Massachusetts
Berry Notes

Volume 13-- 2001

Berry Notes is written by Sonia Schloemann except where other contributors are noted. Publication is funded in part by the UMass Extension Agroecology Program and grower subscriptions. A text version can be e-mailed to you if you contact Sonia Schloemann. Please cite this source if reprinting information.

Summer Edition 2001#1
Volume 13, Number 6
May 17, 2001

Message from the Editor:

New Beginning: This issue marks the beginning of the 2001 summer edition of Massachusetts Berry Notes. You should receive this message weekly for the next 10 weeks. It will contain current pest related information as well as other timely topics and announcements.

Weather concerns: Growers are facing the combined challenges of dry weather and damage from a significant freeze event on the morning of May 7th. Low temperature readings were reported in the mid 20's around the state. See more de-tailed crop specific information below.

Correction on Casoron® in guide: The 2000-2002 New England Small Fruit Pest Management Guide contains an error on the rate of Casoron® herbicide for blueberries and brambles. For blueberries the Casoron® 50WP rate should be 8 lb, not 100 lb. For brambles the rate for Casoron® 50WP should be 8 lb, not 100 lb and the rate for Casoron® 4G should be 100 lb and not 8 lb.

More Websites: Another couple of great websites for small fruit growers are www.fruit.cornell.edu and http://www.uvm.edu/vtvegandberry/. Let me know what some of your favorite websites are and I'll post them in upcoming issues of Berry Notes.

Crop Conditions

The hot weather that prevailed earlier this month broke following a severe frost/freeze event the morning of May 7th. Many plants were in bloom ahead of schedule, especially blueberries, and suffered differing degrees of damage. Unpro-tected strawberries also suffered some damage. The lack of measurable rainfall has prompted growers to begin irrigating their crops. This is very important since the hot weather has pushed the growth of the plant canopy and the roots have to work hard to support it. Currently, strawberry flower clusters are expanding with early varieties in some sites at showing early bloom. Plants under row covers are in bloom and covers should be removed. This means 1) be ready for frost pro-tection, 2) apply bloom fungicides for Botrytis gray mold at 10% bloom, and 3) begin scouting for tarnished plant bug, clipper, and two-spotted spider mites. See more details in the strawberry section below. Highbush blueberries are blooming in the Connecticut River Valley and in most other areas of the state. Many sites suffered frost/freeze damage on May 6/7. Things to look for include evidence of mummyberry strikes on new foliage. If damage is found, be sure to pro-tect blossom tissue from the blossom blight phase of the disease. Raspberries are fully leafed-out and new canes are emerging. Again, the freeze event nipped the foliage of some new primocanes, especially on fall bearing varieties. Grow-ers should be prepared for Anthracnose, Spur blight, and Cane blight management with Benlate ® when new canes are 6-8 inches tall and again when they are 12-15 inches tall. Grape shoot growth has been moving rapidly and is 8" in length in some varieties. Growers should be ready to protect against black rot, phomopsis and downy mildew although disease pres-sure is low due to the dry weather. Hopefully, this will soon change. Keep an eye out for flea beetle.

Environmental Data

The following growing degree day (GDD) and precipitation data was collected for the period, May 2 through May 9, 2001. Soil temperature and phenological indicators were observed on May 9, 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.

(Source: UMass Extension Landscape Message #10, May 11, 2001)

STATE WEATHER SUMMARY For the Week Ending Sunday, May 6, 2001
Prepared by AWIS, Inc.

(Source: New England Ag. Statistics Service, New England Weekly Crop Weather Report, Volume 21, No. 1, May 7, 2001)

Strawberries - Sonia Schloemann, UMass Extension Fruit Team

General: Scouting for two-spotted mite (TSSM), tarnished plant bug adults (TPB) and clipper begins now. TSSM can be especially abundant where row covers were used. So far, TPB have been found in moderate to low numbers in strawberry fields and apple orchards. However, populations may jump suddenly, especially in warm, sunny spells. Damage is most significant just after petal-fall. Clipper weevils are moving into fields from hedge rows, so check plants near the edges by looking for shot-holes in open flower petals and clipped or flagging unopened flower buds or by carefully pulling apart un-expanded flower clusters on late varieties and checking for live weevils inside.

Tarnished Plant Bug: Sticky traps can be used to monitor for tarnished plant bug (TPB) adults. Nymphs hatch within the 7 - 10 days of significant adult activity when daytime temperatures are above 60°. When bloom approaches, we sample for the immature stage (nymph) of this insect by shaking flower clusters. In the past, we used an action threshold for TPB nymphs of an average of 0.25 nymphs per flower cluster or greater than 4 infested clusters out of 30 sampled. The latter threshold allows you to simply note presence or absence of TPB nymphs in a cluster rather than counting them. To save time, a sequential sampling plan may used to determine how many clusters should be sampled. By using Table 1 below, you can make a spray/no spray/keep looking decision by first examining a minimum of 15 clusters. If you find 0 TPB nymphs, you can stop and make a "no spray" decision. If you find more than 0 but less than 3, (or, between 1 and 5 if you are using a high threshold) you must continue sampling. If you find 3 or more TPB nymphs, control is required in order to avoid economic damage to your crop. If the maximum of 50 flower clusters are sampled and no decision is indicated, the grower should sample again in 1 or 2 days. This method allows scouts to spend less time monitoring in fields where popu-lations are very low, or very high. More time is spent sampling fields where TPB populations are close to the threshold. Controlling weeds in and around the planting may reduce populations of this insect, but insecticide sprays may be necessary. If mowing around fields, do so after insecticides have been applied (to control migrating insects). Avoid planting strawberries near alfalfa which attracts high populations of TPB.

Table 1. Monitoring for Tarnished Plant bug in Strawberry

*0.15 nymphs/cluster = 2% damage; **Primarily for processing fruit, 0.25 nymphs/cluster = 4% damage
(Source: N. J. Bostanian, Agriculture and Agri-Food Canada, St. Jean-sur-Richelieu, P. Q. Courtesy Pam Fisher, Ontario Ministry of Food and Ag.)

Two-spotted spider mites: Two-spotted spider mites (TSSM) are active and building up already. Mites should be moni-tored weekly by sampling the field in 5?10 locations. Five to ten leaves should be sampled at each location for a total of 60 leaves. Examine the underside of the leaves for the presence or absence of TSSM. Record the information on a field map so that "hot spots" can be identified and treated. A miticide application is recommended if 25% or more of a 60 leaf sam-ple is infested with TSSM.

Natural predators exist which feed on two-spotted spider mites. One such predator, also a mite (Neoseiulus fallacis), is na-tive to the northeast and often maintains TSSM populations at non-damaging levels. It is equally small but lacks the two spots on its back, is teardrop shaped, shiny, and pale yellow in color. They are also easily distinguished from TSSM by their rapid movement across a leaf in search of prey; (they resemble bumper cars moving forward and backward as they search for food). When sampling a field, presence of predators as well as TSSM should be noted.

Relying solely on the release of commercially reared mites is not recommended since natural populations of N. fallacis are pervasive. It is important to encourage natural enemies of spider mites by reducing the use of broad-spectrum pesticides (especially carbamate and pyrethroid insecticides) which harm natural enemies. One strategy that has worked exception-ally well has been the early-season use of 1% oil with a mist blower. This inexpensive treatment is highly selective: it kills TSSM, but not predatory mites. The resulting imbalance between predators and TSSM allows predators to "mop-up" the remaining TSSM. Please note that oil-incompatible pesticides should not be applied prior to the oil spray.

Strawberry Bud Weevil or Clipper: Clipper monitoring can be started as soon as the flower clusters are visible in the crowns of the plant. The weevils will sometimes crawl in among the unopened buds for shelter. They are most likely to be in rows near woods or hedgerows. Later, look for shot-holes in opened flower petals and/or clipped buds of unopened flowers. In the past, the IPM action threshold for this insect is 1 clipped bud per 2 ft. of row or one live adult. Research done in recent years suggests that many more clipped buds can be tolerated without significant yield loss. A comparison of old and new sampling methods done by researchers at Cornell University (Hortscience 34 (1): 109-111. 1999) can be seen in Table 2 below. Sample at least 5 locations in the field. If you determine that the infestation is limited to the edge of a field, you may only need to spray the border rows. If you see evidence of clipper and determine a spray application is nec-essary, follow recommendations for materials and timing in the strawberry pest management schedule.

Table 2. Revision to monitoring procedure for strawberry bud weevil (clipper).

Courtesy Pam Fisher, Ontario Ministry of Food and Agriculture

New Plantings: Where traditional matted row planting systems are used, strawberries are already in the ground or soon will be. When planting, be sure to check planting depth frequently and make adjustments to your planter as needed. Fol-low up with nitrogen fertilization once a month until September. Apply 20 - 30 lbs of nitrogen (depending on your soil conditions) at each application. Herbicides can be applied once the soil has settled and should be watered in after applica-tion.

As mentioned in the beginning of this message, raspberries are fully leafed-out and new canes are emerging. My observa-tions have been of some significant winter injury in some areas in some varieties, notably on Taylor, Canby and Lauren. Primocanes have shown some freeze injury but will soon grow out of it. Growers should be prepared for Anthracnose, Spur blight, and Cane blight management with Benlate® when new canes are 6-8 inches tall and again when they are 12-15 inches tall. Also, growers can be scouting for tarnished plant bug (TPB) with white sticky traps, and two-spotted spider mites (TSSM) by inspecting the underside of lower leaves in a similar way as described above for strawberries. Raspberry fruitworm, cane borers, and clipper may also be seen soon. Keep an eye out for these insects.

Additional considerations:
o fertilizers and preemergent herbicides should be applied according to label directions.
o irrigation and trellises should be in place.
o scout for crown borer larvae, fruitworm, and sawfly.
o apply post emergence grass herbicides if necessary

Highbush Blueberries - Sonia Schloemann, UMass Extension Fruit Team

The main concerns at this time of year are 1) second stage (blossom blight) mummyberry control, 2) Anthracnose and Bo-trytis control, and 3) cranberry fruitworm (CFW) monitoring and control. Dry weather has stalled the development of most of these disease problems. However, forcasts are for a showery periods over the next week. A Captan®/Benlate® applica-tion can be made for protecting blossoms from the secondary infections of Monolinia vaccinii-corymbosi, mummyberry. This application will also control Anthracnose and Botrytis. Ziram is another possibility, especially for controlling An-thracnose (See article below). Traps are available for the adult moths of cranberry fruit worm or visual inspections of the flower clusters for newly deposited eggs on the calyx end of developing fruit. CFW are active for about 5 weeks and they cannot be controlled with only one post-pollination spray.

Other considerations:
o Fertilizer may be applied as a split between bloom and one month later.
o Dormant plants should be planted as soon as possible. Avoid planting after mid May. Dr. Gary Pavlis recommends rub-bing off the flower buds for the first two years after planting so that the plants can put their energy into sizing up the bushes.
o Make arrangements for pollination. While blueberries are self-fruitful, but cross pollination increases the size of the fruit. Pollinators are needed for this cross pollination. Different varieties vary in their attractiveness to bees and therefore require either more or fewer hives per acre to successfully pollinate them. Bumblebees are better pollinators for blueber-ries but are more expensive to get. Call me for more information on numbers of bee hives needed for good pollination.

Early Season Disease Managemnt - Peter V. Oudemans, Rutgers University

Blueberries are well into bloom at this time. Mummy berry, anthracnose and blossom blight are the major fungal diseases that currently need to be managed. For mummy berry, shoot strikes should be visible and in areas where these primary in-fections are severe the flowers will require protection from secondary infection. Applications of Indar* or Benlate can be used to protect the flowers (see NJ crop recommendations for rates). As bloom progresses the effectiveness of fungicide applications will decline and these fungicides cannot "cure" infections that have already occurred. For maximum control, fungicide applications should made prior to mid-bloom and should not be applied post bloom.

For anthracnose management, the key is to start now. Prevention of spore production can be accomplished with Benlate. Please note that anthracnose is not listed on the Benlate SP label. However, it can be used in New Jersey to reduce anthrac-nose spore production because the material is being used in accordance with the label restrictions (i.e. 1 lb/acre, 3-applications maximum and 21-day pre-harvest interval). Benlate will not protect from infection, it will only reduce spore production. Therefore, applications should be made at the early stage of bloom development. In many areas the timing for Benlate applications have past. Where bloom past 50% protectant fungicides such as Captan or Ziram can now be used. It is my experience that Ziram will provide longer control. Bravo* is labeled in New Jersey, however, can be phytotoxic to flowers, especially at higher temperatures, and has a 42-day PHI. For these reasons, Bravo* should be avoided at this time.

(*Ed Note: These materials are NOT currently labeled for use in Massachusetts. Also, be aware of the PYO restriction on Benlate.) (Source: The BLUEBERRY BULLETIN, May 3, 2001 Vol. XVII, No. 4)

Grapes

Vine Development and Nutrition Considerations - Alice Wise and Warren Stiles, Cornell Univerity

Week of May 7: Shoot growth was explosive this week with the onset of warm weather. By Friday May 11, Chardonnay at the Lab ranged from 6 to 9". Cabernet Sauvignon ranged from 1 to 4" shoots. Disease pressure has been low due to lack of rainfall the last few weeks.

Prebloom Tissue Testing: Dr. Warren Stiles, Cornell's tree fruit nutritionist emeritus, suggests prebloom tissue testing as a means of diagnosing nutrient deficiencies. Prebloom in fact may be the best time for evaluation of boron and zinc needs. Take newly expanded leaves near shoot tips. By sampling early, it allows time to correct problems in the current season. Be sure and communicate to the lab doing the analysis that you need results quickly.
Prebloom Foliar Nutrient Sprays: There are some prebloom sprays considered to be useful in certain situations. Visual verification as well as petiole analysis can be helpful in diagnosis of deficiencies. It is a very good idea when applying foliar nutrients to leave an untreated section of vineyard. This allows comparison of treated and untreated vines. The most common sprays are discussed below.

Nitrogen - First and foremost, N fertilization should be addressed via ground application. Dr. Pete Christensen, emeritus professor at UC Kearney Ag Center, related at the '99 Ag Forum that grapes are relatively inefficient leaf feeders (vs. ap-ples for example). It is not surprising therefore that the vast majority of research trials have found little or no benefit to foliar-applied N. At the Lab, sprays of foliar N over the last few years have produced no visible response. If vines are N-deficient, there might be a response. Some growers feel foliar N is of benefit particularly prebloom sprays. There are many different products from which to choose, including organic options.

Zinc - Considered essential for proper cluster development, berry set and normal shoot growth. Deficiency is seen early summer. New leaves are smaller, distorted and may be chlorotic with darker green veins. Straggly clusters and shot berries may also occur. Soil application of Zn is less effective because Zn is tightly bound in soil. Zinc sulfate, zinc oxide and che-lated Zn are used as foliar sprays; follow label for rates. Apply one time 2 weeks prior to bloom. Some western grape growers consider zinc an essential springtime spray.

Boron - Deficiency is seen as stunted zigzag growth and death of shoot tips, poor set with shot berries, often flattened or oblong. Soil treatment is effective since boron (B) moves with the soil water, however this is best applied in the fall or with the spring herbicide. For foliar sprays, use 0.2 lb./a actual B (Solubor is 20% B, so 1 lb. Solubor = 0.2 lbs. actual B) in 1 or 2 prebloom sprays, 8-12" and early bloom. There should be a minimum of 2 weeks between sprays to minimize the chance for phytotoxicity. Boron toxicity can easily cause leaf scorching/distortion and shoot stunting. Boron interferes with the dissolving of water-soluble packets used for Nova and other products. Dissolve the packet thoroughly in the spray tank and then add B to the spray mix.

Manganese - Deficiency is seen mid-late summer starting as interveinal chlorosis on basal leaves. A herringbone pattern is characteristic. At soil pHís >6.0, e.g. properly limed soils, Mn availability in the soil is relatively low. Where a deficiency is confirmed by petiole analysis, foliar applications of manganese sulfate (2-3 lbs./100 gal.) are recommended as a correc-tive measure. Other manganese products used at label rates may also be effective. Foliar manganese oxide materials are considered to be less effective. (Source: Long Island Fruit and Vegetable Update, May 11, 2001, No 10)

Pest Control News

New Biochemical Pesticide Registered as an Alternative to Conventional Pesticides
US-EPA Office of Pesticide Programs

On April 19, 2000, EPA registered a new biochemical pesticide, the Harpin protein (Trade Name MESSENGER™), as an alternative to conventional, synthetic pesticides such as methyl bromide. This biochemical pesticide is registered for use on field crops, trees, turf, and ornamentals to control a wide variety of fungal, bacteria, and viral pathogens as well as several insect pests. Unlike most pesticides, the Harpin protein does not act directly on the target pest. Instead, it activates a natural defense mechanism in the host plant, called systematic acquired resistance, that makes the plant resistant to a wide range of fungal, bacterial, and viral diseases. The Harpin protein also protects against certain nematodes and fungal diseases that have few effective controls except methyl bromide, a broad-spectrum pesticide that is believed to contribute to strato-spheric ozone depletion and have adverse effects on human health. The Harpin protein is non-toxic and not expected to pose risks to human health or the environment. Because the product is applied at low rates and degrades rapidly in the field, no residues are expected on treated crops. In addition, studies demonstrate no toxicity to humans and no adverse ef-fects on many species of wildlife (e.g., birds, fish, honeybees, aquatic invertebrates, non-target plants and algae). During its experimental use stage, the Harpin protein was used on tomatoes as a component of Integrated Pest Management (IPM) programs, thereby decreasing the use of conventional pesticides by 70% while outperforming them in effectiveness. EDEN Biosciences Corporation of Bothell, WA, was granted registrations for both the Harpin protein and MESSENGERTM (the only product containing this protein as an active ingredient). For more information, please contact Phil Hutton in the Bio-pesticides and Pollution Prevention Division at (703) 308-8260. A fact sheet also will be available on EPA's web site at: www.epa.gov/pesticides/biopesticides. (Source: www.epa.gov/oppfead1/cb/csb_page/updates/harpin.htm, updated Mon-day, May 7, 2001)

General

Bird Control in Small Fruit Crops - Richard C. Funt, Ohio State University

Birds can be a major threat to many small fruit crops. Growers may see 10 to 30% of a blueberry crop destroyed. A flock of 5,000 starlings can consume one ton of food over a 10 day period. It has been observed that mid-season ripening blue-berries can be the most heavily damaged. Robins (young aggressive types), starlings, finches, orioles, and cedar waxwings have been identified in order of importance as birds that cause problems in fruit crops.
Bird damage patterns can vary from year to year and can be localized, depending on the source. Birds can fly 10 to 15 miles from a resting site to feed. It is difficult to stop birds from feeding once they start. They can establish their home territory in late April and May and remain until the crop ripens. Crops near resting areas, wooded lots, and ponds are most vulnerable. Birds generally feed before sunrise and again late in the day or slightly after sunset.

Types of bird repellents:
Physical barrier - Netting, either plastic or rope (known as tobacco netting) has generally been recommended, but it takes a lot of labor, and birds can occasionally get under or eat through it. Nets do offer nearly 100% protection, particularly in high valued crops. Placing the netting over the crop is best. Full field netting must be removed before winter because the ice load breaks it. Ultraviolet light also breaks down the material.

Propane cannons - These cannons give unexpected blasts and should be set at intervals greater than one blast per three minutes. However, neighbors who work early or late shifts and rest during the day may become angry if these are used. Timers can be used to provide flexibility and are turned off during the off-feeding periods.

Electronic sound devices - Some devices simply disrupt bird communications. Other devices use digital electronic sound to produce distress calls. Several Œchips‚ of different calls are available on one device. Some reports say that these de-vices can attract hawks and more hawks scare birds away.
Pistol cartridges and other sound devices - Special cartridges launched from hand guns which explode high in the air near birds can quickly clear a field or wooded lot. They can be an effective manual scare device.

Shot guns are often used, but are generally ineffective. In some cases, protected species can be harmed.

Aluminum pie plates, firecrackers, and Mylar humming lines may work for a few days and are best just before harvest. The same is true for artificial hawks, stuffed owls, or snakes.

Use an Integrated Approach
Using one deterrent system is not effective; therefore, use a combination of methods. Random unexpected noise, position-ing devices near perimeters and flight patterns, using scare devices near the fruit planting, and encouraging predators can be effective.

Here are some tips:
1. Start bird control methods 10 to 30 days before the crop ripens. Watch and be aware of the birds‚ habits and their re-action.
2. Change the method of control. Move devices once per week and change the type of noise.
3. Control birds 30 minutes before sunrise to early morning and late afternoon to 30 minutes after sunset.
4. Consider the amount of fruit loss versus the cost of equipment or material and labor to control birds.

Remember:
Once birds start to eat the crop, they are difficult to remove. Control is based on knowing how birds behave. Start controls before fruit starts to turn from green to pink, red or blue. Use several methods and change positions once per week.

Reference: Bird Control on Grape and Tender Fruit Farms by H.W. Fraser, K.H. Fisher and I. Frensch, Fact Sheet 98-035. Ministry of Agriculture, Ontario, Canada. (Source: Ohio Fruit ICM News, Volume 5, issue 16, May 10, 2001)

SPRAYER CALIBRATION STEPS FOR BOOM SPRAYERS

(1) On an area that best represents the average topography for the area to be sprayed, measure and mark off the Calibration Distance that coincides with your band width or nozzle spacing. See Table 1.

(2) Select a safe speed which can be maintained while spraying. Note and record the engine RPM‚s and the gear selection so the same speed is used during calibration and application.

(3) With the tractor traveling at this selected speed, time and record the seconds needed to travel the Calibration Distance.

(4) Fill the sprayer, engage the pump and adjust the pressure regulator to the desired boom pressure (between 15 and 50 PSI for herbicides). Collect all the water from one nozzle for the same number of seconds needed to travel the Calibration Distance. Example: with 20" nozzle spacing, if it took 35 seconds to travel 204‚, collect the discharge of one nozzle for 35 seconds. The number of fluid ounces collected equals the gallons per acre (GPA) of output of that nozzle. Example: 20 ounces collected equals 20 GPA.

(5) Repeat Step 4 two more times, collecting water from a different nozzle each time. The average number of ounces collected from each of the three nozzles is equal to the gallons of water applied per acre for that boom. Remember to maintain the same pressure and travel speed when spraying.

Table 1. Select the Calibration Distance to be used based on nozzle spacing if broadcast applying, or on band width if band applying.

(Source: PA State University Cooperative Extension, Agricultural Engineering Fact Sheet, PM - 8, via UMass Vegetable IPM Newsletter, May 10, 2001, Volume 12, Number 1)

Using Potassium in Fruit Planting - Eric Hanson, Michigan State University

Many Michigan fruit crops benefit from periodic applications of potassium (K) fertilizers. Shortages are most common on sandy soils, and the crops most often deficient in K tend to be grapes, stone fruit (cherries, peaches) and strawberries.

Determining K needs
Soil tests provide an indication of K needs. The K recommendations for fruit crops based on soil test results are summa-rized in the accompanying table. Keep in mind that a low soil test level does not always indicate a shortage of K. Often, perennial crops absorb adequate levels of K even when the soils tests indicate a shortage. The MSU soil test report also in-cludes a Percent of Bases term, which relates the levels of K, calcium (Ca) and magnesium (Mg) to one another. Soil K above eight to ten percent of bases also indicates sufficiency.

Table 1. Potassium recommendations for Michigan fruit crops.

Tissue analysis can provide a clear indication of the K status of perennial fruit crops. When tissue K levels are below the optimum ranges reported in the accompanying table, the crop is likely to benefit from K fertilizer applications.

Table 2. Optimum K concentrations (% of dry weight) in leaves and petioles (grapes) of Michigan fruit crops.

Deficiency symptoms can also be diagnostic of K deficiency. Lack of K typically causes marginal leaf scorching, where the tissue along the margins of leaves discolors and eventually dies. Leaf margins usually curl in an upward direction. Symptoms may resemble acute moisture stress. In tree fruits and grapes, these symptoms are accentuated on trees carrying a heavy load of fruit. This is because fruit are strong sinks for K, and out-compete leaves for available K. Concord grape-vines have a tendency to develop "black leaf," which is related to K supply. Leaves turn a dark green to black color later in the summer. There is still some question about whether K deficiency is the cause of this disorder.

Which K fertilizer is best?
The K content of fertilizers is expressed as % K2O (potash). Muriate of potash or potassium chloride (60-62% K2O) is the cheapest source of K ($0.15 to 0.20/lb K2O) and is a useful fruit fertilizer but needs to be used with caution. Chloride can be toxic to all fruit plants, with strawberries and raspberries being the most sensitive. Muriate is best used on mature plants where only moderate rates (<80 lb K2O per acre) are needed. If higher rates are needed in deficient plantings, split the amount into two applications a month or two apart. Spread muriate uniformly rather than concentrate it around plants. Po-tassium sulfate (50-52% K2O) is safer than muriate but more expensive ($0.25 to 0.30/lb K2O). Sul-Po-Mag (0-0-22) is essentially a mixture of potassium sulfate and magnesium sulfate. Although it is an expensive K source (about $0.50/ lb K2O), it has value where magnesium is also needed. Bulk blended fertilizers of various analyses may contain K in the chloride or sulfate form.

When should K be applied?
Anytime of the year is acceptable but spring or early summer is best. K does not leach nearly as quickly in the soil as nitro-gen, so applied K should remain available to plants for a year or more. Some growers may find annual maintenance appli-cations are needed on sandier sites.

How much K should be applied?
Consult the accompanying table if soil test results are available. Generally, 70-100 lb K2O per acre will correct most defi-ciencies, and annual application of 30-50 lb/acre will maintain plantings on sandy soils prone to deficiency.

Can I apply too much K?
Yes. Excessive soil K levels inhibit Mg uptake by roots and can induce Mg deficiency. Unnecessary applications of muri-ate of potash can be directly toxic to plants. Of course, applying any fertilizer not needed by the crop is a waste of money.
(Source: Fruit Crop Advisory Team Alert, Vol. 16, No. 5, May 8, 2001)

Grower Questions

Q: Another question for the group. Has anyone noticed strawberry varietal differences in susceptibility to frost? Specifi-cally, has anyone noticed that Northeaster is hurt by frost more easily than other varieties? We got quite cold 3 nights in a row. I have several varieties under row cover. The plants are second fruiting year plants on black plastic (dormant crown system). I was monitoring blossom temps with thermocouples and the open blossoms I had selected were in my Mesabi row and the closed buds were Annapolis. The coldest I saw the Mesabis get was 30.4 F and the closed buds were 33.5. I did not turn irrigation water on as I didn't think I had very many open blossoms and I didn't want to cause evaporative cool-ing and cause more damage. So I figured I would lose a few blossoms here and there.

I know the physics of temperature variation and frost are complex, but Mesabi and Annapolis had very few damaged blos-soms (including the open Mesabi facing the sky with thermocouples in them), but the Northeaster got hammered. Most of the blossoms were still closed buds, with a very few open or at popcorn stage. In looking at buds today that have still not opened, I'm finding that many of them were also frozen. These were one double row over (5 feet) from the Mesabi. My understanding is that closed buds can take down to 25 F. A thermometer outside of the row cover at 1-2 inches above ground level showed that it got to 23 but under the row cover it couldn't have gotten that cold. Our temperature sensor never read less than 28 for air temperature under the cover.

So is Northeaster more sensitive to the cold? Annapolis, Mesabi, and Delmarvel lost no more than 5% of their open blooms. Northeaster is probably at about 30-50% loss so far with many more unknown buds yet to open. Anyone have any insight? (Grower in Eastern New York )

A: Last year, we had 22 degrees during early strawberry bloom. Mesabi was virtually unaffected - it was amazing - only the fully opened flowers were hit. I showed this to U of Minn. Extension Service, it was so unusual. We had some crop on Winona - unopened clusters made it. Honeyoye, Jewel, Latestar, LateGlow, Cavendish, Glooscap all got blasted real bad.

P.S. I broke down and bought frost protection sprinklers for this year. (Grower in Minnesota)

<(©¿©)> An apple a day keeps the doctor away. Two apples a day gets the doctor's OK. Five a day makes you a fruit grower like me.<(©¿©)>

A: Yesterday I spoke with a grower who had a similar frost experience..but different results. He frost protected with irriga-tion and observed considerably more damage to Delmarvel than any other variety. He started irrigation well in advance of damaging temps and had virtually no damage except to Delmarvel. Other varieties were Earliglow and Allstar. Sorry no Northeaster to compare. (PennState Extension Specialist)
(Source: on the Small Fruit Listserve SMALLFRUIT@BOBO.NWS.ORST.EDU)

Let me know what you think. - SGS