Weeds And Diseases Of Garden

Problem-Scab

Scab (Cladosporium cucumerinum, Streptomyces scabies) is a disease of vegetable crops. Cucumbers, beets, cabbages, carrots, aubergines, spinach, onions, parsnips, potatoes and turnips are all susceptible.

Scab infections are well named because the spots on most plants look like scabs, whether they are on the roots or the above-ground parts of the plant. On leaves of members of the squash family, the spots are angular and don't look scabby, but the disease spreads quickly to make scabby-looking spots on cucumbers or rotting areas at the stem ends of melons.

Solution-Prevent problems

Resistant cultivars of many vegetables are commonly available, and it is worth choosing them when possible. For potatoes, check planting stock carefully and discard any potatoes with scabby spots.

The scab that infects crops other than cucurbits is encouraged by alkaline soil. If possible, keep soils at a pH of 5.5 or so, particularly in areas where you are growing potatoes. Apply 13-25mm (1 inch) of compost before planting, too, because it contains organisms that prey on those that cause scab. Finally, practise rotations of at least four years to avoid problems

Problem- mealybugs and scale insects

Solution - Spray outdoors

When mealybugs and scale insects attack outdoor plants, you may have to spray. Dormant oil does an excellent job of killing both types of insects, but remember to use it only in areas where plants become dormant during the winter months and spray before blossoms open in the spring.

Fine horticultural oils are also effective against these insects and have the advantage of being light enough not to injure actively growing plant tissues. In frost-free areas, these oils are a better choice for control as long as you spray before the summer heat sets in. You are usually safe if you stop spraying in early summer.