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Crop Advice & Expertise

5 steps to managing crops under protection

Protected crops present unique challenge to growers, how growers respond can define success.

Conditions in a glasshouse are often distinct from those in a field or even polytunnel and for this reason it is not unusual to find that a product approved for use in one situation cannot be used in another. The regulatory process is a stickler for detail. 

For manufacturers, and consequently growers, this means it can take many years to gather the data needed to support a dossier for registration. Should the regulator require supplementary data, it can take several more years to produce and partly explains why some forms of use can be granted while others are not.

This is just one example of how restrictions can affect the ability of growers to ensure that crops are suitably protected, but there are others. Fortunately, it is within the grasp of growers to overcome many of these challenges, but just as with product regulation, the devil exists in the finer points, explains Jack Hill, Bayer roots and horticulture commercial manager.

“For many growers, the ability to protect crops against pests and diseases has to be balanced with the need to support beneficial insects. In protected environments, especially glasshouses but also polytunnels, there is often significant investment in macro biologicals, so actions to control sucking pests for example must not come at the expense of pollinators such as bees,” he says.
In many situations, this can be easily achieved, as long as some basic principles are observed.

“There are some very effective biological fungicides and insecticides available that fit neatly into a programme with conventional crop protection products as long as they are used strategically. But there are also many conventional products that pose a minimal risk to beneficials as long as they are not mixed with something unsuitable or applied at those times of the day when beneficials are active within the crop,” says Mr Hill.

Preserving crop quality while meeting volume requirements often involves several inter-related considerations. In such situations, the choice of which products to use can be limited. This raises other concerns.

“Crop safety is a foremost consideration, especially in a microclimate that promotes soft, lush growth. Protected crops tend to be more sensitive to some products than field crops, this can increase the risk of damage, so dose rates need to be determined carefully,” he notes.

The proven performance of biological products offering good fungicidal activity, such as Sonata (Bacillus Pumilus QST 2808) and Serenade ASO (Bacillus amyloliquefaciens (formerly, subtilis) strain QST 713) represent an opportunity to protect crops without presenting a risk to beneficial insects or crop safety.

“Application timing relative to disease pressure is always a consideration, but the ethos of an IPM programme is to balance strong conventional products such as Luna Sensation (fluopyram + trifloxystrobin), Previcur Energy (fosetyl-aluminium + propamocarb) and Teldor (fenhexamid) with biologicals.

“The advantage of biologicals in a programme is that they often come with less application restrictions, residue limits or harvest intervals. Where the principles of IPM are practiced to good effect, we see that disease is minimised and crops can be protected up until the point of harvest without concern for residues,” says Mr Hill.

Many insecticides, especially contact-only types, often perform best when applied during periods of relative low pressure. The environment inside a glasshouse or polytunnel is often favourable to insect spread, so application timing often needs to be precise to be effective.

“There is a need to be hyper-vigilant when protecting crops against pests because populations can increase rapidly. The bio-insecticide FLiPPER (fatty acids C7-C20) for example has a place in nearly all soft bodied insect control programmes, but as a contact-only it needs to come into contact directly with the pest. In contrast, Batavia (spirotetramat) is a systemic product that is acquired after the pest feeds on the plant. The two products work differently and provide different types of protection, but neither provide the type of knock-down control needed in times of high-pressure,” says Mr Hill.

Evolutions in crop protection

The nature of crop protection continues to evolve both in how it is achieved, and the products used to deliver it.  There is a clear shift towards biological products and while there are obvious gaps in the disease or pest spectrum controlled, they are improving.

Sonata and Serenade ASO are prime examples of the differences that exist in biological performance.
“Both contain live bacteria, but different strains with each having a different mode of action. Yet, in some crops they can be used to manage the same disease, for example powdery mildew in strawberries,” he says.

Conditions at application can influence performance too.  “There is a reason to believe that FLiPPER works with the dew, so should be applied in the early morning. FLiPPER needs a high-water rate to support coverage and placement of the product, typically a minimum of 400-500 litres/ha depending on canopy size, target species and stage of its lifecycle. Applying to the point of run-off should, however, be avoided, so having an understanding for how these new products work is essential to exploiting their potential to protect crops,” he adds.

To support growers in this endeavour, Bayer has developed a three-point plan for supporting biological performance within an IPM programme.

  1. Use them alongside conventional plant protection products. Biological products should be used when the pest or disease pressure is low thereby allowing the stronger conventional products to be retained for periods of high pressure.
  2. Use biological products as part of an integrated programme. Devise a strategy that incorporates the full spectrum of plant protection products. Using biologicals effectively is as much about understanding when to use other components of a programme or the potential for the plant to defend itself naturally, as it is about the limitations and advantages of biological sprays.
  3. Focus biologicals where they can make the greatest contribution to crop protection. A product’s mode of action should be considered just as much as the disease to be managed when positioning biologicals in a programme.

For example, Lipopeptides, such as those in the bacillus amyloliquefaciens contained in Serenade ASO, work best when the spores of the disease fungi are sporulating. Lipopeptides are derived from the soil, but in many cases are applied to leaf tissue which is distinct from their natural environment. To be effective, they must be applied in advance of the spore germination occurring which means before disease is visible to the naked eye.

Be accurate with application

Ensuring the fungicide, insecticide or herbicide is applied to the point where it is needed most is the basis for good crop protection. Systemic and translocated products can be relied on to move the product to the point of need, but the increasing number of contact-only products, especially fungicides and insecticides, means accuracy of application has taken on a level of importance not previously recognised.

To support growers in making the most of what biological crop protection products have to offer, Bayer has developed a list of five key points.  It was devised with FLiPPER in mind, but can be applied to most products, especially contact-only insecticides.

  1. Avoid hard water (i.e., more than 300 mg calcium carbonate (CaCO3). The negative effects of hard water are more widely associated with herbicides where reduced efficacy can be seen from the effects of dissolved salts (cations) locking up a proportion of the active substance. Hard water has a similar effect on FLiPPER although it is often more immediate.
    Bayer supports the use of the following to correct the effects of hard water:
    X-Fusion from De Sangosse
    Align from IntraCrop
    Tri-sodium salt of citric acid (TSCA)
  2. Avoid mixes with incompatible products. FLiPPER is physically compatible with a range of fungicides and insecticides but should not be mixed with some Bacillus thuringiensis and sulphur formulations. 
  3. Apply when bees or honeybees are not active in the crop. FLiPPER is less harmful to beneficial insects than many other biological insecticides and especially those that also contain fatty acids – use the side effects comparison tool on the Koppert website – sideeffects.koppert.com/side-effects/ – for details.
  4. Apply directly to the pest. FLiPPER is a contact-only insecticide and acaricide meaning it needs to come into direct contact with the pest to be effective. This distinguishes it from translaminar and systemic products which utilise the plant’s vascular network to move the insecticide or fungicide around the plant to achieve protection against pests and pathogens. 
  5. Maintain dose rates. In all situations FLiPPER should be applied at an inclusion rate of no less than 1% of the spray volume.

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