Leaf spot and dry rot of lettuce caused by Xanthomonas vitians (Brown) Dowson

1963 ◽  
Vol 14 (6) ◽  
pp. 778 ◽  
Author(s):  
DE Harrison
Keyword(s):  
Leaf Spot ◽  
Early Spring ◽  
Late Winter ◽  
Laboratory Studies ◽  
Dry Rot ◽  
Complete Destruction ◽  
Western Victoria ◽  
Valley Area ◽  
North Western

During the late winter and early spring of 1960, and again to a lesser extent in 1961 and 1962, many lettuce crops in the Murray Valley area of north-western Victoria were seriously affected by a disease characterized by blackening, dry rotting, and collapse of the affected leaves. The incidence of disease varied from about 10% up to practically complete destruction of some plantings. A yellow bacterium was consistently isolated from affected plants and proved to be pathogenic to lettuce. Laboratory studies have shown that the organism agrees closely with the recorded description of Xanthomonas vitians (Brown) Dowson, which has not, apparently, been previously studied in Australia.

Reproduction of Heterodontus portusjacksoni in Victoria, Australia: evidence of two populations and reproductive parameters for the eastern population

2007 ◽  
Vol 58 (10) ◽  
pp. 956 ◽  
Author(s):  
Javier Tovar-Ávila ◽  
Terence I. Walker ◽  
Robert W. Day
Keyword(s):  
Population Analysis ◽  
Sampling Bias ◽  
Early Spring ◽  
Egg Laying ◽  
Late Winter ◽  
Reproductive Parameters ◽  
Breeding Populations ◽  
Eastern Australia ◽  
Western Victoria ◽  
Far Eastern

Significant differences in the length–frequency composition of catch samples, mass–length relationships and length-at-maturity found between Heterodontus portusjacksoni from western and far-eastern Victoria, suggest the presence of at least two separate breeding populations off south-eastern Australia, with some mixing between these regions. In each region females attain a larger size than males, and collectively those sharks in western Victoria are smaller, present higher mass-at-length, and lower length-at-maturity than those in far-eastern Victoria. These regional differences might be a result of sampling bias, length-selective fishing mortality, environmental conditions, or genetic differences. However, tagging evidence from previous studies and the presence of two bio-geographic provinces in the region support the hypothesis of two separate breeding populations. The essential reproductive parameters for H. portusjacksoni population analysis in far-eastern Victoria were determined, using a novel method to estimate fecundity and the ovarian cycle of an egg-laying species. In this region, females have between 6 and 20 pre-ovulatory oocytes (average = 14, n = 29, standard deviation = 3.71) before the reproductive season. The species has an annual reproductive cycle correlated with water temperature, with ovulation starting during late winter to early spring and a ~6 month egg-laying period. The period from the onset of vitellogenesis to ovulation of oocytes is ~18 months.

Pollen vectors and pollination of faba beans in southern Australia

1991 ◽  
Vol 42 (7) ◽  
pp. 1173 ◽  
Author(s):  
FL Stoddard
Keyword(s):  
Vicia Faba ◽  
Mediterranean Climate ◽  
South Australia ◽  
Early Spring ◽  
Late Winter ◽  
Flower Visitors ◽  
Vicia Faba L ◽  
Faba Beans ◽  
Pollen Vectors ◽  
Western Victoria

Commercial crops of faba beans (Vicia faba L.) in South Australia and western Victoria were surveyed for flower visitors and incidence of pollination. Honeybees were the only pollen vectors. The incidence of pollination was never less than 50% and averaged 80%. The effectiveness of honeybees as pollen vectors contrasts with their ineffectiveness in colder climates, partly because in the Mediterranean climate beans flower in late winter and early spring when bees are in search of pollen. It is unlikely that growers of faba beans in Australia will need to provide supplementary hives to ensure adequate pollination.

The biology of a landlocked form of the normally catadromous salmoniform fish Galaxias maculatus (Jenyns). I. Life cycle and origin

1971 ◽  
Vol 22 (2) ◽  
pp. 91 ◽  
Author(s):  
DA Pollard
Keyword(s):  
Life Cycle ◽  
New Zealand ◽  
River System ◽  
Heavy Rain ◽  
Early Spring ◽  
Ancestral Population ◽  
Late Winter ◽  
Eastern Australia ◽  
Galaxias Maculatus ◽  
Western Victoria

In contrast to most other members of the family Galaxiidae which live and reproduce in fresh water, Galaxias maculatus, the common jollytail of Australia and "whitebait" of New Zealand, is normaIly catadromous throughout its range (south-eastern Australia, New Zealand, and southern South America). In some athalassic inland lakes on the volcanic plains of south-western Victoria, however, a number of populations apparently descended from this species have becomelandlocked. The life cycle of the forminhabiting one of these lakes (the "landlocked jollytail" of Lake Modewarre) may be briefly summarized as follows: Gonadal maturation in the adult fish, which live in the slightly saline landlocked lake, begins around March and is almost completed by about June. The final stage of maturation is not reached, however, until these fish migrate short distances up intermittent inflowing creeks when the latter begin to flow in late winter and spring (July-October). Spawning takes place when the creeks are swollen after heavy rain, the eggs being deposited amongst flooded vegetation in shallow areas of slow-flowing water along the creek banks. Many of the spent fish die after spawning. The eggs, which are stranded when the flood-waters subside, develop amongst the vegetation on the banks above the normal water level. After development is complete reimmersion by the first flood to cover them stimulates hatching. The normal developmental period is probably about 2 weeks, but in the absence of flooding hatching can be delayed up to at least a month after fertilization. The newly hatched larvae are washed downstream into the lake where they feed and grow to maturity. They migrate upstream to spawn in the following late winter-early spring season at an age of approximately 1 year. The fish grow to about 9 cm in their first year, 14 cm in their second, and 17 cm in their third year. The average size of the females is greater than that of the males. The general features of the life history of this landlocked form are compared and contrasted with those of the stream-dwelling species G. maculatus and a number of other salmoniform fishes. The geological origin of the complex of lakes in south-western Victoria inhabited by landlocked galaxiid populations is discussed, and an hypothesis concerning the origin of the Lake Modewarre form from an ancestral population of G. maculatus in the Barwon-Leigh River system is advanced.

Reproductive dynamics of the tiger prawn Penaeus esculentus, and a comparison with P. semisulcatus, in the north-western Gulf of Carpentaria, Australia

1987 ◽  
Vol 38 (1) ◽  
pp. 91 ◽  
Author(s):  
PJ Crocos
Keyword(s):  
Egg Production ◽  
Reproductive Output ◽  
Size Range ◽  
Early Spring ◽  
Minimum Size ◽  
Late Winter ◽  
Limited Area ◽  
The North ◽  
Tiger Prawn ◽  
North Western

The reproductive cycle of female P. esculentus was investigated in the Groote Eylandt region of the Gulf of Carpentaria from August 1983 to March 1985. The minimum size at maturity for P. esculentus was 25 mm carapace length (CL), and 50% of the population were mature at 32 mm CL. The proportion of females which had mated increased sharply above 28 mm CL to a maximum of 80% inseminated in the size range 32-50 mm CL. An index of population egg production, calculated from female abundance, the proportion of females spawning and fecundity with size, was used as an indicator of reproductive output. Egg production tended to be spread throughout the year, but with eggs being produced most consistently in late winter and early spring. Spawning occurred in a limited area within the study area. A comparison of P. esculentus and P. semisulcatus showed that P. esculentus matures at a smaller size (50% at 32 mm CL) than P. semisulcatus (50% at 39 mm CL), fecundity is lower, spawning is nearer inshore and egg production is less strongly seasonal.

Seasonal activity and estivation of lumbricid earthworms in the midlands of Tasmania

Soil Research ◽  
1994 ◽  
Vol 32 (6) ◽  
pp. 1355 ◽  
Author(s):  
RB Garnsey
Keyword(s):  
Soil Moisture ◽  
Adult Development ◽  
Survival Rates ◽  
Soil Surface ◽  
Early Spring ◽  
Lumbricus Rubellus ◽  
Late Winter ◽  
Cocoon Production ◽  
Density And Biomass ◽  
Earthworm Activity

Earthworms have the ability to alleviate many soil degradational problems in Australia. An attempt to optimize this resource requires fundamental understanding of earthworm ecology. This study reports the seasonal changes in earthworm populations in the Midlands of Tasmania (<600 mm rainfall p.a.), and examines, for the first time in Australia, the behaviour and survival rates of aestivating earthworms. Earthworms were sampled from 14 permanent pastures in the Midlands from May 1992 to February 1994. Earthworm activity was significantly correlated with soil moisture; maximum earthworm activity in the surface soil was evident during the wetter months of winter and early spring, followed by aestivation in the surface and subsoils during the drier summer months. The two most abundant earthworm species found in the Midlands were Aporrectodea caliginosa (maximum of 174.8 m-2 or 55.06 g m-2) and A. trapezoides (86 m-2 or 52.03 g m-2), with low numbers of Octolasion cyaneum, Lumbricus rubellus and A. rosea. The phenology of A. caliginosa relating to rainfall contrasted with that of A. trapezoides in this study. A caliginosa was particularly dependent upon rainfall in the Midlands: population density, cocoon production and adult development of A. caliginosa were reduced as rainfall reduced from 600 to 425 mm p.a. In contrast, the density and biomass of A. trapezoides were unaffected by rainfall over the same range: cocoon production and adult development continued regardless of rainfall. The depth of earthworm aestivation during the summers of 1992-94 was similar in each year. Most individuals were in aestivation at a depth of 150-200 mm, regardless of species, soil moisture or texture. Smaller aestivating individuals were located nearer the soil surface, as was shown by an increase in mean mass of aestivating individuals with depth. There was a high mortality associated with summer aestivation of up to 60% for juvenile, and 63% for adult earthworms in 1993 in the Midlands. Cocoons did not survive during the summers of 1992 or 1994, but were recovered in 1993, possibly due to the influence of rainfall during late winter and early spring.

TEMPERATURE RESISTANCE OF GOLDFISH MAINTAINED UNDER CONTROLLED PHOTOPERIODS

1959 ◽  
Vol 37 (4) ◽  
pp. 419-428 ◽  
Author(s):  
William S. Hoar ◽  
G. Beth Robertson
Keyword(s):  
Temperature Change ◽  
Seasonal Variations ◽  
Rapid Growth ◽  
Endocrine System ◽  
Early Spring ◽  
Late Winter ◽  
Thyroid Activity ◽  
Temperature Resistance ◽  
Sudden Temperature Change

Goldfish maintained under controlled photoperiods for 6 weeks or longer were relatively more resistant to a sudden elevation in temperature when the daily photoperiods had been long (16 hours) and relatively more resistant to sudden chilling when they had been short (8 hours). The magnitude of the effect varied with the season. Thyroid activity was slightly greater in fish maintained under the shorter photoperiods. The longer photoperiods stimulated more rapid growth of ovaries during late winter and early spring. The endocrine system is considered a link in the chain of events regulating seasonal variations in resistance to sudden temperature change.

Insecticide sprays, natural enemy assemblages and predation on Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae)

2014 ◽  
Vol 104 (5) ◽  
pp. 576-585 ◽  
Author(s):  
C. Monzo ◽  
J.A. Qureshi ◽  
P.A. Stansly
Keyword(s):  
Natural Enemy ◽  
Early Spring ◽  
Citrus Greening ◽  
Asian Citrus Psyllid ◽  
Late Winter ◽  
Diaphorina Citri ◽  
Citrus Groves ◽  
Arthropod Fauna ◽  
Predator Exclusion ◽  
Insecticide Sprays

AbstractThe Asian citrus psyllid (ACP), Diaphorina citri Kuwayama is considered a key citrus pest due to its role as vector of ‘huanglongbing’ (HLB) or citrus greening, probably the most economically damaging disease of citrus. Insecticidal control of the vector is still considered a cornerstone of HLB management to prevent infection and to reduce reinoculation of infected trees. The severity of HLB has driven implementation of intensive insecticide programs against ACP with unknown side effects on beneficial arthropod fauna in citrus agroecosystems. We evaluated effects of calendar sprays directed against this pest on natural enemy assemblages and used exclusion to estimate mortality they imposed on ACP populations in citrus groves. Predator exclusion techniques were used on nascent colonies of D. citri in replicated large untreated and sprayed plots of citrus during the four major flushing periods over 2 years. Population of spiders, arboreal ants and ladybeetles were independently assessed. Monthly sprays of recommended insecticides for control of ACP, adversely affected natural enemy populations resulting in reduced predation on ACP immature stages, especially during the critical late winter/early spring flush. Consequently, projected growth rates of the ACP population were greatest where natural enemies had been adversely affected by insecticides. Whereas, this result does not obviate the need for insecticidal control of ACP, it does indicate that even a selective regimen of sprays can impose as yet undetermined costs in terms of reduced biological control of this and probably other citrus pests.

Phenological phases of pollination related to climate change

2021 ◽  
Author(s):  
Samuel Monnier ◽  
Michel Thibaudon ◽  
Jean-Pierre Besancenot ◽  
Charlotte Sindt ◽  
Gilles Oliver
Keyword(s):  
Climate Change ◽  
Pollen Season ◽  
Microscopic Analysis ◽  
Allergic Diseases ◽  
Early Spring ◽  
Late Winter ◽  
General Tendency ◽  
New Production ◽  
Start Date ◽  
Generic Term

&lt;p&gt;Knowledge:&lt;/p&gt;&lt;p&gt;Rising CO2 levels and climate change may be resulting in some shift in the geographical range of certain plant species, as well as in increased rate of photosynthesis. Many plants respond accordingly with increased growth and reproduction and possibly greater pollen yields, that could affect allergic diseases among other things.&lt;/p&gt;&lt;p&gt;The aim of this study is the evolution of aerobiological measurements in France for 25-30 years. This allows to follow the main phenological parameters in connection with the pollination and the ensuing allergy risk.&lt;/p&gt;&lt;p&gt;Material and method:&lt;/p&gt;&lt;p&gt;The RNSA (French Aerobiology Network) has pollen background-traps located in more than 60 towns throughout France. These traps are volumetric Hirst models making it possible to obtain impacted strips for microscopic analysis by trained operators. The main taxa studied here are birch, grasses and ragweed for a long period of more than 25 years over some cities of France.&lt;/p&gt;&lt;p&gt;Results:&lt;/p&gt;&lt;p&gt;Concerning birch but also other catkins or buds&amp;#8217; trees pollinating in late winter or spring, it can be seen an overall advance of the pollen season start date until 2004 and then a progressive delay, the current date being nearly the same as it was 20 years ago, and an increasing trend in the quantities of pollen emitted.&lt;/p&gt;&lt;p&gt;For grasses and ragweed, we only found a few minor changes in the start date but a longer duration of the pollen season.&lt;/p&gt;&lt;p&gt;Discussion:&lt;/p&gt;&lt;p&gt;As regards the trees, the start date of the new production of catkins or buds is never the 1&lt;sup&gt;st&lt;/sup&gt; of January but depends on the species. For example, it is early July for birch. For breaking dormancy, flowering, and pollinating, the trees and other perennial species need a period of accumulation of cold degrees (Chilling) and later an accumulation of warm degrees (Forcing). With climate change these periods may be shorter or longer depending of the autumn and winter temperature. Therefore, a change in the annual temperature may have a direct effect on the vegetal physiology and hence on pollen release. It may also explain why the quantities of pollen produced are increasing.&lt;/p&gt;&lt;p&gt;The Poaceae reserve, from one place to another and without any spatial structuring, very contrasted patterns which make it impossible to identify a general tendency. This is probably due to the great diversity of taxa grouped under the generic term Poaceae, which are clearly not equally sensitive to climate change.&lt;/p&gt;&lt;p&gt;Conclusion:&lt;/p&gt;&lt;p&gt;Trees with allergenic pollen blowing late winter or early spring pollinate since 2004 later and produce amounts of pollen constantly increasing. Grasses and ragweed have longer periods of pollination with either slightly higher or most often lower pollen production.&lt;/p&gt;

Cytokinins and abscisic acid in hardening winter wheat

1990 ◽  
Vol 68 (7) ◽  
pp. 1597-1601 ◽  
Author(s):  
John S. Taylor ◽  
Munjeet K. Bhalla ◽  
J. Mason Robertson ◽  
Lu J. Piening
Keyword(s):  
Triticum Aestivum ◽  
Abscisic Acid ◽  
Winter Wheat ◽  
Leaf Tissue ◽  
Triticum Aestivum L ◽  
Early Spring ◽  
Growth Chamber ◽  
Late Winter ◽  
Sequence Of Events ◽  
Freeze Dried

During overwintering in a northern climate, winter wheat goes through a hardening process, followed by dehardening in late winter – early spring. This sequence of events may be partially controlled by changes in endogenous hormone levels. Crowns and leaf tissue from field grown winter wheat (Triticum aestivum L. cv. Norstar) seeded at the beginning of September were collected and freeze-dried at monthly intervals during the winters of 1985–1986 and 1986–1987. Material was also sampled and freeze-dried from seedlings grown in a growth chamber under hardening conditions (21 °C for 2 weeks plus 3 °C for 6 weeks) or nonhardening conditions (3 weeks at 21 °C). The tissues were analysed for cytokinins and abscisic acid. Cytokinin levels, measured with the soybean hypocotyl section assay, declined from October onwards and then rose to a peak in late winter (January and February, winter 1986–1987; February and March, winter 1985–1986), subsequently declining again. Abscisic acid, quantitated as the methyl ester by gas chromatography with an electron capture detector, increased in level from October to December, then decreased to a relatively low level between January and March. Hardened seedlings from the growth chamber contained significantly higher abscisic acid levels and significantly lower cytokinin levels than did the nonhardened seedlings. Key words: abscisic acid, cytokinins, hardening, Triticum aestivum, winter wheat.

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