[5] Especially in the countries where they are invasive and where presumably their natural enemies are absent, Astylus atromaculatus may become sufficiently numerous to cause significant crop damage.

[citation needed] Astylus atromaculatus is undoubtedly poisonous; livestock deaths have resulted from swallowing large numbers of beetles in their fodder or in pastures.

Though this is not a routine event, it has been confirmed by actual investigation, for example when cattle on the Springbok flats in South Africa ingested heavily infested pasture.

Poisoning caused severe diarrhoea with dark faeces and large quantities of mucus, rapidly followed by weakness and stasis of the rumen.

Post mortem, beetles were found in large numbers in the rumen, associated with symptoms of dramatic congestion and irritation of the abomasum and haemorrhagic pseudomembranous intestinal enteritis.

Because no treatment has proven effective for severely poisoned animals, it is necessary to keep livestock out of pastures while the plants are full of beetles, typically in the cool of mornings and evenings while the insects are inactive and not prone to scatter when alarmed by grazing activities.