Evidence for a quiet revolution: seasonal variation in colonies of the specialist tansy aphid, Macrosiphoniella tanacetaria (Kaltenbach) (Hemiptera: Aphididae) studied using microsatellite markers

2010 ◽  
Vol 101 (2) ◽  
pp. 221-239 ◽  
Author(s):  
H.D. Loxdale ◽  
B. Massonnet ◽  
G. Schöfl ◽  
W.W. Weisser
Keyword(s):  
Clonal Selection ◽  
Clonal Diversity ◽  
Late Summer ◽  
Growing Season ◽  
Population Bottlenecks ◽  
Related Field ◽  
Expansion Phase ◽  
Quiet Revolution ◽  
Severe Reduction ◽  
Cyclical Parthenogens

AbstractIn cyclical parthenogens, clonal diversity is expected to decrease due to selection and drift during the asexual phase per number of asexual generations. The decrease in diversity may be counteracted by immigration of new genotypes. We analysed temporal variation in clonal diversity in colonies of the monophagous tansy aphid, Macrosiphoniella tanacetaria (Kaltenbach), sampled four times over the course of a growing season. In a related field study, we recorded aphid colony sizes and the occurrence of winged dispersers throughout the season. The number of colonies increased from April, when asexual stem mothers hatched from the sexually produced eggs, to the end of June. The proportion of colonies with winged individuals also increased over this period. After a severe reduction in colony sizes in late summer, a second expansion phase occurred in October when sexuals were produced. At the season's end, the only winged forms were males. A linked genetic study showed that the number of microsatellite multilocus genotypes and genetic variability assessed at three polymorphic loci per colony decreased from June to October. Overall, the relatedness of wingless to winged individuals within colonies was lower than average relatedness among wingless individuals, suggesting that winged forms mainly originated in different colonies. The results demonstrate that patterns of genetic diversity within colonies can be explained by the antagonistic forces of clonal selection, migration and genetic drift (largely due to midsummer population bottlenecks). We further suggest that the males emigrate over comparatively longer distances than winged asexual females.

Planting Date Affects Survival and Height Growth of Hybrid Poplar

1986 ◽  
Vol 62 (3) ◽  
pp. 164-169 ◽  
Author(s):  
Edward A. Hansen
Keyword(s):  
Hybrid Poplar ◽  
Late Summer ◽  
Growing Season ◽  
Climatic Conditions ◽  
Planting Date ◽  
Planting Dates ◽  
Soil Frost ◽  
Growing Seasons ◽  
Poplar Cuttings ◽  
Energy Plantations

In this study I investigated the effects of planting date for soaked versus unsoaked cuttings of two hybrid poplar clones under irrigated versus unirrigated and weedy versus weed-free conditions. Cuttings were planted each year for 4 years. Survival at the end of the first growing season was generally greater than 90% for all planting dates. At the end of the second growing season survival for trees planted before July 16 was again generally more than 90%. However, cuttings planted from July 30 through August 27 showed a major decline in survival and survival of fall planted cuttings ranged from 6 to 90%. Mortality of late summer- or fall-planted cuttings occurred prior to the beginning of the second growing season and was attributed to frost heaving. The tallest trees were not those planted at the earliest possible dates (April in Rhinelander). Instead, the tallest trees at the end of the first and second growing seasons were those planted in early- and mid-May. This optimum planting period was the same regardless of clone, soaking, irrigation, or weed treatment. Actual optimum planting date would change with location and local climatic conditions. Some climatic indices may prove more universal in predicting when to plant. Although tentative, it appears that for best growth, unrooted hybrid poplar cuttings should be planted in soil warmer than 10 °C. Trees do not grow as well if planted immediately after soil frost leaves the ground. Key words: Energy plantations, plantation establishment, woody biomass, intensive culture, Populus.

Effect of time of sowing on flowering and growth of Townsville stylo (Stylosanthes humilis)

1974 ◽  
Vol 14 (67) ◽  
pp. 182 ◽  
Author(s):  
Mannetje L t ◽  
KHLvan Bennekom
Keyword(s):  
Low Temperatures ◽  
Dry Matter ◽  
Late Summer ◽  
Growing Season ◽  
Sowing Date ◽  
Stylosanthes Humilis ◽  
Maturity Type ◽  
Townsville Stylo ◽  
Late Start ◽  
Spring Sowing

A midseason maturity type of Townsville stylo sown at monthly intervals throughout a year in a glasshouse in Brisbane (27�30' south) started flowering from 42 to 76 days after sowing between February and September, with dry matter yields at flowering ranging from 0.05 to 5.82 g/per plant. Sowings between October and January resulted in flowering after 98 to 157 days, with yields ranging from 26.41 to 54.75 g/per plant. Flowering was mainly determined by daylength, although low temperatures during winter delayed inflorescence elongation. Growth after onset of flowering was measured in plants sown in winter, spring and late summer. Plant weights increased after flowering in all sowings. In the spring sowing this consisted entirely of stem and inflorescence, but in the other sowings leaf was formed after onset of flowering as well. Winter and spring sowings gave the highest, late summer sowing the lowest final yields. The main agronomic implication is that sowing early in the growing season is necessary for obtaining a good first year's yield, but that seed production is little affected by sowing date, ensuring good regeneration even in years with a late start of the growing season.

Seasonal changes in forage nutritive value of common weeds encountered in Missouri pastures

2019 ◽  
Vol 34 (2) ◽  
pp. 164-171
Author(s):  
Gatlin Bunton ◽  
Zach Trower ◽  
Craig Roberts ◽  
Kevin W. Bradley
Keyword(s):  
Tall Fescue ◽  
Crude Protein ◽  
Nutritive Value ◽  
Late Summer ◽  
Growing Season ◽  
Quality Parameter ◽  
Neutral Detergent Fiber ◽  
Weed Species ◽  
Growing Seasons

AbstractDuring the 2015, 2016, and 2017 growing seasons, weed and weed-free mixed tall fescue and legume forage samples were harvested from 29 pastures throughout Missouri for investigation of the nutritive value of 20 common pasture weed species throughout the season. At certain times during the growing season, many broadleaf weed species had greater nutritive values for a given quality parameter as compared with the available weed-free, mixed tall fescue and legume forage harvested from the same location. There were no significant differences in crude protein concentration between the weed-free forage and many weeds throughout the growing season. However, crude protein content of common burdock, common cocklebur, common ragweed, dandelion, horsenettle, and lanceleaf ragweed was greater than that of the corresponding forage sample at multiple collection periods. The digestible neutral detergent fiber (dNDF) content of all broadleaf weeds except lanceleaf ragweed was significantly lower than that of the weed-free forage at all collection periods. Conversely, large crabgrass had significantly greater digestible neutral detergent fiber levels than did the mixed tall fescue forage at all sampling dates. Dandelion and spiny amaranth had greater in vitro true digestibility (IVTD) content than did the forage for the entire growing season. Three perennial weeds—horsenettle, vervains, and late boneset—did not differ in IVTD levels as compared with the mixed tall fescue and legume forage at any collection date. For most summer annual weeds, the trend was toward greater digestibility earlier in the season, with a gradual decline and often lower IVTD by the late summer or early fall. The results of this study will enable producers to make more informed management decisions about the potential benefit or detriment a weed may provide to the overall nutritive value of the pasture system.

Suppression of Glyphosate-resistant Canada Fleabane (Conyza canadensis) in Corn with Cover Crops Seeded after Wheat Harvest the Previous Year

2018 ◽  
Vol 32 (3) ◽  
pp. 244-250 ◽  
Author(s):  
Taïga B. Cholette ◽  
Nader Soltani ◽  
David C. Hooker ◽  
Darren E. Robinson ◽  
Peter H. Sikkema
Keyword(s):  
Cover Crops ◽  
Weed Management ◽  
Cover Crop ◽  
Management Strategies ◽  
Late Summer ◽  
Growing Season ◽  
Integrated Weed Management ◽  
Crop Species ◽  
Herbicide Resistant ◽  
Crimson Clover

AbstractGlyphosate-resistant (GR) and multiple herbicide–resistant (groups 2 and 9) Canada fleabane have been confirmed in 30 and 23 counties in Ontario, respectively. The widespread incidence of herbicide-resistant Canada fleabane highlights the importance of developing integrated weed management strategies. One strategy is to suppress Canada fleabane using cover crops. Seventeen different cover crop monocultures or polycultures were seeded after winter wheat harvest in late summer to determine GR Canada fleabane suppression in corn grown the following growing season. All cover crop treatments seeded after wheat harvest suppressed GR Canada fleabane in corn the following year. At 4 wk after cover crop emergence (WAE), estimated cover crop ground cover ranged from 31% to 68%, a density of 124 to 638 plants m–2, and a range of biomass from 29 to 109 g m–2, depending on cover crop species. All of the cover crop treatments suppressed GR Canada fleabane in corn grown the following growing season from May to September compared to the no cover crop control. Among treatments evaluated, annual ryegrass (ARG), crimson clover (CC)/ARG, oilseed radish (OSR)/CC/ARG, and OSR/CC/cereal rye (CR) were the best treatments for the suppression of GR Canada fleabane in corn. ARG alone or in combination with CC provided the most consistent GR Canada fleabane suppression, density reduction, and biomass reduction in corn. Grain corn yields were not affected by the use of the cover crops evaluated for Canada fleabane suppression.

scholarly journals Fungicide timing for control of summer rots of apples

2007 ◽  
Vol 60 ◽  
pp. 15-20
Author(s):  
K.R. Everett ◽  
O.E. Timudo-Torrevilla ◽  
J.T. Taylor ◽  
J. Yu
Keyword(s):  
Biological Control ◽  
Bacillus Subtilis ◽  
Serratia Marcescens ◽  
Late Summer ◽  
Growing Season ◽  
Early Summer ◽  
The Other ◽  
Effective Control ◽  
Lesion Diameter ◽  
Final Assessment

Control of preharvest summer rot in cv Royal Gala apple in the Waikato district during the 2006/2007 growing season was evaluated There were six treatments and an unsprayed control Three treatments investigated the effect of timing by applying tolyfluanid mancozeb captan and copper sequentially at 1014 day intervals in October and early November (spring) November and December (early summer) or January and February (late summer) The fourth treatment was two applications of carbendazim in early October (flowering) and there were two biological control treatments Bacillus subtilis QST713 and Serratia marcescens HR42 applied at 1014 day intervals from flowering (October) to harvest (February) Compared with the unsprayed treatment the most effective control was achieved by fungicide applications during either November/December or January/February Due to large variation in the data differences were not statistically significant but mean lesion diameter at final assessment for these treatments was 29 and 35 of controls respectively The other treatments did not control rots

scholarly journals Seasonal development of iron limitation in the sub-Antarctic zone

2018 ◽  
Vol 15 (14) ◽  
pp. 4647-4660 ◽  
Author(s):  
Thomas J. Ryan-Keogh ◽  
Sandy J. Thomalla ◽  
Thato N. Mtshali ◽  
Natasha R. van Horsten ◽  
Hazel J. Little
Keyword(s):  
Phytoplankton Community ◽  
Late Summer ◽  
Growing Season ◽  
Early Summer ◽  
Seasonal Development ◽  
Iron Availability ◽  
Iron Supply ◽  
Incubation Experiments ◽  
The Mean ◽  
Iron Addition

Abstract. The seasonal and sub-seasonal dynamics of iron availability within the sub-Antarctic zone (SAZ; ∼40–45∘ S) play an important role in the distribution, biomass and productivity of the phytoplankton community. The variability in iron availability is due to an interplay between winter entrainment, diapycnal diffusion, storm-driven entrainment, atmospheric deposition, iron scavenging and iron recycling processes. Biological observations utilizing grow-out iron addition incubation experiments were performed at different stages of the seasonal cycle within the SAZ to determine whether iron availability at the time of sampling was sufficient to meet biological demands at different times of the growing season. Here we demonstrate that at the beginning of the growing season, there is sufficient iron to meet the demands of the phytoplankton community, but that as the growing season develops the mean iron concentrations in the mixed layer decrease and are insufficient to meet biological demand. Phytoplankton increase their photosynthetic efficiency and net growth rates following iron addition from midsummer to late summer, with no differences determined during early summer, suggestive of seasonal iron depletion and an insufficient resupply of iron to meet biological demand. The result of this is residual macronutrients at the end of the growing season and the prevalence of the high-nutrient low-chlorophyll (HNLC) condition. We conclude that despite the prolonged growing season characteristic of the SAZ, which can extend into late summer/early autumn, results nonetheless suggest that iron supply mechanisms are insufficient to maintain potential maximal growth and productivity throughout the season.

Shoot apical growth and cataphyll initiation rates in provenances of Pinusconforta in Scotland

1976 ◽  
Vol 6 (4) ◽  
pp. 539-556 ◽  
Author(s):  
Melvin G. R. Cannell
Keyword(s):  
Late Summer ◽  
Growing Season ◽  
Height Growth ◽  
Early Summer ◽  
Model Matching ◽  
Matching Method ◽  
Apical Dome ◽  
Terminal Bud ◽  
Component C ◽  
Doubling Times

The dynamics of terminal bud development on seven 3-year-old nursery-grown provenances of Pinuscontorta Dougl. were monitored by sampling buds at 1- to 3-weekly intervals during one growing season. Differences in rates of cataphyll initiation occurred which were analysed in terms of (a) the projected areas of the apical domes, which changed over the season, (b) the relative rates at which the apical domes expanded radially during a plastochrone (square millimetres per square millimetre), as shown by the extent to which the new cataphyll primordia receded away from the domes, and (c) the projected areas of the tissues used to form new cataphyll primordia. Component a was a measure of the size of the apical dome meristems and b was a measure of their rates of 'activity.' A model-matching method is described to measure b.Those provenances which produced most cataphylls during the growing season developed and maintained large apical domes (component a above). There were unexpectedly small provenance differences in the apical dome 'activity' in midsummer (component b defined above), although differences occurred in spring and autumn. Differences in the projected areas of the new cataphyll primordia (component c) were inversely related to cataphyll initiation rates. Apical dome tissue doubling times in midsummer were estimated to be less than 120 h, irrespective of provenance.Inland provenances had small but relatively 'active' apical domes in spring, but they produced cataphyll primordia as products of this growth rather than reinvesting in apical dome 'capital.' Consequently, their apical domes remained small. Coastal Alaskan provenances, on the other hand, developed large apical domes, but these domes ceased to be very 'active' after the end of August. The apical domes on south coastal provenances did not become 'active' until early summer, but their domes were relatively large even in spring, became much larger by late summer, and they remained 'active' until mid-September.Implications are noted regarding cross-breeding of complementary genotypes to increase needle production and height growth.

Summer-growing components of a pasture system in a subtropical environment. 1. Pasture growth, carrying capacity and milk production

1980 ◽  
Vol 94 (3) ◽  
pp. 645-663 ◽  
Author(s):  
G. J. Murtagh ◽  
A. G. Kaiser ◽  
D. O. Huett ◽  
R. M. Hughes
Keyword(s):  
Nitrogen Fertilizer ◽  
Carrying Capacity ◽  
Leaf Growth ◽  
Stocking Density ◽  
Late Summer ◽  
Growing Season ◽  
Fixed Number ◽  
Control Treatment ◽  
Dairy Production ◽  
Leaf Production

SummaryThe leaf growth, carrying capacity and dairy production of four summer-growing pastures were measured in a subtropical area of Australia. The growing season was subdivided into ten 4-week periods and the production was estimated for each period. Carrying capacities were determined by rotationally grazing four paddocks of each pasture over the 4-week period, and varying the stocking density so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.A non-limiting rate of nitrogen fertilizer increased total leaf production of kikuyu by 97% over a control treatment without nitrogen, but the response was not evenly distributed throughout the season. It fell to 50% during autumn when growth on the nitrogen-fertilized pastures was restricted following heavy defoliation during late summer. The use of the tropical legumes, siratro and glycine, in a mixed sward with kikuyu, did not increase leaf production over a kikuyu control pasture. The legumes grew poorly and this appeared to be due to the combined effects of their poor adaptability to the krasnozem soil, a high plant mortality especially during the first winter after sowing, the 4-week grazing interval and strong grass competition.The carrying capacity of the nitrogen-fertilized pasture was 1·3–5·3 cows/ha at the beginning (September–October) and end (April–mid June) of the growing season, and increased to a peak of 7·4–9·7 cows/ha during February-mid March. Nitrogen fertilizer increased the carrying capacity by an average of 131% over that on a kikuyu pasture without nitrogen. The carrying capacities were similar on kikuyu and on a mixed carpet grass-kikuyu pasture, both without nitrogen, but were less on a tropical legume-kikuyu pasture which was grazed at a lighter grazing intensity during autumn to aid legume persistence.Reflecting the experimental method of adjusting the stocking density according to the pasture available, differences in dairy production per cow were small relative to differences in the carrying capacity. Consequently seasonal variation in total dairy production/ha mirrored the carrying capacity. Nitrogen fertilizer increased the average production of 4% fat-corrected milk to 13·2 t/ha/40 weeks, an increase of 133% over the control without nitrogen.The results illustrate the marked seasonal imbalance in growth and carrying capacity for a given pasture, and emphasize the need to use mixed feeding systems to provide a uniform level of nutrition for a fixed number of cows.

Sedimentary Phosphorus in the Bay of Quinte, Lake Ontario

1993 ◽  
Vol 50 (1) ◽  
pp. 190-197 ◽  
Author(s):  
O. A. Oluyedun ◽  
S. O. Ajayi ◽  
G. W. VanLoon ◽  
P. Sly
Keyword(s):  
Fulvic Acid ◽  
Water Column ◽  
Sharp Decrease ◽  
Late Summer ◽  
Lake Ontario ◽  
Growing Season ◽  
Organic P ◽  
Acid Fraction ◽  
Microbiological Activity ◽  
Hydrous Oxides

Phosphorus distributions in sediments of the Bay of Quinte were measured. Principal fractions in most samples were (in order of decreasing concentration) P associated with CaCO3, residual organic P, associated with Fe and Al hydrous oxides, and P in the fulvic acid fraction. Concentrations of P in each fraction were followed at 3-wk intervals from May to October and on some additional dates at two or more sites. There were only two systematic changes in concentration over this time. The amount of P incorporated in the sedimentary biomass increased during the summer, probably at a time of high microbiological activity; this was followed by a sharp decrease and another slower increase in late summer. Available P steadily increased during the growing season, but returned to near the previous year's value 12 mo later. Dissolved P in water adjacent to the sediments showed a peak in concentration corresponding to the decrease in biomass P in midsummer. The results are consistent with a picture of P cycling in which forms of the element are first incorporated in the biomass, but are later released to the water column or to available sites on the sediment upon decomposition of the biomass.

Seasonal changes in the photosynthetic response to CO2 and temperature in apple (Malus domestica cv. ‘Red Gala’) leaves during a growing season with a high temperature event

2015 ◽  
Vol 42 (3) ◽  
pp. 309 ◽  
Author(s):  
Dennis H. Greer
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Malus Domestica ◽  
Seasonal Changes ◽  
Detrimental Effect ◽  
Late Summer ◽  
Growing Season ◽  
Heat Event ◽  
Internal Co2 ◽  
Photosynthetic Responses

Changes in the photosynthetic responses of Malus domestica cv. ‘Red Gala’ leaves to internal CO2 concentrations at leaf temperatures from 15°C to 40°C were followed across the growing season in field-grown trees exposed to a high temperature event in late summer. Light and CO2-saturated photosynthesis (Amax), maximum rates of ribulose 1,5-bisphosphate (RuBP) carboxylation (Vcmax) and maximum rates of electron transport (Jmax) were all highest in spring, although Amax was maximal at 30°C, and Vcmax and Jmax were maximal at 40°C. All attributes declined in late summer and reached minima that coincided with the occurrence of the high temperature event. Modelling suggested many of the changes were correlated with the seasonal climate, although the measurement or current temperature had an overriding effect, especially on stomatal conductance. Marked changes in the temperature-dependency of Vcmax and Jmax occurred across the season and appeared to relate to the seasonal changes in climate, especially temperature. The reduction in photosynthesis at high temperatures was, however, partly attributable to a stomatal limitation of up to 60% at the high temperatures. Non-stomatal reductions in photosynthesis during the heat event could be attributed to detrimental effect on RuBP carboxylation and on RuBP regeneration.

Sign in / Sign up

Export Citation Format

Share Document