Mistletoe (Dendrophthoe neelgherrensis Wigh & Arn. Tiegh.) Parasitism on Yield of Nutmeg (Myristica fragrans Houtt.): Have We Been Underrating the Destructivity?

The impact of mistletoe Dendrophthoe neelgherrensis (Wigh & Arn.) Tiegh. on nutmeg (Myristica fragrans Houtt.) yield was evaluated in mistletoe-infested and non–infested (control) trees during two fruiting seasons (January) in 2017 and 2019. Infested trees in season I and II had 40% and 10% of canopy covered (infestation) with the mistletoe, respectively. For yield determination, one branch was selected per whorl from each control tree. In each infested tree, one branch was selected from each non–infested whorl while two branches i.e. one infested and one non–infested, were selected from each infested whorl. The number of fruits was counted (yield) in each selected sub–lateral branch. Data were analyzed by fitting log–linear models after adjusting for over-dispersion, and comparisons were made using maximum likelihood estimates. There was no significant yield loss per tree at 10% infestation of mistletoe. However, at 40% infestation, yield dropped by 65% (from 6,238 to 2,159 fruits per tree). Yield loss in non–infested branches of infested trees was 37.2% whereas the drop was 89.6% in infested branches of those trees. Similarly, yield loss in non–infested whorls of infested trees was 48.2% whereas the drop was 84.8% for infested whorls of the infested trees. A quadratic yield pattern along the canopy was revealed, but the presence of the mistletoe was not related to the yield pattern of the tree. The study highlighted the destructive impact of mistletoe on nutmeg trees even with 10% infestation reducing the yield obtained from both the infested and non-infested branches and thus, the need for its timely control. DOI: http://doi.org/10.4038/tar.v33i1.8533