|Authors: ||R. Rancane, M. Eihe, L. Jankovska|
|Keywords: ||Venturia inaequalis, warning system, infection risk, fungicide application terms|
Adaptation of the apple scab simulation model RIMpro in integrated plant protection in Latvia was carried out at the Latvian Plant Protection Research Centre during 2003–2006. The aim of investigation was to verify conformity of scab infection risk given by RIMpro to real scab ascospores discharge intensity by use of microscope slide spore traps, as well as to determine the risk border value as signal for necessary fungicide applications.
The spraying program was based on the use of the curative fungicide Chorus 75 WG (a.i. cyprodinil) during 2–4 days after presumed RIMpro infection risk signal as well as noteworthy amounts of scab ascospores on the slides.
Furthermore the appearance and extension of scab on apple leaves and fruits was evaluated.
The terms of noteworthy RIMpro infection risk signals and ascospores discharge coincided in most cases, but intensity level of both indices was not comparable.
Difficulties caused specification of risk value. 300 RIM, presumed in Central Europe, was unconformable.
During trial years the risk value was decreased until 100 RIM (2006); however, apple scab still extended considerably even when fungicides where applied following to such signals.
It was presumed that showings above 50 or 70 RIM have to be considered as the risk signal for fungicides application.
The infection agent was more aggressive, adapted to rigorous weather conditions during a comparably short primary infection period.
In trial years ascospores discharge began within May 9th to 19th and lasted one month with a precipitation amount of 47–64 mm.
The amount of released ascospores varied widely between years from 20 to 200 spores per field of vision during the discharge period.
There were 4–6 critical infection periods with risk value above 50 RIM during all primary infection period yearly.
Subsequently, fungicides applications during the primary scab infection period including the first protective spray before ascospores discharge will be necessary 5–6 times.
In some cases two infection periods could be covered by one application.
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