Stone Fruit - Market rescue

Demand for English cherries, plums and apricots is returning as pest and production problems are overcome, Brian Lovelidge reports.

Cherries have experienced a revival due to intensification of planting, higher-quality varieties and buoyant demand - image: FAST
Cherries have experienced a revival due to intensification of planting, higher-quality varieties and buoyant demand - image: FAST

Cherries

Recent years have seen five decades or more of steady decline in cherry production reversed. The main reasons for this turnaround are the intensification of planting facilitated by new dwarfing rootstocks, the introduction of high-quality, large-fruited varieties and buoyant demand.

From the 1950s to the 1990s the cherry orchard area more or less halved each decade. According to the Ministry of Agriculture Fisheries and Food census statistics there were 6,718ha (16,600 acres) of cherries in 1958-59. Ten years later the figure was 3,399ha (8,400 acres) and the respective average yields for 1968 and 1969 were 30.3 and 8.5cwt/acre, the 1969 crop being badly hit by adverse weather.

That is a far cry from the present situation. Since the dwarfing Gisela series of rootstocks was introduced 10 years ago there has been a gradual increase in orchard area from an all time low of under 350ha to the current 380ha with yields of 80cwt/acre.

That trend will continue, predicts Fruit Advisory Service Team stone fruit specialist Don Vaughan, thanks to the better and more reliable cropping performance and more dependable quality of fruit produced by modern orchard systems based mainly on Gisela rootstocks. In addition consumer demand is at an all time high and is far from being satisfied, resulting in good returns for growers.

Until the late 1970s-early 1980s the industry relied initially on Mazzard (wild sweet cherry) and then F12/1 rootstocks. These were vigorous, producing very large trees. Planted at 9-12m apart or 86 to 110/ha, they required up to 50-stave ladders to pick - making production a very expensive operation. Loss of fruit to marauding birds was also a big problem that was costly to prevent.

To solve such problems East Malling Research Station - as it was then - scientists undertook a programme to breed dwarfing rootstocks. In the early 1970s they produced a series of Prunus avium/Prunus pseudocerasus hybrids - one of which appeared to have the required traits. It was named Colt and was released to nurserymen for bulking up and the raising of trees in 1975.

Although initially regarded as a dwarfing stock, trees on Colt proved more vigorous or semi-dwarfing in commercial production. It wasn't until the growth regulator Cultar was approved for cherries in the late 1980s that growers were able to adequately control the vigour of trees on Colt.

Yet while this rootstock was considered a big advance, it never fulfilled its promise. That was not only due to its vigour. Arguably an even greater shortcoming was its inconsistent and unreliable cropping performance. Only after very cold winters like that of 2009-10, did it produce heavy yields. This situation made marketers' job very difficult because apart from a high-quality product supermarkets demand a consistent supply.

Growers' strong confidence in the latest production systems, based mainly on Gisela 5, can be judged by the fact that they are willing to make a substantial investment in them. Vaughan says that a significant area of intensive orchards is being planted every year, some as a replacement for Colt and some by soft fruit growers wishing to diversify.

In ballpark figures Gisela trees alone cost £12,400/ha. Other inputs including land, fertigation, bird netting and polytunnels or rain covers come to another £37,000/ha. When the trees are in full production, usually from four so six years onwards, this investment can produce yields of around 10 tonnes/ha, worth last season around £3/kg wholesale and double that (£60,000/ha) for supermarket fruit although packaging and labelling costs are much higher.

"There's huge interest among importers (category managers) to get English cherries," affirms Vaughan. "Consumers are prepared to pay £6/kg or more, although as supplies increase prices will decline."

A large proportion of new orchards are covered, largely to prevent cracking by rain as the fruit is ripening. However, cracking can still occur in covered crops when the humidity is high. To reduce humidity manufacturers such as Haygrove have produced a high leg tunnel while the Voen cover is designed for good air flow with the same aim.

"In the 1950s, 60s and 70s, growers made huge amounts of money in good years but just one rain event (at the wrong time) meant they could walk out of their orchards with nothing," Vaughan declares. "Most growers now spray against cracking and a comprehensive Pretect programme does work. But you have to be on the ball and be able to react to the weather."

There are numerous high-quality new varieties around but as with strawberries the trend is for marketing groups to have varieties exclusive to them so only their own members can grow them.

With dwarfing rootstocks most of the fruit can be picked from the ground and thanks to the widespread production of the crop under tunnels or rain covers the operation can continue in inclement weather so that consistent supplies to marketers can be assured.

In recent years a few of the larger growers have invested in grading machines. Uniform-sized fruit in a pack looks more attractive and certain customers may prefer one size to another, says Vaughan. Those able to provide graded fruit, including growers having the job done under contract, have found it worthwhile. Indeed, as supplies increase grading may become a necessity, he predicts.

Plums

Over the past decade or two the area of plums has declined even more rapidly than that of cherries. Defra statistics show that there were 1,369ha in 1997-98 compared with the current estimated 750ha. In the crop's heyday in the 1950s there were there more than 10,000ha but by the late 1960s, when the decline was well established, there were only around 7,000ha (all Ministry of Agriculture, Forestry & Fisheries census figures).

Although the English plum industry is still dominated by Opal, Victoria and Marjorie's Seedling, some foreign varieties show useful potential, reckons Vaughan. One is the German-bred Haganta that is now being planted by some growers. It's a heavy cropping, oval, blue type with good flavour when properly mature and picks in Marjorie's Seedling's season. It has the added advantage of storing well in the new controlled atmosphere bins that extend its marketing season by as much as three or four weeks.

"Imported plums look nice but they're bland," maintains Vaughan. "We need to get consumers asking for English plums and supermarkets must get switched on to them earlier. We also need a good variety to come between Opal and Victoria (to provide better continuity of supply)."

Vaughan says that growers have responded to poor plum prices in recent years by grubbing their less productive orchards. Supermarkets have taken only limited volumes of the English crop and so more have been switched to wholesale markets, which as a result have been oversupplied thus depressing prices.

Apricots

For growers with frost-free sites and the right soils, apricots have good potential, says Vaughan. There is "developing interest" in the crop and some of the big retailers are keen to sell the English product.

"The big problem over the past few years has been bacterial canker to which apricots are very susceptible," he adds. "Some imported trees have gone down badly with it and so more effort must go into ensuring we get clean stock."

Another problem is that apricots can bloom as early as the second week of February making it prone to frost damage. However, they could be grown under high polytunnels provided fruit prices are good enough to justify the investment.

Crop protection for cherries

Vaughan says most pesticides used on cherries are on specific off-label approvals (SOLAs) thanks to the efforts of the Horticultural Development Company. Without one in particular, for Steward, growers could be in dire trouble. Before it was introduced two years ago its target pest, light-brown apple moth, caused considerable damage in orchards.

"Light-brown apple moth came from nowhere and became a problem because the right insecticides were not available," Vaughan recalls. "It was never seen on apple because it was well controlled by the products applied against codling and tortrix moths. Over the past year or two growers have not had any (more) disasters. It's a case of them being aware of the problem and reacting to it quickly.

"Since growers have been using Steward post-harvest to take out the pest's late generation - the one that goes into the winter - it has been almost unknown," adds Vaughan. "However, last year summer fruit tortrix caused considerable leaf damage although it was not as catastrophic as that caused by the light brown apple moth (before the Steward SOLA was obtained)."

The choice of non-pesticide measures for controlling pests and diseases in cherries and plums should be extended thanks to a five-year HortLINK project with three more years to run. East Malling Research entomologist Professor Jerry Cross says he is encouraged by progress so far.

He and his team are developing novel ways of combating problems such as brown rot, plum fruit moth, and aphid and tortrix species including light brown apple moth.

In brown rot's case pathologists have extracted a number of antagonistic yeasts and bacteria from mummified (infected) cherries and plums. At least five of these micro-organisms have suppressed the fungus in laboratory Petri dish tests. The next step is to evaluate their activity on infected fruit.

Cross is investigating means of upsetting the symbiotic relationship between the common black ant and aphids including blackfly on cherries. He explains that because the ants are dependent on aphids for food in the form of honeydew they protect the aphids against predators such as lacewing larvae and ladybirds.

"We've shown that when you exclude ants from infested trees the aphids are eaten by predators," says Cross. "By providing alternative food sources for the ants they are much less reliant on the aphid pests."

One alternative is benign aphids species that feeds on grass roots, he adds. Another approach he is trying is to contaminate ants with spores of a fungus that kills aphids so that they transfer the spores to the pest.

"We're also looking at the use of pheromones for the mating control of moth pests such as the plum fruit moth," says Cross.


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