Garden team tips
What can help with Box Tree Caterpillar?
*Try at home* Look for overwintering caterpillars
The first sign of damage will be from caterpillars that have overwintered any time from mid-March when there are warmer, brighter days. They seem to target the newest foliage on the outside of the plants first and are relatively easy to spot at about 10mm.
*Try at home* Pick caterpillars off by hand
Removing caterpillars from small areas or plants in containers is possible if you are vigilant for signs of damage. In a garden like Ham it takes large numbers of people to methodically and frequently inspect plants to concentrate on the worst areas.
*Try at home* Pruning out damage
If caught early enough, the damage caused by the caterpillar can be removed during pruning. However as the caterpillar damage can sit below fresh regrowth, pruning may reveal the extent of the defoliation caused. This has happened on some of Ham’s low hedges.
*Try at home* Pheromone traps
Use a trap with a pheromone lure to see if the box moth is flying and to trap male moths to reduce numbers breeding. They will alert you to the adult moth being active and the need to visually inspect your plants more frequently.
*For professionals* Biological spray
Professional gardeners can use Dipel a biological spray control. Getting the timing right makes a huge difference. An autumn spray helps to counteract overwintering caterpillars which can lessen numbers in spring. A really warm year like 2018 may mean four generations of caterpillar and Dipel can be used at least twice for each.
*Try at home* Nematodes
We have used Lacewing / wasp larvae (Chrysoperia carnea / Trichogramma evanescens) as biological controls in the garden. We believe that they have helped to reduce numbers. They have also delayed the impact of the caterpillar, allowing gardeners more time to spray or physically remove.