Pest management for home blueberry plants
Table of contents
- Pest management schedule
Blueberries grown in Minnesota have few serious insect pests and diseases. Gardeners who use Integrated Pest Management (IPM) practices may never have a need to apply pesticides to their plants. IPM is a sustainable approach that allows gardeners to reduce pests to a tolerable level by using the best balance of cultural, physical, biological, & chemical management strategies. IPM takes into account the level of damage a pest is capable of causing, as well as the possible risks to humans and the environment associated with each pest management strategy.
In order for IPM to be effective, home gardeners must be able to recognize common blueberry pests and the damage they cause. Gardeners can find additional help identifying common pest problems by using the online diagnostic tools 'What insect is this?'and 'What's wrong with my plant?'. Gardeners can also send a sample to the UMN Plant Disease Diagnostic Clinic.
Cultural controls can be quite effective in protecting blueberries from most insect pests and diseases. The first step is proper care of the plants. Information on caring for blueberries is found in the University of Minnesota Extension publication Blueberries for Home Landscapes". Good cultural practices such as soil preparation, pruning and cultivar selection all contribute to healthy blueberry plants.
In IPM, pesticide sprays are used only when cultural controls are not effective or as a supplement to cultural controls. If using pesticides, gardeners should choose an effective product that has the lowest possible impact on human health, non-target organisms like bees and the environment. Information on the correct way to apply specific pesticides can be found on the product label. If pesticides are necessary, always use them exactly as directed by the product label as mandated by federal law. Home gardeners can also learn about pesticides safety at the Pesticide Environmental Stewardship website or the National Pesticide Information Center website.
Preventing pests before and during the establishment year
The key to growing healthy blueberries is to plant in the correct soil type or to properly amend the soil before planting. Blueberry plants can live up to 50 years, and healthy blueberry plants are easy to maintain after they have been established. Blueberries need more soil and site preparation than most other fruit. Always get a soil test when choosing a site and amend the soil according to the soil test. Soil samples can be sent to the University of Minnesota Soil Testing laboratory.
Blueberry plants prefer a sandy, acidic soil, with a pH less than 5.5. They will grow better in all sites if acidic peat is added to the planting soil. Planting blueberries in sheltered areas helps to protect plants from winter injury. Choose a site that is sheltered but receives full sun as too much shade will decrease blossom production and yield. Information on soil preparation can be found in the publication "Blueberries for Home Landscapes:" http://dev.extension.umn.edu/garden/yard-garden/fruit/blueberries-for-home-landscapes/
Weeds can stunt blueberry plants and reduce yields. Perennial weeds that can choke out blueberry plants include quackgrass, Canada thistle and raspberries. If quackgrass or Canada thistle are growing in the site to be planted to blueberries, kill the weeds the summer before planting. Both quackgrass and thistles are hard to kill by hoeing and pulling. These weeds are extremely difficult to remove from an established blueberry planting. The easiest way to kill quackgrass is to spray the area with glyphosate in late fall. The best way to kill thistle is to spray with glyphosate or clopyralid when the weeds are forming flower buds in late June. Avoid planting blueberries next to a raspberry patch. Raspberries spread through underground runners or through tipping and can easily crowd out blueberry bushes. Remove any wild brambles from the area before planting.
Annual weeds need to be controlled after planting. During the planting year, pre-emergent herbicides can harm blueberry plants. By using a combination of hand weeding and a woodchip or pine needle mulch, gardeners can avoid the potential harm from herbicides while improving the soil for the blueberries. Wood chip mulches and pine needles slowly decay, releasing nutrients into the soil and should be augmented once a year. Sawdust mulches are not recommended, because sawdust can tie up soil nitrogen, causing the plants to be stunted. Landscape fabric can be used to reduce weed problems in the first few years. Some hardy blueberry cultivars can spread underground through rootsuckers, including the cultivars Northland, NorthSky and NorthCountry. The landscape fabric will prevent the blueberries from spreading by root suckers.
Once a blueberry patch is established, few weeds sprout through the mulch, and those weeds that do sprout are easy to remove by hand. Trees and shrubs can be a problem in established blueberry fields. Birds can deposit seeds from a variety of trees and shrubs including chokecherry, honeysuckle, raspberry and elderberry. Always remove tree seedlings before the root systems become too large. The best time to kill or remove tree seedlings is from the middle of summer to late fall. By the second year, the trees are often too large to pull.