A Practical Technique for Applying Rodent Repellents to Acorns

Removal of the acorn pericarp and coating the seed directly with an Endrin-Thiram mixture had some effect in repelling caged squirrels in this exploratory study, but germination was both lowered and delayed. However, the results indicated that some such treatment would be worthwhile to prevent the usual heavy losses of planted acorns due to rodent pilferage. Though successful chemical techniques have been developed for reducing rodent pilferage of coniferous seed, there is yet no effective method to similarly protect seed of the large-seeded hardwoods. Engle and Clark (1959), for example, found that coating oak acorns with an EndrinThiram mixture was of little value; pilfering animals simply shucked-off the external fruit coat (pericarp) and ate the untreated kernel. However, partial success was reported by Johnson et al (1964) who noted that caged squirrels would shun treated acorns if other food supplies were available. Crozier and Merritt (1964) found that pilferage losses of acorns planted in open fields was reduced as alternative food supplies in adjacent wooded areas increased during the spring season. These results seem to suggest that if an application technique with a chemical that would at least partially repel rodents were to be combined with properly timed planting in the spring to take advantage of maximum alternative food supplies, a significant increase in survival of direct-seeded acorns might be obtained. Since the EndrinThiram mixture seems to have some repellency value, even though its effect may be bypassed when animals discard the treated pericarp, removal of the pericarp before chemical treatment might provide a key to the problem.

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Author(s): Clair Merritt, Michael H. Adams

Publication: Tree Planters' Notes - Volume 18, Number 2 (1967)

Volume: 18

Number: 2