Onions are slow to emerge, or grow away following transplanting. Because of this, weed control is essential to reduce competition for moisture and nutrients. Their erect growth habit means that even when they are established they do not compete well with weeds. Pre and post emergence herbicide programs are commonly employed. Inter-row cultivating and hand weeding is also practiced in certain regions. Also read: Professional small scale farming demonstrated
A range of nematodes attack the stem and roots, restricting moisture and nutrient uptake. Stem and bulb eelworm (Ditylenchus dipsaci) is particularly damaging, attacking stems and causing shoot twisting, distortion and young plant death. Seed needs to be nematode free, and soil sterilization and good rotational practice is needed to minimize nematode population build up.
Onion thrips are also a damaging pest worldwide, particularly in warmer regions. They congregate between the young leaf and the plant neck, extensively damaging leaves and slowing growth.
Onion fly or maggot is another major pest that can be controlled using insecticides. Onions are also very susceptible to foliar diseases and bulb rots. Bacterial diseases significantly reduce bulb quality, e.g. Pseudomonas alliicola, which causes slippery skin within the bulb and P. cepacia – slimy or ‘sour’ outer scales. Are you an onion farmer and would want to share insights or correct this article? give us your feed back in the form below:
Neck rot (Botrytis allii), mildew (Peronospora destructor) rust (Puccinia porri) and leaf rot (Botrytis squamosa) are among key diseases that need fungicidal control.
Crops can require 15 fungicide sprays per season.
Soil sterilization, deep cultivation to bury the source of inoculum, and wide rotations are important in helping minimize disease problems.