Swiecki, T. J.; Bernhardt, E. A.; Arnold, R. A. 1997. The California oak disease and arthropod (CODA) database. Pages 543-552 in:  Proceedings of a symposium on oak woodlands: ecology, management, and urban interface issues; 19-22 March 1996; San Luis Obispo, CA.  Gen. Tech. Rep. PSW-GTR-160. Albany, CA: Pacific Southwest Research Station, Forest Service, USDA.

The California Oak Disease and Arthropod (CODA) Database

Tedmund J. Swiecki 1   Elizabeth Bernhardt 1   Richard A. Arnold 2

1 Principals, Phytosphere Research, 1027 Davis Street, Vacaville, CA 95687
2 President, Entomological Consulting Services, Ltd., 104 Mountain View Court, Pleasant Hill, CA 94523

As part of a project to study the impacts of diseases and arthropods on California rangeland oaks (Swiecki and others 1990, 1991a, 1991b), we set out to compile the existing information on agents affecting oaks in California. Our goal was to organize this information in a format that was readily accessible and easy to update. We developed a computerized database, the California Oak Disease and Arthropod (CODA) Host Index (Swiecki and others 1996), to store and organize preexisting and new information on arthropods, microorganisms, and abiotic factors that affect oak health in California.
 

Methods

Review of Literature and Unpublished Data

Although we consulted nearly 2,000 publications during the literature review, our review of the literature was not necessarily complete for all groups of agents, particularly the insects. Because of time and budget constraints, we focused our initial efforts on groups of agents that were likely to cause noticeable damage to oaks. We restricted our initial search for arthropod records to phytophagous insects and mites, concentrating on taxa that are known pests of oaks or other deciduous trees in California and elsewhere. In searching for records on microbial agents, we concentrated our efforts on known or likely pathogens.

We also obtained unpublished records in the form of database files and card files from various sources, including the California Department of Food and Agriculture (CDFA); USDA Forest Service's Pacific Southwest Forest and Range Experiment Station [now Pacific Southwest Research Station]; Jerry Powell, Department of Entomology, University of California at Berkeley; and Isabelle Tavares, University Herbarium, University of California at Berkeley. We have also added records based on our own and others' collections and identifications. To date, we have contacted more than 125 entomologists, acarologists, plant pathologists, mycologists, and other specialists in taxonomy, forestry, and landscape pests, to supplement or confirm information obtained from the literature or other sources.
 

Database Design

Much of the information in CODA is specific to each reported host-agent interaction, including the fields that describe the following: reported distribution of the host-agent interaction; types of growing situations (e.g., range, urban landscape) under which the interaction has been observed; host life stages attacked; host symptoms and agent signs, including the location and maturity of affected plant parts; whether the agent attacks healthy or compromised tissue; whether symptoms listed are a direct or indirect result of attack; and other notes about the interaction (fig. 1). Because of the limitations of available data, many records in CODA do not contain complete information in all of these fields.

CODA also contains information specific to each disease agent, host, and reference. Disease agents and arthropods are identified with hierarchical taxonomic and non-taxonomic codes. True taxonomic synonyms as well as other scientific names that have been encountered in the literature are listed in a synonym field for each agent. CODA also contains descriptions of the included oak host species, and full literature citations and descriptive notes for references (fig. 1).

Because of software limitations at the time that the program was developed, much of the host-agent interaction data is abbreviated or coded. All codes are described in the software documentation, and functions in the access program allow the user to translate all displayed codes on screen and in printed reports (fig. 1). These codes can be used in various combinations to filter records from the database.

We used Paradox® 5.0 for Windows database software (Borland International, Inc., Scotts Valley, Calif.) to tabulate statistics on the CODA database contents. Statistics are based on queries of the January 1996 version of the CODA database files.
 

Results and Discussion

The CODA Software

The categories and format of the information stored in the CODA databases are shown in a sample report for one occurrence record (fig. 1). The information for a given record can be displayed on screen, sent to a printer, or saved to a text file.

Organizing the information found in CODA as a computer database application provides several advantages over presenting the same information in the form of a publication. Many of the records in CODA describe one-to-many relationships, such as an agent which occurs on many oak species. These relationships are easily organized and displayed with relational database software, but are difficult to present as printed material. By using functions built into the CODA software, the CODA databases can be filtered or queried easily to produce subsets of data. This allows the database to be used as a simple expert system for diagnosing pest and disease problems. To remain current, the information in CODA needs to be updated periodically to account for taxonomic changes and add new records and additional details. Compared with a lengthy publication, a database can be updated and distributed to users more quickly, easily, and at a lower cost.

We designed the database to easily handle simple changes in agent names. However, more complex changes, such as those that involve the lumping or splitting of taxa, require careful examination of existing records to avoid introducing inaccuracies into the database. For example, agents originally described as occurring on Q. dumosa Nutt. needed to be reassigned to either Q. dumosa (strict sense) or Q. berberidifolia Liebm. after the taxonomic status of this species was revised (Hickman 1993). Some records contained enough detail to be reassigned definitively, but many records could not be reassigned and have been retained provisionally under a separate host entry for the wide sense of Q. dumosa.

In addition to updating the data in CODA, it will also be necessary to periodically revise the user interface. The current interface software runs readily on most platforms that can run DOS applications, and 87 percent of the respondents to our 1993 user survey (Swiecki 1993) rated the program as easy or very easy to use.
 

CODA Host Index Statistics

Native Host Oak Species

Arthropods

Within the CODA database, the orders Hymenoptera, Lepidoptera, Coleoptera, and Homoptera are represented by the greatest number of species. The most taxonomically diverse collection of oak-feeders is found within the Lepidoptera, which has representatives from 36 families. Most of these are leaf-mining and external foliar-feeding moths. The arthropod family represented by the greatest number of species (126) is the Cynipidae. These are highly specialized gall-forming wasps.

Few non-phytophagous arthropods are currently represented in CODA. However, only a portion of the arthropods that are associated with oaks would be classified as oak feeders. Many insects are predaceous or parasitic on oak-feeding insects and therefore indirectly depend on oaks for their existence. Also, numerous arthropods that do not feed directly on oaks live in tunnels or galls produced by oak-feeding insects. Additional insects are associated with the fungi that colonize living or dead oaks. Still other insects are detritus feeders that opportunistically feed on decaying wood, but are not necessarily limited to oaks. If these additional species are considered, there may be between 4000 and 5000 arthropod species associated with California oaks. This total is more than 10 times the number of terrestrial vertebrates found in oak-dominated hardwood rangeland in California (Guisti and others 1996).
 

Diseases and Microbial Interactions

No oak diseases caused by phytoplasmas (plant-infecting spiroplasmas and mycoplasma-like organisms) are currently included in CODA, although such agents have been found in many woody species, including oaks in the eastern United States (Sinclair and others 1994). Undoubtedly, more nonfungal microbial agents are associated with oaks in California than are currently reported. However, detecting and identifying many of these agents, including bacteria, viruses, and phytoplasmas, are difficult and require specialized techniques. Additional diseases involving nonfungal agents are unlikely to be reported in the absence of targeted research in this area.

The fungi are the best characterized group of microoganisms associated with oaks in California, largely because many fungal fruiting bodies are easy to observe and collect. Many of the associations between oaks and fungi included in CODA have not been published and are known only through herbarium records. Primary pathogens, secondary or opportunistic pathogens, saprophytes, and mycorrhizal species are all represented among the fungi in CODA (table 3). Although a few individual oak diseases have been studied in some detail, most interactions between California oaks and fungi remain unexplored, and the oak-associated mycoflora probably includes many more species than are currently reported.
 

Damage to Oaks Caused by Arthropods and Diseases

Arthropods

Most of the arthropods that attack oaks are native species that appear to be in ecological equilibrium with their hosts. Their aggregate impact on oak health and survival appears to be low when trees are growing under favorable conditions. However, the impact of insect and mite damage may be much more significant when oaks are stressed, wounded, or otherwise disturbed. This is especially true for insects such as bark beetles (Scolytidae) and wood borers. Furthermore, although much of the damage caused by insects does not significantly affect oak survival, the damage, insects, and/or their by-products (honeydew, fecal pellets, etc.) may not be tolerated in urban situations.

Insects that damage acorns can have a significant impact on this vulnerable oak life stage. CODA includes 14 insect species in seven genera which feed on or form galls in or on acorns. Of these, the filbertworm (Cydia latiferreana [Walshingham]) and three species of filbert weevils (Curculio spp.) are most destructive and may destroy a large percentage of the mast crop within a location in a given year (Keen 1958; Swiecki and others 1990, 1991a). Thus, even though relatively few species of insects damage acorns, their impact on oak reproduction can be substantial.

In contrast, at least 350 insect species feed on or produce galls on oak leaves, but the aggregate impact of these insects on the long-term health of mature oaks is generally considered to be minor. Only a few species, such as the California Oak Moth (Phryganidia californica Packard) and the Fruit Tree Leaf Roller (Archips argyrospilus [Wlk.]), are capable of defoliating entire trees or stands of trees. However, these and other moth larvae typically do not cause severe defoliation in successive years, and outbreaks are usually of short duration, so long-term damage to oaks is generally minimal if trees are not also stressed by other agents or factors.

Diseases

Various species of wood-decay fungi, primarily in the Polyporales, constitute the most significant oak pathogens in California. CODA includes more than 40 species of fungi that cause branch or trunk cankers or decay the trunk, root crown, or roots of oaks growing under natural conditions. Canker rot fungi, including several species of Inonotus, are important pathogens of blue oak and other oaks in both rangeland (Swiecki and others 1990, 1991b) and urban settings. Canker rot fungi are wood decay fungi that attack living trees and also kill phloem and vascular cambium, giving rise to perennial cankers (Sinclair and others 1987). Trees colonized by canker rot fungi and other wood-decay fungi usually decline slowly and literally fall apart as large branches, and eventually the trunk, fail.

Mature oaks are also killed by root-rotting fungi. Certain fungi, such as Armillaria mellea and Phytophthora spp., are significant pathogens of urban oaks that are subjected to summer irrigation and stressed by other rootzone disturbances. Other fungi, including species of Ganoderma and several other fungi in the Basidiomycotina, kill mature oaks in undisturbed stands as well as those which become incorporated into urban landscapes.

In addition to causing tree mortality, wood-decay fungi also reduce the quantity and quality of wood products that may be harvested from a stand. On the other hand, these fungi play a direct role in improving wildlife habitat value. Decay caused by these fungi aids in the development of cavities in trees, which are utilized by a number of different vertebrate species. Wood-decay fungi affect the amount of dead and downed wood and standing snags in an oak woodland, which in turn contribute to wildlife habitat value (Tietje and others 1997).

At least 40 species of fungi attack the leaves and/or twigs of living oaks in California. The most common and conspicuous of these are the powdery mildews (Erysiphales) and the anthracnose fungi. Symptoms caused by these fungi are sometimes severe enough in urban oaks to prompt concern, but these fungi normally have little impact on long-term health or survival of oaks in either urban or rangeland conditions.
 

Conclusions

Acknowledgments

References

Figure 1 -- Full-length report for the record of Inonotus andersonii on Q. douglasii printed from the CODA software.

Quercus douglasii Agent: B P F BAS POL

Common: Blue oak Genus: Inonotus

Species: andersonii

Distribution: BA,NV,CI,SV,CC Subsp:

Situation: RL Common: Canker-rot

Stages: 3D Synonym: Chromosporium pactolinum

Maturity Site Symptoms/Sign Status

_______________________________________________________________________________

Flowers:

Acorns:

Leaves:

Branches: M HW WROT,PCANK,FAIL,TCANK,BRES 1d

Trunk: M HW WROT,PCANK,FAIL,TCANK,BRES 1d

Roots:

_______________________________________________________________________________

CODE DESCRIPTIONS:

Agent Codes:

B Biotic (Organisms, viruses, and genetic factors)

P Pathogens (disease-causing agents)

F Fungi

BAS Basidiomycetes

POL Polyporales (Polypores)

Distribution codes:

BA Bay area: Alam,CCosta,Marin,Napa,SMateo,SFran,SClara,Solano,Sonoma

NV North Valley: Butte,Colusa,Glenn,Lake,Sacto,Sutter,Tehama,Yolo,Yuba

CI Central Interior: Alpne,Amadr,Calavrs,EDorad,Marip,Nev,Placer,Tuolum

SV South Valley: Fresno,Kern,Kings,Madera,Merced,SJoaquin,Stanisls,Tulare

CC Central Coast: Monterey,SBenito,SLuisObispo,SBarbara,SCruz,Ventura

Situation code:

R Range

L Landscape

Stage codes:

3 Mature

D Dead

Maturity Codes:

M Mature tissues

Site Codes:

H Heartwood (older wood near center of stem)

W Wounds, includes fire scars, branch stubs, leaf scars, pruning wounds

Symptoms/Sign Codes:

WROT White rot (light-colored decay; spongy, stringy, crumbly, or brittle)

PCANK Perennial canker (discrete lesion that persists 2 or more years)

FAIL Failure (breakage or collapse of limbs, trunk or roots)

TCANK Target canker (regular, concentrically zonate perennial canker)

BRES Basidiocarp-resupinate (a sheet-like fruiting body)

Status Codes:

1 Primary - agent attacks healthy tissue

D Direct symptom

_______________________________________________________________________________

GENERAL NOTES:

-Observations suggest that various types of target cankers, especially those

associated with old branch stubs, may be caused by the interaction between

this fungus and certain trees.

-Probably one of the most significant causes of decay and mortality in blue

oak over much of its range. In the field, distribution of affected trees is

variable, and "hot spots" or disease foci may occur.

_______________________________________________________________________________

REFERENCES:

AUTHOR: Swiecki, T. J.; Bernhardt, E. A.

TITLE: Field notes, observations, and collections

1988-1992

SOURCE:

DATE: 1988-92

NOTES:

These records are based on field observations and material collected from

various oak hosts by T. J. Swiecki and E. A. Bernhardt. Records of these

observations are on file at Phytosphere Research, 1027 Davis Street,

Vacaville, CA 95687-5495. Phone 707-452-8735. Some of the collected materials

were deposited at the UC Berkeley Herbarium.

AUTHOR: Gilbertson, R. L.; Ryvarden, L.

TITLE: North American Polypores

SOURCE: Fungiflora A/S, Oslo, Norway

DATE: 1986

NOTES:

A two-volume monograph on the fungi in the Polyporales that occur in North

America. Contains keys to species, descriptions, notes on distribution,

cultural characteristics, type of rot caused, hosts, and other data.

AUTHOR: Sinclair, W.A.; Lyon, H.H.; Johnson, W.T.

TITLE: Diseases of trees and shrubs.

SOURCE: Cornell University Press, Ithaca, NY

DATE: 1987

NOTES:

A general reference to diseases of trees and woody shrubs. Includes color

photographs of symptoms, descriptions of causal agents, disease cycles,

distribution, host range, and other information.

_______________________________________________________________________________

AGENT NOTES:

-Widely distributed in U.S., to PA, WI, TX, AZ, CA and OR on Quercus,

Populus, Salix, and Carya.

-Causes a white rot of the heartwood of living oaks. Bark cankers are formed

where the fungus invades and kills the sapwood and cambium. Cankers are a

common site of branch or trunk failure. Infection typically occurs at wounds,

especially branch stubs.

-Basidiocarps are annual, sheetlike, often large (to over 50 cm long), and

develop under outer layers of sapwood or bark. The bark and/or sapwood is

ruptured by the basidiocarp as it matures. Spore deposits are bright golden

yellow.

_______________________________________________________________________________

HOST NOTES:

-Subgenus Quercus (Lepidobalanus): White oaks

-Also called mountain white oak, iron oak, post oak

-Deciduous tree with rounded crown, 6-20 m high.

-Endemic to California, blue oak grows on dry rocky slopes of foothills of

Sierra Nevada and Coast Ranges from Shasta Co to Los Angeles Co. Also extends

well out onto valley floors in areas, such as near Burch Creek and the

Sacramento River (Tehama Co) and near Thornton (San Joaquin Co).

-Bark checked, light gray to almost white.

-Leaves 3-6(-8) cm long with petiole 3-9 mm, shallowly and irregularly lobed

or entire, minutely pubescent, dull bluish green above, paler below.

-Acorns maturing the first year, variable in shape, commonly ovoid, nut 2-3

cm long, cap 12-20 mm wide, 6-10 mm deep cup to bowl shaped, scales slightly

tubercled.

-Hybridizes with Q. garryana, Q. john-tuckeri, Q. lobata.

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