Nursery Pest Management of <i>Phytolyma lata</i> Walker (Scott) Attack on Iroko (<i>Milicia excelsa</i> Welw C. C. Berg) Seedlings

Abstract

The establishment of plantations of Milicia excelsa has been constrained by the gall-forming psyllid Phytolyma lata Walker (Scott) that causes extensive damage to young plants. We present findings of an experiment aimed at preventing Phytolyma attack on Milicia seedlings in the nursery using chemical control and physical barrier (screen house). Ninety, 6-month old seedlings of uniform growth were selected from a population of potted seedlings obtained from the same seed source. Thirty seedlings were placed in a screen house (SHS), while thirty seedlings (TRT) were placed in the open nursery under direct sunlight and treated fortnightly with a low concentration (0.05%) of water-based insecticide (Lambda-Cyhalothrin). As control (UNT), 30 seedlings were placed in the open nursery without any treatment. The survival, height and collar diameter of the seedlings were measured fortnightly for 24 weeks. After 10 weeks, the untreated seedlings were attacked by Phytolyma with evidence of leaf gall formation. Though, all UNT seedlings were attacked by the insect no, mortality was recorded during the study, while no gall formation occurred in the TRT and SHS seedlings. There was no significant difference in the collar diameter growth with 90.71%, 97.73%, and 115.48% increase in UNT, TRT and SHS seedlings, respectively. On the other hand, there were significant differences in the total height with 21.98%, 58.19%, increase in TRT and SHS, respectively; while UNT seedlings experienced a negative height growth of -0.27%. The provision of a physical barrier proved to be the most effective management strategy to prevent Phytolyma infestation, while chemical control was a successful alternative.

Key Words: Iroko, gall formation, screen house, Lambda-Cyhalothrin, Phytolyma