Early-season insect management for blueberries
This time of year is a good time to look for some early-season insect pests in blueberry fields.
With the emergence of green tissue on blueberry shoots, there are some springtime insect pests that growers should be thinking about. Although the spring weather has been cool, some pests can be active in this weather, so scouting fields now and preparing for the spring pests coming along in the next month will be time well spent.
Lecanium scale was seen at unusually high levels in a few fields in Ottawa County last year. These small insects have a hard shell covering (3 mm diameter) and are found on stems where they feed on plant sap. When populations are high, scale insects can reduce bush growth and their excretions can make fruit sticky and serve as a medium for sooty mold growth.
Pruning out infested canes is one cultural control that can be used to reduce scale populations, but since this insect is often on fruiting wood, this may not be a preferred strategy. Scale insects are typically attacked by a wide range of natural enemies, and these insects will often respond to an infestation by greatly reducing scale survival. If considering an insecticide application, selection of more biologically-based or selective insecticides will help allow the natural enemies to help reduce scale infestations. A delayed dormant application of oil at 1% by volume can be used to smother and suffocate the overwintering scales, and if there is still only a little green tissue, this approach can be used within the temperature safety range recommended for oil applications (Avoid application before hot or freezing weather or in advance of rain.).
The insect growth regulator Esteem 35WP is registered for use against Lecanium scale at 5 oz/acre, and this will disrupt the scale’s ability to molt to the next growth stage plus it will reduce the scale’s ability to lay eggs. This product is recommended to be applied with a spray oil to improve coverage and performance. View photos of scale insects on blueberry.
Cutworms are the caterpillars of noctuid moths that emerge in early spring and are active night-time feeders. These insects spend the daytime in the leaf litter rolled up in a spiral, and they move up the bush at night to feed on young buds and shoots.
Additionally, spanworms may be active in early spring and feeding on buds. These inchworms can sometimes be seen climbing along shoots, but they also have a great ability to be camouflaged and to keep very still to avoid detection.
Regular scouting of fields is essential to determine the presence of cutworm or spanworm damage. Focus on areas that may have had missing buds before or areas that are weedier since those tend to have higher cutworm populations. A working threshold of 1 percent fruit bud loss can be used to determine the need for chemical control. Cutworms are well controlled by most synthetic pyrethroids or by Sevin.