Today's post for National Invasive Species Week highlights two ambrosia beetles that are detrimental to certain trees. Ambrosia beetles are highly specialized beetles that excavate tunnels in usually weakened or dead trees and cultivate fungal gardens, which they feed upon. Below are two such invasive beetle-fungal complexes that are currently impacting trees and forests in California.
Walnut twig beetle and thousand cankers disease. Walnut twig beetle, Pityophthorus juglandis, is a tiny bark beetle that attacks only walnut trees. The beetle has been in California for many decades but recently became associated with a new fungus, Geosmithia morbida. The fungus kills the phloem and cambium of...
- Author: Jim Downer
As we continue an historic drought in California, trees all over Southern California are showing symptoms of stress, and in some cases have died due to drought and pests that attack drought stressed trees. Despite recent and significant rainstorms, it is likely that trees will again be stressed later in the irrigation season. Trees and other woody plants in nurseries also bear the burden of drought stress as irrigation waters become increasingly salty because of drought effects on wells and reliance on stored water in reservoirs continues.
The Polyphagous shot hole borer is a serious pest of nursery and landscape trees and threatens many species. As such, counties adjacent to Los Angeles are at risk of invasion by this new...