Attack of the Aphids

In parts of New Zealand, restaurants and other businesses in the food industry have had to throw away tons of lettuce since April, due to infestation by the appropriately named Lettuce Aphid (Nasonovia ribis-nigri). The is the first mention I've seen of this aphid in New Zealand, though parts of the western U.S., including California, have also had problems with infestations over the past several years. Lettuce aphids are suspected to be native to the northern hemisphere. The current fear in New Zealand is that the invasion will spread to plant species in the genus Ribes, since they are the preferred hosts on which the aphids lay their eggs.