Efficacy of Three Insecticides in the Control Gall Wasp Leptocybe invasa in Eucalyptus urograndis Seedlings

Abstract

Forestry expertise and plantations managers are struggling to find cheaper and sustainable solutions to contain the losses caused by Leptocybe invasa in the last nine years on the forest stands in Mozambique. Aiming to help find a solution in the control of L. invasa early in the nursery, we conducted an experimental trial at the Niassa Forestry company nursery, located in the Niassa province, northern Mozambique in February 2015. Three insecticides: Acetamiprid, Thiamethoxam, Imidacloprid, with and without adherent and pH regulator were tested. The experiment had seven treatments including the control. The number of seedlings infested by the gall wasp were assessed 15, 30, 45 and 60 days after the seeds were sown in the nursery. Data were analysed in R package. Normality and homogeneity of variances were tested through Shapiro-Wilk and Bartlett's tests respectively. Analysis of Variance (ANOVA) and parametric means test (Tukey-HSD), were used to assess whether there was difference among the treatments. Results showed difference between treatments at 0.01% of significance after 15, 30 and 45 days and at 5% in the 60 days after sowing. With less seedlings infested by the gall wasp, Imidacloprid with and without adherent was almost superior compared to all other pesticides in all assessment. The use of adherent and pH regulators negatively affected the performance of insecticides, except in the Imidacloprid. This study findings should not however, be overall generalized, instead, more research can be conducted to verify the consistency of these results before being widely implemented.