WEED CONTROL
Weeds may be a problem early in crop growth before vigorous vine growth covers the beds as plants become established.
A number of control strategies may be used:
After bed formation, irrigating should be applied to germinate any weed seed.
Spraying with a knockdown herbicide before planting has been an effective method.
Rotary finger cultivators are effective in removing small seedling weeds during early crop growth. Encourage vigorous early vine growth to smother weeds.
PEST CONTROL
A fallow period should follow each crop to prevent build-up of soil-borne pests and diseases. Planting a green manure crop after harvest helps to suppress any regrowth and weeds as well as improving soil structure.
Sweet potato weevil
This is the most serious pest of sweet potato.
Adults are ant-like and lay eggs on stems and roots. The larvae burrow into the roots, making them unmarketable. They can pupate in the stems and be transferred in planting material.
Once established in a crop, this pest is difficult to control. Research has shown that a pre-plant treatment of cuttings with chlorpyrifos combined with foliar applications of chlorpyrifos at 5 and 10 weeks from planting provides significant control.
Planting material collected from an infected crop would require insecticide dipping before planting.
Destroying all crop residues after harvest and crop rotations are the best ways to keep weevil numbers down.
Giant termite
Termites can be a major problem, especially on newly cleared ground where the activity of established colonies has not been identified. Avoiding known termite-infested areas may be successful in the short term. Aggregation techniques to locate and concentrate termite activity followed by a baiting programme is the best way to clear future planting areas of this pest.
Other pests
Leaf-feeding caterpillars may cause problems if infestation is severe enough to cause significant leaf reduction. At the start of the wet season, hungry magpie geese can cause serious damage by trampling crops and eating the roots. Black-footed tree rats are also a problem.
DISEASE CONTROL
Mycoplasma (little leaf disease)
Infected plants have small, pale-yellow, stunted leaves and stems. The infection is spread by leafhoppers and if plants are infected while young, yields are greatly reduced. Control is by regular monitoring for symptoms and the removal and destruction of infected plants.
Fungal disease
Soil-borne fungal diseases can infect the roots but are not a large problem on well- drained, sandy soils.
