Phytophthora
Root and Crown Rot: The problem is most often detected in flowerbeds that have been planted with same species year after year. The plants that are more vulnerable to this disease are Pansies, Petunias, Snapdragons and Violas.
The crown base or lower stem of infected plants normally rot at or near soil line, as the disease progress the entire plant usually turn yellow or wilting followed by complete death of the plants.
Control:
- Crop rotation is recommended for the management of Phytophthora, but do not alternate planting with the above plants, e.g. do not pull out Pansies and plant Petunias or Snapdragons, but use plants like Marigolds, Zinnia, Poppies, Calendula, etc.
- Improve soil drainage – the disease is associated with heavy clay soils.
- Allow the top 1/2 to 1 inch of soil to dry out before next watering.
- It is also important to raise flat planting areas so that the water will drain off rapidly and not saturates soils.
Thielaviopsis
Black Root: Black Root is the fungal disease that usually starts at root tips and through root hair. This disease is a problem on pansies during the late summer months when temperatures are high. The symptoms with seedlings are stunting and a pale green to yellow discoloration of leaves.
Control:
Crop rotation is recommended for the management of black root disease. Avoid planting pansies during late summer hot months.
Snails & Slugs
Causes holes in the leaves of young plants and can chew right through the stems of newly planted seedlings.Damage is worst on shady ,poorly drained site.
Control:
Put down snail bait immediately after planting and re-apply until plants are older and well established.
Cutworms
These green-grey or brown soil living caterpillar maybe 2 inches long.They gnaw both roots ans stems ,but their tell-tale effect is to sever seedlings and young bedding plants at ground level.When this happen look for and destroy the cutworms near the attached plants.
Control:
Sprinkle granular cutworm bait over before planting.
Aphids
Small sucking insects usually found on new growth. They come in shades of green, red or brown and they all have fat little pear shaped bodies. They feed by piercing plants and sucking the juice of plant sap result in leaves being distored, curled and failing to develop. They also secrete a sticky substance called honeydew that often results in the colonization of an ugly sooty black fungus.
Control:
Spray with a suitable insecticide for sucking insects.
Red spider mites
Can be identified as minute red dots on the underside of leaves and is a problem in hot dry conditions. The presence of of fine silk webbing is a tell-tale sign,Leaves turn mottled yellow and fall off prematurely.
Control:
Water the undersides of plants and avoid stressed plants due to lack of water and food. Spray with a suitable incecticide.
Powdery mildew
The white powdery deposit found on leaves, stems and buds of plants such Hydrangeas, Dahlia,Salvia farinacea Verbena and Zinnias.
Control:
Don’t water late afternoon or at night. Make sure sun loving plants are planted in full sun and shade loving plants get enough light. Or spray with a suitable fungicide.
Rust
The red or brown powdery substance found on the undersides of the leaves of plants such as snapdragons calendula and dianthus. Rust takes nutrition from the plant. Bad infestation may result in total lost of leaves and sometims complete death of plants.
Control:
Avoid watering late afternoon or at night and spray with a suitable fungicide.
Beetles
Such as Chafer Beetle are medium sized brown or greyish beetle, which are only active at night, by the day hide away. They make large holes on the leaves and or petals sometime leaving only main veins. They are strongly attracted to light and may become a nuisance in the house during early summer evenings.
Control:
Pick off by hand where possible or spray with a suitable insecticide for chewing insects.
Mealy Bug
These are wingless, oval pinkish or greyish blue covered with white waxy powder. They excrete copious quantity of honeydew over their host plants on which black sooty moulds develop. They generally avoid sunlight and become abundant on plants with dense foliage or plants growing in the shade.
Control:
Hose down with a strong jet of water or spray with suitable insecticide. Ensure the ants are controlled because they may spread infestation. Or spray with suitable fungicide.
