How to monitor aphids in plum and prune: video and transcript

In this video, Farm advisor Richard Buchner demonstrates how to monitor for aphids in plum and prune orchards.

(Richard Buchner speaking)

In this video, Farm Advisor Richard Buchner demonstrates how to monitor for aphids in plum and prune orchards.

(Richard Buchner speaking)

Hi. I'm Richard Buchner, UC Cooperative Extension orchard farm advisor for Tehama County. I'm going to show you how to monitor for leaf curl plum aphid and mealy plum aphid in prune or plum orchards in the spring. Monitoring starts when the leaves appear, and ends about May 15 for leaf curl plum aphid and ends about July 15 for mealy plum aphid.

The goal is to determine if an in-season treatment is necessary to control these insects. There are two steps. First you'll visually monitor 40 trees for aphid damage or signs of aphid. Second, if the treatment threshold suggests a spray, look at leaves to confirm the presence of live aphids.

Important tools to bring to the orchard include a hand lens, the aphid photo identification page from the plum or prune pest management guidelines, clickers to record the aphid presence in the number of trees counted and a monitoring form to record observations.

I've chosen a location that has a previous history of aphid damage. Other good locations to monitor include orchard edges, areas with windbreaks, or zones near natural vegetation.

To save time, instead of walking around one whole tree look at 2 half trees and count them as a whole tree. Make a visual observation for significant aphids on the left half of this tree and on the right half of this tree. Visually observe each whole tree for 15 seconds. After looking at 10 whole trees, move to a slightly different area and repeat the procedure. Continue through the orchard until you observe 40 whole trees.

Look at the tree for signs of aphid activity such as curled leaves, honeydew, sooty mold, and waxy- or silvery-looking leaves. Insects that feed on aphids or ants that farm aphids can signal the presence of aphids, as well.

Aphid numbers are considered significant when 10% or more of a whole tree's leaf surface has signs of, or damage from aphids. If tree monitoring indicates that a spray is necessary, examine 5 leaves per tree on 2 or 3 damaged trees to confirm the presence of live leaf curl plum aphids and 6 damaged trees for the presence of live mealy plum aphid.

Turn leaves over and look for mealy plum aphids. Wingless adults are pale green with three dark green longitudinal stripes on their backs. They look like they are dusted with wax.

Uncurl leaves and look for live, young, wingless leaf curl plum aphids. They are green, brownish green or brownish yellow, shiny, and do not have a waxy coating.

If the aphids are dead, parasitized, or have already left for the summer a treatment is not necessary.

If you find live aphids record a "+" on your monitoring form. A treatment is necessary if monitoring exceeds the treatment thresholds and live aphids are present.

If after monitoring 40 trees you find less than 4 trees with significant aphid damage, no treatment is needed and you can resample trees in 1 week. If you find significant aphid damage on 4 to 11 trees, additional information is necessary. Do an additional 5-minute search of 20 or more whole trees. If more than 16 trees from the combined search have significant aphid infestation, verify the presence of live aphids. If live aphids are present a treatment is suggested. If you find 12 or more trees with significant level of aphid damage, verify the presence of live aphids. If live aphids are present a treatment is suggested.

Consult the Pest Management Guidelines to learn which insecticide to use.

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