Effects of Haulm Killing on Seed Potato Quality

In Northern Finland (65º40'N), haulm killing is used in seed potato production primarily to regulate tuber size. The most common haulm killing method is mechanical-chemical. We studied the effects of mechanical and mechanical-chemical haulm killing methods on seed potato quality, comparing to natural haulm senescence (control). The timing of haulm killing (when no more than 5% of the crop tubers were over 50 mm in size) and the time between destruction and harvest (21–26 days) were similar to practices followed in seed-potato production. Matilda was the cultivar used. In this study, haulm killing clearly increased plant disease pressure, as black scurf (Rhizoctonia solani) could be seen in tubers whose haulm had been destroyed. Black scurf was also observed in mechanical haulm killing. The yield from naturally senesced haulms had less black scurf than the other treatments. In addition, when haulm senescence occurred naturally, crop yield and starch content were highest compared to other treatments.