Amaryllis Borer, Lily Leaf Miner, Crinum Borer, Lelieboorder (Afr.)
by ulrichohlhoff1 (All rights reserved)
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Brithys crini is an incredibly common pest of Amaryllis Lilies. They're the most destructive when caterpillars. First, they'll mine the leaves, causing a windowpane effect. As they grow larger, they feed externally, grazing on the leaf surfaces. Sometimes they'll bore into the bulbs and rhizomes, killing the plant. Advice would be to check lilies daily during peak summertime. Inspect the foliage for caterpillars carefully. Remember to check under the leaves for clusters of circular yellow eggs.
If undetected, caterpillars can destroy plants.
Adults: The moth's forewings are predominantly dark brown to black with paler areas near the wingtips. The thorax and top region of the legs region are covered in dark brown hair. The forewing demonstrates subtle patterns, involving a faded grey patch in the centre. Light brown markings can be seen along the end margin of the forewing. Larvae: Caterpillars are mostly black, covered in cream spots which become larger with each moult. Some instars can appear chequered from a glance. They are about 4 cm when fully grown. The heads are shiny reddish-brown. Pupae: The pupa is shiny reddish-brown. Eggs: The eggs are small, spherical, pearly-white-yellow and are laid in clusters of 20-40 eggs.
Clusters of yellow spherical eggs beneath the leaves of lilies. Mined leaves that are almost see-through. It's sometimes possible to see the caterpillars inside the leaf. Brown patches on leaves which eventually dry and shrivel. Dark brown pellets of frass (insect excrement) can be seen in the bored leaf, or sometimes scattered all over the plant where they have fed. Once grown, the larvae emerge from the leaves and graze outside on the leaf surface. Dug up plants might have caterpillars in the bulbs and rhizomes. Infested bulbs and rhizomes may begin to rot. Heavy infestations can result in plant death.
India, Africa and Madagascar, southern Europe, Southeast Asia, Japan and parts of Australia
It's best to inspect your plants early in the morning because this is when caterpillars are most active. Light infestations spotted early can be easily dealt with by removing the caterpillars whenever they're seen. Look for the discoloured patches where caterpillars have mined the leaves. Heavily infested leaves should be removed and destroyed. You can also plant Crinum moorei between your Amaryllis plants, which acts as a sacrificing plant. The caterpillars should target the Crinum lily, which can make detection easier. Natural pests include parasitic wasps of the families Pteromalidae and Braconidae and ground beetles. Provide cover for predatory insects by strimming and mowing less often, or providing climbing plants and hanging baskets.
Contact insecticides can be used to control this pest. They must be sprayed when the insect is feeding outside the plant. This form of control won't impact insects that feed inside the plant. Organic insecticides can be useful. However, it must be applied more regularly. These contain natural horticultural oils or pyrethrin and pyrethrums. Again, it must be sprayed directly on the insect to work. Synthetic insecticides including either of the ingredients cypermethrin, phenothrin, lambda-cyhalothrin, and deltamethrin are thought to provide sufficient control of these insects. These can still be toxic to some wildlife and a pollutant to aquatic life if residues leach into water systems, so please take care to research products and read instructions carefully before using them. Never spray plants in flower. Removing caterpillars by hand, coupled with cutting off infested leaves is the best treatment for controlling this pest.