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Internal fruit rot of sweet pepper grown in glasshouses has been an increasing problem worldwide since around 2000. In the UK, surveys in 2007 showed infected fruits were present in many crops at levels from 1 to 37%. The disease causes some losses on production nurseries but more importantly also causes rejection by packers and complaints by supermarkets. Losses vary greatly between crops and seasons, and growers are generally unaware a problem may be present until harvest or postharvest. The fruit rot arises through infection of flowers (Yang et al., 2010). Several Fusarium species have been associated with the disease in the UK, notably F. lactis and F. oxysporum. Observations in commercial crops indicate the disease is favoured by high humidity. At present there is no effective method of control. This experimental work aimed to reduce losses to Fusarium internal fruit rot through increased knowledge of factors associated with a high incidence of the disease and use of biofungicides and fungicides to control flower infection.

Botrytis cinerea Pers, ex Fr. can cause diseases on both cane and fruit on raspberry. Previous observations in field crops led to formulation of the hypothesis that infection of canes arose from invasion by mycelium from the petioles of infected leaves and that only mature and old leaves are susceptible. Inoculation studies in protected crops were conducted to investigate infection of raspberry leaves and canes by B. cinerea with a particular emphasis on determining the timing of cane infection in relation to leaf infection. The results obtained in protected crops indicated that cane age rather than the leaf age per se influences the susceptibility of leaves; leaves on young canes were less susceptible to botrytis infection than those on old canes. On older canes, leaves of all ages, ranging from young expanding to old senescent, were equally susceptible. The overall incidence of cane infection from inoculation of leaves was very low; most of cane infection was likely to have resulted from the direct infection of canes and not through invasion via the petioles of infected leaves.

Botrytis cinerea causes disease on both the fruit and cane of raspberry. The incidence of latent and post-harvest fruit botrytis was examined in 19 commercial open-field and protected crops. Many samples showed a high incidence of infected fruit (>50%), even on protected crops sprayed with fungicides. Differences between open-field and protected crops, between sprayed and unsprayed crops and between two varieties (GLen Ample and Tulameen) were not statistically significant. The incidence of latent infection by B. cinerea in unripe fruit did not correlate with the incidence of botrytis fruit rot developing on ripe fruit. Experiments were conducted in two commercial crops to investigate whether the removal of Lateral Leaves and thinning of primocanes during the flowering and fruiting period could reduce the incidence of fruit and cane infection by B. cinereo. Canopy manipulation resulted in considerable decreases in humidity inside the canopy at one site, where the original cane density was very high, (20 canes/m) and not at the second site where cane density was lower (10 canes/m). Canopy thinning did not significantly reduce the incidence of fruit botrytis at either site but reduced the incidence of leaf and cane infection in the dense crop. Results suggest that a significant reduction of cane infection by canopy manipulation can be realised for situations where cane density and disease pressure are high. The present studies suggest that in dense canopies in a protected crop, cane Lesions are more likely to result from direct infection of canes by the pathogen, although the pathogen can readily invade wounds on canes, including de-leafing wounds.

Smoulder, caused by Botrytis narcissicola, is the most widespread foliar disease of narcissus (Narcissus cultivars) in the UK and causes significant losses in bulb and flower yield. A range of current and novel fungicide treatments was examined to determine if control of the disease could be improved and to measure the effect of treatments on bulb yield. In assays on pot-grown plants, carbendazim + flusilazole, epoxiconazole, iprodione + thiophanate-methyl, tebuconazole and vinclozolin reduced lesion size by more than 90%, compared with untreated plants, when applied 1 day before inoculation with the fungus; vinclozolin and tebuconazole were also effective when applied 2 days after inoculation. In field experiments in Cambridgeshire and Lincolnshire, significant reductions were observed in secondary smoulder symptoms (leaf lesions and stem rot) following fungicide sprays. Spray programmes of the novel fungicides azoxystrobin, cyprodinil, kresoxim-methyl, tebuconazole and pyrimethanil were as effective, or more so, than the standard treatments (chlorothalonil, vinclozolin) used by growers. Mixtures of carbendazim + tebuconazole and azoxystrobin + tebuconazole also gave effective control of smoulder. Programmes of four to six sprays, using two or three fungicides with different modes of action, applied alternately, reduced smoulder by 35-69% and increased bulb yields by 7-59%. Although treatment around and after flowering resulted in the greatest control of secondary smoulder, treatment before flowering was required for the highest bulb yields. The choice of fungicides for use in spray programmes to provide effective and reliable control of smoulder, and the possibility of control using fewer sprays, are discussed. [ABSTRACT FROM AUTHOR]

A detailed study of conidial germination, germ-tube growth and the formation of infection structures in Phoma clematidina , the causal agent of clematis wilt, is described for two clematis varieties differing in disease resistance. On both the resistant and susceptible varieties, the fungus entered leaves and stems by direct penetration of the cuticle, often, but not always, following the formation of infection structures. More germ tubes per conidium were formed on the susceptible host, but these germ tubes were on average shorter than on the resistant host. Although germ tubes regularly entered the plant via trichomes, stomata were not found to be sites of entry. Following penetration of the cuticle of resistant plants, germ-tube growth was sometimes restricted to the subcuticular region, and halo formation occurred at the sites where penetration was attempted. Subcuticular growth and halo formation were not observed on susceptible plants. These observations may partly explain the resistance of small-flowered clematis varieties to P. clematidina . [ABSTRACT FROM AUTHOR]

Fosetyl-Al applied once, as a spray in the autumn after fruit picking, gave very good disease control and significantly increased the number of healthy roots and marketable fruit yield in 2-year-old strawberry plants, cv. Redgauntlet. Fosetyl-Al applied twice, after fruit picking and in spring, further increased the number of healthy roots, but yields were not significantly better than the single treatment. A half-rate spray of fosetyl-Al plus a half-rate drench of captafol applied after picking and in spring gave good disease control and a yield significantly better than all other treatments. In the same crop the following year, both of the twice-yearly treatments gave a significant reduction in red core recorded in September and the two-fungicides treatment gave a significant increase in fruit yield. In a second trial, a half-rate spray of fosetyl-Al plus a half-rate drench of captafol applied after picking and in spring again gave good disease control and significantly increased fruit yield. Timing fungicide application, both after fruit picking and in spring according to root development (5 mm or 15-20 mm), had no effect on the level of red core control and little effect on fruit yield. The half-rate fosetyl-Al plus half-rate captafol treatment was significantly less effective when captafol was applied as a spray rather than as a drench. [ABSTRACT FROM AUTHOR]

The range of symptoms caused by the narcissus smoulder pathogen Botrytis narcissicola is described. Healthy bulbs inoculated with B. narcissicola, or grown in soil containing sclerotia, showed lesions in the shoot on emergence (primary symptoms). In commercial fields, B. narcissicola was commonly isolated from the bulb neck and leaf sheath of plants with primary symptoms. Plants infected by B. narcissicola one season, either with natural primary symptoms or following artificial inoculation, frequently emerged with smoulder symptoms the following season. About 40% of B. narcissicola sclerotia were viable after burial in soil for 9 months. It is suggested that infected bulbs and sclerotia present in soil are the major sources of smoulder outbreaks. Secondary infection by conidia was enhanced by damaging leaves, and open stalk ends left after flower picking were found to provide an important site for infection development. B. narcissicola was isolated from bulb necks when plants with symptoms of secondary infection had died down. A disease cycle is postulated and suggestions for controlling smoulder are discussed with reference to the cycle. [ABSTRACT FROM AUTHOR]

Cultures of Botrytis isolated from narcissus were readily identified from their sclerotial characteristics on potato dextrose agar. B. narcissicola was isolated most frequently from typical smoulder symptoms. Infection of narcissus by isolates of B. narcissicola and B. cinerea was investigated using conidial and mycelial inocula on detached leaves and bulb scales. Only mycelial inocula of B. narcissicola isolates consistently caused spreading lesions. Conidial inocula of both species typically failed to colonise healthy narcissus tissue when inoculated in sterile distilled water but B. narcissicola caused some spreading lesions after tissue damage, in senescent tissue, or following the addition of certain nutrients (including pollen) to inoculum droplets. Cultivars differed in the resistance of their bulb scales. The specificity of Botrytis-narcissus interactions is discussed. [ABSTRACT FROM AUTHOR]

The powdery mildews Erysiphe cynoglossi and E. howeana, causing disease on borage (Borago officinalis and evening primrose (Oenothera biennis), respectively, are reported for the first time in Britain. [ABSTRACT FROM AUTHOR]

The article reports of impatiens downy mildew in Great Britain. Infected leaves appeared paler green than normal, with a white, downy growth developing on lower surfaces. Symptoms were initially inconspicuous but lower leaf surfaces quickly became covered with fungus-like growth and premature leaf fall was common. Detailed examination of a representative sample revealed the sporangiophores were monopodially branched at the base, individual branches did not arise in a distinct pattern, apical branchlets were at right angles to the main axis and there was no apical thickening.

Examines the occurrence of wilt disease in a glasshouse crop of column stocks or Matthiola incana in England. Development white fungal growth; Detection of Fusarium oxysporum; Symptoms of the wilt disease.