LONGHORN BEETLE INCURSION IN SA SUGAR INDUSTRY

Dr Carolyn Baker


A member of the cerambycid family, Cacosceles newmannii, commonly called the longhorn beetle appears to have become adapted to sugarcane, and has invaded the Entumeni area.  


From the first isolated records of the longhorn beetle in 2015 in the area, the beetles have now been recorded on 540 hectares, and with a likely containment area of 1 000 hectares.  Naturally occurring in indigenous forests, where few records of its existence are recorded, its migration into sugarcane represents an ecological shift. 

 


Above: Third instar larva in the cane stalk.  (Photos:  Lynette Clennell)


Although little information exists on its biology and behaviour due to its status as a rare insect, SASRI entomologists have established that it has an extended lifecycle (up to two years), largely as a result of a lengthy larval stage, and that a single female beetle is capable of producing up to 2 000 eggs. Larvae hatch from eggs laid in the soil in sugarcane fields and then feed on the roots of sugarcane plants, entering the stalk where they grow and feed resulting in stool death.  It appears that there is only one larva per stalk.



Above: Male adult beetle.


Adult beetles are responsible for the spread of the pest when they emerge from earthen-encrusted pupae during the flying period from November to late February.  Unlike the white grub beetles that are known pests in the industry, and that are active at night, male and female longhorn beetles fly during the day, with males actively seeking females for copulation opportunities.  


In response to the incursion, a set of remedial measures were gazetted in March 2017, that depending on the level of infestation require early harvest and eradication of the crop followed by a fallow for a minimum of one year or until the pest has been destroyed. However, in view of the lengthy life cycle of the beetle it is likely that the recommended fallow should be extended. Further, measures to monitor and prohibit movement of seedcane have been instituted.


Dr Carolyn Baker, SASRI Director, SASA



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