Abstract:
Aphid landing rates, species composition and abundance on lucerne (Medicago sativa), maize
(Zea mays), soybean (Glycine max), wheat (Triticum aestivum) and potato (Solanum tuberosum)
were determined in a small-scale field trial to identify potential crops as prospective border
plants for seed potatoes to reduce the spread of Potato virus Y (PVY) in South Africa. Aphids
were sampled using green bucket traps to estimate aphid landing rates, whereas leaf counts
and sweep-netting were used to identify colonizing species. Of the 34 species or species
groups collected with green bucket traps, 18 were previously known vectors of PVY. The
most abundant vector species or species groups were Acyrthosiphon pisum, Macrosiphum
euphorbiae, Metopolophium dirhodum, Myzus persicae, Rhopalosiphum padi and Sitobion spp. The
only other species that occurred in high numbers, but whose vector status is unknown, were
Acyrthosiphon kondoi and Tetraneura fusiformis. Landing patterns suggest that A. kondoi,
A. pisum and M. dirhodum may be able to discriminate between plant species and select their
preferred host plant, if available within a habitat patch, in the pre-alighting phase, whereas
other species such as R. padi seemed less selective. Results on aphid landing together with
colonization of the crops evaluated suggest that maize and wheat show the highest potential
as possible crop border plants in regions where aphids colonizing Poaceae, and lucerne in
regions where aphids colonizing Fabaceae are abundant. Soybean appears to be less suitable
because cultivars with a high trichome density, which reduces colonization by aphids, are
preferentially planted in South Africa.
