at
9 days after application. Phyrifluquinazon, Sulfoxaflor and Thiamethoxam treatments showed
significant mortality of nymphs than other treatments at 9 days after application. According to
the results, most effective three insecticides, Phyrifluquinazon, Sulfoxaflor and Thiamethoxam
were selected for pot experiment. The above 3 insecticides and untreated control pots were
kept in a Completely Randomized Design with 5 replicates. Only nymph stage was considered
in this experiment. Number of dead nymphs were taken at 1,2 and 3 weeks after application.
Mortality percentages were calculated. The results revealed that Sulfoxaflor and Thiamethoxam
had significantly different mortality percentage compared to Phyrifluquinazon (40%) and untreated control 3 weeks after application. According to Thiamethoxam treatment (69.33%) was
significantly different from Sulfoxaflor (54.66%). However the results revealed that only one
application of insecticide was not enough to control this scale.
