Insect and Disease Management in Lettuce
Insect Pests:
Aphids are the most troublesome insect on lettuce. The use of 3 or 4 per cent Nicotine dust or spraying of 40 % commercial Nicotine sulpahte gives satisfactory control if applied when the temperature is around 18 to 21 0 C.
Diseases:
1. Slimy Soft Rot:
It is the most important diseases particularly in head lettuce. It can be controlled by early removal of the heads and also by keeping the soil uniform in moisture and keeping the surface soil relatively dry.
2. Downy Mildew:
This disease is caused by Bomia lactucae. The typical symptoms are yellow angular areas, delimited by young vines, appearing on the upper leaf surface and sportulation on the lower surface. The lesions turn brown and may coalesce.
Control of disease is by use of resistant varieties like imperial 17, Calmar systemic fungicide effectively control this disease.
3. Mosaic:
It is a virus disease first noticed in the seedling stage. There is a slight inward rolling of the leaves along the main axis followed by a light green to yellow molting of leaves. There may be severe standing and a dull green to yellow molting leaves. There may be severe standing and a dull green to slightly yellow discoloutration of the whole plant. The disease is a seed borne and use of disease free seeds is the only control measure.
4. Tip Burn:
It has been a difficult problem because of multiplicity of cause’s calcium nutrition seems to be basic leading to tip burn. Less calcium is found in tip burn of lettuce. Laticifres rupture near the leaf margins, releasing latex into the surrounding tissue. This cause dark brown spots to from at the points of rapture. Most effectively methods of control are to cultivate resistant varieties such has Salinas, calmor and Monte mar.