Posts Tagged ‘blueberries’

Spotted Wing Drosophila Infestations Found in Blueberry Fields in Maryland

Friday, June 22nd, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

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:

 Figure 1. Blueberries on ground from SWD damage

Figure 2. Blueberry with SWD punctures (arrows)

Figure 3. SWD adult male

Be Sure to Monitor for Spotted Wing Drosophila in Strawberry and Brambles This Year

Friday, March 2nd, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

By now everyone should know that the newest invasive pest, the spotted wing drosophila (SWD), is here in the mid-Atlantic. It was found heavily infesting blackberries and raspberries in central Maryland this past summer and fall. Just about everywhere we trapped for it (I am still trapping adults in February in brambles, SWD overwinter as adults) we have found it on the western shore. We know it is on the eastern shore through trapping efforts by the University of Delaware. What we do not know about the eastern shore is how bad SWD infestations might be this coming season. The first crop that may get hit is strawberries. Information from Oregon and Michigan shows that their strawberries are not attacked to any great extent, but we DO NOT know what the fly may do to our strawberry crop. That is why it would be prudent to put SWD traps out and monitor for the adult flies. Males have a spot at the end of their wings (Photo 1), females do not (Photo 2), but the females do have a strong ovipositor they use to saw into non ripe fruit and lay their eggs—which is why they are such a devastating pest.

Most growers we visited did not think they had SWD on their farm and yet we found it everywhere we looked. The damage is often mistaken for early rotting berries or fruit (Photo 3). Early control is essential, if this fly is allowed to build its population through the summer into the early fall it will be very difficult to control and will be present on your farm basically forever. There are several web sites you can use to build your own traps (just Google spotted wing drosophila traps), or you could ask for help from me or your Extension educator about trapping. The key is to use a very common, inexpensive product as bait in the traps – apple cider vinegar. Traps should be placed in the field within the plant canopy, out of the sun if possible, and checked once a week for flies. Some traps should be located near the edge of the strawberry field and others along a woods edge. There will be many fly species in the trap, if you are not sure you have SWD take it to your local Extension educator for identification.

Photo 1. SWD adult male

Photo 2. SWD adult female

Photo 3. SWD damage to blackberries

Spotted Wing Drosophila Verified in Delaware

Friday, March 2nd, 2012

Joanne Whalen, Extension IPM Specialist;

We finished our 2011 SWD monitoring activities in late September in a commercial vineyard and we did not detect any SWD adults in our traps. However, traps that were set out near the Milford area from September through December did collect flies which were verified by a USDA identifier in January 2012 as SWD. During the 2011 season, this pest made its way to Virginia, Maryland, Pennsylvania and New Jersey, so it was only a matter of time before their presence was confirmed in Delaware. As you start the season you will need to consider this pest when making management plans.

These flies can infest and cause a great deal of damage to ripening fruit, as opposed to the overripe and fallen fruit that are infested by most other Drosophila species. Females damage fruit by slicing through the skin with their knife-like ovipositor, and inserting eggs that develop into small white larvae. These cuts can also be a pathway for fungal pathogens, leading to greater reductions in fruit quality. Therefore, monitoring for SWD is important to avoid economic loss. This insect is a pest of most berry crops, cherries, grapes and other tree fruits, with a preference for softer-fleshed fruit. In areas where it has been detected, it is has become an important pest of cherries, raspberries, blackberries, blueberries, strawberries, grapes, peaches, and plums.

For more information on monitoring, identification and control of this insect pest, please check the following links:

Spotted Wing Drosophila Found in Central Maryland

Friday, September 2nd, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

A sample of fruit flies was given to me by Bob Rouse, a horticultural consultant, from fruit farms he consults for in Central Maryland; these flies were identified by me and then verified by the USDA as Spotted Wing Drosophila (SWD) Drosophila suzukii, the first find in our state. This is not good, but this pest has been moving steadily east over the last few years. The SWD is a temperate-zone fruit fly; native to Southeast Asia that prefers temperatures of 67-85° F. Adults are small (2-3 mm) flies with red eyes and a pale brown thorax with black stripes on the abdomen. The most distinctive trait of the adult male is a black spot towards the tip of each wing; the female does not have any wing spots (Photo 1). Larvae are tiny (up to 3.5 mm), white, cylindrical maggots that are found feeding in fruit. This pest was first identified in the western U.S. in 2008. In 2009 it was found in California, Florida, Oregon, Utah and Washington. In the last year or so it has been found in the Midwest and Pennsylvania. Long-distance dispersal usually occurs with the movement of infested fruit to new areas.

While it is not unusual to find fruit flies in late summer infesting overripe or decaying fruit these particular fruit flies are considered nuisances, not crop damaging pests. However, the spotted wing drosophila female lays her eggs inside healthy unblemished fruit with her saw-like ovipositor (Photo 1). The adult female can damage fruit when she oviposits while larvae contaminate fruit at harvest, causing it to become soft and unmarketable (Photos 2 and 3). It infests thin-skinned fruit such as grape, cherry, raspberry, blackberry (raspberries and blackberries appear to be very susceptible fruit), blueberry, and strawberry, etc. SWD overwinters in the adult stage and flies become active in spring, mate, and lay eggs in the thin-skinned fruit. Multiple generations develop each year wherever this insect can overwinter. At a constant temperature of about 75°F it takes only 9 days from egg to adult. This rapid developmental rate allows it to quickly develop large populations and inflict severe damage to a crop.

The best thing to do is monitor for this pest if you have small fruit. Monitoring will help time insecticide applications for greatest effectiveness. You can use homemade traps to monitor for SWD. There are several sites that explain how to make the traps:

or you can buy commercially made traps:

For any of these traps you will need to add 1 or 2 inches of apple cider vinegar to the bottom of the trap with a drop of unscented dishwashing soap to break the surface tension so the flies will drown. Hang the trap in the shade near berries preferably before fruit begins to ripen. Check the trap weekly for small flies with dark spots at the tip of their wings floating in the fluid. These will be male SWD. Put fresh apple cider vinegar and a drop of soap in each week or so. You also should observe your fruit regularly as it begins to ripen. On cherries and blueberries start checking fruit for punctures the female creates when she lays eggs as soon as fruit begins to develop any color. SWD stings are tiny and a hand lens helps. Pull open suspect fruit to see if there are larvae inside. If you find infected fruit you should spray to prevent the damage from increasing. The infestation level can increase quite rapidly if left untreated. Remove and destroy infested fruit as you monitor. Stings are not readily visible on berries so it is difficult to detect an early infestation by monitoring the fruit alone for damage.

Chemical Management: Malathion will control SWD and has a short PHI, but is very toxic to bees and natural enemies. If monitoring indicates a need to spray, the application should be made as soon as possible. In raspberries or strawberries, sprays may need to be repeated to keep SWD populations low during their prolonged fruiting period in summer and fall. Other possible alternatives to Malathion with fewer negative environmental effects are the spinosyns and neonicotinoids. To get satisfactory control with these alternatives two sprays may be required; the second applied 5 to 7 days after the first. Additional sprays may be needed for berries with a prolonged fruiting period. Be sure to check the label before applying any chemical as the specific chemicals that can be used on one fruit can’t always be used on others.

 Photo 1. Male (left hand side) and Female (right hand side) spotted wing drosophila flies

Photo 2. SWD damage in blackberry

Photo 3. SWD oviposition marks on cherry

Its All About Light

Thursday, April 29th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist;

Production of high yields of quality fruit requires adapted varieties, close attention to disease and insect management, balanced plant nutrients, and good weather conditions. One of the other key areas that growers need to consider is light. Leaves require adequate light levels to produce sugars by photosynthesis. These sugars are then translocated into developing fruit. Sugars also provide the building blocks of other flavor components. With this in mind, a very important aspect of fruit management is to insure even light distribution throughout the plant canopy. This applies equally to small fruits and tree fruits.

The following are some considerations to achieve this even light distribution and to manage for the best combination of yield and fruit quality.

1) Play close attention to plant densities and do not overcrowd plants. While more plants often means higher yields, excess shading at high populations can lead to reduced quality. Crops like matted row strawberries bear the most fruit and best quality fruit on the edges of the row. In most fruit crops, fruits on the interior of dense canopies often have poorer color, reduced sugars, and poorer flavor.

2) Choose pruning and training systems that allow for even light distribution. In fruits such as peaches, this is achieved by pruning so that scaffold branches are arranged in a open form V or vase shaped form. In crops that use a central leader system such as apples, it means pruning to appropriate spacings and orientations between scaffolds to allow for good light penetration. In summer bearing brambles, this means having trellis wires arranged so that fruiting canes are to the outside where they can receive the most light and training new canes to the in the middle. Pruning canes higher will also allow for more light along the length of the cane, however, they should not be so tall that they shade neighboring rows.

3) Thinning fruiting material and thinning foliage is often necessary for good fruit quality, color development, and uniform ripening. Leaf thinning is practiced in grapes for this reason. Thinning of blueberry canes to remove old and weak material is another example as is detail pruning of many tree fruits to remove excess fruiting wood and allow in more light.

Success with Blueberries

Thursday, April 8th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist;

There has been an increase in interest with blueberry production in Delaware over the past 5 years. Blueberries can be a very profitable crop, especially for growers that direct market. As a perennial shrub-like crop, blueberries will take 5 or more years to come into full production but can be productive for decades. It is critical therefore to make sure that plants get off to the right start. Blueberries have exacting soil modification requirements that must be addressed. They are native to areas with acid soils that have high organic matter in the surface but with sand below and with water relatively close to the surface. However, they do not tolerate waterlogged soils.

There are 5 key factors critical to establishing blueberries.

1) Acidify the soil. Blueberries require acid soils with a pH in the 4.5-5.2 range (target 4.8). Most of our cultivated soils have pHs much higher than this. Therefore soils must be acidified. The material commonly used to acidify soils is elemental sulfur. However, sulfur must be converted by microorganisms to release the acidity so it acidifies only when soils are warm. Plan one year ahead of time to acidify the soils. On a sandy loam soil, about 1000 lbs of sulfur per acre are required to lower the pH to the desired level. You should not plant until the soil has been acidified.

2) Provide good drainage. Make sure that water drains away from the planting site and does not collect. It may be necessary to make low, wide ridges to improve drainage and move excess water away from plants. Avoid planting in sites that are poorly drained or that have high water tables in the winter.

3) Increase organic matter in the area that is to be planted prior to planting. This is commonly done through the addition of materials such as peat moss mixed directly into the planting hole (mix at one gallon of peat with backfill soil for each plant during planting). You may also use other materials such as composted saw dust, bark fines, or other partially rotted materials as long as they are acid (have low pHs). You can use up to half by volume of these materials mixed with soil in the hole. Do not use manures, high pH composts, or spent mushroom soil. You may also choose to modify the entire planting strip before planting. Apply 2-4 inches of these organic materials (such as composted sawdust or bark fines) and work them into the soil in a 3-6 foot strip where the blueberries are to be planted.

4) Mulch immediately after planting with a 4 inch layer of organic material. Common materials are aged sawdust or bark mulch. This mulch is critical to protect the shallow roots and provides additional organic matter as it decomposes (reapply as necessary).

5) Install drip irrigation and provide irrigation water through the drip as needed. Blueberries do best in moist (not wet) soil conditions. Drip tubing should be thick walled for long term use and should be placed under the mulch.