Lily borer larvae hatch in early summer

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Lilly borer caterpillarsLilly borer caterpillarsLilly borers are a serious pest of some of our favourite garden flowers like amaryllis and clivia, and if not controlled early, the caterpillars can quickly destroy the plants right down to the bulbs. Read more below on how to control lilly borers organically in the garden.

Lily borer (Brithys crini pancratii), also called the “amaryllis borer” prefer plants in the crinum, amaryllis, clivia, cyrtanthus, haemanthus and nerine families. It is native to the coastal areas of the Mediterranean, but has spread to other areas around the world, wreaking havoc on plants everywhere it goes. Once this caterpillar takes hold of a plant, it can quickly destroy it, which is why vigilance and prevention are the best way to fight this pest. Fortunately, there are both chemical and natural methods that will kill these borers.

To control this pest it is very important to regularly check all your bulbs, but especially your clivias, agapanthus and amaryllis for early signs of lily borer. Tell-tale signs are clusters of tiny eggs underneath the leaves, which are laid in colonies on their host plants by a white moth with a wingspan of about 4cm. In cold winter regions the eggs are laid in early September, and in warmer and coastal regions they are laid all year round.

The larvae hatch from the eggs during the warmer months, and grow into voracious zebra-striped caterpillars which start tunnelling into the leaves to feed. Older larvae will also tunnel into the heart of the bulbs themselves, causing the total collapse and eventual death of the plant. 

CliviaCliviaThe caterpillars mature to approximately 4cm long and are easy to identify with their yellow bodies and bright black and orange-yellow rings, and the black dots on the head and the base look rather like eyes. Another species resembles zebra silkworms. The caterpillars are most active at night or on overcast days.

If you catch them early enough you can pick the caterpillars off by hand, or to control the larvae and break the cycle you will need to spray.

Biogrow’s Neudosan contains potassium salts of fatty acids, and is an environmentally friendly insecticidal soap with improved efficacy against soft-bodied insects and mites. It may be used in organically certified crops, and the crops can be harvested immediately after spraying. This product is known as a fast acting, contact insecticide – miticide, and is very effective against soft-bodied insects and mites, particularly those of the order Homoptera (e.g. aphids, leafhoppers, mealy bugs, psyllids, scales and whitefly). However efficacy is also obtained in the following orders: Thysanoptea (thrips), and Lepidoptera (caterpillars).

Kirchhoff’s Margaret Roberts (Dipel) Biological Caterpillar Insecticide contains Bacillus thuringiensis var. kurstaki bacterium, which targets destructive leaf-eating larvae of Lepidopterous spp, and can be used on vegetables, fruit, flowers, bulbs, clivias, lawns, and herbs, and harvesting of edible crops can be done directly after application. The caterpillars eat the sprayed foliage and stop feeding within a Amaryllis Amaryllis day or so, and they may hang from the leaves before rotting and dropping to the ground, usually within 3 to 4 days.

It leaves no harmful, toxic residues with no secondary poisoning. It is also harmless to bees, birds, fish, pets, wildlife, beneficial insects, and natural predators. However, it can cause harm to the young larvae of butterfly species, although it has no effect on adults. To avoid damage, avoid spraying onto plants visited by adult butterflies.

Bigrow's Pyrol is an insecticide which contains canola oil, and natural pyrethrum. This product provides broad-spectrum control, and can be used as a dormant and growing season insect spray, and kills all stages of insects, including eggs, on contact. This product will give broad-spectrum control of most insect pests such as: aphids, beetles (e.g., Colorado potato beetle. flea beetle, Japanese beetle, asparagus beetle), caterpillars (e.g., gypsy moth caterpillars, tent caterpillar, diamondback moth larvae, leaf rollers), ants, mealy bugs, mites, leafhoppers, scale, whitefly, adelgids, plant bugs, fungus gnats, thrips, sawfly larvae, psyllids, spittlebugs, and phylloxera.

It is truly an insecticide from plants for plants, as it is a proprietary formulation consisting only of naturally occurring plant oils as active ingredients. It does not contain piperonyl butoxide as a synergist, and the active ingredients do not persist in the environment.