A TWO YEAR STUDY OF THE PHYSICAL AND ECONOMIC IMPACT OF VOLES (Microtus montanus) ON MIXED MATURITY APPLE (Malus spp.) ORCHARDS IN THE PACIFIC NORTHWESTERN UNITED STATES

The physical impact of voles in agriculture and forestry has been duly noted by many researchers around the world. The economic impact of the various species, however, has not received much attention other than to note that losses from these animals can be substantial when population levels become high. This study assesses the economic impact of an extremely high population of Microtus montanus (mountain voles) in a large apple (Malus sp.) orchard in northcentral Washington State (U.S.A.) over a two-year period. In this study, 200 trees were harvested, weighed, graded, and compared by the amount of visual damage that could be seen above the soil surface. These values were then compared with cash values received by growers for the season. Production was decreased a weighted average of 36% (31 % for red delicious and 53% for golden delicious) or $3036/ac. ($7500/ha.) during the first year. In the second year, production increased 3.2 fold but still did not reach that of the control orchard. If 30% of the orchards in the state were to suffer the same level of infestation, over $137 million/year could be lost because of poor management and control programs

BURROW-BUILDING STRATEGIES AND HABITAT USE OF VOLES IN PACIFIC NORTHWEST ORCHARDS

Seidel and Booth (1960) wrote that the life histories of the genus Microtus are not numerous in the literature. In support of his observation he cited 6 publications, all dated between 1891 and 1953. Since then the literature has exploded with a proliferation of publications. An international literature review recently revealed over 3,500 citations for the genus. When Pitymys and Clethrionomys are included another 350 and 1,880, respectively, were found. Over the last 10 years approximately 3 new publications on voles appeared every 4 days; a significant output for what some would consider such an insignificant species. Most of the publications were the result of graduate research projects on population dynamics and species ecology. As such, many do not explore more than the rudimentary ecological relationships between the animal and their environments. Unfortunate, as well, is that all but one confined their observations to only a small part of their total environment. For many of these animals, their life underground may be more important for their survival than that above ground. Trapping studies conducted by Godfrey and Askham (1988) with permanently placed pitfall live traps in orchards revealed a significant inverse population fluctuation during the year. During the winter, when populations are expected to decrease, as many as 6 to 8 mature Microtus montanus were collected at any 1 time in the traps after several centimeters of snow accumulation. During the summer, when populations are expected to increase, virtually no animals were collected in the traps. According to current population dynamics theory, greater numbers of animals, including increasingly larger numbers of immature members of the community, should appear in any sample between the onset of the breeding period, generally in the spring, taper off during the latter part of the production season, usually late summer, and then decline as the limiting factors begin to take effect. For us, we trapped more animals in the fall and early winter than we did during the spring and summer. A review of the above literature did little to answer our question. Where are the animals going during the summer and why

Signs of a vector's adaptive choice: on the evasion of infectious hosts and parasite-induced mortality

Laboratory and field experiments have demonstrated in many cases that malaria vectors do not feed randomly, but show important preferences either for infected or non-infected hosts. These preferences are likely in part shaped by the costs imposed by the parasites on both their vertebrate and dipteran hosts. However, the effect of changes in vector behaviour on actual parasite transmission remains a debated issue. We used the natural associations between a malaria-like parasite Polychromophilus murinus, the bat fly Nycteribia kolenatii and a vertebrate host the Daubenton's bat Myotis daubentonii to test the vector's feeding preference based on the host's infection status using two different approaches: 1) controlled behavioural assays in the laboratory where bat flies could choose between a pair of hosts; 2) natural bat fly abundance data from wild-caught bats, serving as an approximation of realised feeding preference of the bat flies. Hosts with the fewest infectious stages of the parasite were most attractive to the bat flies that did switch in the behavioural assay. In line with the hypothesis of costs imposed by parasites on their vectors, bat flies carrying parasites had higher mortality. However, in wild populations, bat flies were found feeding more based on the bat's body condition, rather than its infection level. Though the absolute frequency of host switches performed by the bat flies during the assays was low, in the context of potential parasite transmission they were extremely high. The decreased survival of infected bat flies suggests that the preference for less infected hosts is an adaptive trait. Nonetheless, other ecological processes ultimately determine the vector's biting rate and thus transmission. Inherent vector preferences therefore play only a marginal role in parasite transmission in the field. The ecological processes rather than preferences per se need to be identified for successful epidemiological predictions

Franklin, Richardson, Columbian, Washington, and Townsend Ground Squirrels

The Franklin ground squirrel (Spermophilus franklinii) is a rather drab grayish brown. Black speckling gives a spotted or barred effect. Head and body average 10 inches (25.4 cm) with a 5- to 6-inch (12.7- to 15.2-cm) tail. Adults weigh from 10 to 25 ounces (280 to 700 g). The Richardson ground squirrel (S. richardson) is smaller and lighter colored than the Franklin. Some are dappled on the back. The squirrel’s body measures about 8 inches (20.3 cm) with a tail of from 2 to 4 inches (5 to 10 cm). Adults weigh from 11 to 18 ounces (308 to 504 g). The Columbian ground squirrel (S. columbianus) is easily distinguished from others in its range by its distinctive coloration. Reddish brown (rufous) fur is quite evident on the nose, forelegs, and hindquarters. The head and body measure 10 to 12 inches (25.4 to 30.5 cm) in length with a 3- to 5-inch (7.6- to 12.7-cm) tail. An average adult weighs more than 16 ounces (454 g). The Washington ground squirrel (S. washingtoni) has a small smoky-gray flecked body with dappled whitish spots. The tail is short with a blackish tip. This squirrel is similar to Townsend and Belding squirrels except the latter have no spots. Head and body are about 6 to 7 inches long (15.2 to 18 cm); the tail 1.3 to 2.5 inches long (3.4 to 6.4 cm); and adults weigh 6 to 10 ounces (168 to 280 g). The Townsend ground squirrel’s (S. townsendi) head and body range in length from 5.5 to 7 inches (14 to 18 cm). It has a short bicolored tail about 1.3 to 2.3 inches (3 to 6 cm) long, and weighs approximately 6 to 9 ounces (168 to 252 g). The body is smoky-gray washed with a pinkish-buff. The belly and flanks are whitish. Other species not described here because they cause few economic problems are Idaho (S. brunneus), Uinta (S. armatus), Mexican (S. mexicanus), Spotted (S. spilosoma), Mohave (S. mohavensis), and roundtail (S. tereticaudus) ground squirrels. Ground squirrels are common throughout the western two-thirds of the North American continent. Most are common to areas of open sagebrush and grasslands and are often found in and around dryland grain fields, meadows, hay land, and irrigated pastures. Exclusion: Limited usefulness. Cultural Methods: Flood irrigation, forage removal, crop rotation, and summer fallow may reduce populations and limit spread. Repellents: None are registered. Toxicants: Zinc phosphide. Chlorophacinone. Diphacinone. Note: Not all toxicants are registered for use in every state. Check registration labels for limitations within each state. Fumigants: Aluminum phosphide. Gas cartridge. Trapping: Box traps. Burrow-entrance traps. Leghold traps. Shooting: Limited usefulness

EFFECT OF ARTIFICIAL PERCHES AND NESTS IN ATTRACTING RAPTORS TO ORCHARDS

Artificial perches and nest boxes were placed in three Pacific Northwest orchards to assess their effectiveness in attracting birds of prey to reduce vole populations. The data indicated that birds could be attracted under some conditions, but vole populations were not significantly affected. Additional factors such as vegetative biomass and human activity may limit their usefulness in reducing rodent populations under intensive agricultural conditions

EFFICACY OF METHYL ANTHRANILATE AS A BIRD REPELLENT ON CHERRIES, BLUEBERRIES AND GRAPES

Anthranilitic acid derivatives, used as common food additives, have been explored as bird repellent agents for a number of years. Research in this study show that methyl anthranilate, when exposed to the UV spectrum of sunlight, readily dissipates within 64 hours. The addition of surfactants and extenders did not appreciably alter the degradation curve, nor did they lessen the phytotoxic properties of the chemical. Field trials under IR-4 guidance and support indicate that methyl anthranilate (MA) is an effective, biodegradable, nontoxic bird repellent. In formulation with a lipid molecular binding compound degradation of methyl anthranilate was extended from four to ten days. Phytotoxicity, at effective application rates, was eliminated. Damage to cherries was reduced 43% to 98% depending on cultivar, number of birds present, and crop loads when the treated crops were compared with untreated crops. Depredation of blueberries was reduced 65% and 99% for two varieties. Feeding on wine grapes was diminished 58% to 88%, depending on the affected vinifera. Tasters could not distinguish between treated and untreated fruit nor could certified graders find any reduction in fruit quality

ANTICOAGULANT TRANSLOCATION AND PLANT RESIDUE STUDIES IN CROPS

Three types of assessment techniques explore the possible environmental hazards of two anticoagulant compounds currently used for rodent control. In the first, rheological methodologies were used to assess the ability of pelletized baits to withstand precipitation. From these data, objective information was developed to assist agricultural producers to select a proper bait for a specific climatic period. Bioanalytical evaluations of chlorophacinone indicated that the compound decomposes when exposed to ultraviolet light into four nontoxic elements. Hence, if translocation were to occur, the elements—-not the parent compound—-would be the likely candidates. Finally, radioactive (14C) braomdiolone was tested for translocatability. From the preliminary data developed to the date of this report, little, if any, translocation occurs

EFFECTIVE REPELLENCY CONCENTRATION OF BIRD SHIELD REPELLENT(\u3csup\u3eTM\u3c/sup\u3e) WITH METHYL ANTHRANILATE TO EXCLUDE DUCKS AND GEESE FROM WATER IMPOUNDMENTS

Laboratory studies were conducted to establish the effective repellency concentration (ECR) of Bird Shield Repellent(TM) on mallard ducks (Anas platyrhynchos) and domestic geese for fresh water impoundments. Six concentrations of the repellent compound, ranging from 90 ppm to 2,890 ppm, were placed in small ponds in 2 aviaries and bird behavior monitored for 7 days. Concentrations \u3c360 ppm did not limit either of the test species\u27 activities (drinking or bathing) in the impoundments. Concentration \u3e725 ppm precluded most activity after an initial exposure. Dissolved oxygen tended to decrease after an initial rise and pH increased slightly. Impoundments became discolored with higher concentrations of the repellents\u27 methyl anthranilate precipitates in 24 hr

Disaccharide Intolerance Of European Starlings

The use of disaccharides to discourage bird depredation to agricultural crops has elicited some interest during the last few years. Data developed in these trials indicate that several avian species are intolerant to sucrose because of the lack of sucrase enzymes in their digestive systems. Based on this research it is hypothesized that progressively increasing rates and volumes of solutions would elicit consistent adverse stress reactions. Furthermore, that if birds were intolerant to sucrose, because of their co-evolutionary development with plants, then they should lack the ability to digest lactose. The data developed in these trials does not support either hypothesis. A maximum of 60% of the birds tested showed stress symptoms to 0.75 M sucrose (6.26 mg/Kg body wt.) and 1.00 M lactose solutions (9.15 mg/Kg body wt.) when the birds were subjected to 2 cc treatments. Less than 40% were stressed by the lower concentrations. No adverse reactions were noted with 1 cc concentrations of either solutions or rates. Treating fruit with sucrose did not appear to affect the results until 1.00 M (3.83 mg/Kg) sucrose solutions were applied. No adverse results were obtained with lactose treated fruit

The Use of DMA to Reduce Robin Depredation on Cherries

The use of a biorational pesticide, Dimethyl Anthrantlate (DMA), was investigated for possible use as a robin repellant in an Eastern Washington Research orchard. Applied in low concentrations (2, 4, and 8% with surfactant), robin depredation was reduced an average of 75%. A double-blind taste test showed no consumer aversion for fresh fruit sprayed with DMA two weeks before harvest