Growth In July Research Articles

Onion stemphiliosis in the South of Ukraine

Onion stemphiliosis is a relatively new disease in Ukraine, so a deeper study of Stemphylium, the species composition of the pathocenosis, and isolation and determination of the species belonging of pathogens of the disease are relevant. The purpose of the study was to examine the species composition of pathocenosis, the biofenology of the causative agent of stemphiliosis, and determine the effectiveness of fungicides for further control of stemphiliosis in onion crops. The main research methods were: field – to determine the spread, development, and harmfulness of stemphiliosis; laboratory – to examine pathogens of onion diseases; visual and mathematical – statistical. The method of mycological crops on potato-dextrose agar (PDA) was used in the work. Field surveys in 2019-2021 established the spread and development of stemphiliosis in onion plantings in the Odesa District of the Odesa region. It was identified that the growing season of 2021 was the most favourable for stemphiliosis, when against the background of high humidity and air temperatures, the spread of the disease was 100%, and the development of the disease reached 79%. In onion crops, the disease developed unevenly, its spread was low in June, with rapid growth in July. At the beginning of August, the percentage of the disease reached 80%. Eight types of fungi were identified, of which Stemphylium vesicarium (Wallr.) Simm, Stemphylium botryosum Wallr, Stemphylium herbarum Simm. – are pathogens of onion stemphiliosis. Laboratory studies established the frequency of their distribution in samples. It is proved that five-time spraying with fungicides helps to reduce the further development of stemphiliosis in onion plantings. The high effectiveness of spraying plants with appropriate fungicides with the active substance fluopyram (200 g/l) + tebuconazole (200 g/l) and fluoxastrobin (100 g/l) + prothioconazole (100 g/l) to suppress the development of spores of pathogens is proven. The provisions and conclusions on the phytosanitary condition of onion plantations in the Odesa region are further developed. The results of the research can serve to develop recommendations for production on the implementation of measures to protect onions from stemphiliosis

The Use of Daily Growth to Analyze Individual Spawning Dynamics in an Asynchronous Population: The Case of the European Hake from the Southern Stock

Daily growth patterns and their relationship with reproduction was analyzed in the European hake from the Galician Shelf, where it shows a very protracted spawning with three spawning peaks. The daily growth analysis was performed in otoliths of adult females on the transversal section of the sagittae otolith. Daily increments were measured from the border to the nucleus in females until they were discernible. Results show that daily growth of females decreases during the spawning period because they allocate less energy to somatic growth in favor of the production of gametes, with an increase in growth in July. Lastly, daily growth individual trends showed a “spawning pattern” in 28% of medium and large females, suggesting an individual spawning period of one to two months, with 4–5 valleys of narrow daily increments, likely associated to batch release: individual spawning frequency would be 4–5 days. This is the first time that individual spawning frequency in hake is estimated based on individual data. Finally, the spawning pattern is detected only once per year, indicating that a single female participates only in one spawning peak per year, supporting the hypothesis of the existence of two or more spawning components in the stock.

EFFECT OF THE SOIL TEMPERATURE AND AIR TEMPERATURE ON THE GROWTH OF SILVER BIRCH SEEDLINGS AND THEIR GASEOUS CO₂ EXCHANGE

Gaseous CO2 exchange and shoot growth over a growing season were studied in 3‑yearold seedlings of silver birch (Betula pendula Roth) growing in 10‑litre pots with different soil temperatures. Initially, activation of growth and an increase of CO ₂ exchange were observed in seedlings experiencing higher soil temperatures compared to seedlingsgrowing in colder soil. Also, an increase in stomatal conductance and a higher pigment content were detected. In the seedlings growing in cold soil, a consistent rise of CO ₂ exchange and dark respiration was observed as the air temperature and soil temperature were growing. In the period before intensive growth, the total leaf area in seedlings rooted in warmer soil was more than three times higher than that of seedlings in cold soil. Until July, air temperatures were not high enough to initiate intensive growth. Therefore, a great deal of assimilates in the seedlings growing under higher soil temperature were largely being deposited, particularly in roots and bark. In the absence of powerful attracting points, assimilates were in excess, and photosynthesis was inhibited. A significant difference in CO ₂ exchange and stomatal conductance between the two groups of seedlings was seen at the beginning of the growing season. Later on, as the air temperature was rising, CO ₂ exchange increased insignificantly in seedlings growing in soil of higher temperature. Warming up of the soil smoothed down the difference in CO2 exchange between the two groups of seedlings. In the period of intensive growth in July, CO ₂ exchange in seedlings growing naturally in the field was higher than in pot-grown seedlings. We suppose that the increase in soil temperature early in the growing season results in a rise in the concentration of sucrose in the phloem exudate, and promotes bark thickening. This process is quite pronounced in Karelian (curly) birch – an ecological form of silver birch (Betula pendula Roth var. carelica (Merclin) Hämet Ahti).

Integrated biomarker responses of the submerged macrophyte Vallisneria spiralis via hydrological processes from Lake Poyang, China.

Vallisneria spiralis, a widely distributed wetland plant, was used to reveal how the light intensity at the top of the plant, plant morphology and antioxidant enzyme activity respond to different hydrologic conditions from Lake Poyang, China. By designing a laboratory experiment simulating historical water levels of low, normal and high wetland plant submersion, this study aimed to elucidate the effects of different levels of flooding on growth and antioxidant enzyme activity for V. spiralis. The results showed that the plant crown light intensity of the treated group and control group (CG) first decreased and then increased along with the seasonal variation of the water level. The maximum and minimum values of the plant crown light intensity were observed in April and July, respectively. Similar to the CG, V. spiralis from the normal and low water level (LWL) groups was measured and had higher plant height growth in the flooding period from May to June, and the entire plant biomass also showed a steady growth trend in the same period. However, the plant growth of the high water level (HWL) group was lower during the whole simulation period, with negative growth in July. Antioxidant enzyme activities changed with the seasonal temperature, and the activity of the CG showed a rising trend. Compared with those of the CG, the antioxidant enzyme activities of the HWL group showed a ‘bell shaped’ trend, which was first significantly induced and then significantly inhibited. In addition, the peroxidase (POD) and catalase (CAT) activities from the LWL group in April were also significantly induced. The integrated biomarker response (IBR) index showed that a comprehensive biological index could well reflect the effects of seasonal water levels in Poyang Lake on the growth of the wetland plant V. spiralis. This study indicated that high flooding levels had the strongest negative effect on the growth and enzyme activity of the submerged plant V. spiralis.

Contributions of the North Pacific Meridional Mode to Ensemble Spread of ENSO Prediction

Abstract Seasonal prediction of El Niño–Southern Oscillation (ENSO) employs the ensemble method, which samples the uncertainty in initial conditions. While much attention has been given to the ensemble mean, the ensemble spread limits the reliability of the forecast. Spatiotemporal coevolution of intermember anomalies of sea surface temperature (SST) and low-level winds over the Pacific is examined in ensemble hindcasts. Two types of evolution of intermember SST anomalies in the equatorial Pacific are identified. The first features an apparent southwestward propagation of the SST spread from the subtropical northeastern Pacific southeast of Hawaii to the central equatorial Pacific in boreal winter–spring, indicative of the precursor effect of the North Pacific meridional mode (NPMM) on ENSO variability. Extratropical atmospheric variability generates ensemble spread in ENSO through wind–evaporation–SST (WES) in the subtropical northeastern Pacific and then Bjerknes feedback on the equator. In the second type, ensemble spread grows in the equatorial Pacific with a weak contribution from the subtropical southeastern Pacific in summer. Thus, the extratropical influence on ENSO evolution is much stronger in the Northern Hemisphere than in the Southern Hemisphere. The growth of Niño-4 SST ensemble spread shows a strong seasonality. In hindcasts initialized in September–March, the Niño-4 SST spread grows rapidly in January–April, stabilizes in May–June, and grows again in July–September. The rapid growth of the Niño-4 SST spread in January–April is due to the arrival of NPMM, while the slowdown in May–June and rapid growth in July–September are attributable primarily to the seasonality of equatorial ocean–atmosphere interaction. NPMM contributes to the ensemble spread in equatorial Pacific SST, limiting the reliability of ENSO prediction.

Difference in particle formation at a mountaintop location during spring and summer: Implications for the role of sulfuric acid and organics in nucleation

AbstractNew particle formation (NPF) has been observed frequently at Storm Peak Laboratory (SPL), a high‐elevation mountaintop observatory in Colorado. A detailed analysis of field measurements taken in March and July 2012 at SPL reveals significant and interesting differences in NPF during the spring and summer months. Persistent long‐lasting NPF occurred on a daily basis in March but was absent in July. Bursts of ultrafine particles did occur frequently in July, but such bursts were short‐lasting and did not show any obvious pattern. A global chemical transport model (GEOS‐Chem) coupled with a size‐resolved advanced particle microphysics model is used to interpret in‐depth this observed nucleation phenomenon. The model captures well the observed persistent daily nucleation events in March and the absence of regional‐scale NPF in July. Model simulations indicate that aerosol precursors were dominated by H2SO4 gas in March and by low‐volatile secondary organic gases (LV‐SOGs) in July, which are consistent with previous particle composition measurements at SPL. The observed persistent daily NPF in March and the absence of regional‐scale nucleation in July at SPL indicate that H2SO4 gas plays a much more critical role in the initial nucleation process, although LV‐SOGs dominate particle growth in July. Our analysis suggests that the short‐lasting bursts of ultrafine particles observed at SPL in July are likely associated with nucleation in subgrid power plant plumes, where concentrations of H2SO4 rather than LV‐SOGs are expected to be higher.

Effects of Tillage and Crop Residue Management on Maize Yields and Net Returns in the Central Mexican Highlands Under Drought Conditions

In the subtropical highlands of Central Mexico, where the main crop is maize (Zea mays), the conventional practice (CP) involves tillage, monoculture and residue removal, leading to soil degradation and unsustainable use of natural resources and agricultural inputs. Conservation agriculture (CA) has been proposed as a viable alternative in the region, based on reduction in tillage, retention of adequate levels of crop residues and soil surface cover and use of crop rotation. This study began in 2009 when the highlands of Central Mexico suffered from a prolonged drought during vegetative maize growth in July–August, providing an opportunity for the on-farm comparison of CA with CP under severe drought conditions which 21 climate change models projected to become more frequent. Under dry conditions, CA resulted in higher yields and net returns per hectare as early as the first and second years after adoption by farmers. As an average of 27 plots under farmers’ management in 2009, the maize yields were 26% higher under CA (6.3 t ha−1) than under CP (5.0 t ha−1). 2010 was close to a normal year in terms of rainfall so yields were higher than in 2009 for both practices; in addition, the yield difference between the practices was reduced to 19% (6.8 t ha−1 for CA vs. 5.7 t ha−1 for CP). When all the 2009 and 2010 observations were analyzed in a modified stability analysis, CA had an overall positive effect of 3 838 Mexican Pesos ha−1 (320 $US ha−1) on net return and 1.3 t ha−1 on yield. After only one to two years of adoption by farmers on their fields, CA had higher yields and net returns under dry conditions that were even drier than those predicted by the analyzed 21 climate change models under a climate change scenario, emission scenario A2.

A sustainable rural?

Rural communities and economies face unprecedented social and economic challenges and opportunities. Given the scale and nature of these changes and the inherent difficulties and capacity constraints confronting rural communities in addressing them, sustainable development at the local level seems to be a policy priority. This then is the focus of this Special Issue. It has been argued that sustainable development: ‘meets the needs of current generations without compromising the ability of future generations to meet their own needs’ (World Commission on Environment and Development (WCED), 1987: 2). Understanding which factors contribute to the valorization of rural sustainability is often rooted in ‘hard’ and ostensibly quantitative performance indicators. National, regional or sub-regional measures of performance are used to indicate the socio-economic health and prosperity of a region or sub-region. However, sustainability is also concerned with realistic and sensible social and economic activity and the ways in which the role of legal, financial, social and behavioural aspects of businesses and communities impacts on making rural economies enterprising. Sustainability is a recurrent policy theme. For example, the Department for Business, Innovation and Skills (BIS) launched a Strategy for Sustainable Growth in July 2010. Three strategy areas were identified as priorities for government support:

Creeping Signalgrass Versus Bahiagrass for Cow and Calf Grazing

Bahiagrass (Paspalum notatum Flügge) is the predominant pasture grass in Florida because it is well adapted to the extensive low‐input cattle management typical of Florida's beef production. Creeping signalgrass [Urochloa humidicola (Rendle) Morrone & Zuloaga), syn. Brachiaria humidicola (Rendle) Schweick.] shares many of the desirable characteristics of bahiagrass, but no comparative grazing trials have been conducted. We measured calf body weight (BW) gains on signalgrass and bahiagrass from May to early August (weaning) and monitored cow BW changes from August through October over 4 yr. Calf BW at weaning averaged 250 kg on signalgrass and 235 kg on bahiagrass (P = 0.13), and calf average daily gain was 0.66 kg d−1 for signalgrass and 0.48 kg d−1 for bahiagrass (P = 0.07). Cows grazing signalgrass weighed more (P = 0.03) in October (564 kg) than cows on bahiagrass (513 kg) and had higher (P = 0.01) body condition scores (5.7 vs. 4.7, respectively)]. There was no difference between bahiagrass and signalgrass [8380 and 9580 kg dry matter (DM) ha−1] for forage accumulation from May through October, but forage mass was greater for signalgrass than bahiagrass from July to October. A problem with signalgrass was that 33% of annual forage DM accumulation occurred in a 28‐d period beginning with the start of summer rain. Signalgrass had greater organic matter digestibility (545 g kg−1) than bahiagrass (476 g kg−1), but it always contained less crude protein (87 vs. 107 g kg−1). A freeze (−5°C) reduced signalgrass ground cover to ≈50% and delayed grazing in 1 of 4 yr. Forage production, nutritive value, and livestock gains on signalgrass equaled or exceeded those of bahiagrass, but poor cold tolerance, limited growth before May, and excessive growth in July are potential problems with signalgrass pasture production.

The Indian summer monsoon rainfall: interplay of coupled dynamics, radiation and cloud microphysics

Abstract. The Indian summer monsoon rainfall (ISMR), which has a strong connection to agricultural food production, has been less predictable by conventional models in recent times. Two distinct years 2002 and 2003 with lower and higher July rainfall, respectively, are selected to help understand the natural and anthropogenic influences on ISMR. We show that heating gradients along the meridional monsoon circulation are reduced due to aerosol radiative forcing and the Indian Ocean Dipole in 2002. An increase in the dust and biomass-burning component of the aerosols through the zonal monsoon circulation resulted in reduction of cloud droplet growth in July 2002. These conditions were opposite to those in July 2003 which led to an above average ISMR. In this study, we have utilized NCEP/NCAR reanalyses for meteorological data (e.g. sea-surface temperature, horizontal winds, and precipitable water), NOAA interpolated outgoing long-wave radiation, IITM constructed all-India rainfall amounts, aerosol parameters as observed from the TOMS and MODIS satellites, and ATSR fire count maps. Based on this analysis, we suggest that monsoon rainfall prediction models should include synoptic as well as interannual variability in both atmospheric dynamics and chemical composition.

Evaluation of a deer-activated bio-acoustic frightening device for reducing deer damage in cornfields

Deer (Odocoileus spp.) can cause substantial damage to agricultural crops, resulting in economic losses for producers. We developed a deer-activated bio-acoustic frightening device to reduce white-tailed deer (O. virginianus) damage in agricultural fields. The device consisted of an infrared detection system that activated an audio component which broadcast recorded distress and alarm calls of deer. We tested the device against unprotected controls in cornfields during the silking–tasseling stage of growth in July 2001. The device was not effective in reducing damage: track-count indices (F1,4=0.02, P=0.892), corn yield (F1,9=1.27, P=0.289), and estimated damage levels (F1,10=0.87, P=0.374) did not differ between experimental and control fields. The size (F2,26=1.00, P=0.380), location (F2,25 =0.39, P =0.684), and percent overlap (F2,25 =0.20, P =0.818) of use-areas of radiomarked female deer did not differ between during- and after-treatment periods. We concluded that the deer-activated bio-acoustic device was not effective in protecting cornfields in this study; however, the device may be more effective in small areas such as gardens or for high-value crops that do not grow tall enough to offer protective cover.

Seasonal variation in the feeding physiology and scope for growth of green mussels, Perna viridis in estuarine Ma Wan, Hong Kong

Seasonal variations in feeding physiology and scope for growth of green mussels Perna viridis (Bivalvia: Mytilidae) were investigated in Ma Wan, an estuarine mariculture site located in the southern waters of Hong Kong. Total particulate matter, particulate organic matter, particulate inorganic matter and organic fraction of seston (f), and food availability were monitored monthly from January to December 1998. Feeding rates, including clearance rate, filtration, ingestion and absorption, and absorption efficiency were higher in summer and autumn and lower in winter. Pseudofaeces were produced but the preferential selection of organic materials by P. viridis was not concluded. Scope for growth in July and October were higher than in February. Activities of digestive enzymes including amylase and cellulase in the digestive diverticula and crystalline style were high in May and July and lower in February and October and correlated with f. Faster growth rates obtained for P. viridis in Hong Kong's summer are considered a result of enhanced feeding and absorption at high temperatures and f values.

Magnetic monitoring at Merapi volcano, Indonesia

Merapi volcano, located 30 km north of the heavily populated city of Yogjakarta, Java, is one of the most active of the 129 volcanoes in Indonesia. About every 2 years a new phase of activity is observed. Depending on the past activity the unrest gives rise either to an endogenous dome which partly collapses in the southwest direction or to pyroclastic flows which travel as far as 15 km. The 1990–1997 period has involved a plume emission on 30 August 1990, an extrusion on 20 January 1992, and a pyroclastic eruption on 22 November 1994. The intensity of the Earth magnetic field has been measured simultaneously and digitally recorded at four stations since 1990. Two Overhauser magnetometers with resolution of 0.01 nT have been installed in the summit area to strengthen the volcano monitoring. Outstanding magnetic changes appear to correlate with volcanic activity. Three types of volcanomagnetic signals can be identified: long-term trends up to 15 nT with period >10 years; medium-term cyclic variations, at most 3 nT in amplitude and with 1–2 years period; and small events, reaching 1.5 nT, lasting a few months, and associated with any remarkable volcanic activity. Merapi volcano began a new cycle of activity in 1995 leading to a dome growth in July 1996, and accompanied by 27 nuées ardentes in August. The comparison between magnetic data, seismicity, and surface phenomena suggests that some long-term trends of decade periods could be of thermomagnetic origin, while mid-term volcanomagnetic variations associated with the cycles of Merapi activity could be of piezomagnetic origin. Short-term variations of a few weeks duration, less than 1.5 nT, are well correlated with the 1995–1996 seismic activity.

Growth, leaf temperatures, and leaf conductances of C3 forbs and C4 grasses in a tallgrass prairie in northeastern Kansas, USA

Summary Shoot growth, leaf temperatures, and leaf conductances to water vapor were measured for dominant C3 forbs and C4 grasses (including one sedge) in a tallgrass prairie in northeastern Kansas. Most species, regardless of photosynthetic pathway, completed their vegetative growth in July. Growth after this date was, for the most part, due to inflorescence production. Throughout the summer, leaf temperatures and conductances were similar between the forbs and grasses. There was a tendency toward lower leaf temperatures and higher conductances in the C3 forbs but such differences were not always statistically significant. Thus, dramatic ecophysiological differences expected as a result of photosynthetic pathway alone were not observed in this in situ study of C3 and C4 prairie species.

Effects of nutrients (phosphorous, nitrogen, and carbon) and zooplankton on bacterioplankton and phytoplankton—a seasonal study

The effects of inorganic nutrients (P and N), organic C, and metazoan zooplankton on bacterioplankton production and abundance and on phytoplankton biomass were studied in five experiments (from May to September) in Lake Erken. In addition, the seasonal dynamics of bacterioplankton and phytoplankton were followed in the lake from April to November.Bacterioplankton production was P limited from May to August. N alone never stimulated bacterioplankton production, but bacterioplankton growth was close to colimited by P and N in July and August. Organic C stimulated bacterial production in June and September. Zooplankton enhanced bacterioplankton production in June, when bacterioplankton production was limited by P and C and the phytoplankton biomass in the lake was low. N alone stimulated phytoplankton growth in all experiments. In addition, P alone stimulated phytoplankton growth in May and July, and the combination of P and N stimulated phytoplankton growth in July and August. Zooplankton additions resulted in a decrease in phytoplankton biomass in May and September, mainly owing to grazing on Cryptophyceae.The experimental results indicate that bacterioplankton and phytoplankton growth were uncoupled during most of the open‐water period because P primarily limited bacterioplankton growth and N limited phytoplankton growth. The response of the bacterioplankton community was most likely a direct effect of nutrient additions. Primary production and bacterioplankton production were correlated during the season, but partial correlations analysis indicates that this relationship can be attributed to the fact that both primary production and bacterioplankton production showed strong positive correlations with temperature. We suggest that uncoupling of bacterioplankton production and phytoplankton production may be a common phenomenon in lakes.

Relations between cytokinin level, bud development and apical control in Norway spruce, Picea abies

In conifers such as Norway spruce, the extent of shoot growth is predetermined by the size and number of embryonal organs of the buds laid down the previous year. As it is known that cytokinins have a key role in bud development a possible hypothesis is that the level of cytokinin in the buds during their formation determines their size and complexity. As a first step to test this hypothesis we compared cytokinin levels in buds of different size of annual shoots from 15‐ to 20‐year‐old trees of Picea abies (L.) Karst. Apical buds from the leaders, and from branches in lower parts of the trees, were collected in April, July and August. The difference in size of the buds and the shoots growing from them was considerable in these three positions. Extracts were purified by immunoaffinity columns, and the retained compounds were separated by high‐performance liquid chromatography (HPLC). Quantification was made by enzyme‐linked immunosorbent assay (ELISA), and the accuracy of this method was checked by measurements with liquid chromatography‐mass spectrometry (LC‐MS) and UV absorption. Zeatin riboside (ZR) was the most abundant cytokinin, but isopentenyladenosine (iPA) was also present in all samples. The large apical bud of the leader contained much higher cytokinin concentrations than the considerably smaller buds from lower positions, and during the period of secondary growth in July, similar relationships were found for annual stem tissue from different positions. The possible role of ZR as a controlling factor in bud development and apical control is discussed. Our conclusion is that the level of zeatin‐type cytokinins appears to play an important role in the establishment of differences in bud size and, thereby, the architecture of the tree crown.

Defoliation of a Northern Wheatgrass Community: Above- and Belowground Phytomass Productivity

A defoliation study was conducted on a fair condition, clayey range site that is potentially dominated by northern wheatgrass (Agropyron dasystachyum (Hook.) Scribn.) in south-central Saskatchewan. Vegetation was subjected to a factorial experiment with an initial defoliation in early-May, June, July, or August and repeated at 2- or 6-week intervals until mid-September in the same plots for 3 years. An undefoliated control was also included. Herbage removed, residual live, dead, total and root phytomass were measured. Defoliation reduced all yield components, with the exception of herbage removed. Residual live grass was reduced 37, 57, and 46%, respectively, in first second, and third years; the sedge and forb components of live residual phytomass generally were not affected by defoliation. Compared to control, dead phytomass was reduced 77% in the first year, 67% in the second, and 52% in the third year across treatments. Total herbage yield across defoliation treatments ranged from 68 to 93% of control Total live phytomass (herbage removed + residual live phytomass) in defoliated plots equaled control Herbage removal was greatest when initially defoliated in early July and thereafter at 2-week intervals. When defoliated at 6-week intervals residual live and dead phytomass were generally greater than when herbage was removed biweekly. Yields were higher when the first defoliation was delayed and repeated at 6-week intervals. Generally, root phytomass was not different among defoliation treatments, but total belowground phytomass was reduced 30% in the 0-30-cm depth after 3 year of defoliation. This northern mixed prairie ecosystem is sensitive to herbage removal. Maximum forage yield can be obtained if grazing is deferred until after peak growth in July.

Relationships between staple strength and other wool characteristics of Romney ewes

Abstract Romney ewes were offered pasture allowances of 0.7, l.2, l.7, or 2.2 kg dry matter (DM)/ewe per day for 6 weeks in June—July. Liveweight change, wool growth, fibre diameter, and staple length growth rate were measured during early and late winter and in spring. Fleeceweights were recorded at shearing in December and samples were collected for measurement of staple strength and assessment of soundness grade. Relationships between staple strength and subjectively assessed soundness grade and otherwqol measurements were examined. Increases in staple strength for a 1 gJday increase in wool growth in July—August were: Year 1,3.3 (SE = 0.5) N/ktex; Year 2, low allowance, l.8 (SE = l.2); Year 2, high allowance, 6.1 (SE = 0.9). There were also significant positive relationships between staple strength and both fibre diameter and clean fleeceweight. Ewes growing fleeces of low staple strength had a more pronounced seasonal pattern of wool growth than ewes growing sound fleeces, with the difference being most marked in July-August. Staple strength was not significantly associated with liveweight change, suggesting that variation in strength is caused by variation in the partitioning of nutrients to wool growth rather than to variation in intake.

Use and Partitioning of Montane Habitat by Small Mammals

Structure of the microhabitat used by four species of rodents in a montane environment was investigated using principal-component analysis of trap-site characteristics. Most species of rodents were associated with fallen logs and brush during June but microhabitat use shifted to areas of more herbaceous growth in July–August. This shift was concurrent with rapid herbaceous growth. Females of each species occupied more structured microhabitat than males of the same species. Differential segregation of habitat by sex may be a function of the variability of resource use by the species as a whole. Unused microhabitat does not differ from random with respect to vegetative structure, and reasons for nonuse probably differ among sites.

USE OF THE EXCISED SHOOT ASSAY TO EVALUATE RESISTANCE TO Phytophthora cactorum OF APPLE ROOTSTOCK CULTIVARS

The excised shoot assay was used to evaluate crown and root rot (P. cactorum (Leb & Cohn) Schroeter) resistance of several apple (Malus domestica Borkh.) rootstock cultivars using relative lesion length as a measure of resistance. To determine the best time to assess crown rot resistance, three cultivars, M.26 (moderately resistant), MM.111 (moderately susceptible) and MM.106 (susceptible) were tested monthly for a 12-mo period. The best separation of the three cultivars of known resistance was from the period of February to June and again in November. In another test on 27 apple root-stock cultivars tested quarterly, good separation of known standards was achieved only on the April sampling date. In both tests the organism appeared to overwhelm resistance of the tissue during the most active stage of shoot growth in July and August. Based on the mean for the three dates (April, October and January) the cultivars P. 16, J9, P.2, M.4, 0.3, P.1, M.9, M.26, P.22 and P.18 were significantly more resistant than the field-susceptible rootstocks, MM.106. None was significantly more resistant than M.9 and M.4, the resistant standards.Key words: Crown rot, Malus domestica Borkh, root rot, P. cactorum, rootstocks, apple