Pitch canker continues to be a threat

Pitch canker is an example of what can happen when an exotic pest is introduced into a new environment.

Naturally infected native California species: Bishop pine (Pinus muricata) Coulter pine (Pinus coulteri) Foothill (formerly digger) pine (Pinus sabiniana) Knobcone pine (Pinus attenuata) Monterey pine (Pinus radiata) Monterey x knobcone pine (Pinus radiata x attenuata) Ponderosa pine (Pinus ponderosa) Shore pine (Pinus contorta) Torrey pine (Pinus torreyana) Douglas-fir (Pseudotsuga menziesii) Native species susceptible in greenhouse seedling tests Jeffrey pine (Pinus jeffreyi) Sugar pine (Pinus lambertiana) Native species resistant in greenhouse seedling tests White fir (Abies concolor) Coast redwood (Sequoia sempervirens) Giant sequoia (Sequoiadendron giganteum) Incense-cedar (Calocedrus decurrens)

The pathogen, a fungus called Fusarium subgutinas f. sp. pini, was first discovered in Santa Cruz County in 1986. In that relatively short time it has spread to Alameda, Contra Costa, Los Angeles, Marin, Monterey, Mendocino, Orange, San Benito, San Diego, San Francisco, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Solano, and Sonoma counties. Thousands of trees have died.

In addition to its geographical spread, the disease has spread from Monterey Pine to a number of other pines and (infrequently) to Douglas-fir.

The symptoms of the pitch canker disease are varied. There is often wilting and fading of needles with resin exuded from the infection site. Foliage becomes yellow, then red, then falls from the branch. Pine cones abort and remain closed on infected whorls. Copious amounts of crystallized white resin produced by bole (stem) cankers can be seen on limbs and bark. (Note that a number of other conditions can cause similar symptoms so it is important to get a positive diagnosis for pitch canker.)

Various species of bark, twig and cone beetles are known to transmit the pitch canker. These secondary pests can also cause tree death.

At this time there is no cure for pitch canker. However, there is optimism about the long-term survival of Monterey Pines because a certain level of genetic resistance appears to be present in the population. Currently, efforts are being made to breed resistant trees, but until resistant varieties are available, it is recommended that Monterey Pine not be used in landscape plantings.

People in infected areas are asked to take the following precautions in order to reduce the spread of the disease:

• Use Lysol™ or a 10% bleach solution to sterilize tools and machinery used to prune, cut, or chip trees.
• Limbs and small pieces of wood from diseased trees may be chipped and buried or burned. (Insects may survive in cut wood or chips for many months and the fungus can survive in cut wood up to a year.) Any material removed from the site should be tightly covered with a tarp during transit and taken to the nearest landfill or designated disposal facility. Do not transport diseased wood out of infested counties.
• Logs from diseased trees may be split for firewood for local use but should be seasoned beneath a tightly sealed, clear plastic tarp to prevent the buildup of insects. Do not stack pine firewood next to living pines or transport it to uninfested counties.
• Even seeds may carry the pathogen. Do not transport pine seeds out of infected areas.
• Avoid using potentially infested chips near healthy pines or Douglas-fir.
• Do not transport pine logs out of infested counties.
• Any untreated pine material that originates within infested counties is a potential source of pitch canker disease, unless treated to eliminate the disease.

—the information in this article came from the Pitch Canker website at http://frap.cdf.ca.gov/pitch_canker/. There you can learn about the disease, view a map of the Zone of Infestation, find local contacts, learn about legislation, and much more.