Pick the right moment for best pest control in apples – The Fruit Grower

Thoughts will soon be turning to insect control in top-fruit and growers are reminded of the ever-increasing importance of application timing and spray quality when targeting key pest species in apple orchards. The loss of broad-spectrum insecticides, of which Dursban (chlorpyrifos) is one prominent example, has had a profound knock-on effect on pest populations and their management in apple and pear orchards in recent seasons.

Jonathan believes that where growers have old label Gazelle (acetamiprid) in store, it will be the ‘go-to’ product if the treatment threshold for apple blossom weevil is met at or just after budburst. Apple and pear crops were taken off the label of any new Gazelle product (MAPP number 20034) manufactured last year, but old label produce (MAPP number 13725) can still be used legally in orchards until its use-up date of 31July 2024.

Jonathan adds that risk should be assessed using the beating method, where branches are shaken above collecting trays and the weevils counted. Priority should begiven to areas that suffered damage last year. If five or more weevils are collected in a 50-beat sample, significant damage is likely to occur, and insecticide treatment is justified, although this could be too high where the quantity of blossom in the orchard is low.

He reports that Hutchinsons agronomists started monitoring in mid-February and the first weevil was discovered in the South-East soon after, suggesting that the mild winter has promoted some early migration of adults. “Gazelle will do a good job, but with top- and stone-fruit currently off the label for 2025, another potential solution to consider for apple blossom weevil this year is Spruzit (pyrethrins and rapeseed oil)”, notes Jonathan.

While growers might be reluctant to try an unfamiliar product, with uncertainty about what will be available for weevil control next year, it is a good idea to gain some experience and confidence in the product. Jonathan adds that getting the most out of the contact-acting insecticide, which can be used against apple blossom weevil by way of an EAMU, is about picking the right moment to apply. “If you spray when the temperature is right for good weevil activity, you are likely to get good results with it, but if you apply on a cold and breezy day when they are less active, control can be compromised. It has a shorter persistency than products like Gazelle, so It’s all about timing”.

Jonathan points out that Spruzit has an EAMU for apple sawfly, which is another concern for his cider apple growers, whose aim is to maximise tonnage delivered to their cidermaking customers.

In the past, growers have applied a routine broad­ spectrum insecticide at petal fall to cover several pests, including apply sawfly. However, because of the slightly narrower range of today’s insecticides, he believes they need to be much more circumspect about what is applied and when. This means a greater focus on trapping adults and assessment of egg insertion scars and only treating when thresholds are reached. “Getting the right thing on at the right time is crucial, there is no point in putting something on as an insurance against a range of pests anymore as it might not work in the way you need it to. Monitoring, thresholds, and discussing timing with your adviser is so important. An application may not be when you’ve traditionally done it, so you need some flexibility to spray when pest activity and conditions are right,” he adds.

Whilst the shorter persistence of the pyrethrum product Spruzit requires precise timing for maximum efficacy against these pests, it is good news for the beneficials that growers now work hard to protect. The biorational product hasn’t been used widely in conventional orchards, but Jonathan says that it has been widely applied in organic production and his colleagues don’t report major issues with spider mites in those situations. The key to minimising the impact of red spider mite is to encourage the naturally occurring predatory mite Typhlodromus pyri, which means avoiding the use of broad-spectrum insecticides like synthetic pyrethroids.

The fact that few issues have been seen in organic orchards treated with Spruzit, containing natural pyrethrins, suggests that it allows beneficial insects like ‘typhs’ to regenerate much more quickly and maintain a balance between predator and pest. “It is something that we have got to test as Spruzit use in orchards increases, but it looks like it doesn’t have a significant negative impact on beneficials,” says Jonathan.

With a mild winter, aphid flights could start earlier. Monitoring activity from March onwards will ensure that species like the rosy apple aphid (RAA) and the similar pear bedstraw aphid can be adequately managed.

Jonathan sees Mainman (flonicamid) as being increasingly important in aphicide programmes, particularly with the loss of Gazelle. However, he points out that because of its specificity, it offers no activity on winter and tortrix moth caterpillars when used during the first moth-risk period from green cluster to pink-bud stage.

He says that, if using Mainman during this period, adding something for caterpillar control would be advised, if a risk is identified. ”This year, we still have indoxacarb products like Explicit or Steward, but that might be withdrawn before next year. If that’s the case, Bacillus products, mating disruptors and a pyrethrin like Spruzit could be important options for caterpillar in the near future,” adds Jonathan.

Flonicamid is a translaminar and systemic insecticide, and is able to move from the top of the leaf at application to the underside of the leaf where aphids tend to build. The label recommends a water rate of 200-1,000L/ha and growers should go as high as they can to help optimise spray coverage, which is important in optimising efficacy.