Arecanut Insect Pests

Spindle bug

Biology:

• Egg: Eggs are laid singly between the leaflets of the spindle. The eggs hatch in 9 days.
• Nymph: There are five nymphal stages and it is completed in 15-24 days. The light violet brown nymphs have greenish yellow border. Adult: Adult bugs are brightly coloured (red and black)

• Inhabit the inner most leaf axils, usually below the spindle.
• Both nymphs andadults suck sap. Infested portions develop necrotic patches leading to drying.
• Spindle fails to unfurl.
• Severe infestation leads to stunting of the palm.

Predators: Lacewing, Ladybird beetle, King crow, common mynah, wasp, dragonfly, spider, robber fly, reduviid bug, praying mantid, red ant, big eyed bug, pentatomid bug, earwig, ground beetle etc.

Pentatomid bug

• Egg: The white or pale green barrel-shaped eggs are laid in clusters (25 eggs) on the lower surface of leaves. Egg period is about 4-5 days
• Nymph: Nymphs lack fully developed wings and are tick-like in appearance, ranging in size from 2.4 mm (1st instar) to 12 mm (5th instar). First instars are orange or red in colour and remain clustered around the egg mass. The 2nd instars appear black in colour and subsequent instars (3rd, 4th, and 5th) resemble adults in colour. Each nymphal instar lasts for 10 days.
• Adult: Adults are 12 to17 mm long (approximately 1/2 inch), and have a mottled appearance. Alternating dark and light bands occur on the last two antennal segments. Additionally, the head and pronotum are covered with patches of coppery or bluish metallic-colored punctures and the margins of the pronotum are smooth. The exposed lateral margins of the abdomen are marked 32 with alternate bands of brown and white. Faint white bands are also evident on the legs.

Life cycle:

Damage symptoms:

• The later instar nymphs and adult bugs pierce the tender nuts and suck the kernel sap resulting in drying of kernels and dropping of tender nuts
• Characteristic pinprick black marks are seen at the feeding sites, which subsequently enter into the kernel

Parasitoid:Anastatus bangalorensis

White grub/root grub

• Egg: Adult beetles lay eggs in soil mostly up to 10 cm depth. Eggs hatch in about 1 to 3 weeks.
• Grub/larva: The grub period with three instars is completed in 7 to 8 months.
• Pupa: The pupation takes place in soil in cocoons prepared with mud which lasts about a month
• Adult: The adult beetles are chestnut brown in color and emerge during May-June few days after receipt of pre-monsoon showers, between 6.30 and 7.30 PM.

Life cycle:

Damage symptoms:

• Root/white grubs occur mostly in sandy and sandy loam soils.
• They are voracious feeders of arecanut roots.
• The early instar grubs feed on the roots of grasses and other humus.
• The second and third instar grubs of these beetles feed on tender and mature roots of the palm. In severe cases, the bole of the palm is also eaten up.
• They also feed on roots of intercrops such as banana, cocoa, tapioca, yams etc.
• Feeding on arecanut seedling roots results in dropping and drying of leaves
• Affected seedlings come off easily since the entire root system is usually eaten up.
• Palms with continuous (few years) infestation show a sickly appearance, with yellowing of leaves, tapering of stem, and reduction in yield.
• The palms may topple in case of severe loss of root system
• Natural enemies of white grub/root grub
• Parasitoid: Scoliids wasp etc.
• Predators: False vampire bats, garden lizards, wild boar etc.

Inflorescence caterpillar:

• Egg: Eggs are white, circular and slightly flat and approximately 0.8 mm in diameter. Eggs are laid on flowers from emergence to the end of flowering. Egg period is 5 days.
• Larva: Larvae complete their development within the fruit. The red coloured caterpillar penetrates the inflorescence and remains in the tissue for 15 days, tunnelling and destroying the tissue. After this phase it moves to the base of the peduncle changing into a pupa. As the caterpillar destroys the tissues of the inflorescence, a resin coloured liquid gum is exuded from the fruitlets, which upon exposure to air becomes reddish coloured and as it solidifies turns dark brown.
• Pupa: Pupa 12 mm long and 5 mm wide with a brown color and a few dark spots. Moth emerges from pupa in 7-11 days.
• Adult: The adult moth has a greyish upper wing surface and a cream color underneath with a wingspan of 28-35 mm. The adult can be found during the day or night, flying in a rapid and haphazard fashion.

Life cycle:

Damage symptoms:

• Burrowing and feeding activities produce visible damagesymptoms in the form of frass production and a sticky, gummy exudate.
• Mature caterpillars can damage newly opened inflorescences also.
• In severe cases, they bore into the tender buttons and tender nuts as well.
• Delayed spathe opening, yellowing of spadices, presence of small holes with frass and drying patches on the spathe are the external symptoms of attack.
• Natural enemies of inflorescence caterpillar:
• Predators: Predatory ant, lacewings, ladybird beetles, King crow, common mynah, wasp, dragonfly, spider, robber fly, reduviid bug, praying mantis, red ants, big eyed bugs (Geocoris sp), pentatomid bug (Eocanthecona furcellata), earwigs, ground beetles, rove beetles etc.

Red mite

These mites are small and flat, and usually feed on the under surface of leaves. They are slow moving and do not produce silk, as do many tetranychid (spider mite) species.

Biology:

• Egg: The eggs are laid in groups, often near the midrib or depressions in the leaflet. The freshly laid egg is attached to the leaf surface and a fine white stripe (slender hair like structure) as long as or longer than the egg is present at one end. The incubation period is 8 days for fertilized eggs and 7.3 days for unfertilized eggs.
• Larva: The newly hatched larva is red and has three pairs of legs. A blackish tinge may develop on the posterior end of the dorsum after feeding. The larva typically feeds for 3-5 days and then becomes quiescent for 1.7 to 1.9 days before moulting to the protonymphal stage.
• Protonymphs: The reddish protonymph emerges with four pairs of legs and feeds for 2-5 days prior to becoming quiescent. The quiescent phase lasts from 1-4 days before deutonymphs emerge from the exoskeleton. The female protonymph has an ovoid body with a rounded posterior but the male protonymph has a pointed posterior and a nearly triangular body.
• Deutonymphs: Deutonymphs are larger than protonymphs but resemble protonymphs with regard to feeding and other habits. The active phase lasts 2-5 days and the subsequent quiescent phase lasts from 2-4 days.
• Adult: Females develop dark markings on the dorsum of the body after feeding. The dorsum is smooth, except for the presence of punctae (sculptured depressions). The male is smaller, but similar to the female in shape except for having a tapering of the posterior end of the body. Adult females are larger than males and less active. The life cycle from egg to adult typically requires 23 to 28 days for females and 20 to 22 days for males.

Damage symptoms:

• The reddish mites are easily seen against green leaves.
• Heavy infestations of the mites are typically on the lower surface of the leaves, and yellow speckles and blotches on the leaves are seen from the feeding damage.
• Yellowing of the leaves may often be severe.

Predators: Staphylinid beetle, predatory mite etc.

White mite

• Egg: Adults lay light yellowish rounded eggs on lower surface of leaves.
• Nymph: Nymphs are smaller in size than adults.
• Adult: Adults are greyish green with black blotches scattered over dorsum. Adults possess 4 pairs of legs. There are 30 overlapping generation in a year

• Adults and nymphs present on the lower surface of leaves.
• Adult males feed very little and the main damage is caused by the females and immature stages.
• The colony is found under white webs.
• Feeds on lower surface of arecanut leaves.

Predators: Anthocorid bug, syrphid/hover fly, green lacewing, ladybird beetle, predatory mites etc

Burrowing nematode

• Infested palms show general yellowing, reducing growth, vigour and yield
• Appearance of orange-coloured lesions, blackening of tips of lateral and tertiary roots and rotting of roots

IPM for Arecanut

To know the IPM practices for Arecanut, click here.

Source: NIPHM, Directorate of Plant Protection, Quarantine Storage