Posts Tagged ‘fruit’

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

Sure Looks Like Brown Marmorated Stink Bug Damage – But It Isn’t

Friday, August 26th, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

Over the last few weeks growers have given me damaged pears that at the time I said looked like brown marmorated stink bug damage. Pears on the outside had pits in them where it looked like the bug had fed at one time (Photo 1). When the fruit is cut open there is a brown spot deep inside the pear that looks like brown marmorated stink bug (BMSB) feeding damage (Photo 2). But this spot differs from BMSB feeding in a couple of ways. First it is extremely hard, it is almost impossible to get a knife through it. Almost all of the BMSB damaged pears and apples and other fruit where I have seen a brown spot may be pithy or mealy or firm, but it has never been really hard. Second no yeast was found associated with the spot. In almost every case of BMSB feeding resulting in a dark spot in the fruit we have found yeast. And thirdly there was no stylet wound found in the damaged areas. I have found that if the cut is made into the fruit to the brown spot that the brown spot will then swell in a short time and stick up from the surface of the cut fruit (Photo 2).

The most likely cause of the damaged pear fruit appears to be Stony Pit disease, but even this we are not entirely sure. One problem is that the causal agent of Pear Stony Pit has yet to be isolated, but it can be transmitted by grafting and therefore a virus seems to be the most likely suspect, but no one knows for sure. Insect vectors or infected seed have not been documented as transmission factors for the virus.

The symptoms usually start about three weeks after petal fall, when dark green spots form on the fruit. The areas around these spots continue to grow, but the spots themselves do not. This results in misshapen fruit with pits (Photo 1). Pits often become necrotic and the fruit beneath becomes hardened (Photo 2). If fruit is heavily pitted it may become so hard that it is difficult to cut with a knife. Cracking of the bark, stunting of trees and chlorotic vein-banding have also been reported. One of the very odd things about this “disease” is that symptoms on fruit vary from season to season as well as severity. Trees that show symptoms one year may have no pitted fruit the following years. This type of scenario resembles damage more from BMSB feeding than a virus disease, which makes the diagnosis that much more difficult.

The best management practice seems to be to select virus-free trees for planting. Some of the most severely infected cultivars include Bosc, Comice, and Seckel, while less pronounced symptoms are found on Hardy, Conference, Forelle, Howell, Old Home, Packham’s Triumph, Bartlett, and a few other cultivars.

This is NOT MEANT TO SAY BMSB has not caused severe damage in the mid-Atlantic on fruit and vegetables because it has, just that fruit damage can be attributed to BMSB (as I did) when it was not the causal agent. Stony Pit seems to be fairly common this year in pears and any damaged-pitted fruit should be examined carefully.

Photo 1. Pear fruit with deep dimple in center caused by Stony Pit disease

Photo 2. Dimple area cut open showing extremely hard, raised brown spot

Imidan 70 Now Labeled for Spotted Wing Drosophila on Some Crops

Thursday, July 28th, 2011

Joanne Whalen, Extension IPM Specialist;

It should be noted that Spotted Wing Drosophila has been added to the Imidan 70 label for key crops. (

Spotted Wing Drosophila Confirmed in NJ

Thursday, July 21st, 2011

Joanne Whalen, Extension IPM Specialist;

In addition to Virginia, we just received a report today that the first spotted wing drosophila (SWD) were detected in blueberry fields in New Jersey during the week of July 7. Although we have not found any yet in our limited survey (only one location), it is important that you monitor for this important pest. The following links provide information about identification, monitoring and controls.

Section 18 for Brown Marmorated Sting Bug (BMSB) Management on Stone and Pome Fruit Approved

Friday, July 1st, 2011

Joanne Whalen, Extension IPM Specialist;

This week we received the letter from EPA that they approved our Section 18 request for the use of dinotefuran (Trade Names: Venom from Valent U.S.A. Corporation; Scorpion from Gowan Company, LLC) to control BMSB on stone and pome fruits. This use expires on Oct 15, 2011. Please refer to for more information on use rates and restrictions. Both labels are also available so please contact either David Pyne at the Delaware Department of Agriculture ( or Joanne Whalen ( for more information.


Thrips on Winter Annuals

Thursday, April 14th, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

Vegetable and bramble growers in Maryland have called me often over the last couple of years about fruit problems in their fields possibly caused by thrips. As an overall study of the possible impact thrips may be having on vegetable and fruit quality I have been conducting surveys for their numbers and species. I have taken weed samples throughout the winter and early spring from vegetable fields and high tunnels looking to see if any thrips were overwintering and if so what species they were. Below is a 9-point summary of the sampling program.

1.  For most samples very few thrips were found.

2.  In 14 of the 20 sample sites thrips were found in December through January on winter annuals.

3.  At 9 sample sites thrips were found in March.

4.  The worse sample sites were high tunnels that had chickweed and/or henbit winter annuals growing along the outer or inner edge of the base of the high tunnel (Fig 1). 87% of the sampled winter annual weeds at these sites over the last two years had at least 3 female thrips (one sample had 23 female thrips).

5.  Of the total thrips found 76% were female adults, 19% were males and 5% were immatures or pupae.

6.  Western flower thrips were found to overwinter in Maryland, Delaware, SE Pennsylvania and NE Virginia, although only in low numbers (Fig 2).

7.  Chickweed was found to harbor 66% of all thrips with wild mustards and henbit being the next best winter hosts.

8.  Sampling-sites near high tunnels or woods had a greater probability of containing thrips than sites out in a field.

9.  Farms where thrips were found to overwinter had greater probabilities of infestations during the season.

Even though several thrips species, including Western flower thrips, were found to overwinter in the mid-Atlantic area it does not mean we have a thrips problem. However, growers do need to watch for any early season infestations in their field and high tunnel brambles and not overreact by spraying an insecticide unless really needed. Most brambles can have at least 5 thrips or more per fruit/flower before there is any possibility of damage. The species of thrips you have should be determined only if you think thrips are causing fruit quality problems at low densities. I would be glad to look at your thrips if you send them to me: 2005 Largo Rd, Upper Marlboro, MD 20774 or you can call 301-627-8440 or email me:

Figure 1. Winter annual weeds along outside (under snow) and inside border of high tunnel

Figure 2. The proportion of thrips species found to overwinter at the 20 sample sites


Blossom Damage in Strawberry Due to March Cold Snap

Thursday, April 14th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Plasticulture strawberry growers reported significant damage to early blooms during the cold snap between March 27-29, even with heavy weight floating row covers in place. Temperatures as low as 21°F were recorded in some locations. When temperatures at flower level have the potential to drop below 30°F for extended periods under row covers, then a combination frost protection approach of row covers combined with sprinklers is needed to avoid freeze losses.


Primocane Blackberries

Thursday, April 14th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Until recently, commercially available blackberries were floricane types, that is, they fruit on last year’s canes. Six years ago, the University of Arkansas released their first primocane blackberries, Prime-Jim and Prime-Jan. Primocane blackberries fruit on current season canes, allowing for blackberry production from mid-summer through frost. In subsequent years they have the potential for two-season fruiting – in early summer on overwintered canes and as a late summer and fall crop on current season primocanes – as much as 6 months of production. The first two releases (Prime Jim and Jan) did not have sufficient fruit quality to be used for commercial production and were mostly recommended for home gardens. In 2009, Dr. John Clark at Arkansas released Ark-45, a primocane blackberry which did have good fruit quality and commercial potential. It is recommended for trial in Delaware. Unfortunately it is still thorny which will limit its use. The good news is that Dr. Clark is working on thornless primocane blackberries. We will be testing some of his advanced thornless primocane selections at the UD research station at Georgetown (planted this spring).

What is exciting about primocane blackberries is that they offer extended production potential into the fall. They also offer flexibility in production as they can be treated as a two season fruiting crop summer and late summer-fall (overwintered and primocane production) or single season (primocane only) production late summer-fall. Blackberries are generally well adapted to Delmarva conditions but will shut down if temperatures stay in the 90s for extended periods. Primocane blackberries will be flowering and fruiting much of the time in the cooler late summer and fall. Stay tuned as we follow these blackberry advances.