Driven by the demands of consumers, retailers and processors, integrated pest management (IPM) strategies are becoming increasingly important in the production of soft fruit.
Meeting the needs of growers and their partners along the value chains, a number of technologies are now being used including beneficial insects, conventional and biological pesticides as well as pheromones for trapping and monitoring pests.
According to Defra, in the last 10 years the UK soft-fruit production area has declined from 38,925 hectares to 27,605ha. In the same period, glasshouse grown soft fruit has increased from 28ha to 108ha.
“Alongside glasshouse production, there has been rapid expansion of protected strawberry cropping in the UK, Spain and France using Spanish and French tunnels,” says Simon Jones, UK sales manager at Biological Crop Protection (BCP).
“Here in the UK, larger growers are moving towards 100 per cent covered production. While helping to maximise yields and extend the season, protected cropping has opened up greater opportunities for using beneficial insects instead of conventional pesticides. It has also thrown up some new challenges by broadening the pest spectrum.”
In the soft-fruit sector, strawberry growers are leading the way in IPM. Many are now successfully controlling major pests, including spider mite, whitefly, tarsonemid mite and vine weevil, using programmed introductions of beneficial predators and parasites - biological controls.
“Spider mite is a factor when growing strawberries - growers know at some point in the season they are going to get it,” says Jones. Resistant to many acaricides, this pest is now largely controlled in field-grown and protected crops using the predatory mite Phytoseiulus persimilis. Regardless of whether there are signs of the pest, growers generally routinely introduce Phytosure to the crop when plants have two new fully opened leaves.
“With the hot weather last year there was the potential for spider mite to be a real problem. However, generally in crops where growers introduced Phytosure early on, the pests didn’t get out of control.”
In protected cropping situations BCP also recommends introducing the winged-predator Feltiella. Highly mobile, once established it readily locates isolated outbreaks of the pest throughout a crop. What is more, says Jones, is that the larval stage feeds on all stages of the pest lifecycle, including the inactive diapausing mites.
Where sulphur is used, spider mite control can be boosted using Amblyseius californicus - a predator with greater tolerance to pesticides. Due to stipulations in its Defra release licence, this predator can only be used in permanent structures.
Strawberry crops routinely come under attack from several species of aphids including melon-cotton aphid and potato aphid. In protected crops, growers have a number of biological controls they can turn to. “Aphidoletes is a useful predator as it attacks a wide range of aphid species, but it does require 15 hours a day length,” says Jones. “Otherwise, it is important to correctly identify the aphid species and select the appropriate species of Aphidius - for example Aphidius colemani for melon-cotton aphid.”
Difficult to control using conventional pesticides, Tarsonemid mites attack the whole strawberry plant, including the growing points. Serious infestations generally lead to stunting and eventual death of the plant. According to Jones, Amblyseius (Ambsure) can give effective control of tarsonemid within just one to two weeks - even at high infestation levels,
With the trend towards protected cropping, thrips have become an issue for many strawberry growers. Feeding inside the flowers, this pest causes mis-shapen fruit to develop. “We recommend growers start their thrips control programme as early as possible to get Amblyseius established in the crop before thrips occur,” says Jones. “A multi-pronged approach is best using Amblyseius (Ambsure) to target the larvae and Hyposure, containing Hypoaspis miles, to attack the pupae in the growing media. Last season some growers also applied Orisure, (which contains Orius laevigatus) to thrips hotspots.
Changes in production methods, moving from soil to compost, have resulted in Black Vine Weevil problems for strawberry growers around the country. Compost provides an ideal environment for vine weevil larvae to thrive. A potential devastating pest, it can be controlled biologically by watering microscopic nematodes in to each bag. Containing a low temperature tolerant nematode, Nemasys L gives rapid curative control at temperatures as low as 5°C.
“While pesticide usage in strawberries has dramatically reduced, as things stand biological control doesn’t provide all the answers,” says Jones. Where possible, select a chemical that is IPM compatible - one that will cause minimal disruption to the biological control programmes, he says. Failing that, it is important to apply the chemical as accurately as possible to maximise its effectiveness while minimising its impact on the beneficials.
For example, with no biological solutions for pests such as Strawberry Blossom Weevil, growers have to rely on conventional pesticides. However, research is now underway looking at the potential for using pheromones to monitor and control this and other pests. By using pheromone traps to monitor these pests, it is hoped pesticide application accuracy can be improved thus reducing the number of applications and disruption to biological control programmes.
Another important area is disease control. Botrytis, powdery mildew and red core are common fungal problems in soft-fruit crops.
Thriving in humid and warm conditions, Botrytis primarily attacks dead and dying petals in strawberry crops in flower. With drier conditions powdery mildew can take a hold on the crop. Extended growing periods under protection mean that infections can strike from March to late October.
Implementing a programmed approach to control will keep disease at bay, says Alan Horgan, technical officer at BCP sister company Certis. He says that alternating fungicides will avoid resistance through use of treatments from different chemical groups.
For outdoor crops, Horgan says Repulse (chlorothalonil) delivers excellent early season protection from botrytis. For both protected and outdoor situations, Horgan notes that Talat, containing the two complementary actives fenhexamid and toylfluanid, can significantly reduce levels of botrytis pre-blossom, with additional activity against black spot and powdery mildew. Rovral (iprodione) provides another mode-of-action for botrytis control and is useful to alternate in the programme.
“From blossom onwards, Frupica (mepanipyrim) is a good option. It is one of the most recent additions to the fungicide armoury, with no known resistance. With a harvest interval of just three days, it lends itself to use close to harvest,” he says. It is a botryticide, but is also active against powdery mildew and black spot.
While Repulse, Rovral and Frupica will not adversely affects biologicals, Horgan advises caution when using Talat in relation to an established biological control programme. When integrating Talat into an IPM programme, growers should consult Certis regarding its compatibility with beneficials.
In field-grown crops, Alan Horgan warns of the risk of root disease red core in wet, cool conditions. Spreading in soil water, it is a particular risk following waterlogging and periods of high rainfall.
“Planting on ridges or raised beds will improve drainage and covering the surface with polythene will keep soils drier,” he advises. “Some strawberry varieties are more susceptible to red core than others.”
Horgan recommends an autumn treatment of Aliette 80 WG (fosetyl-aluminium) for good control into winter. “A single application may be enough, but where there is a high disease pressure, an additional two applications of Aliette in spring is permitted under the Specific Off-label Approval system (SOLA).”
To control soil borne diseases, including verticillium wilt and red core as well as tackling pests and weeds, land destined for strawberries should be well prepared and then sterilised. Soil sterilant Basamid (dazomet) can be applied in autumn or early spring. It not only eliminates soil-dwelling problems before planting, but can help reduce the number pesticide inputs required in the crop, resulting in greater crop vigour and higher yields.
IPM IN RASPBERRIES
Although less well established in raspberries, workable IPM programme, minimising pesticide usage, have been developed and successfully implemented for pests such as spider mite, moths, thrips, whitefly and vine weevil.
“Spider mite in raspberries can be successfully controlled using Phytoseiulus and Feltiella,” says Jones. “However, the pest builds up particularly quickly in some autumn fruiting cultivars, such as Autumn Bliss, so it is important that introduction rates reflect this.”
Majestik, the non-chemical physically-acting insecticide, is good for spot treatments of spider mites as well as whitefly and aphids.
Incidences of Raspberry moth are widespread throughout UK raspberry crops, while outbreaks of Double dart moth and Bramble shoot moth tend to be more localised. Feeding on young leaves and buds the caterpillars burrow into the plugs of developing fruit. With good leaf coverage, control can be achieved using the biological control Bacillus thuringiensis (DiPel DF).
In protected raspberry crops thrips can be a problem pest. Brought in on infested plants, thrips can fly in through open vents or be carried in to the crop on equipment or clothing. As in strawberries, biological control programmes centre around the predator Amblyseius cucumeris.
While real progress is being made to minimise pesticide usage in raspberries, there are several problem pests including cane midge, clay-coloured weevil, raspberry beetle and Common green capsid for which there are currently no biological solutions. As in strawberries, Basamid can be used between cropping to reduce pest pressure in the soil profile prior to planting.
For disease control, Horgan recommends a similar approach to treating strawberries ie through alternating chemistry. Fungicide treatments Talat, Repulse and Rovral are all approved for use in raspberries.
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