Combination baits containing cholecalciferol plus an anticoagulant are effective against commensal rodents resistant to anticoagulants, and they likely pose less risk than anticoagulant-only rodenticides due to lower concentrations of active ingredients and shorter time to death. However, these combination baits have not been tested for agricultural rodent pests. Therefore, we established a study to test the efficacy of cholecalciferol plus diphacinone artichoke bract and pellet baits to determine their ability to manage California voles Microtus californicus in artichokes, where resistance to anticoagulants is known to occur. Field tests using radiocollared voles indicated that bract baits were highly efficacious (85 %), although pellet baits were less effective (60 %). Low observed efficacy of pellet baits may have resulted from poor weather following application during the second sampling period; further testing may yield more positive results. We observed a bimodal distribution in timing of death, with one group of voles dying between 4.3 and 5.8 days post-consumption; the other group died between 9.0 and 14.5 days post-consumption. Deaths in the first group were attributed to cholecalciferol, while deaths in the second group were likely due to chronic anticoagulant exposure. Almost double the proportion of voles that died from bract consumption did so during the early period when compared to their pellet plot counterparts. This suggests that voles were consuming greater quantities of bract baits over a shorter period of time when compared to the pellet bait. Collectively, these findings indicate that baiting with cholecalciferol plus diphacinone coated bracts is an effective method for controlling vole populations in artichokes. Key message• Cholecalciferol plus diphacinone could be an effective alternative to chlorophacinone for managing California vole populations but has not been field tested • Our findings indicate that cholecalciferol plus diphacinone bract baits were very effective at reducing vole populations in artichoke fields; pellet baits were less effective • Time to death is quicker with cholecalciferol plus anticoagulant baits than with anticoagulants alone, thereby reducing secondary poisoning hazards • This combination bait shows promise for use in field applications.

Context Pocket gophers (Geomyidae) cause extensive damage to many crops throughout western North America. A variety of methods are available to manage these populations, but data are often lacking on their efficacy and especially their cost effectiveness. Additionally, little peer-reviewed data are available that compare multiple methods simultaneously. Aims We tested aluminum phosphide and pressurised exhaust using the Pressurised Exhaust Rodent Controller (PERC) as burrow fumigants, and compared them to trapping to determine which approach was most efficacious and cost effective. Methods We assessed the efficacy of aluminum phosphide, the PERC machine, and trapping through the use of the open-hole monitoring method after single and multiple treatments over multiple years. We determined material and labour costs for each treatment type and amortised this cost over 1250 days of application to determine which treatment type was most cost effective. Key results Aluminum phosphide had the shortest time for application, but we were able to make far more applications per day using the PERC machine, given our ability to treat multiple burrow systems at once with this machine. Trapping and aluminum phosphide were more efficacious than was the PERC machine. When costs were amortised over time, trapping was the most cost-effective approach even with longer application times, given high efficacy. Multiple treatment applications were needed to maximise the efficacy of management programs. Conclusions For small-scale management efforts, aluminum phosphide was a cost-effective and efficacious option. For a greater number of treatments, trapping was the most successful and cost effective. However, a modest increase in efficacy could make the PERC machine a preferred tool as well. We also stress that regardless of the management approach, multiple treatment applications will generally be needed to manage pocket gopher populations. Implications The present study provides growers with information needed to determine efficient and cost-effective methods for managing pocket gophers. This information can be used to craft an integrated pest-management approach to manage damaging pocket gopher populations.

Although strychnine remains the most effective rodenticide for pocket gopher control, the cholecalciferol plus anticoagulant baits tested would be a good alternative when strychnine is unavailable. C + D may be the best option given that it uses a first-generation anticoagulant as the synergist. © 2016 Society of Chemical Industry.

Vole (Cricetidae) girdling of tree trunks is a common form of damage experienced by tree and vine growers throughout much of the Northern Hemisphere. Management programs that effectively incorporate chemical repellents and vegetation management would be of substantial assistance to growers that experience such damage. Anthraquinone has proven effective as a repellent against voles in lab trials, yet controlled field tests of combined anthraquinone and vegetation management programs are lacking. Therefore, we established a mesocosm-based study in central California, USA, to test the efficacy of anthraquinone and vegetation management for reducing girdling damage caused by California voles Microtus californicus to Clementine citrus trees Citrus clementine under semi-field conditions. We observed a 90-100% reduction in girdling damage for trees following a single application of anthraquinone during two trials in summer and spring, respectively. Removal of vegetation around the base of trees further reduced damage during the summer sampling period, with no girdling observed on anthraquinone-treated trees that were surrounded by bare soil. We did not observe this same relationship during spring, and we observed no relationship between vegetation management in the absence of anthraquinone treatments in either seasonal trial, suggesting that vegetation management had a lesser impact on vole girdling than anthraquinone applications. We observed no decrease in efficacy of anthraquinone across the duration of both sampling periods (5-6 weeks), indicating substantial longevity for anthraquinone. Anthraquinone appears to have substantial utility for minimizing vole girdling damage. Field testing is warranted for additional mammalian species to determine potential uses for other taxa.

BACKGROUND: Effective management of ground squirrels relies on an integrated pest management (IPM) approach. Rodenticides may be included in an IPM program, but they must be efficacious with minimal impact on nontarget species. A zinc phosphide-coated green bait may meet these requirements. We established a study in northeastern California to test zinc phosphide-coated cabbage as a management tool for Belding's ground squirrels (Urocitellus beldingi). We specifically addressed factors that would influence the efficacy of a baiting program, as well as potential exposure risk to nontarget species. RESULTS: We found that prebaiting was an important application strategy, and efficacy increased as ground squirrel abundance increased. Efficacy was also greater in western portions of the study area, likely due to greater bait consumption at western sites. Belding's ground squirrels fed most heavily on cabbage during mid-morning and late afternoon; bait applications shortly before these time periods would increase bait consumption while minimizing nontarget risk. Bait uptake was greatest around burrow entrances. The only nontarget species observed feeding on cabbage was the California kangaroo rat (Dipodomys californicus), although they were never observed feeding on treated cabbage. CONCLUSION: Zinc phosphide-coated cabbage can be an efficacious tool for managing ground squirrels, but there will be limitations on where and how it can be used effectively. It posed a low risk to nontarget species present in our study area, but nontarget risk could vary regionally. The use of a zinc phosphide-coated green bait should only be one part of an IPM strategy for managing ground squirrels.