Dormant Spur Sampling: Videos & transcripts
This video on how to sample dormant spurs of prune, plum, and almond trees was created by retired farm advisor Carolyn Pickel and UC IPM staff.
THE PESTS, PART I
(Carolyn Pickel speaking)
Growers would ask me, well, how do I know [if] I need a dormant spray?
So we came up with this dormant sampling so you could check the tree to see what it actually had.
In the case of prune trees, they still require a dormant spray because of aphid problems: there's a leaf curl aphid and a mealy plum aphid. You can sample the dormant spurs, and the little aphid eggs will be right down in here [shows] but it's like finding a needle in a haystack, because if you have three aphids on this tree it will cause you economic damage.
It's very difficult to find them. But if you do find them, when you do this sample, it does show you [when] you have too high a population; and some growers figure out where in their orchards, like on edges, where they can look for them. And they can use this sampling system to determine if they have to spray for them.
The other insect that you're looking for is the San Jose scale, which can cause severe problems in prunes; and the overwintering mite eggs—not the twospotted mites, it's not these mites that cause the most damage—but it's the overwintering European red mite or brown mite. All those are [in prune trees].
We found out in prunes [that] if you don't spray any broad-spectrum pesticides in the summer time, your San Jose scale will be under biological control. So the other thing you can monitor with the dormant spur is biological control.
Mealy plum aphid eggs are black and laid near buds.
These San Jose scales are in the black-cap stage.
San Jose scales parasitized the previous season will have a round hole where the adult parasite emerged.
European red mite eggs are red and have a long projection.
Brown mite eggs are similar, but don't have a projection.
European fruit lecanium overwinter as nymphs.
HOW TO SAMPLE, PART II
(Carolyn Pickel speaking)
All the insects don't live evenly [spread] in the tree. Some of them will live in the center of the tree. So you want to collect some spurs from the center of the tree, and you want to get some old wood like this [shows]. This is newer wood [shows]; this is older wood.
Parasitized San Jose scale will be on the older wood. And usually we'd like you to sample five spurs on a tree. So you get a couple from the inside, and then you kind of move your way outside and get some from the outside.
This spur here is mostly new wood [shows], and the San Jose Scale is usually found here; and you mostly find that because it's from last summer. It's not a live scale. You'll find the scale and you'll find the hole where the little parasite chewed its way out, and if you see those, you'll know you have biological control in your orchard.
The other way to tell if you have biological control in your orchard: you put out a San Jose scale trap, because you catch both the males and you catch the biological control.
So here is where you look to you find the San Jose scale: inside here [the buds] you find the aphids. Right down in there. You can use a lens and look at them and see what you find. If you get the spurs in the sun you can see them a lot better.
You can also take your samples to the lab. If you can't get to your samples for a day or two, or you want to save them for a meeting, put them in a plastic bag with a moistened paper towel.