Nettle extract effects on the aphid Myzus persicae and its natural enemy, the predator Macrolophus pygmaeus (Hem., Miridae)

The effect of water extract of Urtica urens L. on the biological characteristics and population parameters of Myzus persicae (Sulzer) and its natural enemy, the polyphagous predator Macrolophus pygmaeus (Rambur) was investigated on eggplants. Plant material was extracted in deionized water (1 : 5 w/w) for 24 h. Three applications were made at 5-day intervals using the nettle extract, with deionized water as the control. The effect of the extract on survival, duration of nymphal development, pre-reproductive period, fecundity and longevity of both insects was studied at conditions of 25 +/- 1 degrees C, 65 +/- 5% relative humidity and photoperiod of 16 : 8 h (light : dark). The results showed that the application of nettle extract significantly reduced the fecundity of M. persicae (20% on average) but did not result in a substantial lowering in its intrinsic rate of population increase. However, the predator's biological characteristics and population parameters were not affected by the application of this plant extract. The importance of these results for the use of nettle extract in the management of M. persicae along with its compatibility with the use or conservation of M. pygmaeus is discussed.