As most of you have discovered this is the time of year we begin finding Aphids on our deciduous trees. There is also the appearance of scale insects. It is my experience that where those two critters show up ants, powdery mildew and sooty mold cannot be far behind.
Here are some suggestions:
1). Aphids are small sap suckers that come in about a dozen different varieties. They are here now because there are a lot of young tender, juicy shoots for them to suck on. As they suck out the sap from our trees they poop a clear sticky fluid called “Honeydew” of all things. Ants love this poo and consume large quanti- ties of it. Ants carry the fungus base for sooty mold on their little shoes. So lots of ants are a problem for us. Also ants will set up shop keeping and homestead your pots which is a big problem. Solution: Watch closely as these little guy’s can take over a tree before you even know about it. They are not easy to see on a casual inspection. They are routinely under the leaves and at the very tip end of the new shoots. Lady bugs and Praying Mantids will consume millions of these little aphids every day. The only problem is that the Lady bugs don’t start moving around until it warms up and it is still too cool for the Praying Mantid egg cases to hatch out. Use Insecticidal Soap or agricultural oil (Neem, Volk, or Stylet oil) for control. Try to spray sparingly be- cause these products will also take out our beneficial buddies. You will need to treat the trees at least 3-5 times to eliminate the bugs. Spray early in the morning or late in the afternoon early evening. Do not ap- ply anything to your trees during the heat of the day. You can also defoliate and then spray the tree with a strong stream of water washing all the aphids off.
2). Scale insects are quite a story. I will not bore you with all the details (go to Google and you will see what I mean), suffice it to say that they are really tough customers. They are like the Mike Tyson of bugs. There are 5 types that show up here every year. They love our fruit trees, Apple, Pear, Cherry, etc. are all like candy to them. They will appear as shiny, hard little bumps on the branches, they usually do not get on the leaf. When you smash them sticky juice comes out, that is your tree they are eating inside that little fort they have constructed. They don’t move once they have set up shop. You need to use oil on them at least 5-7 times. Spray every three days for 2 or 3 weeks. Mashing them works good and is very satisfying. Both of these insects will not usually kill your tree but they make everything a big mess, bring a lot of other problems with them and will weaken the tree. If you see Lady bugs or Praying Mantids do not spray; these guy’s are really efficient Aphid predators. For the scale you will need to spray and smash.
3). Powdery Mildew and Sooty Mold should be treated with any of a dozen fungicides. Oil also can help out quit a bit. Pulling off the leaves works good for powdery mildew. Sooty mold (the bark and branches of your tree will appear to be getting dark grey to black in color) is a tough thing to eradicate once it is on your tree. Fungicide will work but it takes many applications over 2 growing season. I have had some success power washing the trees when they are dormant, be careful not to scrub the bark off. Sooty mold appears on our Elms, Oaks, Zelkova’s, and fruit trees mostly, although it is occasionally found on some others.