The Fruit Doctor

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

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