Choosing Blueberry Varieties for Delmarva

Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu and Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Highbush blueberries are long-lived and costly to establish, so choosing the right variety is an important decision with long term impact on the success and profitability of a planting. Many standard blueberry varieties that have been used in commercial production for decades should still be considered for use in new plantings. There are also several active blueberry breeding programs that have released new varieties in recent years, adding to the number of varieties available to growers.

The Mid-Atlantic Berry Guide contains descriptions of many of the available northern highbush blueberry varieties, including disease resistance information. At the University of Delaware research farm in Georgetown we established a highbush blueberry variety trial in 2011. We have also worked with Hail Bennett to evaluate a variety trial established at the same time at Bennett Orchards in Frankford, Delaware. Both trials include mostly newly released varieties that have not yet been well tested. Commentary on the varieties included in these trials is provided below.

The UD trial at Georgetown includes some southern highbush varieties, as well as northern highbush varieties. Southern highbush blueberry varieties were developed from crosses between northern highbush blueberry (Vaccinium corymbosum) and one or more of six related southern blueberry species including Darrow’s evergreen blueberry (V. darrowii) and rabbiteye blueberry (V. virgatum). Southern highbush varieties tend to be more heat tolerant and adaptable to a wider range of soil conditions. Some southern highbush varieties also have reduced chilling requirements, which means that they do not need as much cold during dormancy in order to induce flowering. This is necessary for production in some parts of the South with shorter periods of winter weather, but is a liability in the Mid-Atlantic, where plants may come out of dormancy to early, and be susceptible to freeze damage.

The southern highbush varieties in the Georgetown trial are, in general, very vigorous in their growth, compared to the northern highbush varieties. We have not observed freeze damage to vegetative growth in the southern highbush varieties, but some have had freeze damage to flower buds in some years.

When choosing blueberry varieties it is important to consider various traits in light of your goals for production:

Ripening Time: In Delaware, it is possible to have blueberries ripening from mid-June through August by planting varieties that ripen at different times. Consider when you want to have blueberries available when you choose varieties and how they overlap. For extended direct market sales, as many as eight varieties may be necessary to have continuous supplies. First harvest dates and peak harvest dates for the varieties from the Delaware trials are in Table 1.

Table 1. Maturity of Varieties in the Georgetown Variety Trial in 2015

Variety 1st Harvest Peak Harvest
Reka 11-Jun 15-Jun
Star 11-Jun 15-Jun
Reville 11-Jun 15-Jun
Hannah’s Choice 11-Jun 15-Jun
Sweetheart 11-Jun 15-Jun
Toro 15-Jun 22-Jun
Draper 15-Jun 22-Jun
Bluecrop 11-Jun 22-Jun
Misty 15-Jun 22-Jun
Jubilee 11-Jun 22-Jun
Arlen 11-Jun 22-Jun
Lenoir 15-Jun 22-Jun
Bluegold 15-Jun 30-Jun
Darrow 15-Jun 30-Jun
Legacy 15-Jun 30-Jun
Bonus 15-Jun 30-Jun
Chandler 22-Jun 13-Jul
Liberty 22-Jun 13-Jul
Nelson* 1-Jul unknown
Aurora 2-Jul 28-Jul

* Data from trial at Bennett Orchards.

Berry Size: Varieties that produce larger berries may be desirable for U-pick operations. Very small berries are not desirable for handpicking and take more labor to pick.

Concentration of Ripening: Some varieties have been developed to ripen most of the fruit at one time to accommodate machine harvest, others ripen fruit over several weeks. Varieties that ripen over a long period will give you a long harvest window out of one planting. However, even if hand-picking, a short harvest period can be helpful from a pest management standpoint because herbicide sprays may be applied in a more timely way in blocks that are past harvest, and the number of sprays for diseases and insects that must be planned around the harvest period is reduced. More concentrated ripening also reduces labor for picking.

Plant Vigor/Adaptability: Blueberries are adapted to an unusual set of environmental conditions (acidic soil with high organic matter that is well drained but moist). Some varieties are more adaptable to soils that do not meet these requirements (i.e. heavy clay soils, dryer conditions) than others. If it will be hard for you to replicate the ideal blueberry soil environment on your site, choose varieties noted for their broad adaptability.

Flavor: There is a good deal of variability in flavor between varieties. Some varieties have an “earthy” (dirt!) flavor that is unappetizing to most folks, others, sometimes described as “mild”, tend to have little flavor. If you are direct marketing, flavor will be a prime concern. If you are wholesaling, choose varieties on a combination of yield and flavor, poor flavor types reduce consumer demand.

Recommended Varieties from the Delaware Trials at Georgetown & Frankford

Reka – Early ripening, northern highbush variety with good yields in 2013-15, and early fruiting. Berry size is medium to small. Flavor is good but tart. Berries are dark blue, almost black.

Chandler – Northern highbush variety with moderate yield in 2013-15. Berry size is very large and flavor is good. Ripens later in the season and over a long period. Plant tends toward woody growth and does not produce many shoots from the ground. Upright habit and large berry size could be desirable for pick-your-own.

Aurora – Northern highbush variety with moderate yields in 2013-14 and high yield in 2015. Berry size is medium to large. Matures late with peak harvest at the end of July and picking into August.

Legacy – Northern/Southern highbush variety with good yields in 2013-15. Berry size is medium with good flavor. Late main season maturity. Legacy has southern highbush in its pedigree, but we have not seen freeze damage to flower buds.

Bluecrop – Northern highbush variety with moderate yields in 2013-15. This is a widely planted standard variety with good (familiar) blueberry flavor. Berries are medium in size. Easy and fast to prune. Early main season maturity.

Jubilee – Southern highbush variety with good yields in 2013-15. Berries are medium to small with good flavor. We have not noted significant freeze damage to this variety and it is very vigorous. The only drawback of this variety is the tendency toward small berry size. Early main season maturity.

Lenoir – Southern highbush variety with moderate yields in 2013 and 2014 and high yield in 2015. Berries are medium-sized with excellent flavor. This variety grows vigorously and we have not observed any freeze damage to flower buds in any of the years we have tested it. Main season maturity.

Nelson – Northern highbush variety that was planted only at the Frankford site. It was one of the best yielding varieties in that trial. Late mid-season maturity.

Recommended with Reservations

Bluegold – Northern highbush variety with good yields in 2013 and 2015 but low yield in 2014. Medium size berry with good flavor. Tends to produce many short shoots, and over-flower. Requires lots of detail pruning to maintain berry size and limit overproduction. Main season maturity.

Darrow – Northern highbush variety with good yields in 2013-15. Berry size is very large. Flavor is questionable. Late main season maturity.

Draper – Northern highbush variety with moderate yields in 2013-15. Berries are large with good flavor. Plants seem well adapted and vigorous but yields are not especially high. Early main season maturity.

Misty – Southern highbush variety with good yields in 2013-15. Berries are medium to small with good flavor. Berries have a lot of bloom and are light in color. We have seen some freeze damage on this variety each year, which is concerning, but it has not resulted in low yields. The plant grows very vigorously. Early main season maturity.

Not Recommended

Toro – Northern highbush variety with good yields in 2013 and 2014 but declining plant health and yields in 2015. Berry size is large. Plant tends toward woody growth like Chandler but maybe not as vigorous. Main season maturity.

Liberty – Northern highbush variety with low yields in 2013-15. Late maturing, similar to Aurora, but Aurora is later, higher yielding and more vigorous.

Bonus – Northern highbush variety with low yields in 2013-15. Berry size is very large. Plants have not established well at the Georgetown site. Early main season maturity.

Star – Southern highbush variety with low yields in 2013 and 2014 and moderate yields in 2015. Berries are large with excellent flavor. This is a very nice variety but we have observed freeze damage to flower buds each year which results in yield loss. Early maturing.

Arlen – Southern highbush variety with low yields in 2013-15. Berries are very large with good flavor. This variety has suffered significant yield loss from freeze damage to flower buds each year. Main season maturity.

There are several varieties that were added to the trial after 2011, and we do not yet have enough data on them to make recommendations. They are:

Southern Highbush Northern Highbush
New Hanover

Pamlico

Beaufort

Reville

GeorgiaGem

O’Neal

Hannah’s Choice

Sweetheart

Chanticleer

 

Freezes, Frost and Frost/Freeze Protection

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Fruits and fruit flowers are damaged by temperatures below 28°F and by frost. Temperatures in Delaware reached 21°F or lower on April 6. Another freeze is predicted for Saturday, April 9. The term freeze means that temperatures dropped below 32°F. Frost is the formation of ice crystals on crops and occurs when the dew point is near or below freezing. You can have a freeze without frost and a frost without a freeze. Both are damaging to plant tissue.

Frost and freeze protection methods vary with fruits and the type of freeze expected. Advective freezes occur with freezing temperatures and high winds. This is the most difficult to protect against. For strawberries, two layers of floating row covers may be the most effective strategy for advective freezes. Double covers have been shown to be more effective than single heavy covers in this case. Irrigation along with double covers can provide even more protection if done properly.

Radiational freezes occur on cold, still nights. In this case cold air is near the ground and warmer air is above. Wind machines and helicopters have been successfully used to stir the air and raise the temperatures in orchards in this case. Row covers in strawberries will protect against radiational freezes too.

Irrigation has also been successfully used for frost protection but it has to be done properly. How irrigation works is that as ice forms on plants heat is released. The key is to keep ice formation occurring through the night and continue through melt in the morning. Remember that initially, until ice starts forming, there will actually be evaporative cooling of the plant. The latent heat of fusion (water freezing) will release heat (approximately 144 BTUs/lb of water), whereas evaporative cooling will absorb heat from the plant (absorbing approximately 1,044 BTUs/lb of water) and lower plant temperatures. Therefore, irrigation must start well above critical temperatures. Also, the volume of water needed needs to be matched with the expected temperature drop and wind speed. In addition, uniformity of water application is critical. This is difficult to do in high wind situations.

Established Blueberry Fertilization and Tissue Testing

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

For established blueberries check the soil pH twice a year. Take a random composite 6-8 inch sample from the soil under the mulch in the spring and again in the fall. The pH should stay between 4.5 and 5.0. Sulfur should be added to lower the pH if it is above 5.0 or lime should be added to raise the pH if it has dropped below 4.2.

Apply nitrogen (N) in 2 applications every year to total 60-80 lbs of actual N. Apply 150-200 lbs/acre of ammonium sulfate if pH is above 4.8 or 70-90 lbs/a urea if pH is below 4.8 at bud break. Apply the same amount again 4 weeks later.  Additional N may be needed based on tissue tests. If a fertilizer injector is being used, the nitrogen can be split into smaller applications over the 6-8 week period after bud break when new growth is being produced.

P, K, Ca, Mg, and micronutrient additions in established blueberries should be based on tissue tests. Tissue tests are important tools for monitoring blueberry fertility. Leaf samples should be collected from mature leaves in the mid-portion of current season’s growth the first two weeks after last harvest in July or August. A double hand full of leaves should be harvested from across the field, washed in tap water, dried and sent to a testing laboratory. Below are critical nutrient ranges for blueberries.

Nitrogen (N) 1.7-2.1 % with normal at 1.9 %

Phosphorus (P) 0.06-0.18 % with normal at 0.1 %

Potassium (K) 0.4-0.65 % with normal at 0.55 %

Calcium (Ca) 0.4-0.8 % with normal at 0.6 %

Magnesium (Mg) 0.2-0.3 % with normal at 0.25 %

Iron (Fe) 70-300 ppm with normal at 200 ppm

Manganese (Mn) 50-500 ppm with normal at 250 ppm

Zinc (Zn) 15-30 ppm with normal at 25 ppm

Copper (Cu) 5-15 ppm with normal at 11 ppm

Boron (B) 30-50 ppm with normal at 40 ppm

If levels are below these ranges then the plant is deficient. If deficiencies are found, use the following recommendations:

  • Low N (if N is below 1.7 percent): Increase rate of N application by 10 percent for each 0.1 percent that sample is below desired level. If soil pH is above 4.8, use ammonium sulfate; if below 4.8, use urea. Apply half of the nitrogen fertilizer at bud break and the remaining half four weeks later.
  • Low P (below 0.06 percent): Apply 180 pounds per acre superphosphate (45 percent P2O5) at any time.
  • Low K (below 0.40 percent): Apply 400 pounds per acre potassium magnesium sulfate (K-mag) or 160 pounds per acre potassium sulfate in fall or early spring.
  • Low Ca (below 0.4 percent): Refer to soil test and apply lime as needed if soil pH is below 4.0. Apply 1,000 pounds per acre calcium sulfate in fall or early spring if pH is above 4.0.
  • Low Mg (below 0.2 percent): Refer to soil test and apply dolomitic limestone if pH is below 4.0. If pH is above 4.0, apply 250 pounds per acre magnesium sulfate or use potassium magnesium sulfate (K-mag) at 400 pounds per acre if K is also low. Apply in fall or early spring.
  • Low Mn (below 50 ppm): Apply a foliar spray of manganese chelate at 6 pounds per 100 gallons per acre twice during the growing season. If product label offers a different recommendation, follow label recommendation.
  • Low Fe (below 70 ppm): Apply a foliar spray of iron chelate at 6 pounds per 100 gallons per acre in late summer and again after bloom the following year, but check product label and follow its recommendation.

This information was taken, in part, from the Mid-Atlantic Berry Guide http://extension.psu.edu/publications/agrs-097/view

Spotted Wing Drosophila Update

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Trap catches of SWD adult flies remain constant in most trapping locations throughout the state. Unfortunately, there are no thresholds available based on trap catches. Small fruit growers (especially bramble and blueberry growers) will need to maintain their spray schedules for this very damaging insect pest. Information from surrounding states indicates that they are seeing the same trend. The following links from the University of Maryland and Rutgers University provide good information on monitoring and management options:

https://extension.umd.edu/sites/default/files/_docs/Vegetable%26%20Fruit%20Headlines%20Special%20Alert%20%232%20July%2010%2C%202015%20Myers_0.pdf

http://plant-pest-advisory.rutgers.edu/fruit-ipm-report-7-9-2015/

Update on SWD Trapping

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

As of last week, we had not detected any spotted wing drosophila in our four trapping locations. However, the first suspects were found in Maryland last week and states to our north have started to detect flies in traps. We did find this pest in Delaware during the 2012 season and maggots were found infesting bramble crops. Be sure to consider this pest when making treatment decisions in small fruit, grapes and stone fruit. For more information on monitoring, identification and control of this insect pest be sure to check the following link:
http://www.northeastipm.org/about-us/publications/ipm-insights/spotted-wing-drosophila-in-the-northeast//

Spotted Wing Drosophila (SWD) Monitoring Will Begin Soon

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Spotted Wing Drosophila continues to pose a serious threat to small fruit grown in our region. I plan to start trapping by mid-May in a few blueberry and grape locations. As you will see on the following links, researchers working with this insect are now recommending using yeast and sugar baits versus apple cider vinegar in traps. Traps only give an idea of the presence or absence of SWD in an area, but are not good predictors of population sizes and trap captures do not always occur before fruit infestation. Therefore, preventative spray programs are being recommended in states to our south. They are recommending that growers time treatments to host susceptibility (ripening, meaning fruit that is beginning to color, and ripe fruit) rather than to trap captures. Please see the following link from North Carolina for more information on monitoring and management: http://strawberries.ces.ncsu.edu/2013/04/more-on-spotted-wing-drosophila-monitoring-how-many-traps-should-growers-use/.

Be Cautious When Using Glyphosate Around Perennial Fruits

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Glyphosate has been a very useful tool for weed management and is used in commercial fruit plantings. However, it can cause some unwanted injury to perennial crops under certain situations.

Glyphosate should not be allowed to contact leaves, young green bark, fresh trunk wounds, root suckers, open buds, immature fruit tissues, or fresh pruning cuts. All of these can allow for absorption of the herbicide and injury to the plants.

Dormant and spring applications are recommended and there is less chance of injury. Late summer and fall applications have more risk. This is because in the fall, if glyphosate is taken up by the plant, it will be stored in the bark and wood of the stems or canes, as well as the root system. If glyphosate is taken up by the perennial fruit plant, damage symptoms often do not appear until the following spring. When regrowth occurs in the spring the glyphosate in the plant tissue can be translocated and cause injury to new growth. New growth will be yellow and stunted. In fruit trees, lower branches may appear to have strapped leaves and short internodes.

Fruit plants that have absorbed glyphosate will often be weaker and more susceptible to diseases and insect pests.

Do’s and Don’ts for Establishing Blueberries

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

There has been an increase in interest in growing blueberries in Delaware and we have had several new plantings in Delaware in recent years.

Blueberries are very specific in the type of soil conditions in which they will grow. The ideal blueberry soil will be sandy but with high levels of organic matter, it will have a pH between 4.5 and 5.0, it will be well drained in the surface soil but will ample subsurface water. These are the conditions of southern New Jersey where they are native and where there are large commercial plantings. We only have a small area of Delaware with those characteristics – the “black soils” were marshes were drained in southern Sussex County. In all other areas of Delaware we need to recreate those conditions.

There are five keys to success with blueberries:

1)    Increase soil organic matter before planting

2)    Drop soil pH to between 4.5 and 5.0

3)    Put organic material in the planting hole during planting

4)    Mulch the plants well after planting

5)    Install a drip irrigation system

The following are some more details on each of these keys.

A common mistake that is made is to plant blueberries before the soil has been modified. Normal agricultural soils will have a pH around 6.0 and organic matter below 2%. Blueberries will not grow well in these conditions. It is advised to plan at least one year in advance to modify the soil.

In order to increase organic matter you should plant cover crops and consider amending the soil with additional organic sources such as pine bark fines. Do not use composts that have high pH.

The pH of the soil will need to be modified. This is done by adding elemental sulfur at recommended rates according to soil type and the amount of pH drop required. Again the target is between 4.5 and 5.0. Blueberries are among a group of unique plants that are acid loving. This is in contrast to most other crops that require a higher pH. Sulfur additions need to be done the year before planting. This is because bacteria in the soil need to react with the sulfur to form an acid that lowers the pH. This only occurs when soil temperatures are warm and it takes several months for the full reaction to take place. You cannot apply sulfur in the year of planting and expect the soil pH to be in the acceptable range for good first year growth.

During the year when you are modifying soil, add phosphorus and potassium to bring soil levels so that they are optimum for those two nutrients prior to blueberry planting.

Once soil has been properly modified, you can plant the blueberries. This is normally done in the spring. Fall plantings are possible but there are higher risks to losses in harsh winters. When laying out your planting and deciding on your between row spacing, think about how you will apply mulch and pesticides and whether you will be using netting to exclude birds. Rows will need to be wider if large equipment is used for mulching or spraying, but wide row spacing will increase costs if netting is needed to prevent bird damage.

A key to planting blueberries is to add organic matter to the planting hole. The most common practice for smaller plantings is to use one gallon of moistened peat moss in each hole. Other organic materials can be substituted but they should be low in pH and should be at least partially decomposed. Most commercial composts are not acceptable because lime is added during the composting and the pH is too high for blueberries. Also, composts made with manures as a component will have too high of salt levels and will injure the blueberry roots.

After planting, blueberries should be mulched heavily. Blueberry roots are shallow and need to be protected from high soil temperatures. In addition, the mulch will conserve soil moisture and provide additional organic matter as it slowly decomposes. The best mulch materials are high in lignin and acidic in nature. Pine bark is ideal but is often not readily available. Aged wood chips or ground yard waste that has been aged makes good mulch. Sawdust must be partially decomposed before use to avoid nitrogen deficiencies. Avoid mulches that increase pH.

For most plantings, drip irrigation is recommended for blueberries and is best placed under the mulch. Because blueberries are shallow rooted, frequent irrigations during our hot summers will be needed to get the plants established and growing well. Overhead irrigation can also work if designed properly.

Do not put fertilizers in the plant hole and avoid adding any fertilizer until plants are established. In the first year, blueberries will need about 20 pounds of nitrogen and nitrogen should be in the form of ammonium sulfate or urea. Do not use N sources that contain nitrate.

BBerryTable

Pruning Season

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

March is the major month for pruning tree fruits, grapes, and cane fruits. Pruning earlier than March often stimulates plants too early and can result in later cold damage; pruning after plants have leafed out can result in loss of plant vigor.

On young fruits, pruning is used to develop the plant architecture and to allow for good root systems to develop. On bearing fruits, pruning is used to maintain productivity. In commercial orchards, pruning is done to create maximum fruit bearing surface, to allow sunlight to enter, to allow air to circulate throughout the tree canopy, to promote good spray penetration, to renew fruiting wood, and to maintain growth or vigor in all parts of the tree. Pruning is also a way of regulating the fruit load on the tree in the current season and from season to season.

On bearing tree fruits, the first step is to remove any suckers from the base of the plant. The second step would be to remove damaged or diseased wood. Remove this back to a main branch or scaffold limb and make the pruning cut at the branch collar (do not flush cut). Next, remove any watersprouts. These are rapidly growing upright shoots that form along the trunk or scaffold branches. Depending on the training system, additional pruning or training will be needed to maintain proper plant shape or height. For example, in fruits trained to an open center, remove any inward growing material. For central leader systems, remove excess branches to the main trunk. Finally, thin out flowering wood or spurs as necessary to reduce fruit load and make pruning cuts to encourage future fruiting wood development (this step varies considerably depending on the type of fruit).

In bearing grapes (generally starting the third year after planting), pruning is used to set the fruiting area for the season and for renewing young canes for the next year. Cane pruning is the usual system for Vinifera types but is also appropriate for some hybrids and American types. In this system a permanent trunks is established (often two trunks are established) to the wire, and every year two canes arising from the trunk, each 8-10 buds long, are selected and tied to the wire (one each direction), and all other canes are cut out. Canes should be about the thickness of your little finger and should come out from the trunk as close to the wire as possible. These canes should have buds fairly close together (avoid large thick canes with buds spaced far apart). Another system, often used with hybrid grapes, is the cordon or spur pruning system. With this system, in the second season, one cane is trained to each side of the trunk, and they become permanent arms that remain as the base on which short spurs are established to produce new fruiting canes each year. These spurs are two or three buds long.

In blueberries, a cane fruit, the philosophy behind pruning is to constantly renew the older, decreasingly productive canes by cutting them out and forcing new canes. Plants are continually replacing old canes with new canes while most canes are in a productive, intermediate stage. For mature bearing blueberries, plants should produce at least three to five new canes per year. Start by pruning out all dead wood. Keep the three best one-year-old canes and remove the rest. Locate the oldest canes and prune out one of every six canes, starting with the oldest. Prune out all low branches and then detail prune by remove twiggy wood on older canes to increase fruit size.

Spotted Wing Drosophila Infestations Found in Blueberry Fields in Maryland

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

I have gotten three reports in just the last few days and have confirmed two of them as Spotted Wing Drosophila (SWD, Drosophila suzukii) infestations in blueberries in South Central and Southern Maryland. These infestations started out just like they did last year in blackberries and raspberries. Growers noticed that berries were starting to rot prematurely on the plant and after a short time the berries fell to the ground (Fig. 1). If you look closely at some berries you can see tiny puncture marks in the fruit where the female SWD fly used her ovipositor to saw into the ripening fruit and place her egg inside the berry (Fig. 2). This egg then hatches and the maggot feeds in the berry. The maggots will feed for about one week and then pupate either in the berry or just outside of it. On one farm there is probably going to be about a 20-25% fruit loss and on the others it could be somewhere between 35-60%. The question then becomes what can be done now? Unfortunately there is not much that can be done other than try to reduce the amount of berries that become infested by spraying every 5-7 days. The infestation will be slowed, but the fly population will be very difficult to control because there will be so many other sources of rotting fruit for the adults to lay their eggs and the larvae to develop in.

What needed to be done was for growers to use SWD traps to try to detect the presence of the adults BEFORE they laid eggs in the fruit. Detecting the larvae in the infested fruit is too late to implement an effective management program. If the adults are found early enough insecticide applications can be timed better and can prevent or at least slow an infestation. I can’t emphasis enough that growers of small fruit anywhere in Maryland or the Mid-Atlantic need to have the SWD traps out NOW in their small fruit and they need to check them twice per week for the adult males (Fig. 3). We are not sure why these particular farms have these bad infestations; the growers did not do anything to bring about the problem. Some insecticides that have been shown to work include: Pyrethroids: fenpropathrin, zeta-cypermethrin, and lambda-cyhalothrin; Neonicotinoids: acetamiprid and imidacloprid; Spinosyns: Radiant and spinetoram and the organophosphate Malathion, which has a short postharvest interval (PHI), making it useful to use during harvest (fenpropathrin (Danitol) also has a short PHI). Be sure to READ THE LABEL before applying any insecticide to your crop as some chemicals can be used on some fruit, but not others and postharvest intervals can also vary by fruit crop. Pesticide applications should be rotated to reduce the chance of resistance developing. A more detailed description of the SWD fly, its biology and how to monitor and manage it can be found at the UME fact sheet: http://www.agnr.umd.edu/Extension/agriculture/mdvegetables/files/spottedwingedfly.pdf

 Figure 1. Blueberries on ground from SWD damage

Figure 2. Blueberry with SWD punctures (arrows)

Figure 3. SWD adult male