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Open Access Publications from the University of California


The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish & Wildlife Service. The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited. Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.

To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962. The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years. It is the most widely-recognized conference of its kind worldwide.

Detailed histories of the development of this Conference are found in these publications:

Salmon, Terrell P. 2012. VPC: Fifty Years of Progress? Proc. Vertebr. Pest Conf. 25:3-6.

Marsh, Rex E. 2008. A History of the Vertebrate Pest Conference. Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul. 2004. Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference. Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E. 1982. Twentieth Anniversary of Vertebrate Pest Conferences in California. Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E. 1962. Opening Remarks – Vertebrate Pest Control. Proc. Vertebr. Pest Conf. 1:1-7.


Testing and registration of new control materials

Criteria for registration of vertebrate pesticides are discussed, as required by the U.S. Department of Agriculture, in keeping with the Federal Insecticide Fungicide and Rodenticide Act. Product labels must specifically state the target species of pests on which the material may be used. Field test design requirements are explained as well as standards for reporting test results. Information on environmental and nontarget hazards is required, as are precautions in regard to human safety and precautions for applicators. Explanation of the statement of ingredients, exceptions to the registered-use pattern, and useful precautions are also given. The conditions under which experimental permits are granted are discussed.

The role of industry in developing new materials for vertebrate pest control

Private industry plays an important role in the development and registration of new materials as vertebrate pesticides. The challenges of screening candidate compounds are discussed. In regard to vertebrate pests, toxicity can vary widely, even among closely related species. The challenges of identifying repellents or attractants are even greater than for finding toxicants, while from the private sector standpoint, commercially successful materials must have sufficiently wide application to be economically profitable. Case histories of industry’s contributions to the development of current rodenticides are discussed. Among current challenges are to find active ingredients that are more species-specific, to identify and develop effective repellents against rodents and other mammals that are non-toxic and environmentally appropriate, and to find materials to solve growing bird damage problems.

The role of pest control operators in vertebrate pest control

The status of the pest control industry is described, along with comments on those private pest control operators who conduct control of vertebrate pests. The economics of pest control businesses are considered. Results of a survey of rodenticides most often used by pest control operators are reported. The National Pest Control Association has become involved in conducting field trials toward obtaining data needed for pesticide registration. Good practice statements for some aspects of rodent control are in preparation. Good progress has been made in education PCOs to be more responsive to the requirement to carefully read and follow product labels. Among current challenges are the ability of PCOs to convince clients of the importance of sanitation, as part of a strategy to prevent and control pest problems. We are also working on better communication between the private sector and public agencies and organizations, whose efforts are sometimes mistakenly perceived as in competition.

Animal population ecology and control fundamentals

The difficulty in controlling a pest population is discussed in terms of population modeling theory, in which populations tend to move toward a stable equilibrium. Pest control operations elicit a populational homeostatic mechanism, as well as genetic and physiological homeostatic mechanisms. This demonstrates why pest populations are not exterminated by decades of intensive control of traditional types. What is needed is some self-accelerating method of control that forces the population toward an unstable equilibrium point; new genetic and biological control techniques can provide such effects. Examples are provided of new thinking about population control techniques that exploit the weaknesses in biological mechanisms.

Starlings in the Pacific Northwest

Increasing problems caused by European starlings are described as their population has increased in the Pacific Northwest, causing significant damage in livestock feeding facilities, to fruit crops, and to ornamental holly groves. Starling biology and reproduction is discussed. Experimental methods to reduce damage are described in detail, including use of cage traps and light traps, and development of an avicide using thallium sulphate as the active ingredient.

Starlings in California

The history of European starling expansion in California is described, as well as efforts by the California Department of Agriculture to find effective control methods for this species. In spring and summer, damage is primarily to grapes and soft fruits in orchards and vineyards. From November through March, migrant starlings cause principally around livestock feedlots and other concentrated sources of feed. The use of frightening devices and starling distress calls have so far been ineffective when used at such locations, but they have demonstrated some utility in vineyards and orchards to reduce damage to fruit. Trials with improved trap designs indicate that a more portable trap with a funnel-type entrance may be more efficient than traps previously used. Trials with the toxicant tetraethyl pyrophosphate (TEPP) on cubed apple or raisin baits have shown this material has some promise. Application of bands to some 27 thousand starlings indicates that those banded in California may migrate as far north as Edmonton, Alberta, and that they travel widely throughout the West, finding mountain ranges no barrier to movement.

Methods of controlling blackbird damage to field corn in South Dakota

Recent research efforts to control blackbird damage to corn in South Dakota are described. The primary species responsible is the red-winged blackbird, but other associated species include yellow-headed and Brewers blackbirds, common grackles, and brown-headed cowbirds. The birds’ biology and behavior are described, as is damage assessment in corn fields. Bird banding efforts have revealed typical bird migration patterns and movement. Trapping with Miller-type cannon nets and with modified Australian crow traps have shown success. Other damage control techniques considered, investigated, and/or evaluated include bird-resistant variety of crops, habitat management, use of frightening devices, roost sprays with the organophosphate DRC-632, and baiting with the fright-producing chemical DRC-1327.

Sound in vertebrate pest control

The author discusses the concept of controlling pest animals, primarily birds, using sound as a tool to frighten birds from a specific location, or to deter bird damage. He notes that bio-acoustic sounds that have specific meaning, such as distress calls and alarm calls, often are more effective than sounds that simply are loud, but often are species-specific in effect. However, they do not need to be broadcast at high volume and thus are less objectionable to people within hearing range. Quality, timing, and strategies for the use of bio-acoustic sounds are discussed with many examples from attempts to use these against various bird species, especially European starlings. Reasons for lack of interest in research and commercialization of bio-acoustic sounds for bird control, in North America in particular, are discussed.

The control of vertebrate problem animals in the Province of the Cape of Good Hope, Republic of South Africa

An overview of vertebrate pests in the Cape Province of South Africa is provided, including a history of their management and control. Particular attention is given to predation on livestock by carnivores, which originally was the subject of a bounty system that was largely replaced in 1951 by a system of “Technical Aid”, which includes subsidies to hunt clubs and training of their members and hounds, testing of techniques, and predator control research. By the early 1960s, a cooperative training exchange program established with the U.S. led to the adoption of use of coyote getters and Compound 1080 for control of black-backed jackals in Cape Province. Adaptations of these tools for South African situations is discussed. Other vertebrate pest problems in Cape Province include the cape otter, honey badger, musk cats, mongooses, African wild cat, blackfooted cat, and primates including baboons and monkeys. Notable rodent problems include the hyrax (dassie), Cape gerbille, and giant dune mole, porcupine, and antbear. Among bird pests are the introduced European starling, the quelea, red bishop bird, Cape raven, pied crow, and the black crow. Damage inflicted by these species is briefly discussed, as are typical control methods.

Pest control methods and people

General principles of pest control for the protection of agricultural crops, public health, and natural resources are discussed. The need for the use of pesticides in vertebrate control is compared and contrasted with pesticide use in control of insect pests, weeds, nematodes, and plant diseases. The challenge of using pesticides for vertebrate pests is that many active ingredients are broadly toxic to other vertebrates, including humans and desirable wildlife, and may need to be used in higher concentrations than are pesticides used in insect control, thus posing nontarget risks. The need for understanding the characteristics and fate of pesticides is emphasized, including the need for residue analysis, effect of chemicals on nontarget organisms, accumulation in soil, hazards to applicators and farm workers, phytotoxicity, and contamination of run-off from field into drainage systems. Human perceptions about pests and pesticides are also noted.

Hawaiian sugar cane rat control methods and problems

The problem of rat damage done by Norway rats, black rats, and Polynesian rats to sugarcane in Hawaii is discussed in terms of damage description and economic impacts. Control methods largely depend on the use of various anticoagulant rodenticides formulated on rolled oats with addition of paranitrophenol as a mold inhibitor. These baits are placed in around the periphery of fields in three types of bait stations: temporary stations made of cardboard treated with wax, inverted “T” bait dispenser, and “L”-shaped bait dispenser, with the latter two typically made of plastic pipe. Baiting strategies are described, and the problem of bird consumption of anticoagulant baits is noted. Occasionally, baits made from rolled oats treated with thallous sulfate are used, but prebaiting is required for these to be effective. Better rodenticide baits are needed, especially for the Polynesian rat, and it would be advantageous to have such a bait that could be applied in sugarcane fields by aircraft.

Forest animal damage - research and control methods

This paper focuses on managing wildlife damage in forest environments, with emphasis on the use of vertebrate pesticides in the western United States. Types of forest damage caused by vertebrates fall into the categories of seed destruction, foliage clipping and browsing, and root and bark injuries. Consumption of natural seedfall or following direct-seeding applications for reforestation varies with tree species as well as with vertebrate seed predators, which include both rodents and birds. With Douglas-fir, deer mice (Peromyscus spp.) are cause the greatest losses. For Ponderosa pine, deer mice, chipmunks, and ground squirrels are primarily responsible for seed loss. Seeding in black walnut is primarily impacted by gray squirrels and the eastern fox squirrel. Success with rodenticide treatments in advance of seed applications were only effective for short periods, as rodent populations rebounded quickly. Current efforts are relying on various seed coatings that provide greater efficacy. Clipping by small rodents is a particular problem with newly emerged seedlings; existing seedlings are also damaged by snowshoe hares and mountain beaver in the Pacific Coast states. Contact repellents have been effective but may need to be re-applied periodically. Browsing damage to existing conifer stands is caused primarily by deer and elk, and there is no general solution for this problem. Root injury to seedling and small saplings is most frequently caused by pocket gophers. A variety of animals may cause bark injuries: meadow mice (Microtus spp.) can seriously damage seedlings, while bark damage to both young and also mature trees can be caused by porcupine, woodrats, rabbits, squirrels, and pocket gophers. Bear damage to bark is usually seen on mature trees. Seed treatment formulations using endrin as the active ingredient are described, as are a foliar repellent treatment using TMTD, and the manufacture and use of salt blocks containing strychnine for porcupine control. Pertinent literature citations are provided.

Rabbit control

Biology, damage, management, and control of rabbits (genus Sylvilagus) and hares (genus Lepus) in California are described. This paper places emphasis on control of the common jackrabbit, Lepus californicus, as it is the most significant of the rabbit and hare species in California and the western states in terms of damage and the need for control. Exclusion methods are discussed, including rabbit-proof fences as well as individual plant and tree protectors. A summary of repellents used against hares and rabbits is provided, as well as precautions for their use. They typically provide only temporary effectiveness. A recipe for a strychnine-based poison wash for trees, which has found to be of use as a repellent, is provided. Use of toxic baits to control rabbits and hares is described, with appropriate precautions. Bait formulation and application are discussed in some detail, with use of strychnine as the active ingredient. Recipes are provided for formulating both prebait and toxic baits; the primary ingredient can be barley, oats, root vegetables (carrot, sweet potato, or parsnip), fruit (green pears or cull apples), dry alfalfa leaves, or grain heads using barley or milo.

Bait mixing equipment used in vertebrate pest control

The authority and history of mixing and selling toxic baits for vertebrate pest control, invested in the County Agricultural Commissioners within California, is described. This practice dates from 1917, when legislation prescribed rodent control as a function of the state’s Department of Agriculture. Various types of mechanical mixers, including concrete mixers, mortar mixers, vertical mixer-blenders, and grain mixers are described.

Roof rat populations in Santa Clara County, California

Northern Santa Clara County, California, has changed from an agricultural to an industrial-residential community in the past 10 to 15 years. Maturing shrubbery and fruit bearing trees in residential areas have provided ideal habitat for increased populations of roof rats. Advisory or educational control measures only met with partial response and little success in actually exterminating rats. It took an actual organized health department effort with diphacinone bait blocks to achieve adequate control in a given area of 400+ homes. An interesting legal complication is described as related to public rodent control on private property.

Bats, their public health importance and control with special reference to Trinidad

This review of the public health importance and control of bats is oriented to Trinidad, since this country is well known for its studies of bat problems, especially rabies, and its bat control program. Bat problems which require control are: bat-associated diseases (viral, spirochetal, fungal, bacterial, and protozoan), vampire bats, and house bats. Present methods of bat control and possibilities for future control are discussed, as this is a matter of importance to Trinidad and other countries in Central and South America. Because of its large variety of bats and location, the small island of Trinidad is a natural laboratory to study bat ecology and evaluate control measures. A list of pertinent references is provided.

Animal control in New Zealand

New Zealand has experienced some acute problems as a result of introducing so many species of mammals. Current control methods are quite well developed, but even better organization and methodology are still required to provide additional relief from a number of the problem vertebrates. Introductions, resulting problems, and methods of control are described briefly. Introduced mammals are listed, and the current status and control efforts are described for European rabbit and European hare, deer and other big game, wild goat and pig, and the Australian brush-tailed opossum. Literature citations are provided.

Occupational hazards to pest control operators with special reference to pesticides

Precautions and rules for safe handling and application of vertebrate pesticides are discussed, primarily in relation to applicator safety and agricultural worker safety.

Antifertility agents in vertebrate pest control

The current status of research into potential antifertility agents for vertebrate pests is briefly discussed, noting that the most promising target species are those than breed only once per year. Advantages of suppressed reproduction are listed. Current efforts to develop an antifertility agent for the coyote are described, including an initial field trial of diethylstilbestrol conducted in New Mexico using tallow drop baits.

Diseases derived from wildlife

The issue of diseases in wildlife that are of public health significance is reviewed. Specific diseases that are derived from wildlife in California and known to occur in humans are listed. Habitat management by humans and the actions of humans that alter the environment are discussed in relation to wildlife populations and the diseases they may harbor or transmit. Humans may contract diseases by entering wildlife habitats where the diseases occur, or diseases may be introduced into regions previously free of the disease, causing epidemics. Examples discussed of diseases found in wildlife that have affected humans include rabies; Western encephalitis and St. Louis encephalitis; various tick-borne diseases such as Colorado tick fever, Rocky mountain spotted fever, and Q fever; tularemia; murine typhus; ornithosis; leptospirosis; and others.

The evolution of plague control in California

The history of plague in California is reviewed, as well as efforts to control sylvatic plague when it occurs. Recent information indicates that rodent species that suffer periodic violent epizootics, such as ground squirrels, marmots, and chipmunks, previously thought to be the most important reservoirs of plague, are not the species in which plague persists. Rather, small rodents such as Peromyscus and Microtus appear to be capable of maintaining a quiet state of infection with little or no mortality. Plague is now thought to persist in relatively small pockets where suitable climate, flea vectors, and rodent hosts occur, characteristically in cold mountainous or high plateau regions, or coastal fog belts. Permanent suppression of sciurid rodents can be justified in only a few areas, namely where there is a strong probability of enzootic plague in close proximity to human exposure. Otherwise, we should be prepared reduce squirrel numbers in appropriate areas when they become dense enough to afford an epizootic potential. In recreation areas, flea control is wholly suitable alternative. This calls for changes in the traditional practice of control of ground squirrels and other species.

Highlights of bird control research in England, France, Holland, and Germany

Research on nuisance and depredating birds in England, France, Germany, and The Netherlands is reviewed, both in relation to damage to agricultural crops and the bird-plane strike problem. Bird species most responsible for damage are listed and damage is described, as are current and developing control strategies and materials.