Your parents call you up and ask for help on diagnosing a problem with their hemlock trees. There are numerous white marks at the base of the needles on most of the twigs. It has since spread in eastern hemlock's natural habitat, and is expanding its range every year. Eastern and Carolina hemlocks of all ages are susceptible. Western hemlock and Asian hemlock species are resistant to attack.
Insecticides are effective in the landscape setting.
Treatments include foliar sprays of dormant oils and systemic sprays of Merit. Biological Control research is being carried out for forest settings. They are all beetles. One is being released and the other four will likely be released in the near future.