The effect of sprays of thiophanate–methyl on cane diseases and yield in red raspberry, with particular reference to cane blight (Leptosphaeria coniothyrium)

Spur blight (Didymella applanata), cane botrytis (Botrytis cinerea) and cane blight (Leptosphaeria coniothyrium) were studied in two consecutive seasons in unsprayed raspberries and in plots sprayed with thiophanate-methyl in the first season alone, (a) twice pre-harvest, (b) twice post-harvest, or (c) twice pre- plus twice post-harvest. Pre-harvest, but not post-harvest sprays, gave moderate control of both spur blight and cane botrytis; both diseases occurred mainly on the lower halves of canes, the latter being the less common. Cane blight occurred at the base of canes where they were wounded by old cane stubs. In the first year it was severe; 37% of canes died before harvest in the unsprayed plots. The three spray programmes all decreased cane death due to cane blight and they all increased yield by c. 45% even in those plots sprayed post-harvest where spur blight was severe and not controlled. Clearly this last disease, despite its high incidence, had no effect on potential yield in this experiment. In the second year cane blight was common but less severe and the incidence of its lesions was reduced similarly by all programmes, but only 4% of canes died in control plots. Analysis of the potential yield and the sizes of lesions caused by L. coniothyrium in canes inoculated at fortnightly intervals in the previous year showed that potential yield loss occurred only when lesions girdled canes. A bimodal distribution in the lesion sizes, measured by length or girdling, indicated some endogenous control of lesion development which might explain the marked differences in the effect of cane blight on potential yield in two seasons.     

Effects of straddle-harvester design on cane blight (Leptosphaeria coniothyrium) of red raspberry

A new fruit catching device developed for raspberry straddle harvesters to reduce wounding of young canes and their consequent infection by Leptosphaeria coniothyrium was tested. During picking the young canes were contacted only by the foam rubber on a pair of belts which moved backwards along the harvester at the same speed that the machine advanced. The incidence of canes with cane blight lesions in 1981 was 18% following the use of the new device in 1980, and 79% following the use of a conventional commercial harvester equipped with overlapping metal fruit-catching plates. In comparison with the latter plates, the new device avoided wounding the cane surface directly: when the belt marks on these canes were inoculated with mycelium, however, the disease incidence was 77%. The new device caused wounds in 1980 by ripping leaves from nodes. In comparison with the commercial harvester the new device led to smaller lesions in 1981 and a lower percentage of canes dead above the fruit-catching zone. A modified new catching device tested in 1982 made barely detectable pressure marks on the young canes without bruising them. Only 6·6% of these canes developed vascular lesions after inoculation, an incidence similar to that for unwounded control canes (2·5%). The modified new device is advised for regions prone to cane blight where the cropping system has young and fruiting canes growing together.     

Cane blight (Leptosphaeria coniothyrium) in mechanically harvested red raspberry (Rubus idaeus)

Leptosphaeria coniothyrium, the cane blight pathogen, was the fungus most commonly isolated from vascular lesions developing from mechanical harvester wounds on first-year red raspberry canes. When inoculated to scalpel wounds, it induced similar lesions which were later associated with bud failure and cane death as were infected wounds on machine damaged canes. Cane resistance increased from May until August, inoculations later than July inducing only small lesions and rarely causing bud failure.     

Vigour control, an integrated approach to cane, pest and disease management in red raspberry (Rubus idaeus)

The first flush of young canes of red raspberry (Rubus idaeus) was removed at different dates in spring, using the contact herbicide dinoseb. In comparison with untreated plots, cane removal increased fruit yield, controlled excessive cane vigour, and improved the health status of vegetative canes in a plantation infested by raspberry cane midge (Resseliella theobaldi). At the end of the growing season vegetative canes on treated plots were shorter and thinner, and sustained less physical injury than those on untreated plots. Access to the fruit at harvest was also improved. Reduced competition between fruiting and vegetative canes increased yield in the year of treatment by an average of 35%. Yield was not affected by date of cane removal, but growth of replacement cane was reduced below optimum when first flush cane was removed after mid-May. The later the canes were removed, the less was the incidence of pest and diseases. Cankers and lobate vascular lesions (‘patches’) resulting, respectively, from the feeding of first and second generation midge larvae (with associated fungi) affected fewer canes in treated than in untreated plots. Significantly fewer live larvae of R. theobaldi were recovered in the following winter from soil in plots treated on or after 11 May than from untreated plots. The main effect of vigour control on R. theobaldi and midge blight was that replacement canes provided fewer egg-laying sites (natural splits) than did the first flush canes on untreated plots. The incidence of spreading vascular lesions (‘stripes’) attributed to Leptosphaeria coniothyrium infecting either physical wounds (cane blight) or midge feeding wounds (midge blight) was substantially less in treated than untreated plots. Cane botrytis (Botrytis cinerea) and spur blight (Didymella applanata) were also less common in treated plots. Interactions between vigour control and pest and disease incidence are discussed in relation to the efficient management of cv. Glen Clova in eastern Scotland.     

The effect of temperature on the response of canes of red raspberry cv. Mailing Jewel to infection by Didymella applanata

A single population of container-grown red raspberry plants cv. Mailing Jewel was divided and grown in two environments prior to wound inoculating young canes with Didymella applanata in late July. The plants were then sub-divided and held in one of three contrasting post-inoculation environments. Various assessments were made to examine the effect on spur blight of the different environmental treatments. Inoculation of internodes showed that D. applanta produced longer lesions and more pseudothecia on canes grown in spring in an unheated glasshouse than on canes grown outside, but post-inoculation conditions had little effect on these aspects of disease. Petiole inoculations showed that dwarfing of axillary buds in the first season and lateral shoot failure in the year after infection were most serious on canes grown outside in spring but held at relatively high temperatures in August and September after inoculation. The results indicate that spur blight may have the potential to cause higher yield losses in areas with warmer spring and autumn conditions than those usually experienced in north-east Scotland.     

The Effect of Chitinase on Didymella applanata, the Causal Agent of Raspberry Cane Spur light

In vitro and in vivo studies were conducted to assess the efficacy of the two microbial chitinases Chi I (from Streptomyces sp.) and Chi II (from Serratia marcescens) on Didymella applanata (Niessl.) Sacc., the fungus which causes spur blight of raspberry (Rubus idaeus L.). D. applanata was isolated from canes of diseased raspberries in a plantation in Novosibirsk, Russia. In vitro, the effective concentration of Chi I that reduced the growth of D. applanata was 0.4 U/ml (p = 0.05), but Chi II had no influence on the growth of the fungus in medium. In inoculation experiments on raspberry canes, both chitinases at the rate 0.5 U/ml reduced fungal development. In plantation where canes were inoculated after spraying with chitinase, fruiting bodies of fungus failed to form in all enzyme treatments, whereas a significant number of these fungal fruiting bodies (12.8 per cm²) developed in control treatments lacking chitinases spraying. The chitinases reduced the size of lesions and limited the infection of internal tissues of canes. Field testing of Chi I under natural conditions showed a significant suppression of the independent spur blight. These studies form the basis for further evaluation of ecologically benign control measures for raspberry spur blight.     

Fungi on red raspberry from lesions associated with feeding wounds of cane midge (Resseliella theobaldi)

Two types of vascular lesion are described from the base of canes in plantations infested by raspberry cane midge ( Resseliella theobaldi ); (1) brown lobate lesions ('patches') confined to midge feeding areas, (2) brown lesions spreading proximally and distally from the point of infection ('stripes'). Either or both types of lesion may be presented in individual canes. Isolations from (1) produced principally Fusarium avenaceum ; isolations from tissues where (1) and (2) are contiguous gave Leptosphaeria coniothyrium and F. avenaceum ; isolations from (2) arising from old cane stub wounds in the absence of midge gave L. coniothyrium .
The important secondary role of fungi in the midge blight complex is confirmed, but the involvement of L. coniothyrium in the complex is unclear because it also infects stub wounds on midge-infested canes.     

Fungicide programmes for the control of spur blight, powdery mildew and grey mould on raspberry

Five sprays of dichlofluanid (0–1% a. i.) reduced spur blight (Didymella applanata) on canes and powdery mildew (Sphaerotheca macularis) on fruit more than five sprays of captan (0–1% a. i.). Omission of the first three applications resulted in little increase in disease but when the fourth (full bloom) application also was omitted the incidence of disease was comparable with that on untreated plants. The final (fruitlet stage) application did not further reduce disease incidence. Five sprays of dichlofluanid reduced grey mould (Botrytis cinerea) on stored fruit more than five sprays of captan. There was an increase in grey mould with progressive reductions in the number of sprays. Incidence on canes was slight and was unaffected by treatments. A programme of five dichlofluanid sprays applied at 14-day intervals until c. 2 wk before harvest and supplemented by a single early full bloom spray of either dinocap (0–025% a. i.), binapacryl (0–05% a. i.), triforine (0–025% a. i.), benomyl (0–025% a. i.) or replaced by benomyl (0–025% a. i.) all halved both the number of fruits infected by powdery mildew and the number of spur blight lesions on canes, compared with unsprayed controls. Six applications of any of the following fungicides at 7-day intervals from 23 May until 29 June 1977 reduced powdery mildew incidence on fruit, the last fungicide being particularly effective: dinocap (0–0125%), dichlofluanid (0–075%), binapacryl (0–025%), triforine (0–0125%), bupirimate (0–0075%), ditalimfos (0–01875%) and fenarimol (0–0036%). Only triforine and bupirimate reduced the incidence of mildew on shoots. Dichlofluanid, binapacryl, triforine and fenarimol all reduced the amount of spur blight on canes. The largest fruit occurred on plants sprayed with bupirimate, ditalimfos and fenarimol, and late ripening was associated with triforine treatments.     

Factors affecting the development of cane blight (Leptosphaeria coniothyrium) on red raspberries in Washington, Scotland and Germany

The effects of cultivar, virulence of isolates of Leptosphaeria coniothyrium, cane maturation and wound healing were examined in a series of inoculation experiments carried out over a 3–yr period in three countries in an attempt to explain why cane blight has caused serious yield losses in machine-harvested red raspberries in Europe, but not in the Pacific Northwest of America. Three isolates of L. coniothyrium from Puyallup (USA), Dundee (UK) and Dossenheim (FRG) were pathogenic on the three test cultivars Willamette, Malling Jewel and Glen Isla in all the experiments. Isolates and cultivars differed for aggressiveness and susceptibility respectively but their ranking was dependent on the test conditions and the differences were small and unlikely to explain the differences in incidence and severity of cane blight in raspberry fields in Scotland and the Pacific Northwest. Conditions at Dossenheim were most favorable for lesion development. At all sites, canes inoculated in late summer produced shorter lesions than those inoculated earlier. A delay between wounding and inoculation produced shorter lesions than simultaneous wounding and inoculation.     

Epidemiology of stamen blight of raspberry

Stamen blight, caused by Hapalosphaeria deformans Syd., is a disease of a number of Rubus species. It is widespread on commercial raspberries in Angus and east Perthshire. Evidence indicates that spread is from diseased flowers to the axillary buds of young canes during the summer and entry into these buds is complete by autumn, after which it is unlikely that the pathogen can be reached even by an eradicant fungicide. Attempts to infect young canes artificially, however, have failed. Rain splash appears to be of considerable importance in dispersal, but some spread by wind and pollinating insects could occur. Possible control measures are discussed and the importance of planting canes from spawn beds, where no flowering canes are kept, is emphasized.     

Further studies on resistance to Leptosphaeria coniothyrium in the red raspberry and related species

Rubus pileatus and its F₁ hybrids with raspberry (R. idaeus) were resistant to cane blight (Leptosphaeriu conioth-yriurn), but little resistance was obtained in subsequent backcross generations apart from a hybrid identified in the second backcross. Two hybrids from backcrossing R. coreanus to raspberry also showed resistance. R. pileatus and its F, hybrids produced hard growth, unlike that of raspberries, which may have been associated with a form of resistance that could not easily be transferred to commercial raspberry cultivars. Some of the genotypes used as parents showed intermediate levels of resistance and it is possible that the highly resistant genotype identified in the second backcross arose from a recombination of genes for resistance. Plants with pubescent canes (gene H) were up to 20% more resistant to mycelial inoculation than those with non-pubescent canes (gene h), and the percentage of machine-harvester inflicted wounds with disease symptoms that resulted from natural infection was also less in genotypes with pubescent canes. Many genotypes with intermediate levels of resistance suffered only limited damage from mycelial inoculation and so there are good prospects for breeding cultivars with an effective resistance, despite the limited value of R. pileatus as a donor species.     

Effects of Didymella applanata and Botrytis cinerea on axillary buds, lateral shoots and yield of red raspberry

The viability of axillary buds and the growth and potential yield of lateral shoots at nodes of red raspberry (Rubus idaeus) infected naturally by Didymella applanata or Botrytis cinerea were measured on excised nodes, decapitated nursery canes or on canes from fruiting plantations. In comparison with lesion-free nodes, buds at infected nodes were smaller and fewer of them were capable of growth when excised and ‘forced’, although the difference in growth between infected and uninfected nodes decreased during late winter. After February, those buds at infected nodes which were capable of forced growth did so as early and with a similar growth rate as those at lesion-free nodes. In April, 70% of buds at infected nodes were capable of growth compared with 94% of those at lesion-free nodes. When nursery canes of cv. Mailing Delight were decapitated above infected nodes the emergence of lateral shoots from the terminal infected node did not differ significantly from that at lesion-free nodes. On a range of farm sites in Scotland the emergence of shoots at infected nodes in the cropping region of canes was significantly poorer than from uninfected nodes but substantially better at infected nodes of cv. Glen Clova than at those of cvs Mailing Jewel and Mailing Orion. It is suggested that cv. Glen Clova is relatively tolerant of spur blight and cane botrytis. The length and potential yield of laterals which developed at infected nodes in the cropping region of canes in these three cultivars did not differ significantly from those at lesion-free nodes. In all tests there was no significant difference in growth at nodes infected by D. applanata and B. cinerea which may indicate a common mechanism for suppression of buds.     

Resistance to Botrytis cinerea in canes of Rubus idaeus and some related species

Mycelial inoculation of canes with Botrytis cinerea proved a useful method for assessing Rubus material for resistance. When canes were inoculated in summer resistant genotypes developed relatively small lesions which produced few small sclerotia in the following spring. The size of lesions in autumn generally provided the best discrimination between genotypes. Very strong resistance was found in several species, of which Rubus pileatus and R. occidentalis are the most useful for breeding; hybrids of raspberry with these species or with R. crataegifolius also had strong resistance. The resistance shown by a derivative of red raspberry cv. Chief was less strong, as was the resistance conferred by gene H, which determines cane pubescence.     

Disease measurement in a study of apple scab epidemics

The growth and yield increases in red raspberry which followed the repeated application of benomyl were not due to the suppression of pests. Benomyl had little effect on numbers of aphids and nematodes which, anyway, were insufficiently abundant to cause damage. Benomyl did, however, decrease the earthworm population. In the following years, when benomyl was no longer applied, significantly more canes died from midge blight in the plots treated most frequently with benomyl than in the untreated. This was probably a consequence of increased infestation by larvae of the raspberry cane midge (Resseliella theobaldi) in the benomyl-treated plots because benomyl increased the extent of cane splitting and hence the number of egg-laying sites for cane midge.     

The effect of cane management techniques on raspberry yellow rust (Phragmidium rubi-idaei)

The effects of various cane removal treatments on the epidemiology of Phragmidium rubi-idaei were studied in four experiments in infected raspberry plantations in Wales and Scotland. In 1981, removal of 15 cm high young canes either by cutting or by spraying dinoseb-in-oil reduced infection of a second flush of canes (replacement canes) compared to that of the first flush of canes on untreated plots of cv. Mailing Delight in Wales and of cv. Glen Clova in Scotland. In 1982, removal of 20 cm high young canes reduced infection of cv. Mailing Delight in Wales but in Scotland only removal of 60 cm high canes by cutting reduced infection of replacement canes. Removal of all fruiting canes and old cane stubs reduced rust infection of young canes, but removal of successive flushes of replacement canes did not reduce infection of lateral shoots on the fruiting canes. Dinoseb-in-oil applied to the bases of fruiting canes before emergence of young canes had no effect on infection of young canes in Wales or Scotland. The production of basidiospores was inhibited in vitro by dinoseb-in-oil at concentrations over 1.0 μg a.i./ml.     

Morphological assessment of water stressed sugarcane: A comparison of waterlogged and drought affected crop

Abiotic stress is recurrent occurring problem for sugarcane crop in terms of hindrance in achieving good and high production. In India, drought coverage is 2.97 lakh ha while 2.5 lakh ha under coverage of waterlogging which is one of the reasons behind low cane production and productivity due to alteration in metabolism, growth and development of the plant either in direct or indirect way. Therefore, we investigated the comparison of morphological losses in drought and waterlogging sugarcanes. Morphological parameters assessed were leaf length, leaf width, leaf area, stalk diameter, cane height, cane weight, internodes number and average internodal length. Also, total root weight, dry matter production of stalk, leaves and roots were observed. Results showed that leaf length was marginally increased in drought canes but it was not so in case of waterlogged canes. Besides, there was decrease in total root weight of sugarcane affected by drought by 16.99% while there was increase by 10.06% in waterlogging affected canes in comparison to normal grown canes. In cane height and stalk diameter, decrease by 18.28%, 7.52%, respectively, in drought and 11.41%, marginal decrease, respectively, in waterlogged affected canes as compared to normally grown canes. Average internodal length was also found to increase in both drought as well as waterlogged canes by 39.02% and 36.60%, respectively, in comparison to normal grown canes. Number of internodes was decreased more in drought affected canes than in waterlogged canes. This study concluded that there are higher morphological losses in sugarcane in drought condition than in waterlogging conditions with respect to normal grown canes.     

Differential occurrence of suberized sheaths in canes of grapevines suffering from black dead arm, esca or Eutypa dieback

Compared to healthy canes of Ugni-Blanc grapevines, structural modifications were observed in August in wood of growing canes showing foliar symptoms induced by esca and Eutypa Dieback. The observed changes appeared attenuated in canes of the current season sampled in December. In contrast, Black Dead Arm (BDA) did not induce significant modifications compared to healthy canes. A seasonal pattern in suberization was observed in control canes since a first suberized sheath occurred in mid-July at the interface xylem ring/pith and a second sheath was built up in August till December at the interface primary phloem/cortex. The same pattern was observed in BDA-attacked vines. In contrast, these continuous structural barriers were not formed in July and August in canes of the current season in grapevines attacked by esca or Eutypa dieback, but restored in the canes observed in December. These structural modifications were quantified and these events were discussed in the scope of plant physiology and pathogenicity of the implied fungi.     

Effects of spur blight (Didymella applanata) and premature defoliation on axillary buds and lateral shoots of red raspberry

Nodal lesions typical of natural infections of Didymella applanata were produced on young raspberry canes when wounded petioles were inoculated with mycelium. The buds which developed in the axils of these inoculated petioles were smaller and less likely to produce lateral shoots than those in the axils of delaminated or undamaged petioles, but only when the petioles were inoculated in the field before the end of July. This effect was more pronounced in cv. Mailing Jewel than in cv. Glen Clova which suggests that the latter is more tolerant of D. applanata. Sprays to control D. applanata in the cropping region of canes will probably be effective in Scotland only if applied before the end of July.     

Effect of machine-harvester wounds and Leptosphaeria coniothyrium on yield of red raspberry

When wounds on raspberry canes caused by machine harvesting in the previous year were infected by Leptosphaeria coniothyrium the potential yield per cane was reduced by 45% compared with that of uninfected hand harvested canes. However, the corresponding reduction per plot was less (c. 25%) because the yield of wounded but uninfected canes was not reduced and some canes were not wounded. The advantages and disadvantages of recording potential yield per cane are discussed.     

Effects of Plant Contact, Inoculation Pattern, Leaf Wetness Regime, and Nitrogen Supply on Inoculum Efficiency in Rice Sheath Blight

An experimental design was developed which allowed the measurement of inoculum efficiency (IE) represented by lesions of a leaf-borne disease such as rice sheath blight. In this design. IE is measured as the ratio of newly established lesions on trap plants relative to the inoculum present in a canopy, i.e. lesions artificially established on source plants, IE of the rice sheath blight pathogen, Rhizoctonia solani , was studied under semi-controlled conditions in which the effects of the following factors were measured; contact frequency among host tissues, amount and location of inoculum in the canopy, leaf wetness regime, and nitrogen content of the host plant. The conduciveness of these factors to sheath blight infection was measured in terms of IE which was expressed as the ratio of the density of daughter lesions on trap rice hills to the density of mother lesions on the inoculated quadrat hills. IE generally declined with the three successive batches of trap hills used in the experiments. It was significantly higher at closer plant spacings and under interrupted leaf wetness regimes. IE was not affected by the amount, nor by the location, of inoculum (mother lesions) in the canopy, but was significantly lower in hills with high total nitrogen content.