How to scout for tarnished plant bug on strawberries

Pam Fisher, OMAFRA, Berry Crop Specialist, Simcoe

Tarnished plant bug feed on bloom and developing fruit, causing deformed and cat faced berries (Figure 1) . Decisions based on scouting results can save sprays and prevent damage . Here’s how to do it.

DSCN0035 — Figure 1: TPB damage to strawberries

Obtain a field map. Know where the early season, mid season and late varieties are. You will also need a good hand lens and a pie plate for sampling.

Decide if you will use the low threshold (could result in approx. 2% damage from TPB), or the high threshold (could result in approx. 4% damage from TPB) to make a control decision.

Begin sampling at first bloom. Sample different varieties, or groups of varieties (i.e. early, mid season, late) separately. Travel in a zigzag or random path across the block you are monitoring.

Tap or shake a flower cluster over the pie plate. Look in the pie plate for tarnished plant bug nymphs. (Figure 2) .

Tarnished plant bug nymphs are small green, and generally move quickly. There are 5 growth stages, or instars (Figure 3) . The 4^th and 5^th instar have black dots and wing pads on their back.

Keep track of how many flower clusters are infested with one or more plant bugs. You do not have to count total number of plant bugs. Just count # of clusters infested.

After you have checked 15 flower clusters, refer to the chart below to see if the number of infested clusters is equal or less than the number in the below threshold. If not, check to see if it is equal or greater than the number in the low or high threshold column, depending on which threshold you have chosen. If the number of infested clusters is greater than the number in the below threshold column, but less than the number in the above threshold column, then sample another 5 clusters. Re-check the chart in the same way, until a decision can be made.

tpb thresholds — Thresholds for TPB nymphs on strawberries. Keep track of the number of clusters infested and use the chart to make a spray decision.

Or, for a less precise but simpler method, check 25-50 clusters, keeping track of the total number of TPB nymphs. The threshold is approx 1 TPB nymph in 4 clusters.

Other TPB monitoring tips:

Sample twice a week from bloom until harvest
If plants are wet, plant bug nymphs will be harder to dislodge from the flower clusters.
You may find insects other than plant bugs in the pie plate. Aphids, thrips, springtails, leafhoppers, and minute pirate bugs are common. (Figure 4).