UC IPM Online UC ANR home page UC IPM home page

UC IPM Home

SKIP navigation

 

Research and IPM

Grants Programs: Projects Database

Project description

Updating integrated pest management systems for pitch canker: known and potential insect vectors. (02XN015)
Program Exotic Pests and Diseases Research Program
Principal
investigator
D.L. Wood, Division of Insect Biology, UC Berkeley
Host/habitat Monterey Pine; Pines; Forest
Pest Pitch Canker Fusarium circinatum; Twig Beetles Pityophthorus spp.
Disciplines Entomology, Plant Pathology
Review
panel
Natural Systems
Start year (duration)  2002 (Three Years)
Objectives Refine integrated pest management strategies for pitch canker by determining the relative importance of each of the known insect vectors of Fusarium circinatum.

Refine integrated pest management strategies for pitch canker by determining the risk that wood infesting insects carry the pathogen.

Project
Summary
Pitch canker is a disease of pines and other conifers in California that is caused by an exotic fungal pathogen. A number of species of twig, bark, and cone beetles are known to be vectors of this pathogen. Determining the vector efficiencies of these species will determine their relative importance in development of existing pitch canker infestations, and in the potential establishment of new infestations. This information will be combined with new knowledge about the potential for wood infesting insects to carry the pathogen, and be used to refine the integrated pest management programs for this exotic invasive pathogen.
Final report We made significant contributions in the field of insect-plant-pathogen interactions.

We have trapped and determined the phoresy rate of two species of phloem-feeding engraver beetles (Ips mexicanus and Ips plastographus), two species of sapwood-infesting beetles (Asemum nitidum, longhorned beetle, and Gnathotrichus retusus, ambrosia beetle), and at least two species of twig beetles (Pityophthorus setosus and P. carmeli) occurring in central coastal California in 2003 to 2005. We also determined the spore load of I. mexicanus, I. plastographus, P. setosus and P. carmeli. As far as we know, this is the first report of the number of spores of F. circinatum carried by an insect.

All these insects have a wide host range, and A. nitidum is known to colonize Douglas-fir and Pinus species.

We have also collected symptomatic Monterey pine branches to rear Pityophthorus spp. We determined the phoresy rate and spore load of these beetles. Phoresy rate and spore loads of beetles reared from F. circinatum-infected branches were several-fold higher than those beetles trapped using semiochemicals, suggesting that beetles emerging from the infected host material have a great potential to vector F. circinatum in nature. We successfully demonstrated transmission of F. circinatum by two species of twig beetles, P. carmeli and P. setosus in nature.

We have strong evidence that both sexes of I. mexicanus, I. plastographus, P. setosus and P. carmeli carry propagules of pitch canker, thus both sexes are potentially important in introducing the fungi into host tissue. Natural spore loads on these beetles and their ability to transmit the pitch canker pathogen are important factors in predicting the future distribution of this disease on other hosts in California and elsewhere.

Second-year
progress
Our goal is to trap at least two species of phloem feeding engraver beetles (Ips spp.), several species of deep wood insects (Cerambycidae and Buprestidae), and at least two species of twig beetles (Pityophthorus spp.) occurring in central coast of California.

We captured a total of 8,821 beetles from 11 species in five families in 2003.

We have determined natural propagule load for I. mexicanus and P. setosus trapped in June and August 2003. This is the first report of the number of propagules of F. circinatum carried by an insect. Presently we are determining the natural propagule load of these and other insects from the remaining monthly sampling dates (June-November 2003).

We set up additional traps in the southern most population of native Monterey pines in Cambria, and sampling was initiated for the early April collection and will continue monthly until the end of November.

Recent attempts to isolate and determine the number of propagules of F. circinatum on various species of bark and wood boring beetles have been successful for Ips mexicanus and two species of longhorned beetles in 2004.

We have evidence that males of Ips spp. and some Pityophthorus species initiate galleries and excavate nuptial chambers, whereas females excavate egg galleries only. We have evidence that both male and female P. setosus initiate entrance tunnels. Phoresy rates (proportion of individuals carrying the pathogen) for males and females are different for some species of Pityophthorus, i.e. P. carmeli, males have [a] higher phoresy rate than females, P. setosus and P. nitidulus females have a higher phoresy rate than males.

Natural propagule loads on these insects and their ability to transmit the pitch canker pathogen are important factors in predicting the future distribution of this disease on other hosts in California and elsewhere. The relative importance of the different vector species will enable efforts to reduce spread of the pathogen to be focused on the key vectors.

First-year
progress
We have initiated studies to determine the efficiency with which known insect vectors of pitch canker transmit the pathogen to suitable hosts. Twig beetles are being reared from diseased branch tips to determine the spore load of the pathogen that they carry. Rearing from diseased portions of the branch tips maximizes the proportion of beetles carrying the pathogen and contributing to our database. Insects trapped in pheromone baited traps are used to develop a relationship between the dose of spores experimentally applied to the beetle, and the number of spores that the beetle carries. This will provide a tool for testing vectoring efficiencies of doses of the pathogen that mimic natural doses. We are also identifying trees that have extensive cankers on the main stem in order to rear engraver beetles from these cankered areas and determine the spore load on these insect vectors. To study the risk of spreading pitch canker through the movement of host material containing wood infesting insects, we have located six sites on the Monterey peninsula for trapping wood infesting insects. These sites all have dead and/or diseased trees, and include Indian Village, Spanish Bay, and Pebble Beach Firehouse. Traps baited with ethanol and alpha-pinene are being established at these sites for continual monitoring of wood infesting insect activity. All trapped insect will be screened for the pathogen and identified. This will enable us to assess the risk of spread pitch canker from with the movement of wood infested with these insects.

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright 2014 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   web template revised: October 25, 2014 Contact webmaster.