Purchasing a pot grown Poinsettia is as much a part of modern Christmas celebrations as it is to buy a trimmed fir tree. However, as a native to Mexico they can struggle to survive as a house-plant as it can be difficult to provide the right environmental conditions. If poinsettias become subject to environmental stress they are at risk from a wide range of common greenhouse pests and diseases. Below are the most common you are like to come across.
Cause: This is a very common greenhouse pest easily be transferred from the grower, to the retailer, and eventually to your home. Over the years, hundreds of varieties of scale insect has been introduced into the glasshouse eco-system including many tropical and sub-tropical species. Its success within the glass house environment is down to the speed at which it can multiply, in fact the female scale insect can easily produce 100's of eggs, protecting them either under waxy scales or coverings of 'woolly' wax.
Symptoms: Like aphids, they can quickly colonize the soft tissue parts, feeding on the plants nutritious sap by using specialized mouth parts. Colonies of young and adults alike can quickly colonize areas of the plant such as the underside of leaves or young stems. They will also excrete sugary 'honey dew' which will make the lower parts of the plant sticky. In extreme cases you may see sooty mildew growing on this residue.
Treatment: Due to increase chemical resistance with scale insects it has become difficult to treat them effectively with insecticides. Instead they can be physically removed by carefully wiping them off the leaves and stems with a damp cloth or a soft brush dipped in soapy water.
Cause: Aphids are a well known pest insect that can quickly colonize the soft tissue parts of your plant. They damage and weaken the plant by sucking the sap out of ppressurizedparenchyma cells just below the leave cuticle.
Symptoms: Clusters of these small insects are readily identifiable, normally at the plants tips or on the underside of their leaves. In severe cases, the infected parts can begin to wither due to the quantity of sap being removed from the area.
Treatment: There are many chemical treatments available including a number of organic, but all of these must be applied at the first signs of infection to achieve the best result. For further information click onto:
FOOT ROT, and ROOT ROT
Cause: These rots are caused by a wide range of fungal attacks making exact identification almost impossible. However their action and treatment are very similar.
Symptoms: The earliest signs of this fast acting rot are indicated by the production of smaller leaves which turn yellow before wilting. Flowering will be reduced and the plant will be loose in the pot or ground due to its decaying root system.
Treatment: Any infected plants should be removed and destroyed. Sometimes, improvements in drainage, nutrient availability and changes in the composts pH can indirectly improve the situation but there are no effective chemical cures.
GREY MOULD and POWDERY MILDEW
Cause: This group of fungi can affects many plants and unfortunately they are not host specific. This means that they are able to cross infect plants from a variety of different host plant families.
Symptoms: These moulds can easily be identified by a white or grey powdery coating that can appears on the leaves, stems or flowers of your plant. As the infection progresses this coating will spread to envelope the rest of the plant, eventually killing it.
Treatment: There are a number of effective chemical treatments that can be applied here, but infected plants will need fortnightly applications of a general systemic fungicide.
For related articles click onto the following links:
How to Care for Poinsettias
POINSETTIA CHRISTMAS STORY AND HISTORY
Poinsettia Pests and Diseases