Abstract:
In southern Sri Lanka, information on flower-infesting thrips in food
legumes is scarce. In this study, species composition, distribution and degree
of damage in flowers of cowpea, yard-long bean and mung bean were
determined at 35 farmer fields located in Monaragala District. The survey
was conducted over a period of one year and each farmer field was surveyed
only once during the study. Fourteen cowpea and yard-long bean, and seven
mung bean fields at six major locations, i.e., Thanamalwila, Hadapanagala,
Athimale, Buttala, Kudaoya and Monaragala, were sampled. At least five
plants per field were randomly selected and at least three flowers were
sampled per plant. Collected adult thrips were slide-mounted and identified
using Lucid keys. Megalurothrips usitatus was the only thrip species present
in all three legume species. Thrips infestations were found in all the fields
sampled. In Cowpea, at seven fields (representing 50% of the fields), 100%
of the sampled plants had thrips infestation while in yard-long bean, ten
fields (71%) had 100% infestation. In mung bean, only two (28.57%) had
100% infestation. Among the flowers of three legume species, the highest
overall flower infestation (78.06±5.61%) was found on yard-long beans
followed by cowpea (73.64±5.31%). In mung bean, the flower infestation
was 66.03% (± 8.26%). Infestation in open flowers was found to be
significantly higher than in flower buds with the highest infestation
(69.6±3.59%) in yard-long bean. The highest percentage of bud infestation
(32.02 ±7.93%) was recorded on mung beans.
