The Fruit Doctor

Open flower at a farm near Hereford, England

Last week Haygrove organised a “Specialist Cherry Day” in the Canterbury area of Kent.

The day started out 2 miles from the location by chosen by advisers to King Henry VIII as the best place in England to grow cherries!

The morning was spent at Little Sharsted Farm and the afternoon at Hoaden Court Farm. With more than 100 growers and market specialists attending, Haygrove were very grateful to the owners and staff of the two farms at what is a busy time of year for all fruit growers. We were blessed with excellent sunny weather with the cherries in glorious full bloom.

These farms are located in one of the driest regions of England.

Although overseas followers of this blog will be interested to note that there any ‘dry’ spots in England there has been some debate about the need for rain protection in these areas. However losses reported by Hoaden Court and the value of an 8 ton/acre crop clearly justifies the investment – not least when important customers are relying on the grower to supply.

Prior to the lunch break a short talk was given describing some developments and techniques in Chile and Michigan. The latter focussing on the work of Prof. Greg Lang of Michigan State University on the growing of sweet cherries under ‘high tunnels’. A link to a poster presentation summarising some of Prof. Lang’s recent research work follows.

http://www.hrt.msu.edu/faculty/langg/Sweet_Cherry_Research.html

Select the HIGH TUNNEL CHERRY PROJECT tag to view the poster in MS Powerpoint.

Young cherries, first covered in 2009

Just a quick update on the “Fleece & Floating” post of last month…..

A photograph was promised.

Haygrove Solo Tunnels protecting an early Elsanta strawberry crop (Ledbury, England)

These tunnels have been fitted with polythene that is sufficiently wide to provide a continuous seal along the sides of the tunnel (film and soil in continuous contact).

Solo tunnels: Good seal between polythene film and soil at sides of the tunnel.

The grower has also chosen to fit Haygrove Streamline doors. These doors are also in use on a nearby green asparagus for for the same reason: Excellent sealing of warm air inside the tunnels and resistance to wind.

Growers using these doors have less to worry about during windy weather. In fact the doors allow the crop to remain oblivious to whatever horrible English (or Scandinavian for that matter) weather is happening outside!

Haygrove Streamline Doors fitted to tunnels on an asparagus farm

It has been a cold Winter in Britain, just as elsewhere in the northern parts of Europe and Asia. Fruit crops are generally developing later than they have in recent years. It has been suggested that strawberry crops were running 10-14 days later.

More recently temperatures jumped upwards, taking apple growers by surprise as buds moved from very early bud break to the mouse ear stage within a few days. As is typical of the British climate, the warm air brought rain too leaving many growers ruing missed opportunities to protect orchards from scab, before the inevitable showers arrived.

With the temperatures rising, early strawberry tunnels also came into flower. For the earliest of these, first flowers appeared in the week leading up to 25th March. Even though the cold returned last week, pasture has greened up and there is evidence of Spring everywhere in the South.

It is surprising that there is still discussion about the most effective way to bring on early strawberry crops under tunnels when it seems so obvious in the field!

GOOD SEALING + FLEECE + FLOATING MULCH

In the other countries fleece = ‘row cover’ and floating mulch = “perforated film” or “perforated poly”

When temperatures dropped last week well sealed SOLO tunnels remained warm and when the strong winds hit us at the end of the week growers were able to keep them closed, especially when fitted with STREAMLINE doors.

To avoid damage from Feb-March winds the safest option is to delay tunnel skinning and rely on ‘fleece and floating’ alone or to choose stronger tunnel designs such as the SOLO (with 2mm wall steel).  In Britain the best money still comes from early crops so, for strawberries the industry is gradually moving towards much stronger tunnels.

With stories of ‘fish kill’ due to unusually low water temperatures in Florida perhaps it was the wrong time to visit! Even Florida has a winter.

It has a Winter…..but a very productive one. For a Northern European strawberry grower, Florida can be confusing. Fields are established in September, often using plants lifted up in Canada, and harvest starts in ? The varieties plants are primarily those that require short days to initiate fllowers. Tha main June bearing strawberry varieties grown in Germany, Holland and Belgium are also ’short day’ varieties (Elsanta, Sonata, Cambridge Favourite, Korona etc.) but in those countries there is only a relatively short period during which ’short days’ coincide with temperatures that are sufficient to support growth and development. For the rest of the time the plants must be dormant in order to withstand the Northern Winter. In Florida the initiated flowers don’t wait for the end of Winter. They are expressed immediately and keep coming: Providing a crop from ? right through into April at which point growing conditions in California give that state the edge and Florida drops out.

As the fish kill reports suggest – the climate is not always perfect. Florida strawberry growers cope with many challenges. Rain comes frequently causing several important problems:

RAIN =

• Misshapen fruit
• Collectotrichum crown and berry rots
• Xanthomonas leaf spot.

Growers are increasingly working with field scale tunnels in an attempt to eliminate these problems and to increase early production.

At the Gulf Coast Research Station Vance Whitaker is responsible for breeding better berries for Florida. Work at this station, directed by Craig Chandler, has produced many famous strawberry varieties. Conditions in the Florida winter are so favourable to infection that Vance must be ruthless in discarding any materials that shows susceptibility to crown rots. This research station is right at the front line when it comes to matching horticultural science with the needs of a changing world. Up in Michigan, Ontario and New York there is lots of excitement about small scale, local and very sustainable production. Down in Florida they are scaling up! Working on better systems for the production of various key horticultural crops. Helping growers in Florida and around the Caribbean to meet the rising demand for fresh, clean, fruit and vegetables. In the Caribbean this work is especially important because it is raising farm incomes and the living standards of whole communities. The impact of this is global.

Written from the Eastern Great Lakes areas of North America where tunnels are seen as a route to sustainable farming.

Seeking to extend the growing season and make more crops possible for farmers to grow and sell to local outlets University extension workers have done fantastic work on high tunnel growing systems. Local communities are now reaping a rich and diverse harvest from all that work both in terms of farm incomes, a wave of genuine enthusiasm for local fresh produce, a better understanding of where food comes from and technical know-how.Successful research projects range from high tech field scale systems for covered cherry production at MSU and Cornell, through work on berries and flowers to some wonderful “Community Supported Agriculture” or CSA projects.

CSA type projects are working in both rural areas and cities, not least those such as Detroit, now suffering from a contracting automotive industry. USDA’s Natural Resources Conservation Service (NRCS) has been inspired to offer financial assistance for some New York State farmers to establish seasonal high tunnel systems for crops (http://blogs.cornell.edu/hightunnels/).

Adam Montri of Michigan State University has been lighting up winter grower meetings with his enthusiasm for ‘hoop house’ horticulture. Adam, like many American horticultural extension specialists also runs his own farm in partnership with his wife, growing a wide range of fruit, vegetables and flowers.  To find out more visit Adam’s blog http://hoophouse.msu.edu/blog/index.php

Adam has perfected a technique for growing leaf salads right through the Michigan winter without supplemental heating. Inside a “four season” tunnel and under a layer of row cover (fleece) the crops continue to grow for a monthly cutting cycle despite icy conditions outside. Recent measurements for a similar system managed by Cornell scientists showed that a soil temperature of 33°F (1°C) was maintained under the fleece despite outdoor temperatures down to -9°F (-23°C).

Whereas in Britain growers are more familiar with using terms like “Three Season” to describe the useful life of the polythene films used to cover tunnels and hoop houses the Americans use the same terms to differentiate between types of tunnels. “Four Season” tunnels are those that remain clad through the whole year – Spring, Summer, Autumn (Fall) and Winter. These tunnels are strengthened to withstand snow. With 20” (50cm) of wet snow falling in 24 hrs at several sites during February this extra cost is vital. Field scale tunnels are normally built as “Three Season” structures being de-skinned before heavy snow is expected. This ‘time of’ is actually quite useful for many crops – providing the required rest period for berry and cherry crops, some additional spider mite suppression and cleansing of the soil where unwanted salts have built up during the growing season.

Get growing!

This post is written from Poland. A country gripped by a ‘proper winter’ having experienced -25^oc in January and it is still snowing. Fortunately crops like strawberries are protected by the snow, which accumulated before the lowest temperatures arrived. Even blackberries have benefited from the snow cover where growers have, like Krzysztof Wiesiolek, been prepared for the cold.

Krzysztof Wiesiolek digs down to his blackberry canes under snow over fleece.

For growers who have been able to find an export niche and/or extend the season using tunnels or new varieties Poland is an exciting place to be, despite what are sometimes extreme and unpredictable weather conditions.

Creating a large more stable air volume under tunnels during the summer, without sacrificing earliness, is a challenge. Haygrove’s Marek Jamry is enthusiastic about the high, ‘fixed top leg’ or guttered Greenhouse Series. These have been proven during hot weather. It is also possible to augment the standard design with additional supports as insurance against early snow. Snow, however, remains an important limiting factor so the debate about the most appropriate hoop shape and overall structure will continue. Marek has been consistent in his advice that growers should de-skin when heavy snow is forecast.

In Germany growers have tended to prefer Haygrove Solo tunnels. These are constructed with a gap between each tunnel to facilitate venting and snow removal. The gap also leaves extra space for snow to gather without harming the crop or compressing the side of the tunnels. When vented the Super Solo tunnels provide a surprisingly large, open air space.

Haygrove Solo tunnels, Germany

Haygrove Super Solo tunnels in England. Expecting rain! Sides pulled half down to protect a ripening crop of table top strawberries

For the most part we see tunnels as helping to reduce pest and disease pressure but (!) there are some problems that can sneak up on the unsuspecting grower. In England we have a phrase: “Forewarned is for forearmed” that is very appropriate for the management of tunnel pests or diseases.

Check for spider mites now!

A little more detail about specific pests and some information about diseases will be provided in following posts.  This post will serve as an introduction…….

What is different about tunnels?

They are normally warmer and drier than outdoors – That’s why we build them! Unless they aren’t vented properly and get too hot, tunnels provide a more comfortable environment for plants but the same conditions also favour insects and mites, so there are some important rules that are worth remembering.

Rule 1

Under tunnels it is warmer so both plants and insects grower more rapidly. Life-cycles are completed in a shorter time. Routine pest control operations timed for outdoor crops won’t be right for tunnels. You can often predict this using simple heat unit models but this should not be a substitute for diligent crop-walking or scouting. This is especially important when using modern plant protection products that are not persistent and may only act against a specific life stage.

Rule 2

Get the venting and watering right. A good stand of foliage provides a more stable micro-climate for beneficial organisms. Stressed plants are more prone to certain pests. Spider mites are a good example. Predatory mites such as Phytoseiulus enjoy the relatively high and stable humidity that is characteristic of the air close to the leaf surface. If soil dries out, transpiration slows down causing the humidity to drop and the temperature to rise around the leaves. This harms Phytoseiulus and, worse than that, tends to encourage spider mites.

Rule 3

Get your bios in early! Taking mite control as an example: In England Phytoseilus isn’t normally introduced to open field crops until May, when the risk of frosts and cold winds has declined. Under tunnels we often introduce them in March and certainly before the end of April. This is because WE CAN (the environment is relatively stable and bio friendly) and WE SHOULD because pest mites will come out of diapause and start to multiply earlier than they will outside.

More on all this later.

Here are two useful links. Please remember to check the side effects of any plant protection products you intend to use before introducing bios.

http://www.koppert.com/pests/mites/spider-mite/detail/spider-mites/

http://www.ipm.ucdavis.edu/

Mid Winter, Newent, UK

For northern European growers the new year is kicking off with key staff returning to farms to prepare for the coming season. In Holland there will be glasshouse growers who have only just stopped picking Elsanta strawberries but the majority of English soft fruit growers are looking at snow covered fields or frozen bags at the time of writing. Many will be wondering how to maximise returns in a tight economic situation. Yield is still key to this and were above average for many in 2009 but earliness also has a massive impact. Growers who have succeeded in producing a substantial quantity of strawberries before mid May or raspberries before mid June have probably had the best of the last 2 – 3 years. They are less dependent on growing or market conditions in the Autumn/Fall to get their businesses into profit after months of cash-flow worries.

Well built roller doors, Poland

How to get the earliest crops without artificial heating?

FAVOURABLE SITES

EARLY SKINNING/COVERING

ATTENTION TO THE DETAIL OF SEALING UP STRUCTURES TO RETAIN HEAT

These subjects may be the subject of later postings but for now it is worth noting that all the four points are closely connected.

FAVOURABLE SITES ARE OFTEN ALSO SHELTERED SITES

SHELTERED SITES ARE EASIEST TO SKIN/COVER EARLY AND REPRESENT THE LOWEST RISK WHEN SKINNED/COVERED

YOU WISH TO EXPLOIT THE SITE FOR AS MANY YEARS AS POSSIBLE – PERHAPS ROTATING SOIL GROWN CROPS WITHIN THE STRUCTURE OR INSTALLING SOIL-LESS GROWING SYSTEMS. THIS JUSTIFIES ADDITIONAL INVESTMENT IN THE TUNNEL STRUCTURES: GOOD DOORS, GUTTERS AND OTHER MODIFICATIONS THAT IMPROVE HEAT RETENTION ….. AND…. YOU ADD STRENGTH TO EXISTING TUNNELS OR INVEST IN THE NEW, STRONGER, DESIGNS SUCH AS SOLO, TRELLIS AND TELESCOPIC SO THE TUNNELS CAN BE COVERED EARLIER STILL – OFTEN COMPENSATING FOR THE DELAYING EFFECT OF SWITCHING TO SOIL-LESS SYSTEMS.

Good Sealing

Last week we posted a picture showing a very large number of honeybee hives protected by an enclosure in the middle of a Chilean blueberry farm. The owner knows their value to the crop, perhaps especially for blueberries.

Some of the most frequently asked questions about growing of crops under tunnels are concerned with bees and pollination. These questions have become even more pertinent as legislation governing the use of imported bumble bees has tightened in many countries.

 There are a few basic things to remember:

Bees cannot ‘see’ the polythene films used for tunnels

Honeybees waiting in hives outside don’t know what the temperature is inside tunnels

UVb light is an important steering aid for bees and other insects. Some films block more UVb than others.

Bees aren’t the only pollinating insects

Cherry blossom above a commercial bumblebee hive inside tunnels

During the summer there is normally a surplus of pollinating insects, including a great many different nectar feeding insects. It is rare to hear of fruit setting problems under tunnels that are adequately vented during the summer months. For most berry crops the best temperatures for bees coincide with those for good yields – mostly less than 25^oc. Above that temperature both bees and photosysnthesis slow down significantly.

IN THE SUMMER VENTING IS IMPORTANT FOR GOOD YIELDS, POLLINATION AND FRUIT QUALITY

The danger time is in the Spring, especially when crops are being ‘forced’ to flower early. To gain temperature tunnels are kept closed. Bees kept outdoors may be shivering in their hives unaware that the tunnelled crop is warm and in open flower. In closed, permanent tunnels strawberry growers used to introduce blow flies (as pupae close to emergence) as pollinators to overcome this problem but many countries now have the luxury of bumble bee hives from commercial companies like Koppert http://www.koppert.com/pollination/. Bumble bees are active at lower temperatures than honeybees, pollinate using a ‘buzz’ method that has technical advantages for crops such as tomato and the commercially available species are less aggressive towards crop workers.

A large wild bumble bee in Argentina.

Honeybees are still used under glass for various crops – often in combination with bumblebees. The large size of hives makes this less practical for small tunnels but for large, field scale crops honeybees are worth looking at. Hives used in these situations will tend to lose bees as they waste energy attempting to fly through the sides and roof or are lost to the outdoors. Where bumble bees are not available, tunnel growers are working with honeybee hives however at the time of writing we don’t have sufficient experience to provide reliable advice on this option.

A honeybee hive inside a blueberry tunnel

IN THE SPRING DO NOT KEEP TUNNELS CLOSED DURING FLOWERING UNLESS A DAMAGING FROST IS DUE OR YOU ARE CERTAIN THAT THE NUMBER OF POLLINATING INSECTS INSIDE THE TUNNELS IS SUFFICIENT.

REMEMBER THAT, EVEN IN THE EARLY SPRING, SUNNY CONDITIONS CAN CAUSE FLOWERS TO MOVE FROM WHITE BUD TO PETAL FALL VERY QUICKLY. DON’T BEE LATE!

Bee Steering 

UVb = Light in the ultra violet spectrum between the wavelengths of 315nm to 400nm

Bees do use other cues for navigation and experiments have demonstrated that bumble bees can learn to identify flowers in the absence of UV light but in general terms the impact of bees and other pollinating insects is strongly influenced by it.

When purchasing polythene films for tunnels it is worth asking for clear information about the transmission of light in the UV range. Standard Visqueen films supplied in the UK allow sufficient UVa through to facilitate the work of bees but some films, especially those formulated for use in countries with very high light levels, contain a lot more inhibitors. When these polythenes are used in dull weather or in other countries there may be problems with fruit set.

Bee Information

www.bumblebee.org

www.ibra.org.uk

Mason bee shelter at a Biodynamic farm in Poland: What potential for tunnel use?

Where dogs fly!

Chile Tunnels

Haygrove ventured close to the Antarctic to help with a project growing Ribes in the far south of Chilean Patagonia. A wonderful bunch of INIA scientists, advisers and growers are trying to beat huge winds to produce fresh currants well outside the normal shipping season. On the flight down from Santiago Punta Arenas John Berry was told that Punta Arenas was the only place ‘were dogs fly’ and that it was necessary to have ropes along the street to assist the elderly…In the Summer! Correctly specified and with appropriate windbreaks it should be possible to build Haygrove tunnels to cope with growing conditions close to Cape Horn just as they do in the South Africa Cape region but it’s a challenge.

Wind protection required both for the tunnels and the crops

From these chilly tunnels we visited cherry and raspberry growers in the Central Plain before looking at an exceptional blueberry project north of Santiago. A very high standard of technical management at the farm has resulted in very early blueberry production on the foothills of the Andes with Haygrove tunnels providing additional earliness together with protection from both frost and wind.

Early blueberries, north of Santiago

A big thank you to our hosts and everyone who helped us! You are setting very high standards of hospitality and horticulture – even for bees which is a subject to be discussed later…..

Catering for honeybees

Wet Midlands

Back home in England the West Midlands hasn’t been dry for weeks. Famously Cumbria, 200 miles north of here, recorded 372mm in 24 hours. Ledbury hasn’t been that wet but many growers have been pleased that modern tunnel designs have allowed them to keep covers on over peat and coir grown crops during this difficult time. Telescopic and Solo tunnels have been OK during a series of November storms. Raspberries were still picking in un-heated glass last week but most growers are now concentrating on preparations for 2010.

Waiting for Summer to return