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

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, Phytolym

Tree species Diversity in the Department of Forest Resources Management, University of Ibadan, Nigeria

Trees, which are important for the sustenance of life and the health of our planet, are disappearing at an alarming rate. Consequently, the need for actions to develop effective strategies to conserve them is receiving considerable attention worldwide. Forest genetic resources are fast becoming depleted in most natural forests due to the pressures of deforestation, urbanization, poor management and a regeneration programme that is virtually nonexistent. In Nigeria, the impacts of climate change will further aggravate the plight of many indigenous and exotic tree species as climatic variability may limit the ability of forest trees to quickly adapt to the changing climate. The huge presence of various indigenous and exotic tree species on the University of Ibadan campus and the fact that some of these trees are no longer found in most natural forests underscores the potentials of the campus as an important live gene bank. There is little or no information on the taxonomy, diversity and growth characteristics of many of the trees on campus. This information is very important for their conservation and sustainable management. There is therefore, an urgent need for their identification, conservation and management. An inventory of trees (>10cm diameter at breast height (dbh)) growing within the premises (~1.2ha) of the Department of Forest Resources Management (DFRM), University of Ibadan, Nigeria, was conducted as a case study of the species quality (richness and diversity) and quantity (volume) found on the University campus. The trees were identified to species level and the total height, merchantable height, canopy cover, diameters at the base, breast height and top of each tree was measured and volume calculated. The health status of trees was visually assessed based on the presence or absence of disease symptoms and pest attack. Data were analysed using descriptive statistics. A total of 27 species from 15 families were identified with Eucalyptus torrelliana F.V. Muell. and Gmelina arborea Roxb. representing 19% and 18%, respectively. A mixture of 14 indigenous and 13 exotic tree species was found within the study area including some threatened indigenous species such as Milicia excelsa (Welw) C. Berg. and Khaya grandifolia Thompson. The mean total height, merchantable height, volume and dbh were 15.57 ± 0.73m, 9.11 ± 0.57m, 6.68 ± 1.10m3 and 44.58 ± 3.58cm, respectively. Eleven percent of the trees were in a ‘very good’ state of health (i.e. no signs or symptoms of pest and disease attacks) while 4% were in a ‘bad state’ (major leaf defoliation, leaf galls, growth of epiphytes and stem rot). It was also observed that only 16% of the trees had straight boles while others had crooked and epicormic branches. The study indicated high species variability within a small area of 1.2ha. There is a need for policy intervention to aid the identification, documentation and conservation of forest genetic resources in the University. Keywords: Species diversity, University of Ibadan campus, Climatic variability, Tree healt

Control of Phytolyma lata Walker (Scott.) Attack on Milicia excelsa (Welw.) C. C. Berg seedlings under plantation conditions

In this study, five Phytolyma pest control measures which included: a mono-species plot (protected by mesh netting: T1), mixed-species plot (Milicia + Terminalia), mixed-species plot with foliar chemical treatment (T3), mono-species with foliar chemical treatment (T4) and untreated mono-species plot of Milicia excelsa seedlings (T5), were set up in a completely randomized block experiment with four replications. The total height, collar diameter and number of leaves were monitored fortnightly, while the Relative Growth Rates (RGRs) for height and diameter were estimated after 24 weeks. Data were analysed using descriptive and inferential statistics. The treatment effects significantly influenced height, collar diameter and foliage production, but the block effects were negligible. The highest mean height was in T1 (104.35 ± 2.93 cm), while the lowest was in T5 (68.15 ± 5.37 cm). The RGR for height (median = 0.013 cm-1 week -1) and diameter (median = 0.024 cm -1 week cm-1) were highest for T1, while T5 had the lowest (0.005 cm cm-1 week-1 and 0.012 cm cm-1 week-1, respectively). The provision of a physical barrier (perimeter fence) proved to be the most effective management strategy to prevent Phytolyma infestation, while the mixed-species layout was a promising alternative.Keywords: Psyllid, Mixed-species plots, Iroko, Relative growth rat