Create a Yates account today!
Sign up to join the Yates Garden Club for monthly e-mails packed with seasonal inspiration, tips for success & exclusive promotions.
Plus if you’re a Garden Club member you can take part in the Yates Growing Community - a blog to share successes, get advice & win prizes in fun challenges along the way!
Enter the email address associated with your account, and we'll email you a new password.
Coleoptera
Heteronychus arator
The African Black Beetle is an introduced pest species. In NZ it’s mostly found in the upper North Island. Larvae are easily mistaken for NZ grass grubs, although they're a different species to native grass grubs (Costelytra giveni) and bronze beetles (Eucolaspis brunnea).
Damage to garden plants is caused by both the adult beetles and their larvae. Adults mostly feed on plant shoots and stems, just above or below the soil surface (they can burrow as far as 15cm deep). They fly in swarms, most often on warm nights – especially in autumn, less often in spring. Flying beetles are attracted towards artificial lights.
Black beetle larvae feed on grass and plant shoots below soil level, causing dead patches, yellowing and severed stems. Larvae generally cause damage to lawns from summer to early autumn, December - March.
The summer season is the easiest way to diagnose black beetle larvae in a lawn, because the other, similar grub species tend to cause damage from autumn into winter. This summer activity means black beetle is a particular pest of warm season grasses like kikuyu and couch.
Most grass varieties are susceptible to attack, severely impacting lawns and pasture areas. Warm-season lawn types are particularly at risk.
Both potted plants and plants in the ground are at risk. Young plants and seedlings are particularly vulnerable to attack.
Ornamental garden plants may also be impacted.
Usually, there is just one generation of African Black Beetle per year. However, depending on environmental conditions, it can take up to 2 years to complete their lifecycle.
Beetles are glossy black, oval-shaped and 12-15mm long. On the underside of the body are light-brown bristle-like structures (setae). The head is short, broad and angles downwards. At the front of the head are chewing mouthparts. On either side of the head are a pair of compound eyes and short, golf-club-like antennae. Behind the head, on the upper side of the body, is a large trapezoid-shaped plate (pronotum) which is the front segment of the middle section of the body (thorax).
Attached to the underside of the thorax are 3 pairs of legs which are lightly covered in spines. The upper portion of the leg is slightly flattened while the lower leg is thinner and thread-like. However, in males, the lower portion of the front legs are also slightly flattened. At the tips of the legs are claws. The hindlegs are the largest pair which are used for digging. Adult beetles are slow crawlers, on the ground.
Adults have 2 pairs of wings, the outermost wings are hardened forewings (elytra) and used to protect the delicate membranous hind-flight-wings. While at rest, forewings fold down over the flattened hindwings and meet in the centre of the body, forming a distinct straight line. At the top of this line is a small triangular-shaped plate known as the scutellum. Along the length of the forewings are straight, mostly parallel indented lines.
The grub-like larvae have a creamy-white body with an orange-to-brown rounded head capsule, and black jaws. The hind section of the body is generally swollen and grey-blue to green in colour, due to the visible contents of the gut. The body is long and heavily segmented, naturally curls into a C-shape, and grows up to 25mm long. At the front, along either side of the body, at each segment are a pair of orange-brown spots which are used for breathing (spiracles). On either side of the head are a pair of compound eyes and at the front of the head are chewing mouthparts. Attached to the underside and middle section of the body are 3 pairs of thin 5-segmented legs. Larvae are wingless.
Share
Share this article on social media