Plants produce anti-herbivory compounds that can be extracted and used in commercial repellents.
Malhi and Kaur (1996) tested the effect of neem oil (Nimbecidine ® emulsion 100% @5 ml/litre) to prevent damage from house crows (Corvus splendens) and house sparrows (Passer domesticus) on sprouting wheat. Damage was 22 % lower in treated pots than in control pots. To prevent carrion crow (Corvus corone) losses of sunflower seeds at plantation, Destrez et al. (2022) covered seeds with a mixture of spices (chili peppers and pepper) and an odour agent (geraniol) and observed 22 % less seed loss in treatment furrows compared to controls. Extracts from tabebuia species were applied to repel Hispaniolan woodpeckers (Melanerpes striatus) from cacao pods, but the relative risk of damage was not reduced in comparison to untreated controls (RR = 1.43) in this Dominician Republic (Mitchell and Bruggers 1985).
In a Tanzanian study, Ngowo et al. (2005) evaluated the potential of cinnemamide to prevent damage from multimammate mice (Mastomys natalensis) on maize seeds. The relative risk of damage in treatment plots (RR = 0.51) indicated a damage reduction compared to control plots.
