Chemical structures of p-menthane monoterpenes with special reference to their effect on seed germination and termite mortality

A series of p-menthane monoterpenes was investigated to confirm any correlation between their bioactivity (effect on seed germination and termite mortality) and chemical structure. The germination percentages of Brassica rapa seeds at a concentration of 0.1 mg/Petri dish of (+)-pulegone, isopulegol, piperitone, (?)-dihydrocarveol, terpinen-4-ol and (?)-menthol were found to be 21.6, 27.3, 27.3, 29.1, 42.9 and 43.4, respectively. The lethal concentration 50 values of carvacrol, (+)-pulegone, thymol, (?)-menthol and (?)-terpinen-4-ol for termites (Reticulitermes speratus) were 0.34, 0.50, 0.65, 0.92 and 1.26 (mg/Petri dish), respectively. Of all the compounds tested, phenols produced the highest levels of termite mortality, with ketones and alcohols also showing bioactivity. An assessment of the bioactivity revealed that the presence of a phenol group was effective for termite mortality, with a carbonyl group also showing strong bioactivity. The presence of an alcohol or isopropyl group in a ring also contributed to the bioactivity, whereas the presence of an isopropenyl group at the same position, however, exhibited an inhibitory effect on seed germination. In conclusion, the bioactivity of the p-menthane monoterpenoids was dependent upon the presence and position of certain functional groups and the degree of saturation in the functional group of the side chain.     

Thinning effect on height and radial growth of Pinus thunbergii Parlat. trees with special reference to trunk slenderness in a matured coastal forest in Hokkaido, Japan

To evaluate the effect of thinning on a mature coastal Pinus thunbergii Parlat. forest in Hokkaido, northern Japan, we established four study plots with different thinning intensities (control and 20, 40, and 60 % thinned at individual base; each 20 m × 20 m) and monitored them for 10 years. Radial growth of individual trees in the 60 % thinned plot was significantly greater than that in the other plots, whereas height growth in the 60 % thinned plot was significantly lower than in the other plots. Applying the height growth contribution index, which represents the trade-off between relative height growth rate and relative diameter growth rate, revealed that individual trees in the control and weakly (20 and 40 %) thinned plots had invested more in height growth compared to trees in the 60 % thinned plot. Though higher trunk slenderness value (>80) indicates higher susceptibility to meteorological disturbance such as wind storm and heavy snow, trunk slenderness in the control and the weakly thinned plots increased significantly compared to that in the 60 % thinned plot. In this study, 44.3 % of trees in the control plot had trunk slenderness values >80 over a period of 10 years. The number of trees with trunk slenderness values >80 also increased in the weakly thinned plots. In contrast, no increase was observed in the 60 % thinned plot. In Japan, the thinning intensity is legally supposed to be <35 % of stand volume, which is not enough to improve tree architecture in terms of trunk slenderness.     

The Control of Wood Inhabiting Fungi (with special reference to their Growth and cultural characteristics). Pakistan Forest Institut,Peshavar

Ohne Zusammenfassung     

Effects of serpentine substrate on vegetation and soil development with special reference to Picea glehnii forest in Teshio district, Hokkaido, Japan

Characteristics of vegetation and soils in the serpentine area of northern Hokkaido were studied in comparison with non-serpentine areas of the same region, and with other serpentine areas of Japan and elsewhere in the world. The relationship between vegetation and soils is discussed.

Although forest vegetation of northern Hokkaido is generally represented by deciduous forest, coniferous forest, predominantly Picea glehnii, develops in the serpentine area. Deciduous trees are limited both in number and in size. Forest floor is densely covered with Sasa kurilensis. The shrub layer is also well developed, whereas the herb layer is poor but contains characteristic species. Soils developing in the serpentine area are determined as Podzol (Wet Iron Podzol), while Brown Forest Soil is commonly found in the non-serpentine areas of the region. The serpentine soils are shallow and moist, showing general morphology and chemistry of podzolic soil in upper horizons of the profile. In lower horizons, however, physico-chemical properties are strongly affected by the parent rock. In comparison with other serpentine areas of Japan and elsewhere, northern Hokkaido is unique in that the vegetation is represented by a relatively closed forest of fair-sized trees, and the soils by a podzol.

Such Picea glehnii forests and podzolic soils are considered an intrazonal phytogeocoenosis strongly affected by serpentine substrate. In this regard, the cool and humid climate as well as undulating relief of northern Hokkaido are also important factors for the development of the unique phytogeocoenosis.     

Antagonism of some Bacillus species to a Rhizoctonia solani Kuhn isolate and its effect on the germination of Pinus nigra Arn. seed

The antagonistic activity of some Bacillus species to a Rhizoctonia solani isolate was tested and the effects of a Bacillus subtilis strain on the germination of Pinus nigra Arn. seed were studied.     

Effect of growing site,sampling date,wood location in trunk and drying method on concentration of soluble proanthocyanidins in Betula pendula wood,with special reference to wood colour

Proanthocyanidins (PAs), which are common phenolic compounds in plants, are considered to be mainly defensive compounds against different kinds of stress, e.g. herbivory. In addition to increasing after stress, they may condense and/or oxidize to form coloured compounds when cells die, which may affect both the resistance of xylem to rot and its colour. This is important in the mechanical wood industry. The effects of some biological factors (growing site, sampling date, wood location in the trunk) on the concentration of soluble PAs (sPAs) were studied in fresh and dried birch wood. Those factors that affected sPA concentration most were sampling date and radial location. Drying method also had a great effect on the sPA concentration, which in turn correlated with the colour of the wood.     

“Top-dying” of Norway spruce,Picea abies (L.) Karst., with special reference to Rhizosphaera kalkhoffii Bubák IV.

The height increment pattern of healthy and diseased Norway spruce over the period 1961–75 was studied to test the association of some climatic factors with height increment reduction and eventually foliar browning. Air temperature during December-March inclusive, high velocity wind (22->34 knots) duration during December-March incl. and rainfall during May-August incl. over the same period 1961–75 were examined. It was shown that the last outbreak of “top-dying” in Scotland started in 1971. A correlation analysis and a stepwise multiple regression analysis were conducted to find possible relationships between annual height increments and climate. Results suggested that the coincidence of extreme values of the three considered climatic factors during the period 1971–75 may be responsible for the sharp decline of height increments in 1971 and severe outbreak of the disease.     

A review on <Emphasis Type="Italic">Trioza erytreae</Emphasis> (African citrus psyllid), now in mainland Europe,and its potential risk as vector of huanglongbing (HLB) in citrus

The African citrus psyllid (AfCP), Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), recently has been found in northwestern Iberian Peninsula (Spain and Portugal). The insect is an important citrus pest because it transmits the phloem-limited bacteria Candidatus liberibacter spp., the causal agents of huanglongbing (HLB), the most devastating disease affecting citrus. The bacteria can be acquired by both AfCP nymphs and adults, but only adults can spread the pathogen. HLB has been detected neither in the Iberian Peninsula nor in Madeira and the Canary Islands, where the psyllid was recorded more than a decade ago. In the latter European islands, the eradication programmes of AfCP failed. Chemical-based control strategies are costly, could trigger increases of other pests and may have negative impact on the environment. The adoption of rigorous quarantine measures is extremely important for areas free of the psyllid. These measures likely represent the most effective prevention strategies for psyllid containment, because the geographic expansion of psyllids in citrus is mainly due to human activities, especially by the transport of plants and freshly harvested fruits from infested to uninfested areas. Many natural enemies may contribute to the reduction of its populations and consequent spread; hence, conservation biological control should be emphasised, especially in areas where the psyllid is not abundant. Classical biological control programmes should also be implemented in HLB-free areas by introducing effective AfCP parasitoids. In areas where HLB is detected, biological control is difficult to apply, and a rigorous chemical control program targeting the psyllid could complement this strategy. This report is an updated review of AfCP and strategies for its control in anticipation of its possible further spread in Europe and the Mediterranean Basin.     

Abundance-dependent transmission of the pinewood nematode, <Emphasis Type="Italic">Bursaphelenchus xylophilus</Emphasis> (Nematoda: Aphelenchoididae), to the Japanese pine sawyer, <Emphasis Type="Italic">Monochamus alternatus</Emphasis> (Coleoptera: Cerambycidae), adult in its pupal chamber

The transmission ratio of the pinewood nematode (PWN), Bursaphelenchus xylophilus, to the emerging adult Japanese pine sawyer (JPS), Monochamus alternatus, in its pupal chamber is a determinant of the number of the nematodes carried by JPS beetles. To investigate the factors affecting the transmission ratio, we counted the number of the nematodes carried by 36 newly emerged JPS beetles and the number remaining in and around their pupal chambers, and then estimated the transmission ratio (the number of nematodes carried by a JPS adult as a percentage of the total number of nematodes aggregating in and around its pupal chamber). The total number of nematodes aggregating in and around a pupal chamber ranged from 0 to 19,041, and the number of nematodes carried by a beetle ranged from 0 to 18,920. The transmission ratio correlated with neither the water content of the wood around the pupal chamber nor the degree of wood discoloration caused by blue-stain fungus. The transmission ratio varied with the abundance of the nematodes aggregating in and around the pupal chamber. In pupal chambers with more than 1,000 nematodes, almost all the nematodes were transmitted to the beetle. However, in pupal chambers with fewer than 1,000 nematodes, the transmission ratio varied greatly, from 0 to 100%. These results suggest that aggregation of many PWNs in the pupal chamber might stimulate transmission of the PWNs to the JPS adult and that this abundance-related transmission might contribute to the large variation in the number of PWNs carried by the JPS beetle.