Many folks have started spraying in the fall for Cinara aphids and balsam woolly adelgid, which frequently results in twig aphid control the following spring. If you aren't one of those people, you will probably need to treat for twig aphids this spring.
Twig aphid control is only important the year of sale and year before sale. There is no need to control twig aphids in younger trees, as the new growth will hide the needle curl. If there is damage and even reduced growth, the trees tend to set extra buds for the following year, and growth will not be slowed down at all. But if it takes 2-3 years to harvest all the trees out of a block, a grower may end up treating 4-5 years in a row for twig aphids.
Traditionally, people treated right before bud break. Since most were using the granular formulation of Di-Syston, this was the a good approach as it was important to wait until all the eggs had hatched. This product is no longer available for use and other products can be applied much earlier in the spring.
The loss of Di-Syston will especially impact the smaller growers who may not have spray equipment. Most larger growers have switched more and more to using tractor-driven airblast mistblowers as the price of Di-Syston increased during recent years. This equipment gets good twig aphid control provided there are enough access roads. Adding a material to the pesticide to increase droplet size is helpful to both reduce drift and get better coverage. Be sure to scout in the middle of the block after April 15 where coverage may have been light to make sure control is adequate. But if you don't have a mistblower, you will need to decide how you will treat in the spring.
A high pressure sprayer is always the best choice for pesticide application as you will get the best coverage. For twig aphid and mite control, it is not necessary to crank up the pressure or use a straight-stream spray pattern as you would with balsam woolly adelgid control. Instead, reduce the pressure, broaden the pattern, and you will find you will get better foliage penetration. Don't try to treat more than 2-4 rows at a time, even in smaller trees. Unfortunately this application method is slow, and smaller growers often can't afford these sprayers. If they hire someone else to spray their trees, and the weather doesn't cooperate, they risk not getting their trees sprayed at all.
If you are a smaller grower, a backpack mistblower may be the answer. This equipment gives enough coverage to control all Fraser fir pests including woolly adelgid. It gives much better coverage than a regular backpack sprayer. There are several lower acreage growers that only use this to apply insecticides. The sprayer is not for the physically weak! It is heavy, but even I can handle it on steep ground. It sprays faster than I can walk, but you can change the settings to reduce spray output. And priced between $600-700, most growers can afford it. You will find you will apply around 50+ gallons of water per acre which means a lot of trips to fill up, so having a nurse tank is helpful.
Whatever equipment you use -- mistblower, backpack mistblower, high pressure sprayer -- be sure to treat trees from opposing directions. Try spraying some trees with plain water to make sure you are getting good coverage. And DON'T TRY TO SPRAY WHEN THE WIND IS MORE THAN 10 MPH or IF IT'S ABOUT TO RAIN. It's just a waste of pesticides, time and effort, and makes the entire industry look bad.
There are many choices in pesticides for spring pest control. I'll go over these in another post. But remember, for many of them you can spray beginning in March -- which is just next week! (Guess we'll have to get rid of the snow first!) Don't wait until the last minute as you never know if the weather will allow you to spray or not.
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