Effectiveness and persistence of cinnamic aldehyde as an antifeedant on rats under storage conditions

- 5% cinnamic aldehyde in bait is effective antifeedant against the house rat Rattus rattus.
- Antifeedant effect persisted for a period of 27 days.
- Formulation with sodium bicarbonate as an emulsifier prevented rodent damage for up to 15 days.

The house rat, Rattus rattus (Linnaeus), is responsible for causing severe damage in outdoor commercial grain stores where rodent proofing is not possible. Rodenticides are the preferred option for preventing rodent attacks. However, secondary poisoning and development of bait shyness and resistance among rodents after exposure to toxic chemicals has increased the search for new, safe, ecofriendly and effective control methods, which can prevent damage for a long duration. In the present study, the effectiveness and persistence of cinnamic aldehyde as an antifeedant against R. rattus were evaluated. Cinnamic aldehyde treated bait at 5% concentration was effective as an antifeedant and secondary repellent against R. rattus in bi-choice feeding tests. The antifeedant effect was retained for at least 14 days after treatment. There was no significant difference between consumption of treated and untreated bait during the first four hours of exposure of rats under bi-choice feeding tests, indicating absence of a primary repellent effect of cinnamic aldehyde. Feeding bait mixed with 5% cinnamic aldehyde continuously for 27 days in bi-choice feeding tests revealed the persistence of the antifeedant effect. This study demonstrated that 5% cinnamic aldehyde can be used under field conditions to prevent the damage caused by house rats for long durations. A formulation of 5% cinnamic aldehyde containing sodium bicarbonate as an emulsifier prevented rodent damage in terms of consumption of wheat grains, number of cuts on bags, quantity of grains spilled from bags cut by rats and percent damage due to rat urine under simulated storage conditions in laboratory pens for durations up to the experimental period of 15 days. Study of feeding behaviour in feed scale consumption monitoring also confirmed the secondary repellent effect of cinnamic aldehyde against the house rat. Our results indicate that the sodium bicarbonate emulsified formulation of 5% cinnamic aldehyde has the potential to protect stored products from rodent damage in a manner that is effective, persistent and environmentally acceptable.