ÜBER DIE ANFLUGDICHTE VON APHIDEN AUF FARBIGE SALATPFLANZEN 1,2

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Abstract
Blattläuse, u.a. Aphis fabae Scop, und Myzus persicae Sulz., landen auf gelblichen und grünen Sommersalaten signifikant häufiger als auf braunblättrigen. Die Anlockwirkung im Gelb‐Grün‐Bereich wird gesteigert, wenn die Farbe der Umgebung zu der des Salates kontrastiert (nackter Erdboden, weißlich‐grüner Winterweizen), während die Hemmung des Landereizes durch rotbraune Färbung davon kaum beeinflußt wird. Wahrscheinlich erkranken braune Salate deshalb weniger an Salatmosaik als gelbe und grüne, weil die Häufigkeit der Vektorenbesuche auf ihnen herabgesetzt und damit die Gefahr einer Virusinfektion durch blattlausübertragbare Viren verringert ist.Summary: ON THE LANDING FREQUENCY OF APHIDS ON COLOURED LETTUCE PLANTSDifferent coloured summer lettuces of the Quedlinburg Assortment (Saatzuchtleiter Fabig) allowed tests of the landing reaction of aphids, especially Aphis fabae Scop, and Myzus persicae Sulz., on plants of different colours to be compared with Moericke's findings using artificial coloured carriers. Direct captures of landing aphids, as described by H. J. Müller (1962), showed twice as many aphids, and from three to five times as many Myzus persicae, on green varieties Ramses and Rhenania and on yellow‐green Rudolfs Liebling than on the almost completely dark reddish brown Indianerperle. However the brown‐red but yellow‐green striped variety Pirat was landed upon by almost as many aphids as the green varieties.When the yellowish and yellow‐green varieties Rudolfs Liebling and Ramses were planted within a plot of whitish‐green young winter wheat, many more aphids alighted than would have been expected if chance only had operated. Fewer alighted on the whitish‐green Rhenania in the same situation. The dark brown Indianerperle received few aphids when grown among wheat. The landing impulse on yellow and green lettuces is thus increased when their colour contrasts with that of the surroundings, but this does not apply to the brown varieties.Colourless glass dishes, filled with water, were used as traps and set in the middle of plots of different coloured lettuces (using many replicates during the whole growing period) caught only twice as many aphids among yellow as among green or brown varieties; this was due to an edge effect. The stronger the impulse to land on a lettuce variety, the more aphids are caused to land at the edge of the plot. Thus only a few reach the trap in the middle. When yellow dishes replace the colourless traps, a much higher number of aphids is caught among reddish‐brown lettuces.Brown lettuce varieties are known to show a lower incidence of lettuce mosaic than yellow or green varieties. This is presumably due to the smaller number of aphids alighting, thus diminishing the chance of infection.

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