Ecology and management of rodents in no‐till agriculture in Washington, USA

Abstract

No-till farming is an important approach to sustainable agriculture because it can conserve soil and water resources. Unfortunately, rodent populations can thrive under no-till conditions because burrow systems are not disrupted by annual plowing and plant residues build-up on the surface, providing cover and insulation. This can result in substantial crop damage. We assessed rodent populations, habitat use, food habits, and crop damage in a no-till cropping system in Washington, USA. We also conducted preliminary trials of methods to reduce rodent populations and crop damage. In the fall, many more rodents were captured in fields with unharvested crops than in fields containing only plant stubble, suggesting that rodents leave fields after crop harvest, providing that suitable habitats are nearby, even when adequate cover is still available in harvested crop fields. By spring, the number of voles captured was much lower relative to fall. Despite this, capture rates were much higher in surrounding permanent grass areas than in crop (barley, wheat, pea) fields, suggesting that these grassy areas serve as refugia for rodents. Furthermore, the permanent grass cover type was the landscape variable most associated with rodent capture rates. In three winter pea fields, rodents removed 5-15% of the pea plants over winter. Examination of stomach contents revealed that voles mainly fed on grain plants in spring, but that their diet was more diversified in fall. Deer mice fed heavily on grain plants in both spring and fall, but also used insects as food. Metal barrier exclosures (9 m × 9 m), extending above and below ground, did not prevent access by rodents. Rodent populations in areas treated with zinc phosphide on grain were comparable to untreated areas 1 year after application of the rodenticide, perhaps because of immigration and recruitment, suggesting that baiting does not provide a long-term solution to rodent damage in no-till agricultural fields.

Effectiveness of rodenticides for managing invasive roof rats and native deer mice in orchards

“…Previous studies on roof rats have found that elevated baits are typically more effective than bait placed at ground level (e.g., Campbell et al 1998), while bait is typically broadcast on the ground for deer mouse control (e.g., Witmer et al 2007b). As such, we were not sure how deer mice would respond to elevated bait stations.…”

An efficacy test of cholecalciferol plus diphacinone rodenticide baits for California voles (Microtus californicusPeale) to replace ineffective chlorophacinone baits

“…Additionally, most species of voles exhibit strong population cycles, whereby they reach very high densities (>2471/ha) every 3À5 years. Severe damage to agricultural and forestry resources occurs at these peak densities (Witmer & VerCauteren 2001;Witmer et al 2007;Witmer & Proulx 2010).…”

Perspectives on Existing and Potential New Alternatives to Anticoagulant Rodenticides and the Implications for Integrated Pest Management

“…In open settings such as croplands or orchards, the task is much more difficult and the chance of success is small. Although research in this area continues, there are few successes to report at this time (Pelz 2003;Witmer et al 2007cWitmer et al , 2008b). …”

“…Many of these manipulations are not done just to reduce rodent habitat (which may be an incidental benefit) but for other reasons such as to reduce vegetative competition with crops or trees, to reduce soil pathogens, or to prepare sites for planting. Burning, plowing, disking, herbicide application all reduce vegetative cover, at least for the short term, and usually greatly reduce rodent populations Witmer et al 2007c). Plowing and disking have the additional advantage of disrupting the burrows of rodents (Salmon et al 1987).…”

“…These methods have been used extensively in reforestation, orchards, and traditional agriculture. Understandably, farms that have implemented no-till agricultural practices to reduce erosion, water loss and improve soil fertility have continued to suffer from high populations of rodents because the soil is not disturbed to an adequate depth and plant stubble (residues) are left on the surface (Witmer and VerCauteren 2001;Witmer et al 2007c). Problems from rodents are compounded when grassy refugia are left along the periphery of crop fields that rodents can make use of when crop fields are rather bare (Brown et al 2004).…”