The box tree moth is well camouflaged. Even the tiny eggs are hard to spot. This article will inform you about dates, characteristics and measures.
Although the box tree moth (Cydalima perspectalis) can cause great damage, it lives most of its life cryptically, that is, hidden and protected from predators or human intervention. Early detection of an infestation can give you and your box trees (Buxus) a decisive advantage. So that you can find and recognize the eggs safely, we have summarized everything that is important for you.
The eggs of the dreaded box tree moth can be recognized early, so that a particularly early fight is possible. For this we explain exactly when the box tree moth lays eggs and how to recognize them and then remove or kill them.
When does the box tree moth lay eggs?
In our latitudes, the box tree moth goes through four to six generations a year - eggs are laid at least four times. The development of the caterpillars to the adult moth capable of mating happens faster or slower depending on the weather, which is why unfortunately no fixed time of the year can be given for the oviposition. You only know exactly when eggs will appear on your plants if you observe the moth flight yourself using a box tree moth trap. If you are looking for such a trap, you can buy the Plantura moth trap in our shop. This helps to detect an infestation with the borer at an early stage. However, the development of the moths is roughly as shown in the table below: The overwintered caterpillars develop and, after mating, lay eggs on the host plant - often our boxwoods - in June and July. The same thing happens a second time around September. The larvae that hatch from these eggs, after a bit of scraping on the foliage, hide in a sheltered corner and hibernate there in a cocoon until next spring.
| month | April | May | June | July | August | September |
|---|---|---|---|---|---|---|
| Development State | Caterpillars (overwintered) | Cocoons | Moths, Eggs | Eggs, Caterpillars | Cocoons, moths | Moths, Eggs, Caterpillars |
| Generation | Generation previous year | Generation 1 | Generation 2 | |||
Unfortunately, it doesn't stay with the eggs for long: It only takes about three days for a hungry caterpillar to hatch from an egg. In addition, due to the storage over a longer period of time, eggs and larvae can usually be found at the same time. Once you've observed moths or found them in traps set up, you should check your boxwoods daily for eggs.
Note: Incidentally, up to four generations of the moth are theoretically possible, since development is greatly accelerated by heat. Three generations per year are not uncommon in southern Germany.
Recognizing Box Tree Moth Eggs
In the eight days that a female moth lives, mating takes place and about 150 pale yellow, lenticular eggs a few millimeters in size are laid. The outer leaves of previously unaffected box trees are preferred. In a so-called egg mirror, around 20 eggs lie close together on the underside of the leaf. Shortly before hatching, many black dots can be seen in the egg mirror when the black head capsules of the larvae shimmer through the skin of the eggs. After the first of up to six larval stages has hatched, the caterpillars are still yellowish and feed on the inner, protected areas of the host plant.
Remove or Kill Box Tree Moth Eggs
There are three good ways to get rid of box tree moth eggs:
Fight box tree moths by pruning
Because it is the feeding of the larvae that damages the boxwood, killing or removing the eggs before hatching would be very effective in preventing damage. This project is unfortunately quite difficult to realize because of the short time in which the eggs are available. A simple and efficient method is to make a cut no more than two weeks after the moth flight observed. At this point, the eggs and young larvae are still on the outside of the boxwood and can be removed with the cut. Packed in a tightly sealed bag, the section can be disposed of with the residual waste.
Fight box tree moths with beneficial insects
Another possibility is the release of beneficial insects: Several species of parasitic wasps of the genus Trichogramma parasitize the eggs of the box tree moth and kill off the young life inside. Eggs of the small parasitic wasps can be ordered in cardboard cards and hung in the box trees when the butterfly begins to fly. After hatching, the parasitic wasps go in search of suitable eggs. This environmentally friendly technique has already worked very well in greenhouse trials, but many factors can reduce its efficiency outdoors - wind, predators or other preferred egg clutches may reduce success.
Protect box trees from box tree moths
One last option is to use safety nets to stop the eggs from being laid in the first place. These must then be spread over each box tree for three weeks from April to September or depending on the appearance of the moths. It goes without saying that the chic of a well-kept boxwood hedge is significantly reduced in this way. Once the egg-laying period has passed and the larvae attack your boxwood, all is not lost: This special article provides information on how to combat the boxwood moth . Because your entire garden should never suffer from the control of pests, we have compiled biological ways of controlling borers here.
In this special article you will find out how to recognize the dreaded caterpillars and how to get rid of them.