Cool, damp conditions at this time of year increase the risk from a range of foliar diseases including rusts, leaf spots and powdery and downy mildews – whether on crops such as pansy and viola, cyclamen or primula; or on stock being overwintered, in unheated tunnels for example.One that’s particularly damaging and difficult to manage is Botrytis, which is why I’m having a look at it in this first blog on the disease issues you need to be on top of through autumn and winter.Sound cultural practice is the first line of defence for them all. Adequate ventilation and air movement will avoid zones of high humidity, which favour foliar diseases, building up in glasshouses or polytunnels. You may want to consider installing fans if you haven’t already – even with the vents open it is surprising just how little air movement there can be over quite large areas, especially at floor level.Good plant spacing helps too, especially in crops with relatively dense arrangements of foliage where diseases like…

  Botrytis, which we talked about in my last blog, is just one of the foliar diseases that pose a risk in the cool, damp conditions at this time of year. Two others to watch out for are powdery mildew and downy mildew.Despite their similar names they’re completely unrelated: powdery mildews are fungi while downy mildews are oomycetes, the same group of micro-organisms as those troublesome root diseases Pythium and Phytophthora. Oomycetes share some of the superficial characteristics of fungi but much of their genetics and biochemistry are totally different.It’s useful to talk about powdery and downy mildews together here, though, as understanding their similarities and differences is key to managing them well. It’s often easy to confuse the symptoms but you need to get it right as not all products effective on the one can control the other.A good ‘rule of thumb’ is that the fungal growth and powdery sporulation of powdery mildew tend to be seen on the upper surface of the leaf while the downy…

  Rust diseases can strike at most times of the year but, like Botrytis and mildews which we featured in my last two blogs, they can be a particular problem in glasshouses and polytunnels during the colder months when it’s often a challenge to keep crops well ventilated and humidity under control.Rusts are caused by a huge group of fungal pathogens. There are well over 150 genera, Puccinia being the most significant. Estimates of the number of species vary but run to many thousands. Most of them, however, are highly specialised, having evolved to grow on just one, or sometimes several, host plant species. They usually have highly complex life-cycles, needing two different host plant species to complete them­ in some cases and involving several different kinds of spores.All, however, need humidity and wet leaves to spread and germinate; and all produce powdery survival spores in the characteristic ‘rusty looking’ pustules produced on leaves and stems.One reason rusts are tricky to manage is that the…

As well as Botrytis, mildews and rusts, which we’ve looked at over my last three blogs, there are other, less well-known pathogens that can damage leaves, stems and flowers in autumn and winter, particularly on crops such as pansy, primula and polyanthus.Leaf spots can be caused by several kinds of fungi. Precise diagnosis can be tricky as symptoms vary depending on the crop and pathogen involved, with more than one type of fungus sometimes present.Generally, though, you’re looking for small, dark, distinct spots, usually on older leaves first but spreading to younger foliage if the infection takes hold.On pansy, small purple-brown spots with a slightly greasy appearance are probably the result of Ramularia lactea; tan-coloured spots that merge into areas of scorched-looking tissue are more likely R. agrestis.Alternaria violae infections on cineraria lead to irregular dark brown to black spots; on other crops, the leaf spots tend to be greenish-yellow or buff.All the good husbandry that we have talked about…

  With spring round the corner, and sowing, transplanting and potting lines operating at their peak, root health takes even more of a priority than usual.Root diseases caused by species of the oomycete pathogens Pythium and Phytophthora are particularly difficult to manage. Although they share some characteristics with fungi, some aspects of their biology and biochemistry are dissimilar meaning only certain fungicides, such as Subdue, have a mode of action able to control them.Different Pythium and Phytophthora species grow best at different temperatures: some Pythium species can grow and spread at below 15°C.Cultural controlThese oomycetes spread readily in water ­­– including in over-moist growing media and in irrigation systems, especially if recycling the water – so cultural control starts with good irrigation management.Avoidance of overwatering is key, along with use of a free-draining growing medium. Water drawn from sources other than mains or boreholes ­– collected from greenhouse roofs or…

  Ornamental crops can come under stress of one kind or another at any time but spring is arguably when it’s most likely.Tender young shoots and buds will still be at risk from cold damage at that point in the year whether plants are on the nursery or in transit in the supply chain. It’s the stress caused by overheating, lack of water and too much or too little light, however, that can be more difficult to spot and manage.Sudden changes in the weather, for example from cool and dull to hot and bright, can be particularly damaging if plants can’t adapt fast enough – think how quickly the temperature can climb in a greenhouse on a warm, windy day that would keep the vents closed. Modern monitoring systems (which we talked about in an earlier blog) can help you manage the greenhouse environment much more responsively; fans to keep the air moving and stop hot spots can also help.Research into crop quality issues thought to be linked to stress, such as that conducted on pansy mottle for AHDB in the last…

   Last time we looked at some of the less-than-ideal conditions that can occur on the nursery, or on the way to your customers, that put your plants under environmental stress. While plants can respond to protect themselves, at least in the short term, those responses take energy and can shut down some important parts of their metabolism, inevitably taking their toll on growth and development. Even when the stress is eliminated, the crop may never catch up so quality suffers with consequences for plant performance in the garden or landscape.An element of the stress response that is increasingly well understood is how it affects plant proteins.Proteins form the structural elements of cells and tissues but they’re also the enzymes that control all of the thousands of different biochemical processes in the plant – such as photosynthesis, nutrient transport, and regulation of flowering.Proteins are large, complex molecules, each with a specific job, formed from long, folded, chains of much…

Getting the best from your crop protection sprays while minimising waste and avoiding risks to the operator, any bystanders and the environment relies on accurate application. That in turn depends on the sprayer being well maintained and set up.Whether it’s a pistol, lance or short pedestrian-operated boom; knapsack or mounted equipment, your spray kit should be fully inspected and calibrated regularly by a competent person. The start of the season is an ideal time to remind yourself what this entails – and a thorough check now could avoid downtime later.Some sprayers have, by law, to pass a regular ‘MoT’ test under the National Sprayer Testing Scheme (NSTS). Small boom sprayers up to 3m wide, and equipment such as slug pellet and micro-granule applicators, need a first test before they are five years old, and then every six years.Sprayers with booms wider than 3m have to be tested before they reach five years old, and then every three years. Orchard-style air-blast sprayers that some tree growers use also…

For sprayers, calibration is all about making sure you’re applying a known spray volume over a given area, so you can apply the correct dose of the products you’re using.The principle is the same whatever the type of sprayer: you’re measuring the amount of spray over a set time and combining that with a calculation of the time taken to cover a known area.Hand-held sprayers. With hand-held equipment, the speed you walk during spraying is a key factor – so when you’re calibrating, it’s important to choose an appropriate pace for the conditions you’ll be working in. Remember, you’ll need to maintain that pace consistently while working, including while wearing PPE. For most people that’s going to be around 3km an hour, the equivalent of 50m in a minute – but will be affected by the layout of the crop area and any obstructions such as greenhouse stanchions.Nozzles and operating pressure should be those you’ll be using on the crop. Your nozzle choice may depend on the product and on the crop being sprayed so you…

How do adjuvants improve spray applications?What are the key properties to look for in an adjuvant?The waxy cuticle that coats the leaves of most plant species has evolved to do two important jobs: it helps seal the leaf tissues to control evaporation from within and makes raindrops bead-up and run off, keeping the leaf surface clean, dry and inhospitable to pathogens.When you’re trying to spray your crop, however, that cuticle really works against you. If droplets bead and run off, the active substance goes with them. Even if they don’t run off they can dry without spreading so the active far from covers the entire surface. And unless it remains in solution, a translaminar or translocated active has little opportunity to penetrate the cuticle into the leaf tissue.Insects have a waxy protective outer cuticle, too. It works in much the same way, with implications for your pest control sprays.In an earlier blog we talked about the increasing importance of adjuvants in tank mixes. Adjuvants help by reducing the…

How does the label information help me get the best from a crop protection product?What’s the difference between an on-label and an EAMU authorisation?Read the label. In our business we have to, because it’s a legal obligation to take ‘all reasonable precautions’ when using pesticides ­– and to do that, says Defra, you must ‘consider the product label as a whole’ before you begin using any plant protection product.But there’s more to it even than that. ­Although all the most important information about the product and authorised crops must appear on the label, it’s not just the sticker on the pack: it also usually includes a sheet or leaflet that arrives with it. Understanding what to look for on this label gives you a head-start when it comes to getting the best from a product – after all, its information is a distillation of the research and trials needed for the product’s authorisation. The label, as much as what’s in the pack, also has to be officially approved before a product can be sold.Search out a…

What information can I find on a crop protection product label?What information is available in an EAMU notice?Last time, we reflected on the complementary roles of products with label approval and those with extension of use (EAMU) authorisations when it comes to crop protection for ornamentals.We’ll now have a look in more detail at what you can find out from the label information on an ornamentals-specific product such as our fungicide Switch, and from the EAMU conditions for using a broad-spectrum fungicide such as Amistar on ornamentals. All product labels and all EAMUs follow a standard format and the information they contain can really help your decision-making.Ornamentals on the label: SwitchThe first section in the label leaflet states the product name and official registration (MAPP) number. Check the number is the one most up to date (you can do that by searching the product name on the official database held by the Health and Safety Executive) and that the approval is still in force. Switch is…