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Tuesday, June 29, 2010

Other noteable blackberry insects - harvest pests

Update, June 2012
This post remains one of the most frequently visited posts on this blog, but a significant change in blackberry pest management has occurred since it was first written in 2010.  Spotted wing drosophila (SWD, Drosophila suzukii) is now the most common and significant harvest period pest in North Carolina caneberries (blackberries & raspberries).  See here for all our posts on SWD.

Blackberry harvest is well underway and looks to be excellent. If it's any indication, the fruit in my blackberry plots and the Sandhills Research Station has been delicious. Although with sweet, ripe fruit come pests who are just as interested in eating them as we are. Harvest season pests must be handled particularly carefully because fruit will quickly move from field to fork. Because of this, any decision to use pesticides should be take carefully and as always in accordance with the label. A few notable harvest pests have begun showing up in our research plots.

Stink bug eggs and newly hatched nymphs on blackberry leaves at the Sandhills Research Station. Photo: HJB

Stink bugs (several species) are attracted to both developing and ripe fruit. In blackberries and raspberries, it appears that stink bugs feed on the receptacle, inserting their mouth parts between druplets (see here for a great video of stink bug feeding on raspberries from Dr. Doug Pfieffer at Virginia Tech). This feeding may result in single druplet damage near the insertion point. This single druplet damage may render fruit unmarketable for commerical growers, but fruit with single druplet damage is still edible for home growers. Stink bugs can, however, render fruit inedible if they are disturbed and release their defensive chemicals (the "stink" in stink bug) which will foul the fruit. Stink bug fouled fruit tastes just like a stink bug smells. There is no threshold for stink bugs in caneberries, either for fruit damage or for contamination. Frequent, regular harvest will help reduce stink bug exposure to ripe fruit, and therefore the opportunity for insects to foul them. A related fruit feeding insect, leaf footed bugs, can cause similar druplet damage to stink bugs but will not foul fruit. Leaf footed bugs, as their name suggests, have pronounced, leaf-like structures on their legs (not actually their feet).

Update, June 2011
I've noticed some links from other sites directing to this post.  Stink bugs are not believed to cause "white druplet" damage to blackberries.  Stink bugs feed on the blackberry receptacle (the white core of the fruit), and the insertion of their stylets may damage single druplets on either side, resulting in leaky or otherwise damaged druplets.  This injury is very different than white druplets, as shown here. Several white druplets on one side a blackberry berry are associated with sun scald (especially if they are on the side of the fruit facing away from the plant).  Some varieties (i.e., Apache) are more susceptible to white druplets than other, especially in the southeast.

Leaf footed bug on blackberry leaf. Note druplet damage on berry in background. Photo: HJB

The other most notable harvest pest of caneberries are green June beetles. These large scarab beetles feed on many summer fruits, among them caneberries. They are attracted to overripe fruit initially, so good harvest practices can minimize their impact as well.

There are insecticide options for both stink bugs and green June beetles, but these should not be the first line of defense.

Green June beetle on blackberries at the Lower Coastal Plain Research Station, 2009. Photo: HJB

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