Cranberry fruitworm damaged blueberries. When several (3 or more) berries are damaged and large amounts of frass are present, it's likely that the fruitworm larvae have already exited the fruit to pupate. Photo: Bill Cline
Bill Cline, NCSU blueberry and muscadine pathologist, has posted a nice summary of some of the causes of "funny looking" blueberries in the southeast at the NCSU Plant Disease & Insect Clinic
blog. Among the pathogens & mechanical injuries described is one type of insect damage, cranberry fruitworm (above). I wanted to add two more funny looking blueberry issues to the list.
Cherry fruitworm injury on ripe and unripe blueberry fruit in Bladen County, NC. 7 May 2010. Note entry hole on unripe fruit. The other fruit on this branch appear uninfested. Photo: HJB
Cherry fruitworm
Cherry fruitworm (Grapholita packardi) are similar to cranberry fruitworm, in that they feed internally on blueberries. Unlike cranberry fruitworm, however, cherry fruitworm feed on only 1 to 2 berries, and there is no visible frass outside the fruit. The injured fruit are often stuck together where the larvae exited one and entered the other. The fruit which was damaged first (on the right in the photo above) ripens early and will often fall off the bush if it rains before harvest. Cherry fruitworm may be present in fruit at harvest, and the pink to red larvae will exit the fruit if it is chilled. You can read more about cherry fruitworm here.
Blueberry maggot
Blueberry maggot larvae feeding internally in ripe fruit, July 2011. Photos: Shawn Banks, Johnston County, NC Horticulture Agent.
The third most common internally feeding blueberry insect in North Carolina is blueberry maggot (
Rhagoletis mendax). We run a large scale blueberry maggot monitoring program throughout North Carolina's commerical blueberry growing counties (see our trapping data
here), and blueberry maggot populations are extremely low in these areas. For the last 3 years, however, I have gotten reports of blueberry maggot damage in homeowner or small scale, direct market plantings. Blueberry maggot flies have one generation in NC, and the offspring from this year's flies start showing up around the beginning to middle of July (a little over one month after the first blueberry maggots are typically caught (25 May). Early ripening blueberries are at less risk of blueberry maggot attack. Ripening time in combination with the fact that blueberry maggot flies like to spend their time in large plants suggest that rabbiteye blueberries are at greater risk of blueberry damage. Blueberry maggot infested fruit will feel soft when picked, and the carrot-shaped larvae (approximately 1/2 inch long) will exit the fruit when chilled.
Blueberry maggot larvae can be distinguished from
SWD (our new potential blueberry pest) by size: blueberry maggot larvae are 1/2 inch at their largest, while SWD are approximately 1/4 inch at their largest, and shape: blueberry maggot larvae are carrot shaped as illustrated above, and SWD larvae are more tapered at both ends.
More information
My blueberries look funny - NCSU PDIC Blog
NCSU Plant Disease & Insect Clinic Blog
