Removing the potentially beautiful trees that line our streets and shade our yards and supply much needed food for the most important resident, bees, is extreme and unnecessary.
The city simply needs to adopt a dormant oil/lime sulphur spray regime, that has been effective everywhere, and stick to it.
Using horticultural oils in favour of insecticides is now widely recommended, since oils pose little risk to humans, other mammals, birds or beneficial insects; don’t cause pests to build up a chemical resistance; evaporate quickly; and can be applied using a pump garden sprayer from any number of stores plus it’s a once a year thing. It’s also very effective on the eggs of the caterpillar (they are not worms) that we see nesting in our beloved ornamental and fruit trees but there are some trees that can’t tolerate it so check the list on the label before you buy.
Simply follow the directions for application rates and timing. It’s simple and easily doable because you can spray between a wide range of temperatures, above 4°C and below 27° C, after leaf drop and before bud break.
Dormant oils treat the overwintering eggs of insects that curl leaves in the spring (such as aphids), the overwintering of eggs of tent caterpillars and leaf rollers, mites that overwinter on conifers, and scale nymphs and adults. These oils kill pests by either blocking the spiracles through which they breathe (suffocates them) or interferes with their metabolism by directly penetrating the outside cuticle and destroying internal cells.
Spray in the morning to allow quick drying of the spray. If the tree is left soaking wet on a really cold night, it could injure the bark but I’ve never had it happen in my orchard and I’ve sprayed on a sunny, above 4 degree December or January day a few times. Only one application is necessary with this combination spray before buds start to swell but I recommend a fall and then an early spring regime for 2014/2015 because the tree bark on the city trees will be covered in eggs this fall and it may be difficult to spray every single one of them in one go. Note: BTK is a safe option once the caterpillars are allowed to take over but it’s an after the fact solution, better to avoid the problem altogether with dormant oil/lime sulphur. There is a printable sheet with clear information at www.plantworld.net or read the information label on the dormant oil/lime sulphur bottles.