The use of weather data and counts of aphids in the field to predict the incidence of yellowing viruses of sugar‐beet crops in England in relation to the use of insecticides

Abstract

SUMMARYPartial regression equations were calculated that relate the mean percentage of plants infected with yellowing viruses (beet yellows and beet mild yellowing viruses) in sugar‐beet crops at the end of August to the number of days during January, February and March when temperatures fell below – 0.3 °C (31‐5 °F) and the mean temperatures in April, for the 21 yr, 1951–71, using weather records from Rothamsted Experimental Station. Regression analyses were also made to find the effect of other factors including mean and minimum temperatures for the same months, and also mean counts of ‘green aphids’, mainly of the vector Myzus persicae, on sugar‐beet plants during May and June. Significant relationships were established with all factors, but ‘frost‐days’ and April mean temperatures accounted for the greatest percentage of the variance in yellows incidence.The calculations were made separately for the years from 1951 to 1958, when no routine advice was given to farmers about aphid control, and 1959–71 when a ‘spray‐warning scheme’ was in operation, and many crops were sprayed at critical times to prevent aphid‐ and virus‐spread. Weather factors had the same effects in both periods, but for any particular weather less virus was spread in the second period than in the first, although there were sufficient aphids, i.e. the numbers expected from the prevailing weather conditions. There was no evidence that insecticide treatment used in any one year affected aphid‐incidence in subsequent years.Regression analyses on weather variables were also calculated separately for each of seventeen beet‐sugar factory collection‐areas, using weather records from local weather stations, and also the Rothamsted weather records. Unexpectedly, the fit of the regressions was always better with Rothamsted weather data than with local weather records. Mean yellows‐incidence for the different factory areas declined from south to north, and there was a linear relationship with the square root of the latitude above 50 °C. At the same time the correlation coefficients relating yellows‐incidence to ‘frost‐days’ became smaller and less significant, and those showing dependence

Epidemiology of insect‐transmitted plant viruses: modelling disease dynamics and control interventions

“…Analysis of vector numbers and activity in relation to weather variables led to practical forecasting schemes being developed for some viral diseases, e.g. beet yellows (Watson & Healy, 1953; Watson et al ., 1975) and barley yellow dwarf virus (A'Brook, 1983). Multivariate methods were used to associate disease incidence of non‐persistent viruses with the range of aphid vector species trapped (Madden et al ., 1983).…”

Decision making in controlling virus yellows of sugar beet in the UK

“…In the early years, simple relationships were developed between temperatures in winter and early spring and virus yellows incidence at the end of August 21. Subsequently, Watson et al 22 established the first forecast model for predicting virus yellows incidence. This model used the number of frost days (ie when the minimum temperature over grass fell below −0.3 °C) and the mean April temperature at Rothamsted Experimental Station (now Rothamsted Research) in Hertfordshire.…”

Overwintering of peach‐potato aphid and severity of attacks in sugar beet in relation to winter and spring temperature

“…They do overwinter anholocyclically in clamps, however, which are the principal sources of infestation (ENGSBRO 1970;HEIE 1959). Overwintering in clamps is of major importance for how widespread the first attacks will be in the beet fields in spring (BALE et al 1988;WATSON et al 1975). This overwintering depends primarily on the temperature during the winter months (BROADBENT et al 1949).…”

“…This overwintering depends primarily on the temperature during the winter months (BROADBENT et al 1949). The spring temperature is one of the most essential factors affecting severity of attacks in late spring and early summer (WATSON et al 1975). This paper attempts to clarify the relationship between peach-potato abundance in beet fields with winter and spring temperatures.…”