African black beetle occurs from Maryborough south. It could probably spread further north. Strict quarantine should be observed against transfer of live specimens or contaminated material. Black beetle is a native insect and occurs in all cane areas, but is more common in areas with wetter soils. Both species are found with paspalum and similar grasses.
Damage
Beetles of both species damage plant and ratoon cane. They chew ragged deep holes into young ratoons, causing dead hearts. A shoot attacked near the base cannot recover. Shoots attacked above growing points may side shoot. In southern areas, attack by either species is much more common and heavy in spring than in autumn. Damage by from African black beetle is most common when cane is newly planted into old pasture country. There are reports that Q137 and Q145 are especially prone to attack by African black beetle.
Description
Grubs of both species grow to 25-30mm long. The soft part of the body is blue to grey-white, and the head rough surfaced and dark red-brown. They do not have a tell-tale hair pattern like canegrubs. Beetles of two species are very similar in appearance. They are shining black above, andred-black underneath. The upper surface of the back is smooth and the wingcovers have several parallel fine ribs along their length. The black beetle is usually about 15mm long, but can vary from 12-17mm long. African black beetle is slightly smaller, 9-15mm long. African black beetle has two rows of grooves on the back of the last segment beneath the rear of the wingcovers, these are not present in the black beetle.
Life Cycle
Both species have a one year life cycle. The beetles mostly emerge from midsummer until the end of autumn and then rest during winter. They become very active in spring, when they damage cane. Egglaying begins early in September and continues until February. Eggs of both species are laid singly in soil. They hatch in about 2-4 weeks depending on temperature. Both species go through 3 grub growth stages which take about 3 months in total. The pupal stage then lasts 2 weeks. Over the spring-autumn period there is usually a range of insects at different growth stages present at the one time. Grubs feed mainly on organic matter in the soil. Older grubs may feed on roots of grass.
Control
If breaking up grassy country for cane be aware that these pests could be present. Control includes repeated ploughing and several months of fallow. Growing a legume (bean) is a good idea as it is not a favourite food of these pests. Autumn planting is preferred to spring planting, because beetles are less active in autumn. Also the autumn-planted cane will have grown too large to be worried by beetles which become active in spring.
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Black Beetle | Adult black beetle attacking a shoot |
