When something is attacking your fruit tree (or you think it is), the most common response is to kill it. Killing method may be crushing, bagging or spraying, often without being sure if the victim caused a problem or not. One tool your can use determine the real cause is limb tapping onto a beating tray.
Limb tapping involves lightly tapping (or beating) a tree branch while holding a catch tray (beating tray) under the branch. The tap dislodges most insects and some mites that are hiding in the foliage. Commercial orchardists use this technique frequently from bud break in the spring to leaf fall after harvest. Fruit tree gardeners and home orchardist may also find it useful.
After you tap the bugs from a limb onto your tray, wait a couple of seconds for the insects to grab on to the tray, then tip it sideways to dump leaves and other trash off that will get in the way of seeing the insects and mites.
The challenge, after you have tapped, is to identify the critters that you have dislodged. Most of them probably don’t cause tree or fruit problems; hopefully you will find lots of good guys that eat the bad guys. The first thing you will observe is that some of the new arrivals on your tray just sit there and some run or skitter around. The runners are usually good guys or predators; they need to run to catch a meal and move on to the next one. The ones that don’t move (bad guys) are more likely to be plant feeders, plants don’t require chasing.
To sort the good guys form the bad guys you may need guides to help you identify them. For the good guys see this PDF document. For the rest see these resources for gardeners and these resources for commercial orchardists. To identify some you will need a magnifying glass to see what they look like. A hand lens of 15X to 30X is best, the higher magnification for the really small ones and older eyes.
I am working on a simpler visual identification tool specifically for BC Coastal fruit tree growers. If you have images of pests and predators that you are willing to share, please email them to me.
Once identified, the damage bad guys cause can be determined. Low populations of bad guys require watching, but maybe not killing. These pests are food for the predators or good guys. If you have high numbers of predators these bad guys may never get the chance to do any damage. There are a few insects such as the Campylomma (Mullein plant bug) that feed on other insects until the supply runs out, then they feed on the fruit.
Here is a Utah State video showing how to make one type of beating tray. My version is an 18” X 18” piece of plywood with white cloth stretched across it. You can also use plywood painted white or a piece of white cardboard. A broom handle can be used to make a limb tapping bat. Make sure to pad the bat and tap the limb lightly.