Abstract
Seed potato crop in the north-western parts of India is largely grown after paddy in strict compliance to various components of the Seed Plot Technique, with planting during the first fortnight of October and haulm-cutting in the last week of December for minimum exposure to virus-transmitting aphid vectors. Owing to the government restrictions on the date of seeding and transplanting of paddy to maintain the level of the underground water table, the harvesting of paddy often gets delayed in the region. However, quality seed potatoes can be produced only if the planting and haulm cutting dates are adjusted as per the activity of virus-transmitting insect vectors. Therefore, we conducted field experiments for 2 years to study the effect of planting dates on plant growth parameters and tuber yield of two popular cultivars Kufri Pukhraj and Kufri Jyoti. Vector populations were also examined in all the planting dates until dehaulming. Results showed that the yield of seed-size tubers was at par for the first three dates of planting (15 Oct., 25 Oct., and 05 Nov.). The number and yield of over-sized tubers decreased sharply, and that of under-sized tubers increased with progressive delay in planting. The activity of virus-transmitting aphids and whiteflies remained low from mid-November to mid-January, with an appreciable effect of the daily temperature. Hence, planting up to the last week of October and dehaulming before the second week of January do not affect the yield of seed-size tubers significantly. On the other hand, to ensure the quality of the product, continuous monitoring of vector activity is necessary.
