First report of the parasitic invasive weed field dodder (Cuscuta campestris) parasitizing the confamilial invasive weed common morning-glory (Ipomoea purpurea) in Shandong, China.
On 20 September 2019 and 18 July 2020, I. purpurea was found to be parasitized by a dodder species (also Convolvulaceae) in Lushan Mountain, Shandong province, China. Within an area of ~100 m2, dozens of individuals of common morning-glory were parasitized by the leafless stems of dodder. After removal of the haustorial connection of the dodder stem from the I. purpurea stem, brownish black lesions around uneven holes were visible on the I. purpurea stem, with broken haustoria clearly visible to the naked eye remaining in the I. purpurea stem. Anatomical results showed that the haustoria of dodder penetrate I. purpurea stem and xylem elements to connect the vascular systems of both the parasitic and host plant. Based on morphological characteristics of stems, inflorescences, calyx, corolla, stamens, and capsules as described in Costea et al. (2006), this dodder was identified as Cuscuta campestris. The identity of the dodder species was further confirmed by molecular analysis. This is thought to be the first report of the parasitic invasive weed C. campestris parasitizing the invasive weed I. purpurea in Shandong province of China. This is also the first report of Cuscuta species parasitizing confamilial Ipomoea species.