Published online by Cambridge University Press: 27 March 2009
The incidence of Sclerotinia sclerotiorum (Lib.) de Bary infection in poppies (Papaver somniferum L.) was assessed 9 days before dry maturity in a field experiment which incorporated the effect of nitrogen and phosphorus fertilizer and fungicidal sprays. Infection occurred mainly on the lower stem in the leaf axils.
Nitrogen fertilizer (100 kg N/ha) had no effect on the incidence of Sclerotinia infection but phosphorus fertilizer (100 kg P/ha) increased the incidence from 19% of plants infected to 39%. Fungicides (2 kg benomyl, 50% a.i., plus 2 kg mancozeb, 80% a.i./ha) applied at 10-day intervals from flowering till harvest reduced the incidence of Sclerotinia infection to one third that of non-sprayed treatments.
Sclerotinia infection occurred late in the crop and had little effect on the dry-matter yields of terminal main-stem capsules, lateral branch capsules or stem and leaves but it did influence the distribution of morphine within the plant. The morphine concentration of terminal capsules was lowered by 13% but the concentration of lateral capsules increased by a similar amount giving a total capsule morphine concentration and yield which was similar in both infected and non-infected plants.
The morphine concentration of the stem and leaves of infected plants was 75% greater than that of uninfected plants but the overall morphine concentration of total plant was similar in both infected and non-infected plants. This distribution pattern was interpreted as a result of the restrictive influence of Sclerotinia infection on the vascular system which disrupted the normal translocation of morphine.