Starting Friday and over the weekend, a number of area blackberry growers have reported high numbers of lygus bugs in their fields. I checked on one field this morning, and indeed the level of infestation is astonishing. Somewhere in the area of ten early stage nymphs can fall out from a few shakes at a single spot at any number of points all across the field. This is without precedent in any type of berry and merits some thought and discussion.
The field that was viewed this morning was in full harvest with a lot of fruit in the yet green to pink stage. Primocane was still growing vegetatively with no flowering. I do not think lygus presents any harm to the quality of the fruit or the vegetative plant, other than as an incidental contaminant in the baskets of harvested fruit, much along the lines of what we have recently seen with stinkbugs. Lygus bug feeding damages the flower and developing fruit, so once the druplets have made and the fruit has formed, these bugs will no longer be able to harm it. Since the field examined today has next to no flowers, the nymphs must be feeding on sap from the newly developing vegetative tissue. Whether this causes harm to the plants remains to be seen.
Beyond the contamination of harvested cited above, the possibility that this colossal lygus population shifts over to later bearing varieties which are entering into flowering would give some reason for concern.
Fortunately, blackberry growers have several options available to them to control these pests. One of the best combinations we found from our work in managing lygus in strawberries has been a pyrethroid + neonicotinoid applied when the lygus are very small as they are now. Always bear in mind that this powerful combination of pesticides will weigh heavily on beneficials. Additionally, the neonicotinoids registered in blackberries present some issues with maximum residue limits (MRL's) to fruit exported to Canada.
Organic growers have few options short of border weed removal and vacuuming available to them unfortunately.
There are pesticides mentioned for management of lygus bugs in this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
Attached Images:
Lygus nymphs. Note the five spots on the back of the larger nymph. The smaller nymphs, for example the two on left, would be very easy for the pest manager to handle..