The Fruit Doctor

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!