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Iris Borer Caterpillars



P_irisborer

Iris Borer Caterpillars

Usually appear in

Spring to Autumn.


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Caused By:-     The Moth Macronoctua onusta

Description

Although these are not as yet in the UK it is only a matter of time before they may invade these shores. Iris borers(Macronoctua onusta) spend the winter as eggs on dead leaves, stalks and plant debris at the base of irises. In spring, they hatch into tiny caterpillars and climb up new growth where they eat a pin hole size hole in the leaf and begin tunnelling down to the rhizomes. As the pinkish caterpillars eats its way down the leaves like leaf miners they leave streaks on the leaves that appear dead. Eventually they reach the rhizome and eventually grow to about 40mm long. In Summer the caterpillars move into the soil where they pupate. The Adult moths emerge in the Autumn. Female moths complete the life cycle by laying eggs on old iris plants in the Autumn where eggs remain until next spring. The eggs are almost spherical, creamy with a greenish tinge and are about 0.5 mm in diameter. The mature caterpillars are fat and pale yellowish-pink with brown heads. The pupae are reddish brown, about 30mm long and 5mm wide. The adult moths have brown front wings and lighter brown hind wings with a wing span up to 40mm inches. They are seldom seen because they only fly at night. One major problem with this borer is that it can cause other bacterial disease to enter the plant and cause rhizome rot.


Control

There are several things that can be done about this pest. First of all good plant hygiene is essential. Remove and destroy by burning old iris leaves, stems, and plant debris. This will get rid of most of the eggs that will start a new infection the following year. Crushing the caterpillar between the fingers. Timing an insecticide application when the eggs are hatching can help reduce an iris borer infestation. A repeat treatment 10-14 days after the first application may be necessary. Some Siberian Irises are more resistant to this pest. Nematodes are available to help control this pest.
See also these other Eelworms CHAFER GRUBS, CHRYSANTHEMUM EELWORM, DIEBACK, EELWORMS, ENCHYTRAEID WORMS, LEAF AND BUD EELWORM, LEATHERJACKETS, LILY VIRUSES, NUT WEEVIL, ONION EELWORM, NARCISSUS EELWORM, PEA AND LEAF POD SPOT, PHLOX EELWORM, POTATO CYST EELWORM, ROOT KNOT EELWORMS, SLUGS, SNAILS, SLUGS, VINE WEEVIL, WILTING, WIREWORM, WORMS.



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