A colder spring has led to a delay in the development of some insect pest populations but they are still likely to appear and preparations should be made to protect vulnerable plants. One of these pests is the invasive Box Tree moth, which is gradually moving up the UK from the south of England. This non-native pest spread to the UK from France a few years ago. New generations are now being reported across the channel, so we should assume that it wont be long before their UK cousins are also active.
The first step is to monitor and catch the adult male moths with Box Tree moth pheromone traps. These traps should be placed near Box Tree hedges and plants , they release a pheromone into the surrounding area that attracts the male moths into Box Tree traps where they are caught. They do not catch the female moths, so you may still see Box tree moths flying near traps but not entering. The pheromone lures contain a tiny amount of pheromone that is often not visible, even when supplied in see through plastic vials. The pheromone vial is removed from its silver foil pack and placed in the top of the trap. The vial itself is not opened , as the pheromone seeps through the plastic giving a measured dose to attract the male box tree moths. These pheromone lures should be replaced every six weeks to ensure the traps are active during the Box Tree moth flying season, which can have 2-3 generations lasting into the autumn. Unfortunately Box Tree pheromone traps despite being capable of catching high numbers of Box tree moths are not always enough on their own to protect Box plants. However there is now a biological and natural pest control solution in the form of nematodes.
Box Tree Caterpillar Killer nematodes are applied directly onto the Box tree caterpillars once they are observed on the plants. These microscopic eelworm like organisms enter the caterpillars releasing a natural bacteria inside the caterpillar that kills it. The nematodes then reproduce inside the body of the caterpillar to produce more nematodes. The key to a sucessful treatment of Box Tree Caterpillar nematodes is applying at the right time and in the right conditions. Nematodes are U.V sensitive, so should not be applied on bright sunny days , they also require lots of moisture, so applying with plenty of water is important. They should also be applied on overcast days or humid days when there is plenty of moisture. The nematodes have a limited amount of time to find and kill the caterpillars, so trying to get them into direct contact with the caterpillars is important. Sprayers are the best way to apply this form of nematodes, as the sprayer can help direct the nematode solution directly onto the caterpillars inside the hedge or onto the leaf canopy where the caterpillars are present. These can be small sprayers or knapsack sprayers but should have all filters removed to avoid the nematodes getting stuck inside the sprayer. Sometimes more than one application maybe required, as it can be difficult to infect all the caterpillars with one application.
Box Tree general health can also be improved with the use of bio stimulants, especially after an attack by Box tree caterpillars or diseases like Box Blight. One of these products is called Soil Boost, a plant based biostimulant that helps the Box plants put on more top growth and root growth leading to a healthier plant. This makes the plants more resilent to attack from pests and diseases.