Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Testing damage thresholds for caterpillars and aphids on cabbage in five European countries - report on a collaborative project done in 1985 and 1986.

Abstract

Simple damage thresholds based on the percentage of cabbage plants infested with larvae of Pieris rapae, P. brassicae, Plutella xylostella and Evergestis forficalis and with cabbage aphids [Brevicoryne brassicae], were verified in field trials in Austria, UK, German Federal Republic, Ireland and Switzerland in 1985 and 1986. Pest control based on the tested threshold values reduced the average amount of insecticide (deltamethrin and pirimicarb at 5 ml and 75 g a.i./ha, respectively) used by 50% and the average number of sprays by 25%, in comparison with a regular spray programme at fortnightly intervals. Yield and the proportion of marketable cabbages did not differ significantly between threshold and routine plots. When insecticide was not applied, the weight of cabbage heads was reduced by up to 50% and that of unmarketable heads by 89% due to B. brassicae and up to 77% due to Lepidoptera larvae. In all experiments, the mean percentages of unmarketable heads due to attack by B. brassicae and Lepidoptera were 23 and 31%, respectively.