Twig Aphids 2020
Twig aphids are shaping up to be a problem this spring in western North Carolina. Many fields had high twig aphid egg counts going into the season, and though it’s often been wet and cold, that’s what these pests are adapted to.
There hasn’t been a lot of good weather for putting out twig aphid treatments either. With many wet and windy days, good spray days have been few and far between.
So it’s little surprise that now that buds are breaking, there are still a lot of twig aphids in fields. Cooler temperatures also tend to delay natural predators. To date I’ve not seen any of our primary twig aphid predator, hover fly larvae. But thankfully, lady beetles are really showing up strong! We’ve seen many lady beetles in fields across the region.
It’s important to recognize not just the adult lady beetle, but also the eggs, larvae and even the pupae of these important predators. The presence of any of these stages in your trees means that they are on the job and giving you free pest control.
So what should you do if you treated, but are still seeing twig aphids?
One key is, are you also seeing predators? If so, it may be best to just let nature take its course and not retreat. Once temperatures warm, shoots will start to expand more quickly and grow out of the vulnerable phase when aphids can cause needle curl. And even if there is a little bit of damage, typically the tree will grow out of most of it by fall.
Sometimes, you can spot predators while walking through your trees, but you can also scout for them. Beat foliage over a plate and look for predators the same way you do twig aphids. You can also spot predators by pulling off twig aphid infested shoots and looking among the needles for them. Remember you’ll see a lot more pests than predators, but every predator you spot will eventually eat hundreds of aphids.
Treating after bud break seldom controls twig aphids well. The aphids are protected by the new growth which is difficult to get wet with spray. Even if you do get chemical in, that shoot is in the process of expanding, which effectively reduces the rate of the product and makes it less likely to give good control. However, as the predators are larger and moving about, they are much more likely to be killed by insecticides. These predators are reducing aphid numbers and will ultimately reduce the amount of eggs produced for next year. If they are killed off, you’ll just be fighting twig aphids again in 2021.
If you scout and there aren’t predators present and still a lot of aphids, it may be necessary to retreat very valuable trees. Systemic insecticides applied with a high pressure sprayer may reduce twig aphid damage in some cases. Be careful not to damage tender growth with high pressure. Do not use the same products that you applied before bud break. Repeated use of the same materials have created resistant twig aphid populations.
For more information on twig aphids including photos, videos, and control recommendations see: christmastrees.ces.ncsu.edu/bta/