Spicing up restoration: can chili peppers improve restoration seeding by reducing seed predation?

Abstract

Seed predation by rodents presents a significant barrier to native plant recruitment and can impede restoration seeding efforts. In nature, some plants contain secondary defense compounds that deter seed predators. If these natural defense compounds can be applied to unprotected seeds to inhibit rodent granivores, this approach could improve restoration seeding. Capsaicin is the active ingredient in chili pepper (Capsicum spp.) seeds that creates the burning sensation associated with human consumption of hot peppers. This compound has a similar effect on other mammals and is believed to have evolved as a deterrent to rodent seed predators. We used seed-coating techniques to attach powder ground from Bhut Jolokia (Capsicum chinense) peppers to native plant seeds and evaluated the efficacy of these seed coatings for deterring rodent seed predation and enhancing native plant recruitment using laboratory and field experiments. Laboratory feeding trials demonstrated that native deer mice (Peromyscus maniculatus) consumed far fewer pepper-coated seeds compared to untreated control seeds. Field seed-addition experiments consistently demonstrated that rodent seed predation reduced native plant recruitment over the 4-year study. Coating techniques used in the first 3 years were not persistent enough to reduce rodent seed predation effects on plant recruitment. However, a more persistent coating applied in conjunction with late-winter sowing negated rodent seed predation effects on recruitment in year 4. Our results demonstrate that coating seeds with natural plant defense compounds may provide an effective, economical way to improve the efficacy of plant restoration by deterring seed predation by ubiquitous rodent granivores. Implications for Practice• Coating native plant seeds with natural seed defense compounds can reduce rodent seed predation and increase seedling establishment in restoration seeding efforts. • Applying a capsaicin coating to spring-germinating seeds sown in late winter can increase native plant recruitment, while reducing the total cost per established seedling. • The current coating technology is not persistent enough to protect seeds throughout the winter, so future work is needed to extend seed-coating efficacy in order to apply this technology for fall applications.

Seed enhancement: getting seeds restoration‐ready

“…Similarly, the inoculation of microorganisms in the coating improved seedling emergence and survival of two species on degraded rangeland in the Qinghai–Tibetan Plateau (Liu et al ), while seeds coated in salicylic acid improved plant survival and growth for native grasses in Australia (Pedrini ). Seed predator repellents incorporated in seed coatings reduced seed consumption rates from rodents (Taylor et al ) and improved plant establishment (Pearson et al ).…”

“…In spite of some evidence of successful application of seed priming and coating to treat seeds of native species, most of this work has been conducted in controlled experimental settings, and the costs and benefits related to the employment and scalability of these technologies have rarely been investigated. A baseline approach to estimate economies of seed coating should compare the cost for each successfully established plant from treated and untreated seeds (Pearson et al ). Additionally, many external variables should be considered beyond the cost of seed coating material and personnel time.…”

Deterring rodent seed‐predation using seed‐coating technologies

“…Extensive research demonstrates that rodent seed-predation can greatly reduce native plant recruitment (Brown & Heske 1990;Howe & Brown 2001;Larios et al 2017) thereby hindering restoration efforts (Nelson et al 1970;Gurney et al 2015;Pearson et al 2018). We evaluated the efficacy of various seed-coating formulations for reducing D. ordii seed-predation on Great Basin wildlands.…”

“…The aversive effects of ghost pepper are well documented (Nolte & Barnett 2000;Hansen et al 2016;Pearson et al 2018), as are the effects of neem (Oguge et al 1997;Hansen et al 2015). The success of the neem oil coating is particularly exciting because neem has also been shown to repel insects (Ogbuewu et al 2011), prevent plant-parasitic soil pathogens (Akhtar & Mahmood 1996), and deter feeding by birds (Mason & Matthew 1996).…”

“…Rodent consumption of planted seeds often limits the success of restoration efforts (Nelson et al 1970;Gurney et al 1996;Pearson et al 2018). To date, few techniques exist for dealing with seed loss from rodent predation (Longland & Ostoja 2013;Pearson et al 2018). Finding a solution to rodent seed-predation is complex, as the presence of rodents can be beneficial to some aspects of restoration.…”