Comparative bio-efficacy of botanical formulations against three major sucking pests of lettuce under protected cultivation

Abstract

Aphid, mealybug and whitefly are major sucking pests limiting lettuce (Lactuca sativa L.) yield, prompting interest in botanical alternatives to synthetic insecticides. A randomized block trial evaluated eight botanical formulations, a standard azadirachtin check (1500 ppm, T8) and an untreated control (a total of nine treatments, three replications), with counts recorded at 1, 3, 5, 7, 10 and 14 days after spray (DAS). Pre-treatment populations were homogeneous for aphid (P = 0.272) but not mealybug (P = 0.006) or whitefly (P < 0.001), so baseline-adjusted analyses were used throughout. A linear mixed model (square-root-transformed counts; treatment × DAS + block baseline covariate, plot as random effect) showed a significant treatment × DAS interaction for all pests (P < 0.001); block effects were non-significant. At 14 DAS, T8 gave the lowest populations of all pests (1.8, 2.2 and 2.0 individuals for aphid, mealybug and whitefly), followed by neem seed kernel extract 3% (T1), at par with T8 for aphid population and for aphid and whitefly area under the pest population curve (AUPPC), but significantly poorer for mealybug. Henderson–Tilton efficacy at 14 DAS averaged 94.3% for T8 and 91.5% for T1, while insecticidal soap 2% (T7) was weakest (65.7%) and least consistent (CV = 20.4%), especially against mealybug (55.9%). AUPPC confirmed this ranking, and clustering of efficacy profiles grouped T1 with T8, distinct from other botanicals and from T7. Neem seed kernel extract 3% is identified as the most promising broad-spectrum alternative to the standard check for integrated pest management in lettuce.