The blueberry aphid spreads shoestring virus. There is a latent period of 4 years between infection of the plant and expression of symptoms. Shoestring-infected wild blueberries also have been found in the wooded areas.
The most prominent symptoms are elongated reddish streaks about 1/8 inch wide by 1/2 to 3/4 inch long on current-year and 1-year-old stems, especially on the side exposed to the sun. During blossoming, flowers of infected bushes exhibit pinkish to reddish petals. Infected leaves often are straplike, hence the name "shoestring." Many leaves on a bush might appear this way, although in some cases just a few clumps near the crown will show this symptom. A few leaves may show red-vein banding or reddish streaking along the midrib of the leaf. In some cases, an "oak leaf" pattern will show on the leaf blade. Other leaves may be crescent shaped and partially or totally reddened. Infected stems may appear crooked, especially the tip-end half.
Aphid control is critical to preventing the spread of shoestring virus. The first insecticide application should begin when aphids first appear on the terminals of the stems, usually by late May or early June. Two or three sprays may be required throughout the growing season to keep aphid levels low. The long latent period makes identifying infected bushes before they serve as sources of inoculum impossible, so roguing is not feasible or effective. Clean planting stock is critical. Bluecrop shows resistance. Also, diseased wood used for propagation is another way to spread the virus from one field to another.