1. Mechanical and silvicultural
There is no practical control method for beech scale infestations in natural forests. Extremely cold temperatures below -30°C will kill beech scale insects not protected by the snow cover. Control measures can be implemented periodically for scale insects on ornamental trees. For instance, to prevent the dissemination of scales, a strong jet of water or a soft brush can be used to remove the insects from the bark (CCDMD 2009).
An organophosphate insecticide should be sprayed on the bole and main branches in September or October to kill the crawler stage of the beech scale (Abgrall and Sautrenon 1991; Houston and O'Brien 1983) and lime sulphur can be applied as a spray in the spring (Rose and Lindquist 1982). These are effective treatments that have been used for many years on individual trees in Europe and North America.Products registered in Canada for the control of scales in general, on ornamental trees, contain the following active ingredients: malathion or calcium polysulphide. Caution
There are many different chemical pest control products available. They may be toxic to plants, animals, humans or the environment in general. A number of these products pose potentially lethal risks to humans. To protect human health and the environment from pesticide-related risks, Canada adopted the Pest Control Products Act (PCPA). The Pest Management Regulatory Agency (PMRA; http://www.hc-sc.gc.ca/ahc-asc/branch-dirgen/pmra-arla/index-eng.php
) is responsible for administering the Act. A pesticide product label indicates the class designation (domestic, commercial, agricultural), the potential risks to human health and the environment, and the conditions and restrictions pertaining to product use. Compliance with the label directions and restrictions is mandatory. The provinces may also regulate the use of pesticides within their respective territory. For more information on these products, contact PMRA at the following E-mail address: firstname.lastname@example.org
A ladybird beetle, Chilocorus stigma, feeds on the beech scale (Houston and O'Brien 1983). In 1986, Baylac studied the potential of using a predator named Lestodiplosis sp. In spite of the hopes that Houston (1983) had for biological control, there appear to be no viable biocontrol options for the beech scale at present. Advances in biological control will require that research be directed at predators and parasites that occur in the regions of origin of beech scale, that is, in northern Greece and Iran, in the Caucasus and in the watershed of the Black Sea (Gwiazdowski 2006). Control trials with the entomopathogène Lecanicium muscarinum have demonstrated its pathogenicity against the beech scale. However, other researches are needed before it can be used in the natural environment Laflamme et al. 2009).
4. Genetic resistance
Beech trees that appear to have some resistance have been identified in Nova Scotia (Mielke et al. [ND]). However, less than 1% of beech harbour resistance to beech bark disease (Houston 1983, 2005). These trees appear to have lower nitrogen concentrations in their bark.
5. Stages in an integrated disease management program
The beech scale plays a precursor role in beech bark disease. According to Mielke et al. (ND), silviculturists should implement the following measures in response to beech scale invasion:
- Reduce the proportion of beech in the stand by first removing older trees with rough bark.
- When Neonectria faginata attacks begin, continue to reduce the proportion of beech in the stand and cut down all infected beech. Use herbicides to treat root sprouts produced by infected trees, but retain beech trees that show little or no damage.
- As the killing front advances, remove dead and dying beech and treat root sprouts with herbicides.
- Monitor stand health and retain beech that are resistant; they may represent less than 1% of the stand.
- Scale-infested wood should not be moved to uninfested areas (McCullough et al. 2000).
This is essentially a salvage cutting approach with the ultimate goal of increasing the proportion of disease-resistant beech (Houston 2005).