Article taken from Agronomist & Arable Farmer, March 2018, written by John Swire.
Spirotetramat, Bayer's new active ingredient said to give excellent control of sucking pests, could be available to protect a wide range of fruit crops this season.
It was granted emergency approval in 2017 to control a severe outbreak of woolly apple aphid, and the manufacturer is hoping for full approval in early spring.
""If that happens, growers will be able to use it on apples, pears, cherries, plums, currants and strawberries," said Bayer product manager Tim Lacey.
Spirotetramat complements IPM systems, Mr Lacey said. Its action controls a wide range of pests, including aphids, whitefly, leaf curling midge, pear sucker and mussel scale, but has a very good profile on natural pest predators.
""There is no contact activity," he explained. ""It works by breaking the pest's life cycle - it has to be ingested, after which it is converted into the active form.""
This typically delivers control rates of 94% for aphids and leaf curling midge, and 82% for scale.
Spirotetramat is highly systemic, and is readily transported in xylem and phloem, reaching all areas of new growth.
The new active typically takes three to four weeks to take effect. The application period for woolly aphid is from end of flowering to start of ripening, the period when aphids start to migrate to new growth.
Keep a watch for SWD
Soft and stone fruit growers should be keeping an even sharper eye out for spotted wing drosophila (SWD) in the coming weeks to ensure timely and effective control this season.
Populations of SWD are expected to increase further in 2018, continuing a six-year trend fuelled by a high reproductive rate and problems with larval control.
Agrovista fruit agronomist Simon Warren said a recent AHDB study had confirmed the pest's presence in all fruit-growing areas of the UK.
While most soft and stone fruit can be attacked, cherries are the most susceptible crop and, left unchecked, can suffer complete crop loss.
Accurate monitoring and effective control are increasingly important to prevent damage, said Mr Warren. ""Insecticides are working, but cannot be relied upon solely," he added. ""An integrated approach is key to long-term control.""
He advised early monitoring around winter habitat of hedges and woodland using pheromone traps placed around the edge of the crop can give an insight into SWD activity and help reduce numbers overwintering or entering the crop. Growers should place two traps/ha at least 7m into the crop, with weekly checks or replacement of attractant.
Ultra-fine netting can aid control, and good orchard hygiene is essential to reduce numbers coming in, he added.
""Prevent waste from falling to the ground, including fruit, pick regularly as delaying will increase SWD levels, and remove waste from the field," he advised.
Tracer, Exirel and Hallmark remain the most effective pesticides, closely followed by Calypso, Vulcan and Pyrethrum SEC, all applied with a surfactant such as Roller to increase coverage and absorption.
Spraying in the early morning and late evening when SWD activity increased will help optimise control, said Mr Warren.
Effective thinning can boost returns
Delegates also heard about the cost benefits of a carefully planned and managed thinning programme from John Portass, of Wisbech Contract Farming. He has been fine-tuning his system in Gala orchards in Cambridgeshire to maximise the percentage of best quality fruit of the required size to meet the demands of premium brands, and is now achieving excellent returns.
""Our aim is to grow 65t of Gala/ha that taste as good as a 40t crop," Mr Portass said.
Historical thinning costs averaged £1,285/ha, using several applications of ammonium thiosulphate followed by two to three hand-thinning operations, the latter accounting for the bulk of the £25.70/t cost on a sot/ha crop.
Helped by modern orchard design, Mr Portass has now replaced this operation with chemical fruitlet thinners using handing thinning as a final resort to achieve optimum fruit size.
""We want to produce high colour Gala at 68-78mm, and we need to set our fresh crop load by mid-July at the latest," said Mr Portass. ""To do that, we need to complete thinning by halfway through the growing period. This has little effect on crop tonnage but helps us hit target numbers early.""
This is based on judicious pruning to achieve optimum fruit numbers. On Galaxy Bi-Baum stock (planted at 3xlm spacing in 2011) the aim is to achieve 70 fruits/stem and 112 fruits/tree on straight Galaxy, producing an average fruit size of 66g in both cases. This puts 75% of fruits in the 65-78g range. Overall, hand and mechanical pruning totals about 50-60 hours/ha.
All trees are then treated with ammonium thiosulphate to thin blossom, typically in three applications - the first at the bottom of the tree, the next at the whole tree and the final spray at the top.
This is followed with either a Brevis (metamitron) application at around 8mm fruitlets, or MaxCel (6-benzyladenine) plus naa spray at the 10-lSmm fruitiet stage. Hand thinning starts in mid-June, thinning to singles and doubles to target numbers.
The new regime has cut thinning costs to an average of £685/ha, or £10.54/t, well under half the historical spend. Ongoing trials show additional income on a 65t/ha crop of almost 12% (£2,790/ha) from thinning to achieve 80% grade-out, compared with a nonthinned orchard producing 70% gradeout, said Mr Portass.
Precision services for orchards
Variable rate applications and crop development monitoring are among the benefits that precision farming technology could deliver to orchard growers, said Jack Harris, of Agrovista's precision services department.
The sector is no stranger to precision farming, as a combination of weather stations and software provides detailed weather forecasts and pest and disease forecasting under Agrovista's Growers Choice Interactive service.
Of the further precision farming options, the viability of using drones to monitor orchards has been tested through initial flights in Kent, and on-themove soil assessments that could samples several hectares in one hour, had also delivered useful information.
""We believe drones could be used in orchards to assess tree numbers and sizes and to map good and poor areas for detailed analysis and potential variable rate inputs," Mr Harris said.
""They could also be used to monitor crop development to help thinning decisions and to size and grade fruit on the trees to aid harvesting.""
Work is needed to fine-tune crop monitoring, as drones are currently used to assess arable crops in a horizontal plane, rather than a vertical one, he added.
Measurement and mapping of various soil parameters including soil type, pH, organic matter content and topography in an orchard near Wisbech have also showed promise. Mr Harris used a Veris U3 on-the-go soil sampler, which can be towed by a pick-up truck or small tractor.
Information can be gathered to establish yield potential, as well as variable rate lime, fertiliser and organic matter inputs. Such measurements can be fed into algorithms to establish nitrogen leaching and water-holding capacity of soils. Other tech being trialled includes crop sensors mounted in fertiliser spreaders that scan crops and alter fertiliser rates.
Protecting new SOHI chemistry
Paul Bennett, technical head of fruit at Agrovista, advised growers to take steps to protect the latest SDHI · chemistry that provides a valuable new weapon against apple scab and mildew.
Like many other approved products, Sercadis (fluxapyroxad) and Fontelis (penthiopyrad) have a single mode of action, so need to be used in the right combination with products from different FRAC (Fungicide Resistance Action Committee) groupings to reduce the risk of resistance developing, he advised.
""We must protect the integrity of these products by using them sensibly," said Mr Bennett.
""The new SDHis are classed as FRAC group 7. These should not be used more than four times per season, and no more than two back-to-back.""
Potential partners include the DMI fungicide, Topenco (penconazole) and multi-site fungicides that carry the lowest risk of resistance such as Captan or Delan Pro (dithianon).