INTERESTING INSECTS

By N A Martin (2010, revised 2018)

Poroporo fruit borer, Poroporo stem borer

Sceliodes cordalis (Doubleday, 1843)

Margaritia cordalis Doubleday, 1843

Daraba extensalis Walker, 1866

Eretria obsistalis Snellen, 1880

Sceliodes mucidalis Guenee, 1954

Richard Mally and other authors published a paper in 2015 on a study of African moths whose larvae feed internally in fruit of Solanaceae. They discovered seven previously unknown species, but also concluded that the genus Sceliodes was synonymous with Leucinodes. They used evidence based on morphological characters and a study of mitochondrial DNA. Species of Leucinodes are found in Africa, Asia and Australasia.

This native moth is found in New Zealand and mainland Australia where it’s two main native host plants, Solanum aviculare and S. laciniatum, occur. In New Zealand it is present throughout the North Island. In the South Island it is present in Nelson and Marlborough, and in coastal or near coastal areas of the Canterbury and Otago down to Dunedin.

Conservation status: Widespread, not threatened, a minor pest of some crops.

Annual cycle of the poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HA]

The insect overwinters as a caterpillar in a cocoon. This winter rest is called diapause. In the spring the larvae pupate, and moths emerge in November and December. The adult moths have distinctive pale brown triangular wings and hold their abdomens curled up in a distinctive manner.

Mating and egg-laying

The newly emerged female moth emits a pheromone (a mixture of volatile chemicals) that attracts male moths. After mating, female moths lay white eggs either on green fruit by the calyx or on the underside of leaves by the midrib. During egg-laying, the ovipositor is moved over the leaf or fruit surface. When it touches a suitable crevice, one or more eggs are laid. The eggs turn red after 1-2 days.

Caterpillar behaviour in fruit

Caterpillars hatching from eggs on fruit crawl over the fruit before chewing a hole in the skin. They then tunnel just below the skin. Older caterpillars burrow into the centre of the fruit and feed on the developing seeds.

Caterpillar behaviour in leaves and shoots

Caterpillars from eggs laid on leaves, either crawl to a nearby fruit or burrow into the midrib of the leaf. These caterpillars later leave the leaf and burrow into the shoot. The caterpillar moults (changes its skin) five or six times.

Cocoons, pupae and moth emergence

When fully grown, and just before leaving the fruit or shoot, the caterpillar turns red. The caterpillar comes out only at night and presumably its red colour makes it more difficult for predators to see. The caterpillar finds a crevice and spins a cocoon, which it covers with any debris from its immediate surrounds, e.g. lichen, decayed wood, paint, making it very difficult to find. The caterpillar turns white and after a few days, pupates. Seven to ten days later, an adult moth emerges. There are usually two generations per year. Caterpillars forming cocoons from mid to late February onwards stay as larvae until the following spring.

Female moth of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae); note the large abdomen compared with male, top view showing up turned abdomen. Creator: DSIR photographers. © Landcare Research. [Image: 3H8]

Female moth of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae); note the large abdomen compared with that of the male; top view showing up turned abdomen. Creator: DSIR photographers. © Landcare Research. [Image: 3H9]

The newly laid, white, eggs of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae) are laid by the fruit calyx. They turn red after a day. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GN]

Red eggs of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae) by leaf vein of poroporo (Solanum aviculare). Creator: DSIR photographers. © Landcare Research. [Image: 3H2]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore a tiny hole (arrow) into green fruit of poroporo (Solanum aviculare) and mine under the skin, which may split as the berry grows. Creator: DSIR photographers. © Plant & Food Research. [Image: 3H0]

Mature caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae) make a large hole in the skin as they leave the fruit of poroporo (Solanum aviculare) to find a cocooning site. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GP]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore into the midrib of leaves of poroporo (Solanum aviculare) causing the leaf tip to wilt. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GS]

Newly emerged caterpillars of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae), may bore into the midrib of leaves of poroporo (Solanum aviculare) causing the leaf tip to wilt. Leaves often retain this distinctive bend. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GL]

Poroporo (Solanum aviculare) shoot with wilted leaves after a caterpillar of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), has bored into the stem. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GM]

Large larvae of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), burrow into shoots or into the centre of berries of poroporo (Solanum aviculare). Larvae turn red when they are mature and about to leave the plant to find a cocooning site. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GR]

Large larvae of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae), burrow into shoots or into the centre of berries of poroporo (Solanum aviculare). They turn red when they are mature and about to leave the plant to find a cocooning site. Creator: DSIR photographers. © Plant & Food Research. [Image: 3H1]

Larvae of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae) spin cocoons in cracks or crevices, such as a broken stem. They cover their cocoons with debris that camouflages them and makes them very difficult for humans and presumably birds to find. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GT]

Cocoon cut open to expose pupa of Leucinodes cordalis (Lepidoptera: Crambidae); note the moulted skin of the larva. Creator: Tim Holmes. © Plant & Food Research. [Image: 15UQ]

Cocoon cut open to expose pupa of Leucinodes cordalis (Lepidoptera: Crambidae); note the moulted skin of the larva. Creator: Tim Holmes. © Plant & Food Research. [Image: 15UR]

Side view of pupa of Leucinodes cordalis (Lepidoptera: Crambidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15US]

Rear end of pupa of Leucinodes cordalis (Lepidoptera: Crambidae) showing hooks used to hold on to the cocoon during adult emergence. Creator: Tim Holmes. © Plant & Food Research. [Image: 15UT]

The moth’s distinctive wing shape and colour pattern, plus the upturned abdomen, provide strong indicators of this moth’s identity. There are, however, other moths with similarly shaped wings that also have an upturned abdomen, so some caution is needed when identifying the moths.

The damage caused by the caterpillars to their native host plants enables their identification. The presence of shoot-boring caterpillars and red caterpillars in fruit of capsicums, eggplant fruit and pepinos is also characteristic of this species of moth.

Male adult moth of the poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae). The upturned abdomen is characteristic of both male and female moths. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GQ]

Female moth of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae); note the large abdomen compared with male, top view showing up turned abdomen. Creator: DSIR photographers. © Landcare Research. [Image: 3H8]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore into the midrib of leaves of poroporo (Solanum aviculare) causing the leaf tip to wilt. Leaves often retain this distinctive bend. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GL]

Poroporo (Solanum aviculare) shoot with wilted leaves after a caterpillar of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), has bored into the stem. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GM]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore a tiny hole (arrow) into green fruit of poroporo (Solanum aviculare) and mine under the skin, which may split as the berry grows. Creator: DSIR photographers. © Plant & Food Research. [Image: 3H0]

Typical damage to fruit of poroporo (Solanum aviculare) caused by a larva of Leucinodes cordalis (Lepidoptera: Crambidae); note the surface mine and large exit hole. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GO]

Predators

Birds such as silvereyes can attack cocoons if they find them. They will eat the overwintering caterpillars and pupae. Spiders may catch and eat the adult moths. The tiny neonate caterpillars may be eaten by predatory insects or mites and the mature caterpillars may be caught and eaten by birds and insect predators.

Parasitoids

At least four species of Hymenoptera (wasps) are parasitoids of the egg and caterpillar stages. At least two species of egg parasitoid have been found; both belong to the family Trichogrammatidae. One egg parasitoid, Trichogrammatoidea sp., turns the moth egg black, which makes it easier for humans to find.

A parasitoid, belonging to the family Ichneumonidae, lives in larvae while they burrow in the plant. The female has a long ovipositor that presumably helps it to lay an egg in the larva in the plant. The caterpillar containing the parasitoid larva makes a normal cocoon, but is then killed by the parasitoid, which spins its own cocoon in which it pupates. The adult ichneumonid chews a hole through both cocoons in order to emerge.

Another wasp parasitoid belongs to the family Pteromalidae. The female stings the caterpillar in its cocoon and lays eggs alongside the caterpillar. The white parasitoid larvae feed on the caterpillar, which shrinks; when the parasitoid larvae are fully grown, they pupate in the caterpillar cocoon. When the adults emerge, they chew holes in the cocoon to escape.

Pathogens

Several insect pathogenic fungi have been found infesting pre-pupal larva. One form of the fungus, Cordiceps, produces long fruiting bodies while other forms of the fungus covers the insects with white mycelium. Two Hyphomycete fungus (Hirsutella subulata Petch and Metarhizium anisopliae (Metschn.) Sorokin), a microsporidian fungus (Nosema sp.), and two viruses a nuclear polyhedrosis virus and a Cytoplasmic polyhedrosis virus, have also been found infecting caterpillars.

The black egg of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), has been attacked by a parasitoid wasp, Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae). Creator: DSIR photographers. © Landcare Research. [Image: 3H3]

Adult female ichneumonid parasitoid (Hymenoptera: Ichneumonidae) reared from poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae). Note the long ovipositor that is probably used to insert an egg into the caterpillar while it is in the berry or stem of a poroporo plant. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GY]

Cocoon of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae) cut to show the black ichneumonid parasitoid cocoon. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GV]

Cocoons of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae). One cocoon has an exit hole of the ichneumonid parasitoid. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GU]

Adult pteromalid parasitoid (Hymenoptera: Pteromalidae) reared from cocoons of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae). Creator: DSIR photographers. © Plant & Food Research. [Image: 3GZ]

Small larvae of a pteromalid parasitoid (Hymenoptera: Pteromalidae) on the head of a prepupal caterpillar of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae). Creator: DSIR photographers. © Landcare Research. [Image: 3H4]

Pteromalid larvae feeding on an over-wintering caterpillar of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae). Creator: DSIR photographers. © Plant & Food Research. [Image: 3GW]

White pteromalid pupae in cocoon with dead caterpillar of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae). Creator: DSIR photographers. © Plant & Food Research. [Image: 3GX]

Overwintering caterpillars of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae), with fruiting bodies of a fungus Cordiceps sp.. Creator: DSIR photographers. © Landcare Research. [Image: 3H6]

Overwintering caterpillars of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae), with fruiting bodies of a fungus Cordiceps sp.. Creator: DSIR photographers. © Landcare Research. [Image: 3H5]

An overwintering caterpillar of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), covered in spores of the insect pathogenic fungus, Beauveria sp. (?= Cordyceps sp. Creator: DSIR photographers. © Landcare Research. [Image: 3H7]

Host plants all belong to the family Solanaceae. They include two native species, Solanum aviculare and S. laciniatum, which are often called poroporo. Other plants that are attacked in New Zealand and Australia included the crops, capsicum (Capsicum fructescens), eggplant, (S. melongena) and pepino (S. muricatum) and the weed, Apple of Sodom (S. linnaeanum).

Caterpillars of this moth bore into the midrib of leaves, shoots and fruits. Leaves may wilt after the newly hatched (neonate) caterpillar invades the mid rib. Shoots may similarly wilt and young leaves die after the caterpillar bores into stems. When the neonate caterpillar burrows into a green fruit, it first tunnels just under the skin forming a mine visible on the outside. The older caterpillar burrows deep into the fruit and feeds on the developing seeds.

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore a tiny hole (arrow) into green fruit of poroporo (Solanum aviculare) and mine under the skin, which may split as the berry grows. Creator: DSIR photographers. © Plant & Food Research. [Image: 3H0]

Typical damage to fruit of poroporo (Solanum aviculare) caused by a larva of Leucinodes cordalis (Lepidoptera: Crambidae); note the surface mine and large exit hole. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GO]

Large larvae of poroporo fruit borer, Sceliodes cordalis (Lepidoptera: Crambidae), burrow into shoots or into the centre of berries of poroporo (Solanum aviculare). They turn red when they are mature and about to leave the plant to find a cocooning site. Creator: DSIR photographers. © Plant & Food Research. [Image: 3H1]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore into the midrib of leaves of poroporo (Solanum aviculare) causing the leaf tip to wilt. Creator: DSIR photographers. © Plant & Food Research. [Image: 3GS]

Newly emerged caterpillars of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), may bore into the midrib of leaves of poroporo (Solanum aviculare) causing the leaf tip to wilt. Leaves often retain this distinctive bend. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GL]

Poroporo (Solanum aviculare) shoot with wilted leaves after a caterpillar of poroporo fruit borer, Leucinodes cordalis (Lepidoptera: Crambidae), has bored into the stem. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3GM]

In the late 1970s, poroporo was grown on a large scale in Taranaki for the extraction of a precursor for the manufacture of pharmaceutical steroids. The poroporo fruit borer damaged some of the green shoots that were being harvested. This led to research on the biology and control of the insect, which in turn resulted in most of the information and photographs used in this factsheet.

Metal outdoor signs are available for placement in reserves, Regional and National parks, urban parks and school grounds. They can be bought from Metal Images Ltd, www.metalimage.co.nz/products/botanic-labels. The Bug Signs are listed near the bottom of the ‘Fauna Species list’. The signs come in two sizes, 100 x 200 mm, 194 x 294 mm. The signs can be bought ready mounted on a stand that needs to be ‘planted’ in the ground, or they can be bought unmounted with holes for fixing into your own mounts.

Signs for the Poroporo fruit borer are best placed by a poroporo bush of either species. The bush will live for several years. After it has died, another could be planted near the sign, or the sign moved.

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Large Bug Sign (5008) for Leucinodes cordalis, Poroporo fruit borer, 194 x 294 mm. Creator: Metal Images Ltd. © Metal Images Ltd & Entomological Society of New Zealand. [Image: 2R10]

Small Bug Sign (5008) for Leucinodes cordalis, Poroporo fruit borer, 100 x 200 mm. Creator: Metal Images Ltd. © Metal Images Ltd & Entomological Society of New Zealand. [Image: 2R11]

Clearwater JR, Galbreath RA, Benn MH 1986. Female-produced sexual pheromone of Sceliodes cordalis (Lepidoptera: Pyralidae). Journal of Chemical Ecology 12(9): 1943-1964.

Dhana SD 1984. A nuclear polyhedrosis virus of the poroporo stem borer, Sceliodes cordalis (Lepidoptera: Pyralidae). New Zealand Entomologist 8: 67-68.

Mally R, Korycinska A, Agassiz DJL, Hall J, Hodgetts J, Nuss M. 2015. Discovery of an unknown diversity of Leucinodes species damaging Solanaceae fruits in sub-Saharan Africa and moving in trade (Insecta, Lepidoptera, Pyraloidea). ZooKeys 472: 117-162.

Martin NA 1999. Arthropods and molluscs associated with poroporo (Solanum aviculare and S. laciniatum): an annotated species list. Journal of the Royal Society of New Zealand 29: 65-76.

Mercer CF, Wigley PJ 1987. A microsporidian pathogen of the poroporo stem borer, Sceliodes cordalis (Dbld) (Lepidoptera: Pyralidae) : I. Description and identification. Journal of Invertebrate Pathology 49(1): 93-101.

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Thanks to Chris Mercer for information about the fungal pathogens.

Thanks to Eric Scott for helpful suggestions.

Thanks to Brian Patrick for information about the distribution of the moth in the South island

The New Zealand Plant & Food Research Institute Ltd (Plant & Food Research) for permission to use photographs.

Landcare Research New Zealand Limited (Landcare Research) for permission to use photographs.

1 April 2018. NA Martin. Bug signs updated

1 August 2017. NA Martin. The scientific name changed from Sceliodes cordalis to Leucinodes cordalis.

5 June 2015. NA Martin. Added additional synonyms. Distribution: changed. Life stages: added photo of pupa. Recognition: added photographs. Natural enemy table added and information updated. Host plants: added photos of damage. Details of Bug Signs added.