MSc

Field dodder (Cuscuta campestris Yuncker) is an obligate stem-parasitic weed native to North America that has spread to various parts of Asia. Cuscuta infestations cause substantial reduction in both the quantity and quality of crop. Recently, cuscuta infestation is reported in many seasonal crops and the severity of these infestations has also intensified following the floods in 2018. If cuscuta infestation is not managed timely, it is too strenuous for mechanical removal; hence, pre-emergence management is the only option. Post-emergence applications of herbicides control cuscuta and also damage the host plant and hence not a viable option in most of the cropped situations.
The present study entitled "Occurrence, germination ecology and management of dodder (Cuscuta campestris)" was conducted from July 2023 to October 2024 to investigate the occurrence of C. campestris in the central zone of Kerala, assess the effect of various ecological factors on its germination and to develop effective post-emergent chemical management strategies against this parasitic weed.
Survey was conducted throughout Kerala to identify the distribution and host range of C. campestris, with focus on the districts of Thrissur, Ernakulam, Palakkad, Kozhikode, and Malappuram. The weed was common in converted rice fields, agricultural fields, rice fallows and roadside wastelands. The incidence was observed in 42 host species belonging to 22 families. Of these, 90% were dicots, and the rest (10%) were monocots. Some of the crops infested with cuscuta were tapioca, banana, bitter gourd, cowpea, chilli, brinjal, tomato, amaranthus and a few ornamental plants. The most preferred weed hosts are Mikania micrantha and Sphagneticola trilobata, which belong to the family Asteraceae.
The experiments were conducted to study the germination response of seeds to various dormancy breaking treatments, pH, burial depth, and moisture levels. Due to the presence of hard seed coat, germination percentage was only 33%. Sandpaper scarification and concentrated H2SO4 treatments resulted in more than 80% germination. Soil moisture status also influenced seed germination and irrigation at alternate and two day interval favoured good germination (85%). The lowest germination (18%) observed in fully saturated soil. The highest germination (85%) was observed at neutral pH (7)
with reduced germination at both higher and lower pH levels. Emergence was the highest from surface soil layer (92%) and reduced at depths beyond 2 cm. Germination was unaffected by light or dark conditions. A temperature range of 28-33 °C favoured germination, but significant reduction observed at 38°C.
Field experiments were conducted at various cuscuta infested locations where the host plants were singapore daisy, tapioca, bitter gourd, and ornamental plants, to evaluate the effects of different chemical sprays on cuscuta and to assess the level of phytotoxicity on both the parasite and the host. Initial results on singapore daisy showed 100% cuscuta control with 5% solutions of urea, ammonium phosphate sulphate (Factamfos), diammonium phosphate (DAP), copper sulphate, ammonium sulphate, and ammonium chloride. A lower concentration of 3% solutions of urea and ammonium phosphate sulphate solution resulted in 86% and 93% control, respectively, by 10 days after treatment (DAT). Solutions of 19-19-19 (5%) and nano urea (4 ml/L) were not effective and resulted in only 13% and 20% control with no injury to host. While herbicides like glyphosate, glufosinate ammonium, and 2,4-D effectively controlled cuscuta and caused significant host damage. Urea and ammonium phosphate sulphate (at 3% and 5%) were the most effective, selectively controlling cuscuta with minimal host phytotoxicity on crops like tapioca and shrubby ornamentals.
The survey on C. campestris revealed its extensive distribution in converted rice fields and wastelands, mainly infesting dicots, and affecting crops such as tapioca, banana, bitter gourd, cowpea as well as various weeds and ornamental plants. Seed dormancy due to hard seed coat and scarification enhances its germination, while neutral pH gave higher germination. However, saturated soil and deep seed burial inhibit its emergence. The study indicates the possibility of using foliar sprays of urea or ammonium phosphate sulphate at 3 and 5% concentrations, along with an adjuvant for managing cuscuta in crops like tapioca, bitter gourd, ornamental plants. However, regrowth was observed within a week post-spray, indicating repeated treatments for sustained management.