Posts Tagged ‘strawberry’

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:

Strawberry Planting Season

Friday, September 9th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Planting season is here for plasticulture strawberry systems. In our area, most strawberries are planted using plugs produced by rooting tips. While plugs are more forgiving than bare root plants, actions prior to planting and at planting still can affect future performance. The goal is to have quick, uniform rooting across all plants on the bed so that proper sized crowns are produced before going into winter.

The first key is to have a firm, high, uniform raised bed with black plastic mulch tight against the soil. This allows heat to transfer to the soil, warming the root zone, and promoting fall growth. Loose plastic will not do this.

Liming should be done ahead of time if necessary to raise pH and provide Ca and Mg if necessary. Base fertilizer should be applied to the bed before formation to provide necessary P and K and adequate but not excessive N for fall growth (60-75 lbs N is recommended at bedding).

Whether you are planting by hand using a dibber to make holes or are using a water wheel transplanter, uniform planting depth is critical. Workers placing plugs should be trained to place plants so that crowns are not buried or are not above soil level. If buried, crowns will be susceptible to rots and plants may die or be stunted. Buried buds may not be able to leaf out. If planted too shallow, plugs will be susceptible to drying out before being able to root. In addition, during planting, workers should not plant weak, diseased, or damaged plants

Water is also critical during establishment. While we are having a spell of rainy weather, you cannot always count on rain during the establishment period. Drip irrigation should be run to wet the bed. However, this is usually not enough. Plants should receive water at transplanting in the hole and should also be watered overhead during the establishment period for best results.

Planting date is critical for plasticulture systems. While row cover management can be used to control growth, planting at the proper date will make row cover management in the fall much simpler. The ideal planting window is the first half of September, prior to September 20, for most areas in our region. Strawberries planted in this window should produce adequate numbers of branch crowns in the fall period and can then be covered in late November or early December for winter protection.

Later plantings (after September 20) will require earlier row covering to trap some heat and put on adequate fall growth.

In high tunnels, the planting window in the fall will be wider because of the extra heat provided and later plantings can be successful. However, some earliness will be lost.

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

Mustard Seed Meal as a Chemical Fumigation Alternative

Thursday, August 4th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

With September strawberry planting season approaching for the annual plasticulture system, growers will be preparing beds and fumigating in the next 2 weeks. While several chemical fumigants are registered for strawberries, new fumigant use restrictions will make their use more of a challenge. In addition, strawberry growers that are organic or are using high tunnels with limited rotation are looking for effective fumigation alternatives.

One natural fumigant alternative that has shown great promise is mustard seed meal. According to researchers Dean Kopsell and Carl E. Sams, “studies conducted at The University of Tennessee showed that mustard seed meal has extremely high concentrations of isothiocyanates (ITCs). The seed meal is also a fertilizer source of nitrogen and other nutrients. When incorporated into the soil, ITCs act as effective biofumigants, reducing populations of pathogenic fungal species (Sclerotium, Rhizoctonia, Phytophthora, and Pythium), nematodes, weeds, and certain insect species.” ITCs are the same compounds found in some commercial chemical fumigants.

Specific studies with strawberries showed yield increases of as much as 50% compared to untreated controls using mustard seed meal. Additional research is going on in the region (Virginia, Maryland, Delaware, and Pennsylvania) with this material.

For mustard seed meal to be effective as a fumigant it has to be thoroughly worked into the bed area and plastic layed immediately after incorporation. The bed must remain evenly moist so the meal can break down (dry pockets will have delayed break down and can cause problems later) so a moist soil is important. A waiting period of 20 days is advised similar to a commercial fumigant before planting.

Current supplies of mustard seed meal come from Tennessee and costs $1.00-1.20 per pound. Recommended rate is 1000 lbs per mulched acre.

Because mustard seed meal is a natural compound, fumigant restrictions do not apply. It is also OMRI certified for organic production.

Spittle Bugs Common in Strawberry this Year

Friday, May 27th, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

Many strawberry growers have seen the meadow spittlebug (Philaenus spumarius) in their strawberries this year. Some of these growers include high tunnel growers who have never seen spittle bugs before in their high tunnel strawberries. The spittlebug is an annoying pest on strawberries that under extremely high numbers can stunt plants and reduce berry size. But they are more of a nuisance especially to u-pick growers as the pickers object to being wetted by the insect excretion (the spittle, even though it is harmless).

Spittlebugs can be recognized by the white masses of foam found on leaves, petioles, and stems of plants (Fig. 1). The yellow-green nymphs produce this covering to protect themselves from predators and desiccation. Initially the nymphs feed at the base of the plants, but later move up to more tender foliage. Feeding may cause leaves to become wrinkled and dark-green. Although fruit may be stunted under heavy spittle bug populations, yield loss rarely occurs. High spittlebug populations are often correlated with weedy (including legume cover crops like clover) fields, so proper weed control is important. Nymphs feed for five to eight weeks before entering the adult stage. Newly emerged adults (called froghoppers) are bright green and darken over time to a dull brown. They are very active and readily jump when disturbed. Adults are present on foliage May through November but do not produce any spittle. Adults lay white to cream-colored eggs in the stems and leaves of plants from July through October. These eggs will overwinter and hatch next spring. There is one generation per year in Maryland.

Treatment is rarely necessary for spittlebugs, but u-pick growers need to keep populations to one spittle mass per square foot through prebloom to placate customers. It will be necessary to spread plants and inspect the crowns as well as leaves and stems. Control is considered at one spittlebug per square foot for u-pick operations and 5-6 per square foot (a high population) for everyone else. Aphid control products such as Assail, Thionex, Nuprid, etc. will control spittlebugs too.

Figure 1. Spittle on stems of plants produced by spittle bugs


Fasciation in Vegetables and Fruits

Friday, May 27th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

In recent visits to watermelon fields in Delaware for pollination and fruit set surveys, we found a high number of pollenizer plants in one field that had one or more fasciated stems.

Fasciated stems are ones that are flattened and look like several stems have been fused together. They may be fan shaped in appearance. We also commonly see fasciation in strawberry fruits which develop a “cockscomb” appearance. Fasciation occurs when a growing point changes from a round dome of cells into a crescent shape. Subsequent growth produces a flat stem, flower, or fruit. In some cases fasciation is the result of several embryonic growing points fusing together, with the same flattened or fan-like appearance.

Although the causes of fasciation are not well understood, it is most likely because of a hormonal imbalance. Use of herbicides that are hormone analogs (such as those in the growth regulator or 2,4-D family) can often cause fasciation.

Fasciation can also be due to a random genetic mutation. In some cases, these mutations have been taken advantage of to produce new plants (many ornamentals) that then are propagated vegetatively to keep the fasciated appearance.

Fasciation can also be induced by one or more environmental factors, most commonly cold damage in the spring. Fasciation may also be induced by physical damage to the growing point.

Plant pests may also cause fasciation. Pathogens (bacteria, fungi, virus), insects, and mites, and insects may damage growing points or cause plants to produce excess hormones that will result in fascinated plants.

Go to the Purdue Plant and Pest Diagnostic Laboratory site for a picture of a fascinated sweet potato stem:


Fungicide Recommendations for Strawberry Disease Control

Friday, May 6th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Anthracnose Fruit Rot
Strawberry anthracnose can be extremely destructive during warm, wet weather causing significant fruit rot. Symptoms of anthracnose include blackish-brown circular spots on maturing green fruit and soft, sunken (flat) circular lesions on ripe fruit. On ripe fruit, lesions can expand rapidly and are often covered with a pinkish-orange spore mass. Spores are spread from infected to healthy fruit with splashing water. Control of anthracnose always begins with a 7 to 10-day preventative spray program no later than 10% bloom and/or prior to disease development. For control apply the following combinations:

Application #1:
captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A

Application #2:
captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl. oz 2.08SC/A
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A

Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

For subsequent applications, alternate:
captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A plus captan (M3) at 4.0 lb 50WP/A
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

To help manage fungicide resistance development, do not make more than 2 consecutive applications of either:

Pristine (pyraclostrobin + boscalid, 11 + 7), Cabrio (pyraclostrobin, 11) or Abound (azoxystrobin, 11) before switching to another fungicide chemistry.

Botrytis (gray mold) and blossom blight can cause serious losses in strawberry plantings in high tunnels and the field if not controlled properly. Development is favored by moderate temperatures (59 to 77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5 to 10% bloom and every 10 days until harvest. During periods of excessive moisture, spray intervals of 5 to 7 days may be necessary. Rotate fungicide chemistries to aid fungicide resistance management.

Application #1:
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP/A
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A

Application #2:
Elevate (fenhexamid, 17 – See restrictions) at 1.1 to 1.5 lb 50WDG/A
Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz. 38WG/A

Application #3:
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A

For subsequent applications, alternate:
captan (M3) at 4.0 lb 50WP/A
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A.

From Rutgers Plant and Pest Advisory, Veg Crops Edition, by Andy Wyenandt, Ph.D., Specialist in Vegetable Pathology and Wesley Kline, Ph.D., Cumberland County Agricultural Agent


Strawberry Deformities

Friday, May 6th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Strawberry harvest is underway in the region and a common observation, especially with the earliest berries, is that there is a significant amount of deformed or misshapen berries. The most common cause of these deformities or odd shapes is weather issues during pollination. This year, low temperature damage was likely to flowers, even under row covers. Cold affected berries will have blunted tips or may appear folded. Conversely, high temperatures and drying winds can dry out some of the stigmas in strawberry flowers, especially in the center of the flower causing doughnut shaped berries. Boron deficiencies can also cause deformed berries, so can damage from spray materials – anything that affects pollination and seed development. Tarnished plant bugs can also feed on strawberry seeds and therefore cause odd shapes to develop. Growers new to the plasticulture system may also note that berries have odd shapes, especially in the large primary berries. This is most often just a characteristic of the variety. Some of these varieties produce fasciated berries that look like cockscombs.


High Temperatures Can Affect Strawberry Yields

Friday, April 29th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Harvest of high tunnel plasticulture strawberries is well underway in the region and field harvest is beginning on plastic. Matted row strawberry harvest is still a few weeks off in most areas.

We have had several days in the mid 80s recently and this should remind growers that while the danger from frost should be over, effects of high temperatures can also greatly reduce strawberry productivity.

When daytime high temperatures reach a certain critical level, strawberries reproductive development will be affected. Flowering will be reduced or will stop altogether. The critical high temperature where flowering is affected and overall impact on flowering will vary with variety. Of the common strawberries being grown on plastic mulch in the annual system, ‘Camarosa’ is the most sensitive and will stop flowering and grow vegetatively when temperatures are above 86°F. ‘Chandler’ will handle somewhat higher temperatures. In matted row strawberry culture, it has been shown that strawberry size in ‘Earliglow’ is greatly reduced once temperatures reach the high 80s.

Growers wanting to maintain fruiting in years where May temperatures reach the high 80s or 90s should consider irrigating with overhead sprinklers during the day to cool plants (direct cooling and evaporative cooling). Use low volume sprinklers and set them to come on when air temperatures are above 85°F and come off when temperatures drop back below this level.


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.