Abstract:
Rice (Oryza sativa L.) is the staple food in Sri Lanka, but various pests cause significant losses.
Rice leaf folder (RLF; Cnaphalocrocis medinalis) is one of the major rice pests. While synthetic
pesticides are commonly used, they pose environmental concerns. This study aimed to evaluate
the bio-efficacy of a formulated botanical pesticide (nano-emulsion) for RLF management under
laboratory and field conditions during the 2024 Yala season. Laboratory experiments were
conducted at the Rice Research and Development Institute, Batalagoda with nine treatments; T1
nano-emulsion I at 80 ml/16 l, T2 nano-emulsion I at 100 ml/16 l, T3 nano-emulsion I at 120
ml/16 l, T4 nano-emulsion II at 80 ml/16 l, T5 nano-emulsion II at 100 ml/16 l, T6 nano-emulsion
II at 120 ml/16 l, T7 Azadiractin at 7.5 g/l EC, T8 Chlorantraniliprole at 200 g/l SC and T9
untreated control. Experiments were laid out as a Completely Randomized Design with three
replicates. Results showed that T6 and T7 treatments had 80% mortality, followed by T8 with
100%. Based on laboratory results, five treatments were selected for field evaluation: T3 (T1), T6
(T2), T7 (T3), T8 (T4) and T9 (T5) were selected for field evaluation. Field trials were conducted
in farmers’ fields in the Kurunegala district using a Randomized Complete Block Design (RCBD)
with three replicates per treatment. Each plot measured 500m2. Live larval counts were recorded
from 25 damaged leaves at 3, 5 and 7 days after treatment. Data were analyzed using CATMOD in
SAS, with mean comparisons performed using Tukey’s test at p<0.05. The highest larval count
was recorded in T5 (45) and the lowest larval count was count in T4 (0). T1 recorded a higher
larval count (11) than T2 (5) and T3 (5). This study suggests that the tested botanical pesticide;
nano-emulsions, represent a sustainable alternative to synthetic chemicals.
