Highbush blueberry plants usually require six to eight years to reach full production and range from 5 to 8 feet high at maturity. The climate and soils of the Pacific Northwest are conducive for good growth, development and high yields. Depending on the region, average yields of mature blueberry plantings range from 7 to 10 tons per acre for early-season cultivars such as ‘Duke’, and even greater in many mid- and late-season cultivars such as ‘Liberty’, ‘Legacy’, ‘Elliott’, and ‘Aurora’. A good understanding of plant physiology is important for good management practices to sustain these high yields and achieve good quality fruit over time.
Water initially moves into the root by osmosis, because the dissolved chemical components of the root cells are higher than that of the surrounding environment. This creates a root pressure that extends into the xylem cells, or water pipes of the plant. Water moves out of the plant as a vapor through the somata, or pores, on leaves. This is called transpiration.
Whip growth occurs later in the season than lateral growth, typically starting in June in Oregon’s Willamette Valley. The number of whips per plant is affected by pruning severity and light exposure to the base of the plant. Some cultivars, such as ‘Duke’ and ‘Berkeley’, do not produce whips from the base of the plant, instead producing most whips from higher up on the bush.
The development of pink and then blue color starts at the end of the second phase of berry growth. Sugars increase and acids decrease during phase three. Berry weight is dependent on cultivar, crop load (severe pruning will increase berry size), stage of development (berries increase in size after turning fully blue), and the number of seeds per berry (in most cultivars). Berry firmness is mainly affected by cultivar but is also impacted by ripeness, cultural practices and weather.
- Cell division, where the berry increases in size but is still green.
- Embryo development, where the berry does not increase in size much.
- Cell expansion, where each cell increases in size.
After pollination and fruit set, the berry goes through three phases of growth:
- The calyx, which ends up at the tip of a berry.
- The corolla, or fused petals.
- About 10 stamens that each have a pollen-containing anther at their tip.
- A pistil, with an ovary at the base containing many ovules (which become seeds if they get fertilized by pollen).
The number of flushes varies with cultivar, length of the growing season, vigor (pruning severity or crop load), and management (particularly fertilization with nitrogen). Growth must slow in late summer for flower buds to develop. Late flushes of growth are also more sensitive to frost damage in autumn.
Most highbush blueberry cultivars have one to three flushes of growth per growing season. Whips often have more growth flushes than lateral shoots.
Blueberries grow well in the Pacific Northwest. To get the most out of your bushes, it helps to understand the form and function of each part of the plant.
Also, while no cultivars are completely immune to bud mites, certain varieties seem to be more susceptible. Those that ripen early in the season and set buds late in June are more prone to infestation. Thus, V. ashei, a late ripening species is less likely to be heavily infested than say, the early season highbush blueberry, V. coymbosum. Look for blueberry varieties that ripen later in the season to curtail the incidence of blueberry bud mites.
These tiny creatures can be found through most of eastern North America extending from the ocean provinces of Canada to southern Florida and into Texas. Mild winters in the southern areas of its reach result in the most severe infestations.
Just as most organisms, bud mites have several natural enemies. A fungal parasite and several types of predatory mites have been shown to feed on blueberry bud mites. Unfortunately, they have not been shown to be very effective in blueberry bud mite control.
As a result of this damage, fruit, of course, will be affected. Berries will be misshapen and uneven often accompanied by the signature red blisters of blueberry bud mite damage. Large mite populations can decimate most, if not all, of the berries.
In extreme cases of blueberry bud mite infestation, you certainly won’t need a microscope to see blueberry bud mite damage. These mites feed on the buds scales and leaf and floral parts within the bud. The resulting damage appears as red blisters within two weeks of infestation. Continued feeding by the mites may eventually kill the whole bud.
Once the evidence of blueberry bud mites has been ascertained, an application of an approved miticide one month apart immediately following harvest, can give sufficient mite control. Apply the spray as early as possible before the mites infiltrate too deeply into the buds, destroying the tissues that produce the successive year’s fruit.
As spring buds open, mites leave their overwintering sites and move up the stem to the base of young shoots to feed and eventually procreate. As the population grows, the mites move farther into the center of the bud. By late summer, mites are deeply rooted in infested buds. There is continued feeding, egg laying and colony growth through the fall and winter, peaking in December or January. Mild winters tend to boost population growth, followed by the most severe bud damage in the spring.
Blueberry bud mites are white and only about 1/125 inch long. Since they are so tiny, how to you go about identifying blueberry bud mites? Well, yes, you would need a microscope which would show it to be a soft arthropod with two pairs of stubby legs near its anterior end; other mites have four pairs of legs. The mite is spindle shaped, sac-like and, with only two legs, can barely move.
Rich in antioxidants and vitamin C, blueberries are touted as one of the “super foods.” Sales for blueberries and other berries have increased exponentially, as have prices. This has led many gardeners to cultivate their own blueberries. While it’s more than worth it to grow your own berries, cultivating blueberries is not without its share of pitfalls. Amongst the disasters that might befall your berry plants is blueberry bud mite damage. What are blueberry bud mites and how can you control blueberry bud mites?
While it?s more than worth it to grow your own, cultivating blueberries is not without its share of pitfalls. Amongst the disasters that might befall your plants is blueberry bud mite. What are blueberry bud mites and how can you control them? Find out here.