Massachusetts Berry Notes

Weather continues to pose the most difficult challenge facing growers this season. Continued intermittent precipitation and cooler than normal temperatures have kept disease management in the forefront and slowed fruit development. At this writing, a frost warning has been issued for tonight (5/31) in normally cold spots. Strawberries that were not under rowcovers are in generally in late bloom except late varieties and/or late sites. A late-bloom fungicide application for Botrytis gray mold is recommended this year. Tarnished plant bug (TPB) nymphs are beginning to emerge. Post-bloom control measures for TPB are only needed on late varieties/sites. Rowcovered fields are being harvested with variable yield and quality. Blueberries are in late bloom. Freeze damage from early May appears to not be too significant. There is little evidence of mummyberry this year because of the dry weather during the primary phase of this disease. Botrytis blight may still be a concern with continued wet weather. Cranberry fruitworm moths are active now. Summer raspberries are approaching bloom. Be ready for Botrytis gray mold protection during bloom. Check fields for tarnished plant bug and mites. Blackberries are beginning to bloom. Winter injury on some varieties was severe. Surviving plantings have exceptional blossom-set. Yields may be impressive this year. Red currants and Gooseberry fruit-set is also quite heavy this year, especially on ‘Red Start’ red currants and ‘Invicta’ gooseberries. Watch out for powdery mildew. Grapes are showing a wide range of development from 6” shoots to early bloom. Disease management is the highest priority right now. This is covered thoroughly in the Grape section below. Thoughts will soon shift to canopy management which is also discussed. Finally, this is the time to place mating disruption ties in the vineyard for Grape berry moth.

Mark Your Calendars: June 11, 2001. Twilight Meeting at Bramble Hill Farm in Amherst MA. Come learn about a newly established annual strawberry production system being used at this and other farms, as well as a unique mulching system using waste wool from their sheep. Livestock, vegetables and greenhouse crops are all integrated into this farm system. Bramble Hill Farm consists of 128 acres of rolling pastures and crop-land in the center of Amherst. .

Directions: Bramble Hill Farm is located at 593 South Pleasant St. (Rt. 116) in Amherst. Travel south on Rt. 116 from the center of Amherst for about a mile and Bramble Hill Farm is on your right. One contact hour toward pesticide license recertification is offered for attending this meeting.

The following growing degree day (GDD) and precipitation data was collected for the period, May 17 through May 23, 2001. Soil temperature and phenological indicators were observed on May 23, 2001. This information is intended to be used as a guide for monitoring the developmental stages and planning management strategies of pests in your location.

STATE WEATHER SUMMARY For the Week Ending Sunday, May 27, 2001

(Source: New England Ag. Statistics Service, New England Weekly Crop Weather Report, Volume 21, No. 4, May 29, 2001)

Slugs in Strawberries – Scout Now

In my visits to strawberry farms over the last week, I have noted very high populations of slugs feeding on grasses and other plants in surrounding or bordering fields. This is an indication that the population levels may be high enough to cause problems as berries begin to ripen. I encourage strawberry growers to scout their fields and surrounding areas this week; and to place slug traps as well.

Slugs are dark gray, black, yellow or brown wormlike mollusks. They may be covered with spots and range in size from three-fourths to one and a half inches long. Slugs have become a common pest of strawberries, vegetable, field crops, and ornamentals throughout the US and Canada. Large numbers of slugs can be found in a wet year when the preceding winter was mild, especially in heavily mulched fields.

A slug is often described as a snail without a shell. The head of the slug has two sets of tentacles. The eyes are on the tips of the upper tentacles. The lower tentacles, which are shorter, are used for tasting and smelling. The mouth is located between and below the lower tentacles and is equipped with a radula, a tooth-covered rasp that the slug uses to grate plant tissue. The slug glides along a path of mucus that is secreted by the pedal gland located just below the mouth.

Newly hatched slugs resemble the adults but are much smaller. The average life span of the slug is from nine to thirteen months, and an adult can lay from 300 to 500 eggs during its lifetime. Because the eggs are very resistant to cold and drying, they are often the only life stage to overwinter. The adults can survive mild winters and winters where they are well sheltered in the ground.

Slugs injure plants by chewing holes of various sizes in the fruit. Because slugs often feed at night, the only evidence of their presence may be glistening patches or streaks of dried slime seen on the plants and the ground nearby.

One way to sample slug populations in strawberries is to dig holes four inches in diameter and six inches deep and cover them with asphalt shingles wrapped in aluminum foil. The reflective surface keeps the hole dark, cold and moist – and ideal hiding place for slugs. The hole also can contain a shallow dish containing beer as an attractant. Slugs exhibit homing behavior and a tendency to aggregate. They will return to a secure hiding place night after night and will also seek out other slugs.

In some years, slug damage can be high even when large numbers of slugs are trapped. Treating fields with poisonous slug baits in the fall and again in early spring provides some control. Unfortunately, the straw mulch, which provides many benefits in terms of disease and weed suppression, encourages high slug populations. Slug populations are often highest in fields that were in sod the previous year. – This article was adapted from Strawberry Production Guide For the Northeast, Midwest and Eastern Canada, produced by the Northeast Regional Agricultural Engineering Service, Cooperative Extension. (Source: Fruit Crop Advisory Team Alert, Vol. 16, 8 , May 29, 2001)

Raspberry Fruitworm – Sonia Schloemann, UMass Extension Fruit Team

Infestations of raspberry fruitworm, Byturus unicolor, are evident during the prebloom period from the leaf feeding done by the adult form (small brown beetles) of this insect. Larvae (worms) that are later found inside the fruit can cause significant yield losses if they are not controlled.

Field Symptoms - The first indication of raspberry fruitworm is often be the presence of small yellowish-white worms mixed in with harvested fruit. Earlier detection is possible if you know what to look for. The first indications is the tell-tale leaf tattering or eliptical holes in the leaves that results from the feeding by adults on unfolding leaves. The next indication is injury to the unopened blossom buds also done by the adult beetle. Finally, adult feeding injury can also be found on open blossom petals and fruit recepticals. When this feeding is severe, entire fruit clusters can fall off the plants.

Life Cycle - Adult beetles emerge from the soil during late April and early May, about the time the first leaves of raspberries are beginning to unfold. They begin to feed along the midrib of partially folded leaves. Beetles later seek protection between the blossom buds where they attack the soft tissues of the supporting pedicles. As buds begin to separate, the insects attack the blossom buds, making large entrance holes to feed on floral parts.

Female fruitworm beetles deposit their eggs on unopened blossom buds. Sometimes eggs may be laid inside buds or on developing fruit. The grayish-white eggs hatch after a few days, and the larvae commonly bore through the bud and enter the receptacle where they begin to tunnel. As the larvae increase in size, the tunnels are made larger, ultimately becoming grooves in the receptacle adjacent to the berry. When infested fruit is picked, some larvae remain attached to the interior of the fruit and end up in the harvesting basket. Those that remain on the receptacle soon drop to the ground where they pupate and remain over winter.

Control – There is some evidence suggesting that this insect is more of a problem in weedy planting. If early damage is noted (leaf tattering), cover sprays should be applied prior to bloom. Adults (beetles) tend to be most active and noticeable on plants in the early evening hours. Sevin (carbaryl), malathion, and Pyrellin are among the insecticides labeled for this insect.

Blueberry Scorch Disease (Sheep Pen Hill disease)

As petals drop, this is the time of the season when blueberry scorch symptoms become more visible. While we can do very little to control aphids during bloom, this is a good time to rogue diseased bushes to minimize the further spread of the Blueberry scorch disease. If growers are sure that suspect bushes have the scorch virus, they should be pulled out.

Blueberry scorch disease is caused by blueberry scorch virus (BBScV), belonging to carlavirus group of viruses. Primary symptoms of this disease are blighting of both flowers and new vegetative growth at peak bloom. Blighted blossoms fail to produce fruit and infected plants in general are less vigorous than healthy plants. Bushes once infected, may show symptoms each year. Symptom expression may very from year to year. Initially, only one or few branches may have blighted flowers and leaves, but after a few years the entire bush may show symptoms. Two major species of aphids Illinoia pepperi and Ericaphis spp. (previously referred to as Fimbriaphis fimbriata) occur on blueberries in New Jersey. In laboratory experiments using both these aphid species, we were able to transmit BBScV from infected Chenopodium (Lambsquarter) plants to healthy Chenopodium plants. Virus transmission under field conditions can occur from early may to mid-August when aphid populations are present. Removal of infected bushes will decrease the amount of virus inoculum in the field and thereby reduce the spread of the virus to healthy plants. Under greenhouse conditions, this virus can be transmitted by rub inoculation and by grafting. Therefore, it is possible that BBScV may be transmitted under field conditions by mechanical injury. Control of aphids combined with removing and burning of infected bushed over a 2-3 year period should reduce further spread of this virus. (Source: Blueberry Bulletin, Vol. 17, No. 6, May 23)

Long Island Grape Update

Week of May 21: After a month of drought, there were two plus days of solid rain. More rain is predicted for the weekend. The cool temperatures are undoubtedly slowing shoot growth. Chardonnay shoots ranged from 8-16". Some Syrah shoots are 2 ft. already.

Like other eastern regions, there are some local rumblings about inconsistent budbreak in Cabernet Sauvignon. Cab Franc seems to be doing well for the most part. Merlot looks a little uneven as it always does at this time of year.

Pest Control: The current rainy period (May 22-potentially May 28) amounts to a major infection period for all the fungal diseases. Disease control becomes a priority now. What to do if disease shows up? First and foremost, continue to maintain a tight spray schedule to protect new foliage and berries when they set. JMS Stylet Oil will eradicate powdery mildew infections. Copper eradicates downy mildew infections. Ridomil has post-infection activity for downy but should not be used on a raging epidemic due to concerns over resistance. Ridomil is very resistance prone so this is a very real concern. The sterol inhibitors, Elite and Nova, have post infection activity against black rot. This means they can be applied up to 72 hrs after the beginning of an infection period and prohibit black rot. Remember that a properly functioning sprayer, proper rates, enough water and good coverage all factor into the equation. So does canopy management. Some blocks are begging to be shoot thinned right now. This will help immensely with spray penetration.

Use of the Strobilurins: In early April, we heard extensively about the use of strobilurins from Dr. Wayne Wilcox. Growers should consider in practical terms how Abound, Sovran or Flint might be a part of their schedule. First, these are excellent protectant fungicides. They are retained in the waxy cuticle of the leaf and thus are rainfast. For this reason also, they are poor post-infection materials as they do not get down into the body of the leaf where the fungi become established. If strobies are applied post-infection, lesions will develop. However, sporulation from those lesions will be greatly reduced.

Because the strobilurins are resistance prone (to both powdery and downy mildews), all three companies have agreed on identical labeling for resistance management purposes. Do not make more than four sprays per season of any strobilurin on winegrapes, with a maximum of three applications in a row. Also, logic dictates that these products are not the best solution for established infections. JMS Stylet Oil (for PM) or copper (for DM) would be better choices.

Abound is very phytotoxic to Macintosh apples and related types. Sovran is phytotoxic to certain types of sweet cherries. Flint is phytotoxic to Concord grapes.

All three products are very good vs. black rot. Flint is the strongest of the three for powdery mildew control, although Sovran and Abound also are very good. Abound offers good downy mildew control while Sovran and Flint will not hold up under heavy downy pressure. If downy is a concern, tank mix a full rate of Ridomil or half-rate of mancozeb or half-rate of captan with Sovran or Flint. All three strobies appear to be equally mediocre vs. phomopsis. Again, with rainy weather in May or June or if phomopsis has been a past problem (hence levels of inoculum might be high), tank mix with a half-rate of mancozeb or captan.

As for timing, labels are fairly flexible. It is likely that many growers will use a strobilurin to replace the SIís in the prebloom and early postbloom sprays. With prebloom through early fruit set a period of high susceptibility for all four diseases, it makes sense to use the cadillac materials at that point. Whether additional strobie sprays are used before or after that period will depend on weather/disease pressure, price and philosophy of the grower. Read the labels thoroughly to understand the use of these materials.

Strobilurin Tank Mixes: There have been a lot of questions about tank mixing with these new materials. According to grape pathologist Dr. Wayne Wilcox, there is no solid data on the possibility of tank mixing strobies with copper. He hasnít heard of any problems; strobies wonít promote uptake of copper nor do they change the pH of the solution. Thus the prudent thing is to proceed with caution until there is more information. Conditions under which copper is phytotoxic - cool, wet weather-still apply. Donít forget the spray lime if the label calls for it.

What about strobies with Stylet Oil? JMS rep Jeff Simons says this combination should not be a problem. At first glance it seems unnecessary as both do a good job with powdery mildew. There might be a fit, however, if there is an existing powdery mildew infection. Strobilurins are very prone to resistance so that inclusion of Stylet Oil would hopefully get those members of the fungal population that might otherwise survive the strobie spray. Also, properly applied, Stylet Oil can be very effective for control of European red mite.

Stylet Oil and Thrips: JMS rep Jeff Simons reports that Stylet Oil should help to knock back populations of western flower thrips. Excellent coverage is absolutely necessary as is a 2nd follow-up spray 7 days later. It is also important to time the first spray early, as the population is building. It will be more difficult to obtain satisfactory control if the first spray is applied to a full-blown raging population. While I have not seen data on this, those looking for a softer method of control might try this option. (Source: Long Island Fruit & Vegetable Update, No. 12, May 25, 2001)

Crop Load Adjustment in Grapes

Annual pruning of grapes is necessary to balance the amount of fruit production with the amount of vegetative growth to insure high yields of high quality fruit. Pruning severity is based on the strategy of Œbalanced pruning‚ which dictates the correct number of buds to retain, or Œcrop load‚ which determines the amount of fruit to retain based on the vine‚s pruning weight. Many growers prune vines lightly during the early spring to assure adequate bud number in case of damage by a late frost or freeze. Now that the danger of frost and freeze is over (we hope) and grape shoots are growing rapidly, growers can go back through the vineyard and adjust the crop load by removing shoots and clusters. New shoots are easily broken off by hand without the need for pruners. Growers should pay close attention to the fruitfulness of shoots. Shoots from primary buds have full fruiting potential, whereas secondary buds and latent buds on older wood produce shoots with little or no fruiting potential, depending on cultivar. Ordinarily, all secondary shoots and shoots from older wood should be removed. However, on early budding varieties that suffered frost damage this year, the secondary shoots should probably be retained. Shoots should be spaced evenly along the trellis if possible and at a density of about six shoots per foot of row. Cluster thinning (removing one or more of the clusters on each shoot) done before bloom results in the least yield reduction because the remaining cluster(s) generally set more berries. However, on tight clustered cultivars, cluster thinning after bloom can result in looser, less rot susceptible clusters. (Source: Facts for Fancy Fruit, 2001-06 May 23, 2001)

Massachusetts Cultivated Blueberry Growers Association Spring Picnic Meeting – Saturday, June 9, 2001, 12:00 noon Denny Brook Farm, Westboro, MA. Bring a chair and lunch. Call Sonia Schloemann (413-545-4347) or Lillian Grove (508-366-2363) for directions.

UMass Vegetable Team Twilight Meeting – Monday June 25, 2001. 6:00 pm. Calabrese Farms, Southwick, MA. Call John Howell (413-545-5307) for details and directions.

Massachusetts Berry Notes is a publication of the University of Massachusetts Extension Fruit Program which provides research based information on integrated management of soils, crops, pests and marketing on Massachusetts Farms. No product endorsements over like products are intended or implied.

Crop Conditions and Pest Summary

Twilight Meeting

Environmental Data

STATE WEATHER SUMMARY For the Week Ending Sunday, May 27, 2001

Strawberries

Slugs in Strawberries – Scout Now

Raspberry Fruitworm – Sonia Schloemann, UMass Extension Fruit Team

Blueberry Scorch Disease (Sheep Pen Hill disease)

Grapes

Long Island Grape Update

Crop Load Adjustment in Grapes

Meetings