Pests and Diseases
Good growing conditions will help ensure plants are naturally more resistant to pests and diseases Listed below are some of the potential problems and suggestions for their control: –
Aphids/Greenfly causes distortion of the foliage and is the main cause of spreading viral diseases.
Control using Bug Clear, Provado Ultimate Bug Killer or an Organic Control such as Scotts Natures
Answer Pest Control.
Blackfly/Melon Cotton Aphid – a more difficult to control member of the aphid family which is more common in the greenhouse. Use Provado Ultimate Bug Killer.
Capsid Bug – causes distortion of the growing tip by puncturing resulting in mottling and ragged looking leaves. Often the damage is done before symptoms show. Provado Ultimate Bug Killer, being systemic, will give some defence.
Earwigs – often harbour in the tops of canes, wood panel fences and split wooden stakes! Being nocturnal the evidence is only obvious by the leaves and/or petals being eaten in an irregular pattern. Seal cane ends with cane caps, or putty. Vaseline on stems will prevent earwigs from getting into blooms. Woodlice powder will give some control on fences.
Dahlia Smut – pale yellow spotting of the lower leaves which slowly develop into brown spots, which dry up and fall out! Spray with a copper based fungicide and rotate planting wherever possible. More prevalent in wet seasons.
Powdery Mildew – associated with dryer weather and appears as a white powdery coating on the surface of the leaf. Use any general purpose fungicide such as Systhane Fungus Fighter.
Thrips – cause a puckering of the foliage and can badly mark the flowers, particularly pinks and whites. The yellow sticky traps available for use in greenhouses can help monitor a potential problem. Use Provado Ultimate Bug Killer or Bug Clear.
White Rust –is the most serious disease affecting Chrysanthemum growers up and down the country. Pale yellow green spotting on the upper surface of the leaf is the first tell-tale sign. Yellowish brown/white pustules soon accompany this on the underside of the leaf. Remove and burn affected leaves as soon as possible. As spores need moisture to germinate and spread, keeping the humidity as low as possible will help as will keeping foliage dry and ensuring plants are well spaced to ensure adequate ventilation. Good hygiene is important at the end of the season. Stools can be kept with the safest way of cleaning stock to use hot water treatment on the dormant stools after trimming back all green growth. Immerse stools in hot water at 45 degrees Celsius for a maximum of 5 minutes. Stools should then be immersed in cold water before planting up ensuring no cross contamination can take place. The only fungicide available now to the amateur grower that we can recommend is Systhane Fungus Fighter. Many chemicals used in the garden are currently under review.
Virus – plants, which show a severe mottling of the leaves with yellowing of the veins and an obvious stunting in the growth, may well be infected with virus. Such plants are best removed and destroyed.
Also be vigilant and keep an eye out for Caterpillars, which can damage flower heads.
Slugs and snails can very quickly decimate young plants and there are various methods of controlling them.
Over watering after potting up or planting out can often be the cause of root death resulting in plants getting away to a very slow start.
PLEASE NOTE always use pesticides and fungicides safely following instructions and do not exceed recommended dosage rates.