Cabbage centre grub
Cabbage centre grub (CCG), is a minor and occasional pest of brassica crops in Australia. CCG are common during summer to autumn in Queensland and New South Wales (NSW), whilst higher numbers in spring are observed in southern areas of Australia. Hosts include canola and brassica crops such as cabbage, cauliflower, Chinese cabbage, broccoli, Brussels sprouts and radish.
Description
CCG larvae are small (12 mm), cream coloured with a dark head and reddish-brown stripes running lengthwise along the body. Adult moths are mottled brown, at maturity are 12 mm long and their wings form a flattened tent shape over the body. Eggs are creamy coloured, oval and are usually laid on the soil surface or leaves. Eggs hatch and larvae emerge, feeding on leaves before they pupate just below the soil surface at the base of the plant before emerging as adult moths. Warm weather favours the activity of CCG and several generations can pass within a year.
Larvae attack the basal leaves and flowers of brassica crops. Young CCG larvae often feed alone, protected by a silken webbing, whilst mature larvae find shelter within growing points or the crown of the plant. CCG larvae tunnel into the growing points of plants, causing damage to the terminal bud. Leaves can become webbed together and large blisters can form.
Control
Several natural predators including spiders, assassin bugs, ladybird beetles, lacewings, ants and native earwigs all provide some level of control over CCG. Therefore, reduce broad spectrum insecticide use where possible to encourage these populations. Check seedling stock for eggs and larvae and if found, remove or replace stock. Prior to sowing, plan to allow adequate space between rows to enable maximum spray coverage. Cultivation of the soil and ploughing in crop residues may also help manage CCG populations.
Monitor crops for symptoms of a CCG infestation as control is easiest at the first sign of infection while larvae are still visible. Often diamondback moth control programs will provide adequate control of CCG, however should an outbreak occur insecticides can be applied. Decis Options® is registered for use in cole crops; cabbage, cauliflower, Brussels sprouts, broccoli, etc.
References
Cesar (Viewed Dec 2019), ‘Cabbage centre grub’, http://cesaraustralia.com/sustainable-agriculture/identify-an-insect/insect-gallery/pest-insects/moths-and-butterflies/cabbage-centre-grub/
Dimsey, R, Carey, D and Henderson, S (2010), ‘Brassica Best Practice. Integrated pest management’, Department of Primary Industries, Pg 12 – 13, https://ausveg.com.au/app/data/technical-insights/docs/TL197.pdf
Ekman, J, Tesoriero, L, and Grigg, S (2014) ‘Pests, Diseases and Disorders of Babyleaf Vegetables” A field Identification Guide, Applied Horticulture Research, Pg 91, http://ahr.com.au/wp-content/uploads/2015/03/AHR_Babyleaf_Proof3.pdf
Hanock, A (2017), ‘Cabbage centre grub damaging summer canola’, SARDI, Pestfacts Issue 2, https://www.pir.sa.gov.au/research/services/reports_and_newsletters/pestfacts_newsletter/archive/pestfacts_newsletter_archive_2017/pestfacts_issue_2_2017/russian_wheat_aphid_widespread_in_some_areas2