Effects of fungal diseases on linseed (Linum usitatissimum) growth and yield, 1988–1990

Abstract

SUMMARYEffects of diseases on growth and yield of linseed (cv. Antares) were assessed by controlling diseases with fungicide treatments in field experiments at Rothamsted from 1988 to 1990. Fungicide seed treatments decreased the incidence of Alternaria lesions on cotyledons and stem bases of emerging seedlings in 1989 but decreased emergence in 1990. The incidenceof leaf browning, associated with Alternaria spp. and Botrytis cinerea, was less in 1989 and 1990 than in 1988 when the period, in July, between flowering and harvest was wet, but the incidence of powdery mildew was greater in 1989 and 1990 than in 1988. Fungicide spraysdecreased leaf browning in 1988 and powdery mildew in 1990. In 1988 there were more capsules per plant and the crop was taller than in either 1990 or 1989, when July and August were hot withperiods of dry weather. The incidence of plants with dark brown stems, associated with Verticillhun dahliae, was greater in 1989 and 1990 than in 1988, but was not greatly affected byfungicide treatments. The incidence of Alternaria linicola on sepals, capsule cases and seed from capsules sampled before harvest was decreased by fungicide treatments. Other fungi isolated from these tissues included A. alternata, A. infectoria, B. cinerea, Fusarium spp. and V. dahliae. Yields of grain and oil were increased by fungicide treatments in all three years, but the yield increases were greatest in 1988 when fungicide treatments also increased 1000-grain weight. The incidence of fungi on the harvested seed was not greatly affected by fungicide treatments.

Effects of diseases on the growth and yield of spring linseed (Linum usitatissimum), 1988–1998

“…Thus, both yield and yield losses associated with diseases were greatest in years when the period between flowering in June and harvest in AugusdSeptember was wetter than average, whereas in drier years there appears to have been little effect of diseases on yields. These yield loss relationships occurred because wet weather at this time favoured the development of leaf browning, grey mould and pasmo, the most serious disease problems, whereas powdery mildew, which was favoured by dry weather, has little effect on yields (Fitt & Ferguson, 1993). The decrease in yield associated with increase in summer temperature in these experiments may have been related to effects of verticillium, which is favoured by high soil temperatures (Fitt et ul., 1991) but these effects could not be assessed by use of fungicide sprays.…”

“…Field experiments using fungicides to control foliar diseases have shown that such diseases can affect growth and decrease yield of spring linseed (Fitt et al, 1991;Fitt & Ferguson, 1993;Fitt & Harold, 1995) but the frequency of damaging epidemics has not been determined. Furthermore, there is little information about relationships between measurements of disease severity, such as the percentage area of leaves, stems or capsules affected by lesions at different times in the season, and plant growth or yield loss.…”

“…Use of fungicides has greatly increased yields in such wet seasons through control of Alternuria spp. and B. cinerea (Turner, 1987;Fitt & Ferguson, 1993). However, development of powdery mildew (Sphaevotheca lini Tsvetkow) is favoured by dry weather in June/July and disease caused by l?…”

Temperature and Effects of Seed‐borneBotrytis cinereaorAlternaria linicolaon Emergence of Linseed (Linum usitatissimum) Seedlings

“…These differences may occur because B.cinerea generally survives in the seed testa as thin-walled hyaline hyphae, which are easily killed by surface sterilization (Fitt and Ferguson, 1993), whereas A. linicola survives as thick-walied resting hyphae (Maude, 1996) which penetrate the seed more deeply and are not easily killed by stirface sterilization. Thtis, these results suggest that seed-borne inocuitim of B, cinerea from stored linseed seed is probably not important as an over-witttering stage for this pathogen or as a mechanism for dispersal in the UK, although it has caused problems in fibre flax crops in the Netherlands ( Van der Spek, 1965).…”

“…Both pathogens are spread by windborne spores which can infect the crop tissues between flowering and harvest, especially when wet weather occurs during this period (Van der Spek, 1965;Vloutoglou et al, 1995b). A combination of these two diseases on leaves, flowers and capsules consistently caused losses of up to 50% in wet seasons in field experiments at Rothamsted (Fitt and Ferguson, 1993). During capsule maturation, splits appear in the capsule walls and these pathogens can easily enter through them to colonise the seeds.…”