Sharp eyespot disease of cereals.

SIGLEAvailable from British Library Document Supply Centre- DSC:DX86316 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Effects of fungicide timing on the severity of eyespot on winter wheat or winter barley inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides

Plots of winter wheat or winter barley inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides were sprayed with carbendazim plus prochloraz either at growth stage (GS) 30/31, or at GS 33/39 (wheat) or at GS 51 (barley). At GS 30/31 > 75% of the shoots of both wheat and barley had eyespot lesions in 1986 and 1987 and there were, on average, < 2 leaf sheaths left to penetrate before the fungus reached the stem. In 1988, the incidence of eyespot was 10–50% at GS 30/31 and there were three leaf sheaths left to penetrate. Spray treatments generally reduced the severity of eyespot lesions on stems at GS 83 in both W-type and R-type plots of wheat and barley. The early spray treatment (GS 30/31) generally controlled eyespot better than the late treatment in both W-type and R-type plots. Spray treatments often increased yield, but differences in yield responses were not clearly related to differences in control of eyespot.Peer reviewe

The development of eyespot on stems of winter wheat and winter barley in crops inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides

In three contrasting seasons (1986-1988), W-type isolates of Pseudocercosporella herpotrichoides generally became established on stems of winter wheat or winter barley plants more rapidly than did R-type isolates. After growth stage (GS) 30/31, eyespot lesions became visible on stems more quickly, and by GS 71 both the incidence and severity of stem lesions were generally greater in plots inoculated with W-type isolates than in plots inoculated with R-type isolates. However, by harvest there was little difference in eyespot incidence or severity between W-type and R-type plots in 1987 or 1988; in 1986, the difference was maintained until harvest. In 1986, the winter was cold and basal leaf sheaths of wheat died quickly in the spring; a severe eyespot epidemic did not develop although the leaf sheaths of many plants were severely infected at GS 30/31. However, the incidence and severity of eyespot were greater in early-sown than in late-sown plots. In 1987, the winter was mild and basal leaf sheaths of wheat and barley did not die rapidly. The leaf sheath severity score was 3-4 at GS 30/31 and thereafter P. herpotrichoides steadily penetrated the remaining leaf sheaths and became established on the stem so that a severe epidemic had developed by GS 71. In 1988, when the crops were late-sown and the winter mild, a late severe epidemic developed even though the leaf sheath severity score was only 1-3 at GS 30/31. On barley in 1987, the differences between W-type plots and R-type plots were greater than on wheat, but in 1988 there were few consistent differences. The effects of seed rate on eyespot incidence and severity were not significant in 1987 or 1988, although eyespot was generally less at the low than the high seed rate.Peer reviewe

Prediction of Eyespot Severity on Winter Wheat or Winter Barley Inoculated with W-type or R-type Isolates of Pseudocercosporella herpotrichoides

In crops of winter wheat (1986-88) or winter barley (1987-88) inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides and sown on different dates (1986) or at different seed rates (1987, 1988) eyespot epidemics developed in different ways. Methods of measuring eyespot incidence/severity during crop growth were compared for their ability to predict eyespot severity at grain filling. Regressions were calculated for eyespot severity score at GS 71 on earlier measurements, either at GS 30/31 (11 methods) or from GS 22 to GS 65 (3 methods). Based on measurements at GS 30/31, all the methods predicted eyespot severity at GS 71 well in plots of winter barley inoculated with W-type isolates (r, 0.83-0.97) but the accuracy of predictions in plots inoculated with R-type isolates was very variable (r, 0.09-0.71). Predictions for 1987 and 1988 were less accurate in wheat than in W-type plots of barley, but did not differ between W-type and R-type plots (r, 0.70-0.89). When the wheat data for 1986 were also included predictions were less accurate, especially in R-type plots (r, 0-0.59). Generally, it was easier to predict eyespot severity at GS 71 in W-type than in R-type plots, especially in barley and in wheat before GS 37/39. Predictions of eyespot severity at GS 71 based on measurements before GS 25 were inaccurate for both wheat and barley. After GS 25 the accuracy of the prediction was generally good in W-type plots and did not improve greatly except in wheat after GS 59. However, there was a steady improvement in the accuracy of the prediction in R-type plots of barley from GS 24 to GS 53. Assessments of eyespot incidence on stems predicted eyespot severity at GS 71 more accurately than assessments on leaf sheaths on wheat after GS 37/39, but were not as good on barley until GS 53.Peer reviewe

Assessment of eyespot and other stem base diseases of winter wheat and winter barley

A dichotomous key is presented which describes the symptoms of eyespot, sharp eyespot and brown foot rot (Fusarium spp.) on winter cereals at the seedling through to adult plant growth stages. Sampling and disease assessment methods for these diseases are also described

Development of eyespot on winter wheat in the UK. II : Infection and lesion development on stems in relation to thermal time

Non peer reviewe