Taken from The Fruit Grower, February 2017, written by Rachel Anderson
New crop protection products for top fruit
Given that many conventional crop protection products are being withdrawn from the market, top fruit growers will be pleased to learn that BASF has this year launched two new solutions. These include the new integrated pest management (1PM) tool RAK 3+4 and the new fungicide Sercadis for the control of scab and mildew on apples and pears.
The company's fruit and vegetable specialist Simon Townsend told delegates at Agrovista's fruit technical seminar, held at Brands Hatch, Kent, that RAK 3+4 is a pheromone based mating disruptor that helps control the populations of codling and tortrix moths. It works by releasing artificial pheromones into the orchard to create a cloud of female pheromones.
""The males cannot work out which direction [to go) to find the nearest female and they lose interest, hence mating is disrupted," said Simon.
He said that about one week before the first flight of the adult moths, which is generally around blossom time, growers should hang up one pheromone dispenser on the top one-third of every six or seven trees. He asserted that the system is ""certainly a very good anti-resistance strategy"" and, from the point of view of consumers buying the apples, ""there are clearly no residues."" He added that the system - which works out at about the same cost as putting on a full codling programme - is also harmless to beneficial insects, can be used on organic crops, and has the bonus of having a useful effect on a wide range of other tortrix moth species. These include the large fruit tree tortrix (Archips podana) and the dark fruit tree tortrix (Pandemis heparana).
Delegates also learned that the product Sercadis, which is in the SOHi class of fungicides, also offers growers an additional benefit. In this case, said Simon, it's the fact that the product makes the trees' leaves much larger and greener. He noted that a trial run at Brogdale Farm in Kent in 2016 showed that ""it was very apparent how good looking the whole tree was following a Sercadis treatment. That made us think that perhaps we should measure the leaf area."" Data showed that the leaf area of those trees treated with a tank mixture containing Sercadis (at 0.3 litres/ha) and Delan Pro were 60sq.cm compared to about 40sq.cm in the untreated plot.
Simon also explained that Sercadis works and moves in several different ways on the leaf. For instance, the rain-fast product's surface area on the leaf expands after it has been rewetted because the crystals change their shape and bind strongly to the leaf's waxes. He said: ""They act as a protective source for a slightly larger area. I think this is the reason that we are getting such robust cover over time."" He informed growers that the product, whose active ingredient is fluxapyroxad (Xemium), has a flexible dose rate, so they ""can tank-mix it appropriately."" He added: ""We are in a climate where we need to look after our active ingredients and protect them from developing resistance. And one of the best ways of protecting against resistance is to use the products either in alternation or in mixtures. And definitely, if your back is against the wall with high pressure, I would use it in a mixture with a strong protectant fungicide."" He suggested, for example, that if they want robust scab control growers could use a tank mix of Bellis and Sercadis.
The copper situation - a big issue
The arrival of these two new crop protection solutions has perhaps cushioned the blow for the top fruit industry, which this year faces a couple of new restrictions to its crop protection armoury. Simon reminded growers that the dose of Dithianon, and the number of times it can applied, has been restricted. ""Effectively it's a tank mix partner now. But don't despair - we've got Delan Pro - it's our way of keeping Dithianon registered. It contains two active ingredients, Dithianon and KHP.""
Restrictions have also been placed on two copper-based products - a move that Agrovista's Head of Fruit Paul Bennett described as ""a big issue for conventional growers and organic growers"". He noted that copper is particularly handy as it is used as an early treatment for scab by apple and pear growers and gives some protection against bacterial canker on stone fruit crops. However, the only fruit crop that the copper-based protectant fungicide Cuprokylt now has approval for is grapevines. Paul said: ""There's no approval for apples, pears, plums, cherries, or any other fruit crop."" Similarly, the copper based product Headland Copper, used by top fruit growers as a ""good option for scab"", ""does not have a pesticide label at all," said Paul. ""It's now purely for use as a foliar feed."" He added: ""Stone fruit growers use copper routinely at certain times of the year to prevent canker infection so it's a big issue for organic and conventional growers.""
Fortunately, hope could be on the horizon as Agrovista has spoken to the AHDB's senior crop protection scientist Viv Powell, who is pursuing getting mutual recognition for some of the copper products that have approval for use in various European countries. ""Something is being done," said Paul, ""otherwise it's going to be very difficult to grow organic fruit and probably some stone fruit as well.""
He also informed growers of a handful of other products whose labels have changed. These include:
- Systhane 20EW - growers can use this product until 31 September 2017
- Syllit 400FC (Dodine), that was going to disappear but which growers can now use for at least the next 12 months
- Apollo 50SC (Clofentazine) The new on-label use for fruit is going to be restricted to apples and pears with no on-label approval for cherries and plums. Bennett said: ""My information from the manufacturer is saying that the soft fruit EAMUs are going to be redone but not the cherry and plum EAMUs.""
- Deacon (Tebuconazole) The new labels for Tebuconazole products will no longer have fruit on the label. However, the existing products with the existing label can be used until 30 April 2018.
- Folicur - Growers are now only allowed one application during the season or one post-harvest.
Mycorrhizal fungi
As the horticulture industry's range of conventional crop protection chemicals continues to diminish, the top fruit sector is investing in new ways of helping its orchards stand up to pests, diseases and other forms of stress. Agrovista is launching a new service in February whereby growers can inoculate their existing orchards with an arbuscular mycorrhizal fungi-based product, Plantworks' RGPro.
Agrovista agronomist Tom Johnson revealed that the service has been set up following several enquiries from growers who were interested in finding out how to use the product on their existing trees. He reminded growers that mycorrhizal fungi form a symbiotic relationship with plants, colonising their roots and increasing their root uptake area by 700 times. This enables them to better absorb nutrients and water, and helps the trees to better cope with stresses such as drought, water logging and plant pathogens.
Tom has innovatively fitted a Stocks Ag Rotor Meter typically used to place granules, slug pellets or fertilisers into the field - to a root-pruner blade to create a new device. The new system enables RGPro to be inserted close to the small fibrous roots of the trees, 15-20cm into the soil. Loddington Farm Ltd in Kent will be carrying out the work as a contracted service that will operate at a speed of approximately one ha/hour, said Tom. He added that the trees could also be root pruned at the same time and that January to March is the best time in which to carry out the activity. Growers who are interested in the service should, in the first instance, contact their local Agrovista agronomist.
Canker
RGPro is also one of several biological soil amendments that are being trialled by scientists at NIAB EMR as part of the five year, AHDB Horticulture TF 223 project - a key focus of which is the development of an IPM strategy for apple canker. Dr Robert Saville explained that RGPro and products such as plant-growth-promoting rhizobacteria and trichoderma are being evaluated for their effect on Nectria (canker). He said: ""We are doing this in two stages - the nursery phase and the newly-established orchard phase.""
A stool-bed has therefore been set up at NIAB EMR, where the different soil amendments have been used on different plots at the planting stage. The researchers have, said Robert, been going through a cycle of growing and cutting down the plants to establish the stool from which the rootstocks will be produced. The rootstocks are being harvested this year and will then be assessed to see how well each soil amendment works against canker. The newly-established orchard phase saw NIAB EMR work with Worldwide Fruit and Avalon Produce late last year to set up trials using canker-susceptible varieties on two sites that are prone to canker. Robert said: 'They will be assessed for canker infection during the established phase.""
Plums
Imported plums can often be a disappointment - the novelty of their good looks disappears once people take a bite. For this reason, fruit consultant Leon Jahae is investigating which plum varieties could be grown in the UK to replace these imports. Leon explained: ""There's a lot of poor quality fruit [plums] available, and that's often to do with harvesting times. They get picked early and shipped for long distances, and for a lot of marketing organisations or retailers, shelf-life is more important at that stage than the flavour or eating experience."" He noted, for example, that Japanese plums look beautiful because they boast nice colours and shape, but often when you buy them it's a disappointment. They get picked because of their looks and not their eating quality.
And so, despite plum growing currently being in decline in the UK, Leon Jahae hopes that soon British-grown plums could substitute plums and other imported fruits such as apricots, peaches and nectarines. Leon revealed that, as ""we are not making the most of the genetic material that's available," a couple of years ago he began looking into plums from different European countries - including Germany, Italy and Romania. The criteria he looked for included whether a variety is split tolerant or resistant, disease and virus tolerant, has an ability to produce good quality yields and has a good shelf-life.
Leon also explained that the plums he has been looking at fall into three categories:
• smaller, dark blue plums, with a weight of at least 30g, high Brix levels, and a harvest time from the end of June until the end of October
• large, orange-fleshed plums weighing at least 45g that vary in colour from violet/red to dark blue. These also have a harvest time from the end of June until the end of October.
• niche plums such as greengages, hybrids; for example, a cross between a Japanese and a European plum like Prunus cerasifera (cherry plum), and Mirabelles.
Leon said: ""We have been selecting different plums over the last few years, looking at different material - what is interesting now and what will be interesting in years to come. In total, we have around ten promising selections. We are producing trees from different selections, which will be planted in large-scale trials in the next season in the UK."" Promising selections include, for example, a yellow plum that was harvested on 15 September and has a Brix level of 19.5.
Virtual weather stations
Agrovista's top fruit technology could soon become even more sophisticated because the company is investigating the possibility of incorporating virtual weather stations into its Growers Choice Interactive (GCI) pest and disease forecasting service.
Agrovista's Alex Radu said that the company is currently trialling the MeteoBlue weather forecasting service, which can update its rain and temperature forecasts every 15 minutes. Last year, 35 of these virtual stations were tested around Europe - in the Netherlands, Belgium, Germany, France, Switzerland and the UK. This year, said Alex, the plan is to test a further four in the UK. He also asserted that the technology, which is already in use in some parts of Europe, could save growers money in the long run. ""Virtual stations are very easy to create - just a few clicks and you are done. There's no maintenance required, you don't need to service the station in the field, and they are considerably cheaper than the [field] station... so if virtual stations do prove to be accurate it's got to be a massive saving for growers.""
However, Alex revealed to delegates that the technology needs a bit of fine-tuning before it can be incorporated into GCI. For example, the overall results of last year's tests showed that, whilst temperature data was very accurate, some inaccuracies were recorded. This included the relative humidity (RH) values that were forecast by MeteoBlue, that were slightly lower than the ones recorded in the field. It also included the infection risk, which was overestimated by the model. Alex said: ""In a nutshell, if we had followed the MeteoBlue model we would have been all right and covered all the scab infections.
But currently the model does not give you that edge of whether or not they [the orchards] need treatment."" For that reason, the RH and infection risk models are going to be updated this season. ""It's a work in progress - we are getting there," said Alex - who predicted that, once it's teething problems are overcome, it could complement a main, on-farm weather station or even maybe replace the physical weather stations.
Delegates also learned that, this spring, Agrovista is trialling a powdery mildew model into its GCI package - which now includes an apple sawfly model.
Insect pests making a comeback
Top fruit growers need to be 'on the ball' and watch out for problematic pests that are making a comeback. Several experts warned that a handful of pests - including apple sawfly (Hoplocampa testudinea) and leafhopper - are once again becoming more common. It is thought that the decline in the use of broad spectrum insecticides, which gave incidental control of some pests, is causing this phenomenon.
Agrovista's Paul Bennett said: ""Any major change to a management system is going to have a consequence and it may be that over a period of seasons, say every fourth or fifth season, you have to make a change just to bring down the populations of things like sawfly and leafhopper."" Agrovista's horticultural consultant Alex Radu noted that: ""Apple sawfly used to be a fairly localised issue and not many growers in Kent were complaining about it. It was fairly common in the Midlands, but it is becoming more common in Kent as well now."" Paul added: ""It's certainly the case that, particularly in Kent, I saw very low levels of sawfly on farms that I hadn't seen sawfly on in years. I think this is a pest that can go from extremely low levels to extremely high levels in one season - it's something that you need to be on the lookout for.""
With the return of this pest in mind, Agrovista has this year introduced a tried and tested apple sawfly model into its Growers Choice Interactive (GCI) pest and disease forecasting service. Paul noted: ""It's quite timely that Alex has managed to get the sawfly module of GCI in place for this season and we are confident of its accuracy."" Paul also warned growers that apple sawfly is particularly harmful to crops because, when the larvae emerge from the fruitlets after petal fall, they ""immediately penetrate the nearest fruitlet and then, when they are more mature, they will migrate to other fruitlets in the same cluster. It's not like codling in the sense that it ruins that fruitlet - it ruins the whole cluster."" Paul therefore advised growers to monitor for the pest by using white sticky traps during the bloom period followed by an insecticide treatment if necessary.
Apple (pear) bud weevil
Apple bud weevil (Anthonomus pin) - appropriately referred to by the industry as the pear bud weevil - is another insect that has become more of a problem and, unfortunately, it can cause significant yield losses in pear crops.
Dr Michelle Fountain, an entomologist at NIAB EMR, noted that the drop in broad spectrum insecticide use has caused a return of this particular weevil. ""Essentially we removed the use of broad spectrum insecticides in pear orchards because pear sucker is now resistant. We know that earwigs and anthocorids are very important for the control of pear sucker. So, we don't want to kill off these lovely predators with the use of broad spectrum insecticides.""
Michelle revealed that she has carried out some unfunded work to try and learn more about the biology of this pest after pear growers started to complain about it. She said that, whilst there is still much more that needs to be learned about the weevil's lifecycle, trials at East Malling have so far shown some useful results. For instance, trials in both the laboratory and the field revealed that Calypso gives effective control of the pest, with laboratory results showing that the product gives up to 90% efficacy. Moreover, following orchard inspections, Michelle learned that the pear bud weevil, which both feeds on and lays eggs in the flower bud, is active at night and tends to mate in the warmer evenings in the spring. She said: ""This spring activity is quite important because there are fewer predators in the spring than there are in the autumn around harvest. So, if we can treat [this pest] in the spring rather than the autumn this might be a better time, thus avoiding damaging our natural enemies.""
In addition to the pear bud weevil, apple sawfly and leafhopper, several moths are also making a reappearance, explained BASF's Simon Townsend. He said: ""Growers need to bear in mind that we are in a changing world - a world without chlorpyrifos. We don't have the use of broad spectrum insecticides now, and I think that, as time goes on, we may well expect new pest species to emerge and they need to be controlled with appropriate measures. In some UK trials we have encountered a resurgence of moth pests that have not previously been a problem, such as Blastobasis."" He added: ""If Blastobasis has been found at all in the previous season use an insecticide timed to control it in the subsequent season.""