Ermine moths spend the winter still as eggs. The individual, shield-shaped eggs have a diameter of about 0.4 mm and are deposited in groups on small branches – similar to snout moths – with the eggs overlapping like roof tiles.
The tiny caterpillars hatch in March/April, feeding around fresh shoots and forming a common web in which they live, protected from their natural enemies. The yellow-green caterpillars have two dark spots on each of their body segments and grow up to 20 mm long.
Once they have completed five instars, they begin to spin a cocoon in which they pupate. These cocoons are often very close to each other in their web nest. The moths emerge from these cocoons in June or July, begin to mate and deposit their eggs for the next year, following an egg development phase of 10 days.
The white moths have a wingspan of approximately 25 mm and their forewings are covered in countless, small black dots. The insects do not develop a second generation, which usually limits the damage caused.
The spindle ermine only lives on European spindle plants. Additionally, there are other, closely related species, which live on sloe, for example, one that feeds of bird-cherry or another on apple trees.
At first, only some shoot tips are covered by the web, while entire plants appear covered in a fine web during heavy infestations. The webs contain large numbers of caterpillars.
- Host tolerance: the hosts usually recover well from an infestation and grow new shoots.
- Destroy caterpillar nests with a strong jet of water.
- Cut off cocoon nests.
- Use of insecticide sprays: products based on bacillus thuringiensis or the natural substances azadirachtin and pyrethrum are suitable for home gardens.
- Refer to the Austrian plant protection product register (Register for authorised plant protection products in Austria) when choosing a product.
Search terms for the plant protection product register:
Gespinstmotten (ermine moths); freifressende Schmetterlingsraupen (free-moving feeding caterpillars); fressende Insekten (feeding insects); beißende Insekten (chewing insects); Zierpflanzenbau (ornamental plant cultivation); Zierpflanzenkulturen (ornamental plant cultures).
Note: unfortunately these terms cannot be combined in one search at present!