The production costs up to harvest remain the same, so harvesting a low percentage of lettuces will clearly affect your profits.
This is a fast-growing crop and any setback is serious. You cannot play catch-up with lettuce; you need to do it the right way from the start. Transplants must be planted into moist soil and be moist themselves as well. Do not plant them into dry soil and trust that irrigation will make up the shortfall.
The lettuce plant reacts very quickly to stress, no matter how short this might be, in order to maximise its chances of surviving to bear seed later. And recovery after stress takes time. This mechanism can be seen when you sow seeds in very hot conditions. A few may germinate, but the rest will wait, despite the conditions becoming favourable for germination. Instead, they may only germinate when the first plants are nearly ready for planting.
The plant should be in active growth mode at planting, with enough nitrogen in the plug for it to continue growing at its maximum rate. Also, ensure that the plants are not covered by soil, there are no gaps and all plants look the same.
The first nitrogen application should be carried out very early, within the first week of transplanting. This ensures constant vigorous growth and contributes greatly to the uniformity of the crop so that as many heads as possible are ready to cut at one time.
Walk through your lands often. One of the things to look for is uniform growth. If you find patches that are at different stages, you need to determine why this is so. Usually it’s related to water or nitrogen.
Examine individual plants that are not growing at the same pace as the others. Check the roots. Often J-rooting is the cause of stunting, as bent over roots will not function properly. Remind your staff not to take shortcuts when planting.
Disease And pests
One of the most important things to look for is the first signs of disease. It is far easier to control a disease if you catch it as soon as the first symptoms appear. Apart from the initial damage, when fungus becomes reproductive, millions of spores are released, making the likelihood of a greater percentage of infection a certainty.
This applies to both fungal and bacterial diseases. The saying ‘A stitch in time saves nine’ is highly applicable here. The same applies to insect pests. Early detection means easier control; in the case of bollworm, late detection usually equates to no control at all.
Saving thousand of rand
After harvesting, look at the market price and calculate the cost of not doing regular inspections by the number of bollworm-damaged heads left behind. A 10-minute walk on the land can often save thousands of rand.
It can also save labour costs; when there is damage, harvesters have to examine each head carefully before packing, and this wastes a great deal of time.
Bill Kerr is a vegetable specialist and a breeder of a range of vegetables.