Yellow top borer

Yellow top borer (Chilo infuscatellus) is an exotic plant pest not present in Australia. This insect is a serious threat to Australia’s sugarcane industry.

Yellow top borer (Chilo infuscatellus) is a stem boring insect which is a serious pest of sugarcane. It also infests maize, rice and sorghum crops. The yellow top borer caterpillars damage these crops by boring or tunnelling inside plant stems (Figure 1).

Notifiable status

Yellow top borer (Chilo infuscatellus) is not a notifiable plant pest/disease in NSW.

However, if you suspect Yellow top borer (Chilo infuscatellus):

• Call the Exotic Plant Pest Hotline 1800 084 881
• Email biosecurity@dpi.nsw.gov.au with a clear photo and your contact details

A full list of notifiable plant pests and diseases can be found in Schedule 2 of the NSW Biosecurity Act 2015.

Description

Yellow top borer moths have small yellow-brown bodies with 20-26 mm wingspans. They have 2-3 dark spots on their light sandy-yellow to chocolate-brown forewings. The males have dirty-white hindwings while the female moths have silky-white hindwings (Figure 2).

Caterpillars have dark brown heads, with five light-violet, longitudinal stripes along the sides of their dirty-white bodies. Fully grown caterpillars are up to 25 mm long.

The flat, oval, creamy-white eggs are about 1 mm long. They are laid in 2-4 overlapping rows on 10 mm long egg clusters.

Damage

Yellow top borer caterpillars kill the plant growing points and cause “dead hearts” (the youngest still unfolded leaves wilt and die), broken stalks and reduced sugar contents in infested sugarcane crops (Figure 3). They can cause “white heads” (empty or partially filled heads of discoloured grain) in infested rice crops.

The tunnels inside the plant stems allow other pests and diseases into the infested stalks which can also increase crop losses. Infested plant stems are easily broken by wind.

Young sugarcane crops up to 10 weeks old are preferred by the caterpillars, which can kill the plant growing points within 12-18 days of entering the plant stems. Yellow top borer caterpillars can cause 30-75% yield losses in sugarcane crops in India.

Lifecycle

Yellow top borers have four lifecycle stages: eggs, caterpillars, pupae and moths.

Female moths lay their egg clusters parallel to the leaf mid-rib on the undersides of the host plant’s three top leaves. The eggs hatch into caterpillars after 5-9 days incubation.

The caterpillars first feed under the top leaf sheaths before tunnelling into the plant stems. Inside the plant stems caterpillars become pupae before emerging as moths.

The female moths live for 4-9 nights after emergence, when they mate and lay their eggs on local host plants. Yellow top borers can have six successive lifecycles in a year, with each lifecycle lasting 4-6 weeks.

Host range

The main host plant of yellow top borer is sugarcane (Saccharum officinale).

Other hosts include barley (Hordeum vulgare), ikri (Saccharum fuscum), juar (Andropogon sorghum), maize (Zea mays), millet (Panicum spp.), oats (Avena sativa), rarhi and batri (Saccharium spontaneum), rice (Oryza sativa) and sorghum (Sorghum bicolor).

Spread

Yellow top borers are spread from farm-to-farm by infested plant material, farm machinery and vehicles. The caterpillars move about and inside a host plant, while the moths fly between the host plants at night.

Distribution

Yellow top borer is a native insect of Asia and is found in Afghanistan, Bangladesh, Cambodia, China, India, Indonesia, Korea, Laos, Malaysia, Myanmar, Nepal, Pakistan, Papua New Guinea, the Philippines, Sri Lanka, Tadzhikistan, Taiwan, Thailand, Timor, Uzbekistan and Vietnam.

Actions to minimise risks

Put in place biosecurity best practice actions to prevent entry, establishment and spread of pests and diseases:

• practice “Come clean, Go clean”
• ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements
• source propagation material of a known high health status from reputable suppliers
• monitor your crop regularly
• keep records