Impacts of Teratosphaeria leaf disease on plantation Eucalyptus globulus productivity

The effects of Teratosphaeria leaf disease (TLD) on Eucalyptus globulus are varied, and it is currently poorly understood whether infection by TLD can cause long‐term growth effects. Such information would greatly assist disease management and pruning regimes on E. globulus plantation sites, resulting in both financial and ecological benefits. Two trials were established to quantify the effects of TLD on long‐term growth. The first was a 2‐year fungicide exclusion trial that aimed to determine initial growth losses between trees treated with fungicide and untreated trees. It was found that tree growth was not affected until a threshold value of 20% damage was reached. Volume was reduced by 17% between treated and untreated trees over the course of the 2‐year trial. The second trial, a 5‐year growth study, used differentially affected adjacent stands (one infected and the other unaffected) to look at the longer term effects of more severe defoliation (44–60%) caused by an epidemic of TLD. Results recorded 5 years after the epidemic showed that trees recovered to regain normal growth trajectories after the epidemic, but growth was retarded by ca. 1.2 years for both height and diameter compared with that of the adjoining unaffected stand. As the growth of trees was not permanently reduced by the epidemic, it is concluded that the financial impacts of TLD are more likely to be associated with the loss of income resulting from extensive branch death in the lower crown after leaf and stem infection, which makes the affected stands not suitable for pruning and hence prevents them from being managed as a higher value solid wood crop.     

Quantifying stem discoloration and decay following pruning and thinning an Acacia hybrid plantation

Acacia hybrid (Acacia mangium × A. auriculiformis) is widely planted in Vietnam, and part of the estate is managed for solid timber products. This requires pruning and thinning – practices that through mechanical wounding can facilitate the entry of fungal organisms, leading to stem defects. The extent to which this happens in Acacia hybrid has not been previously studied in Vietnam. A destructive survey was conducted in a 3‐year‐old Acacia hybrid plantation at Nghia Trung in Binh Phuoc province, 18 months after the imposition of pruning and thinning treatments. Pruned trees had a higher incidence and severity of discoloration and decay in the stem than unpruned trees; thinning increased the incidence of stem decay and the severity of discoloration but not the severity of decay. An interaction between pruning and thinning did not influence the incidence of stem decay but did increase the severity of discoloration in thinning treatments. Across treatments, levels of discoloration and decay were <30% and <5%, respectively. Modification of current pruning practices may be necessary to ensure that decay levels are kept within acceptable limits at an anticipated harvest age of 7–8 years.     

Association of Eucalyptus globulus leaf anatomy with susceptibility to Teratosphaeria leaf disease

Resistance of Eucalyptus globulus juvenile foliage to Teratosphaeria leaf disease (TLD) damage has been shown to be under genetic control. Constitutive traits of juvenile leaves such as stomatal density (counted with wax on and with wax removed), total phenolics, total leaf wax, leaf mass per area (LMA) and leaf anatomical features were assessed to determine differences between pairs of resistant and susceptible families. Anatomic features assessed included cuticle, epidermis, palisade spongy mesophyll and total leaf thickness, as well as palisade cell size, shape and intercellular airspace. One interprovenance, one intraprovenance and two within‐family contrasts were used to compare resistant and susceptible pairs of families of Australian origin. The more resistant families had a significantly higher LMA and smaller percentage airspace compared with susceptible families. It is argued that one of the mechanisms by which E. globulus resists TLD involves the closely packed palisade mesophyll cells that increases LMA and reduces airspace, thereby restricting pathogen spread once infection has occurred.     

Maximising growth and sawlog production from Acacia hybrid plantations in Vietnam

New Forests - Management options to optimise sawlog production from Acacia hybrid (A. mangium?×?A. auriculiformis) combining thinning and fertiliser treatments were applied at six...     

Effects of postmilking teat treatment on the colonization of Staphylococcus aureus on chapped teat skin

Sixteen Holstein cows were used to test the effect of postmilking teat treatment on colonization and intramammary infection by Staphylococcus aureus on chapped teats. Treatments were (1) chapping the teat and using 1% I2/10% glycerin postdip solution, (2) 1% I2/10% glycerin postdip solution on nonchapped teats, (3) chapping the teat and using 10% glycerin postdip solution, (4) chapping the teat and not using a postdip solution. All mammary glands were free of S aureus teat skin colonization and intramammary infection at the start of the study. Teats selected for chapping were dipped in 1N NaOH prior to 3 applications of S aureus broth culture; cultures were applied at 12-hour intervals on all teats. Treatments were applied after each milking for 30 days and were initiated after the second broth dip. Teat skin swab specimens and milk samples were collected before treatment application. Teat skin condition was scored daily. Nonchapped teats (treatment 2) did not support skin or orifice colonization by S aureus. Treatment-1 teats healed most rapidly and supported less colonization in skin and orifice than did treatment-3 and -4 teats. Teat skin scores and skin colonization were lower for treatment-3 than treatment-4 teats. A correlation between teat skin colonization and teat skin conditions was found. Two intramammary infections were found in treatment-4 quarters and 1 in a treatment-3 quarter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Problems of hypothesis testing of regressions with multiple measurements from individual sampling units

Problems with hypothesis testing arise when regression analysis is applied to data sets which contain multiple measurements from individual sampling units. These sampling units might be individual trees from each of which several measurements were taken at different positions on each tree, or they might be individual plots in each of which many trees were measured, or they might be individual plots each of which was measured at several ages. The problems arise because application of ordinary least-squares regression to such data sets leads to underestimates of the covariance matrix of the parameter estimates and the residual variance of the regression equation. Thus, it would not be possible to carry out properly the statistical tests involved in matters such as a covariance analysis or the determination of the most appropriate form of the equation to be fitted to a data set. Theory already exists to solve these problems in cases where the measurements are all made at the same set of conditions in each sampling unit: this is often the case with data from designed experiments. Forestry data sets are often not of this nature and these solutions are generally inappropriate.Using a simple example, the present work explains how problems of hypothesis testing of regressions arise with these data sets. Six theoretical attempts to solve the problems are reviewed. All these theories apply only asymptotically, that is when the number of sampling units is very large. Their small sample behaviour is unknown and their usefulness is therefore questioned. Practical methods for handling such data sets are suggested. In particular, a technique to analyze data in two stages has been found most useful. A number of examples of forestry problems from the literature are described to demonstrate the range of circumstances under which these difficulties occur.     

Screening for host responses in Acacia to a canker and wilt pathogen,Ceratocystis manginecans

In Vietnam, the productivity of Acacia hybrid (Acacia mangium x A. auriculiformis) plantations is being threatened by an aggressive canker pathogen, Ceratocystis manginecans, and selection for tolerance is the main control strategy. A pot trial was established in Binh Duong province to screen for the host response of nine Acacia genotypes (six Acacia hybrid clones, two A. auriculiformis clones and mixed provenance seedlings of A. mangium) to artificial inoculation with three isolates of C. manginecans. Lesion lengths as measured on the inner bark suggested that the two A. auriculiformis clones were relatively more tolerant to C. manginecans than the A. mangium genotype. In contrast, the lesion lengths of all six Acacia hybrid clones fell between the A. auriculiformis and A. mangium genotypes. The results of this study indicate that among the Acacia hybrid clones, BV10 showed the most tolerance to C. manginecans. Chemical analysis of crude sapwood extracts sampled from the lesion provided some evidence that induced phenolic compounds, particularly tetrahydroxyflavanone and condensed tannins may have a defensive role in the Acacia—C. manginecans pathosystem. However, results were not consistent across individual Acacia hybrid clones and A. mangium genotypes.     

Wood‐rotting basidiomycetes are a minor component of fungal communities associated with Acacia hybrid trees grown for sawlogs in South Vietnam

Acacia hybrid (Acacia mangium × Acacia auriculiformis) clones are widely planted in Vietnam with a total of approximately 400,000 ha to meet the demand for pulpwood, sawn timber and wood chip exports. Silvicultural techniques such as pruning and thinning have been applied to improve productivity and sawlog quality of Acacia hybrid plantations. However, those techniques may also create opportunities for wood decay fungi to enter the Acacia hybrid stems through wounds and cause stem defects that reduce sawlog quality and the value of the plantation. The presence of fungal decay agents in Acacia hybrid trees was examined in two Vietnamese plantations. In July 2011, just prior to a second thinning, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Phan Truong Hai for the isolation of fungi. In July 2012, approximately 18 months after pruning and thinning treatments, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Nghia Trung for the isolation of fungi. DNA sequencing of the rDNA ITS identified the isolates. In May 2015, approximately 4 years after thinning and fertilizer treatments, discoloured and decayed wood samples were taken from the above (7‐year‐old) Acacia hybrid plantation at Phan Truong Hai for fungal identification. DNA was extracted directly from discoloured and decayed wood samples and fungal rDNA ITS amplicons sequenced on a Roche 454 sequencer. The results showed that silvicultural treatments did not affect the fungal communities associated with discoloured and decayed wood of Acacia hybrid plantation at Phan Truong Hai. A total of 135 fungal species or OTUs (operational taxonomic units) were identified, including 82 members of Ascomycota and 52 Basidiomycota.     

The Effects of Increasing the Supply of Nitrogen,Phosphorus, Calcium and Potassium to the Roots of Merton Worcester Apple Trees on Leaf and Fruit Composition and on the Incidence of Bitter Pit at Harvest

Merton Worcester apple trees in pot culture were supplied for four consecutive years with N, P, Ca and K at two rates. Apples of this cultivar differed from those of cvs Cleopatra and Jonathan both in their response to nutrient supply variations and in the interrelationships among the levels of mineral elements in the fruit and bitter pit incidence at harvest. The association between fruit levels of N, P, K and Mg previously observed in the other two cultivars was absent in Merton. In two years a positive association appeared in Merton between K level and bitter pit incidence. Doubling the K supply reduced fruit Ca level and increased protein N level and bitter pit incidence. A threefold increase in the Ca supply had the opposite effect on each of these variables. Bitter pit incidence was not affected by doubling the P supply, but was increased by supplying extra N, some of which was in the form of ammonium ion. The differences found between Merton Worcester and the two cultivars studied previously under the same cultural conditions demonstrate that any conclusions in this area concerning apples in general are valid only if they are based on findings over a number of seasons in a wide range of cultivars.