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With temperatures heading up, and in some cases record highs beaten, what precautions should you take when applying sprays and fertilisers to help plants get through the summer months?

Volatilisation
Spraying in hot weather not only causes evaporation of the liquid, but before it can enter the leaf the active ingredient vaporises and can be carried onto neighbouring plants where it can kill and injure.

JKW (Japanese Knotweed)
Many people are looking to spray JKW now – for best effect wait a little longer until it has ‘flowered’. The uptake of spray will be greater and there will be more translocation down to the growing points in the root, to reduce next years growth. Other methods apart from spraying are: cut & fill or stem injection – the latter being the most effective at reducing regrowth year on year.

Volatilisation #2
This term can also refer to the loss of Nitrogen (ammonia gas) from soils. Hot weather brings people out in their gardens and there is a great temptation to instantly recreate Wimbledon or the green turf at Lords.

When fertiliser is applied on high pH soils (above 7.5) in warm weather the nitrogen is lost through the soil surface as ammonia gas which is environmentally unfriendly, bad for grass and a waste of resources. Standard release fertilisers, spread this time of year, can also scorch or brown the turf. Slow release nitrogen fertilisers are safer or choose soluble organic liquids like Maxicrop Concentrate, a pure seaweed extract, which can provide nourishment and protectant properties for the turf.

Wetting Agents
Prolonged dry weather evaporates moisture from the soil leaving it water repellent. Wetting agents help to cure dry patch and decrease the need for extra watering of soil or turf.

Granular wetting agents like Scotts H2Pro allow moisture to penetrate the soil freely down to the roots where it is needed most. Grass will stay greener and healthier as roots develop in length to ‘chase’ the moisture - leaving them less vulnerable to sudden spikes in temperature.

Brown hedges?
Could it be conifer aphids or another cause? If you can discount hard trimming, sun scorch and root compaction, then there is a good chance conifer aphid or another sap-sucking aphid is feeding on the hedge.

Typically irregular brown patches will start lower down and gradually spread in random areas upwards and outwards as successive legions of aphids move home for new feeding opportunities. Contact or physical pesticides work, as their name suggests, by touching the insect while systemic sprays get into the plant tissue which is then passed on to the sap sucking culprit.

Spraying
Most plants & weeds suffer stress during a drought. Effectively this means their normal growth cycle is interrupted and the plant ‘shuts up shop’ by reducing loss of moisture from its leaves (mostly undersides) and putting its growth enzymes into neutral. Any pesticide application has a much harder time entering the plant so best advice is to wait until a good shower has passed before spraying.

For more information and advice visit www.progreen.co.uk

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