Aphids cause significant losses in many agricultural crops
and in many cases cause repeated insecticide sprays,
which increase the risk of resistance. Therefore, other
alternatives are needed to control them. The toxic, antireproductive,
and feeding deterrent effects of a mannosebinding
lectin isolated from bulbs of
Phycella australis
Ravenna (Amaryllidaceae), named
Phycella australis agglutinin
(PAA) was assayed on nymphs of the aphids
Acyrthosiphon pisum
Harris and
Myzus persicae
Sulzer fed
with an artificial diet. After 72 h of PAA exposure, lethal
concentration (LC
50) values were 109 and 313 μg mL
-1 for
A. pisum and
M. persicae, respectively, while LC
90 values
were 248 and 634 μg mL
-1. Sub-lethal concentrations
of PAA significantly reduced the aphid fecundity at a
concentration of 80 μg mL
-1. Only a total of 5.7 descendants
per female were recorded for
A. pisum (32% control
progeny) and 12.4 for
M. persicae (39% control progeny).
Acyrthosiphon pisum was strongly deterred by PAA under
choice conditions, as after 72 h exposed to 80 μg PAA mL
-1
of diet, the feeding deterrent index was 0.91 for
A. pisum
and only 0.38 for
M. persicae. In conclusion, the mannosebinding
lectin isolated from bulbs of
P. australis showed
acute and chronical insecticidal activity against the pea and
green peach aphids.
