Irish potato (SolanumtuberosumL.) needs sound production practices for good yields.
From selection of planting materials, planting, pest and disease control, harvesting and post-harvest handling, everything must be done right.
The crop’s seeds should be sourced from a certified dealer, where they have been well-graded and are uniform in size. Certified seeds are usually free of deadly diseases like bacterial wilt which causes extensive losses.
Prior to planting, perennial weeds in the field should be controlled using non-selective herbicides that are present in the market like Touchdown.
The farm should be ploughed to a fine tilthe and soil amendments like farmyard manure incorporated and all the weeds removed. The depth should be about 40cm since potato roots can go deeper.
Once the farm is ready, preferably at the onset of rains, furrows with a depth of at least 15cm should be prepared and all the fertilisers required placed. It’s important to note that fertilisers should be incorporated into the furrow prior to planting since the plants will require maximum nutrients level 21 days after germination as they start to tuberise.
The furrows should be 75cm apart and seeds should be 30 to 35cm (size 1) or 35 to 40cm (size 2) apart.
This will ensure that the plants will have sufficient space to establish and minimise competition for nutrients. After placing the seeds in the furrows, they should be covered leaving the field nearly flat.
SCOUTING FOR PESTS
Weeding manually or a second herbicide application can be done after planting in case there are weeds. This will ensure that germination of the potatoes will happen weed-free. Germination usually takes place after two weeks when sprouting is noticeable.
Serious crop management practices usually begin after germination since it’s at that stage that pest and diseases start to establish.
Scouting for pests and diseases is, therefore, very important during the vegetative phase of the crop. With proper nutrition, pest and disease control, a potato plant can grow as tall as 1.2m high.
Sucking pests especially, aphids, and whiteflies are the top enemies of the crops. Others include tuber moth, caterpillars and the American leaf miner (Tuta absoluta). Insecticides such as Karate, Actara, Match, Dynamec and Pegasus effectively eliminate the pests. Caution should be taken to use the insecticides in the correct manner to achieve desired results.
The most destructive disease is potato blight, caused by a fungus called Phytophthora infestans. The disease affects both the leaves and the stems and once established and no control measures are taken, it can cause up to 100 per cent loss within five days.
The affected parts will have dark water soaked lesions and after a few days, the whole plant surface appears ‘as if the crop has been set on fire’. Weekly spray regime with fungicides is effective in managing the disease and increasing yields.
A preventive fungicide named Daconil is applied when the conditions that favour disease development (high humidity and fluctuating temperatures) are prevailing.
Once the disease is noticed, a rotational programme involving Ridomil and Revus on a seven-day cycle is followed. This will help to maintain the crop in a clean-state, free of pests and diseases.
Githeng’u is a horticultural expert, Egerton University