Pests Getting Started This Spring

Hasn't the weather been fun the last few weeks? Talk about a yo-yo! That's hard on us, and it's hard on bugs too. Warm weather allows them to mature and reproduce quicker and survive better. Cold and wet has the opposite effect. So what are people seeing now?

BTA

I haven't been out in the field yet, but Doug Hundley has reported seeing three instars of twig aphids. If you will recall, these aphids begin hatching from their eggs in mid to late March. They molt four times before becoming an adult which can produce more live young.  So what does that mean? What's an instar?

Remember that insects don't grow like mammals do. I have a new puppy, and every few days I think -- Gosh he seems bigger. Insects don't do that. They grow in stages since they have to shed their skin (molt) to get bigger. Different species of insects mature differently. Twig aphids have four molts so there are four instars. If Doug was seeing three different sizes of aphids, that means that the twig aphids are hatching and growing and fairly far along with their life cycle. But also remember that twig aphids hatch over a several week period. The oldest aphids he saw were probably the first ones to hatch. Usually it takes until April 15 for all the aphids to hatch out. I would think that with our periods of snow and cold which seem to come every week, that it will take that long for the twig aphids to completely hatch. However, if you are using any insecticide except for granular Di-Syston or Thionex, any materials you spray now will work fine. It will last long enough. These two work best when applied after all the eggs have hatched.

So is it best to wait later in April to early May to treat for twig aphids? Not necessarily. First of all, the longer you wait, the more you at the mercy of the weather. The other factor are cones. Cones can reduce the effectiveness of insecticide applications. The bracts on the cones protect the aphids. When the cones are very small, the aphids can't get under these bracts. So if you have a lot of cones and are spraying for twig aphids, it would be better to treat sooner than later. Otherwise you will have to remove all the cones. Of course, you'll probably do that anyway.

Dimethoate has proven effective even when the cones are more mature, so if you get caught with bigger cones, consider switching to that material.

HRM

Brad Edwards reported seeing some rust mite activity recently. The presence of rust mites in the spring may affect what pesticides you want to use. If you treated in the fall with Talstar and don't have and twig aphids this spring, you might still need to spray if you have rust mites. And if you were going to spray anyway, the presence of rust mites may make you want to add a miticide. Remember that Talstar, Apollo, and Savey don't have any activity against rust mites. They only control spider mites. Dimethoate controls rust mites but not the eggs. If this materials is used -- especially early in April -- you might have to reapply come May. Sanmite and Envidor control all stages of both rust mites and spider mites, making them worth the extra cost.

So how do you know if you controlled your twig aphids last fall or if you have rust mites? That's right. You need to scout!