Interaction between nutrient supplies and aphid numbers on potato (2001-2002)

We set up our experiment on 11 potato varieties with 4 treatments and 4 replications in Hungary in 2001 and 2002. The aim of the experiment was to investigate the interaction between the nutrient supplies of potato and the change in the numbers of aphids feeding on the potato plant. In our experiment we sorted 4 nutrient levels according to the recommendations of soil analyses and variety holders. During the growing period we counted the numbers of aphids feeding on the potato leaves every week and controlled the virus infestation with ELISA-method after harvesting. Using the data we concluded that there is an interaction between the nutrient supplies of the potato plant and the numbers of aphids feeding on the leaves. The numbers of aphids on the plots with good nutrient supplies exceeded the numbers of aphids counted on the control plots. In 2001 and 2002 we counted 1150 and 1205 aphids per 100 plants on plots with nutrient supplies in the peak time of swarming compared to the control plot with numbers of 799 and 978. Beside nutrient supplies weather conditions influenced the numbers of aphids, too. Different temperature and rainfall conditions in both years affected the intense and progress of swarming. This can be the reason for the appearance of the first aphids (in the last week of April in 2001 and in the first week of May in 2002) and the time of swarming (15-18 June in 2001 and 28-31 May in 2002). Summer heat and hot days lowered the numbers of aphids. In 2002 following the heat in June and July the population escalated. After harvesting we confirmed our hypothesis from the tuber samples by ELISA-method: The virus infestation was higher on plots with intensive growing practice than the virus infestation on the control plots. In 2001 the rate of PLVRV infestation on Agria variety of the control plot yielded 18.7%. At the time of the 3rd treatment it increased to 37.2%. In 2002 the control had an infestation rate of 12.6% and 40.2% at the time of the 3rd treatment. In 2001 the rates of PVY infestation were 15.2% and 23.4% respectively and in 2002 they were 14.8% and 18.2% respectively. As the interaction between nutrient supplies, changes in the numbers of aphids and the virus infestation are not yet well known, further experiments are required.