Childers canegrub
Description
Adult beetles are 18 - 23 mm long, shining yellow-brown to nearly black with no hairs or scales on their backs.
Larval instars are best identified by using a hand lens with a magnification of 10 to identify the hair pattern (raster) and number of hairs on the grub’s rear end. If the grubs don’t contain a raster then they are not canegrubs. The raster of CC is almost oval-shaped, has approximately 35 long hairs in 3-4 rows on each side, with the central area naked and oval-shaped, with overlapping hairs at each end. CC is sometimes confused with French’s, negatoria and noxia canegrubs however CC have more hairs in their raster and the two sides are separate with no over-lap of hairs at the end. The larvae of CC is also smaller than other canegrub species.
CC larvae prune roots from newly ratooning sugarcane in spring and early autumn resulting in poor ratoon growth, yellowing leaves and, in severe cases, the stools can die. Three grubs on average per stool can cause economic losses. Plants which haven’t been severely damaged may recover during late spring and early autumn, which can result in patchiness of growth across paddocks.
CC have a two-year life-cycle with adults emerging after good rains from November to January. Females aren’t strong fliers and use pheromones to attract males and then mate on the soil surface. Eggs generally hatch after two weeks and emerging grubs feed on organic matter. The emerged grubs undergo a number of stages and it is not until the following spring that they cause the most damage to roots and stools. Feeding damage lessens at this point and then the grubs pupate in their second winter or early spring. Beetles will develop after about 4-6 weeks, however they will not emerge from the soil until triggered by optimal weather conditions.
Control
Sugarcane blocks at risk of CC infestation should be monitored in autumn with a view to treat, if necessary, in the following spring. Control is warranted in crops where two or more ratoons are expected, if one canegrub is present per stool. In crops where one ratoon is expected, then an average of three or more second instar CC warrants control.Confidor® Guard is registered for the control of Childers canegrub in sugarcane and peanuts. In sugarcane, Confidor Guard is generally applied in spring or summer either at planting, or at first working, or at half-open drill stage, or at fill-in or final drilling. If larvae are likely to be present at or soon after planting, then early application is recommended to target younger larval stages. Higher rates should be used under high disease pressure or to obtain longer residual activity. In ratoon sugarcane crops, Confidor® Guard can also be applied subsurface behind a coulter disc.
References
Samson, P, Sallam, N and Chandler, K (2013), ‘Pests of Australian Sugarcane: Field Guide’, BSES Limited, https://sugarresearch.com.au/wp-content/uploads/2017/03/Pests-of-Australian-Sugarcane-Field-Guide.pdfSamson, P, Chandler, K and Sallam, N (2010), ‘Canegrub Management and New Farming Systems’, BSES Limited, https://sugarresearch.com.au/wp-content/uploads/2017/03/166910_Canegrub_management_and_new_farming_systems.pdf
Sugar Research Australia (Viewed December 2019), ‘Canegrubs’, https://sugarresearch.com.au/pest/canegrubs/
Sugar Research Australia (2013), ‘Childers Canegrub B14016’, https://sugarresearch.com.au/wp-content/uploads/2017/02/Childers-canegrub-B14016.pdf
Walker, K (2005) Childers Canegrub (Antitrogus parvulus), PaDIL, http://www.padil.gov.au/pests-and-diseases/pest/main/135631