No abstract

The hemiparasitic plant, Dendrophthoe falcata (L.f.) Etting. known as Loranthus is a stem parasite, mostly prefers Mangifera indica L. (mango) as its host. Remarkable damage of the mango crop due to the adverse effect of Loranthus was identified in the field area. The occurrence and host preference of the D. falcata was systematically studied at eight field sites of Vizianagaram District. The vegetative, reproductive and parasitic characteristics of D. falcata were recorded periodically. The effective management strategies to control Loranthus were not employed in the study area because of the lack of knowledge on the host-parasite interaction. Keeping in mind, the investigation was conducted (October 2018 to June, 2019) in mango fields of Vizianagaram District of Andhra Pradesh to explore the biology, the host specificity, the occurrence, the pollination, the bird-host-parasite interaction and the effective control methods of D. falcata.

A b s t r a c t A r t i c l e I n f oTrianthema portulacastrum L., commonly known as desert horse purslane is a member of Aizoaceae, interfere with many economic crops and treated as one of the serious weed in India and around the world. It is a native plant of South Africa but widely distributed in India, Sri Lanka, Pakistan and many parts of the world. It has become a noxious weed due to competition for yields in many crops and causing significant reduction in the yield. For instance, its infestation in cotton, maize and direct-seeded rice reduce crop yields by 32-60%, up to 60-70% infestation of this weed has been reported in pigeon pea and soybean fields and 80-90% in maize and brassica fields. The common weed control methods such as cultural practises, mechanical and herbicide treatments does not consider for the effective management of this weed due to their failures. Recently, the successes of Biological control agents over many herbs and alien weeds attracted researchers with their eco-friendly tactics. Therefore, a systematic field study was conducted for preliminary screening of natural enemies against horse purslane weed which would be an effective biocontrol agent after extensive work. An ascomycetes fungus, Gibbago trianthemae Simmons was isolated from parasitized leaves of horse purslane and the identity was confirmed by relevant literature and the biocontrol potential of the pathogen evaluated.

Trianthema portulacastrum L. (commonly known as horse purslane) is a noxious weed of several economically important field crops in tropical regions of the world. An intensive work on the screening of the biocontrol agents was accomplished through in vitro epidemic study to control weed populations. The foliar disease symptoms on infected weed plants caused by fungal pathogens represented as round to irregular maroon spots with dark borders and the epidemic was identified as leaf spot disease. The pathogen allied with the infection of horse purslane was isolated from infectious propagules by inoculation of leaf bites on a nutrient medium, potato dextrose agar (PDA). The causal agent of leaf spot was confirmed as Gibbago trianthemae Simmons by Koch's postulates. The mycoherbicide ability of G. trianthemae has been examined through visual (standard area diagram) and statistical methods (analysis of variance using the Microsoft Office Excel-Data Analysis Tool Pack 2007). The results revealed that the pathogen causes significantly (P < 0.05) severe infection on host weed and destructs the weed population by leaf spot diseases. The findings of the research suggested that the isolate G. trianthemae is highly virulent and host-specific, and recommended for further studies as a promising biocontrol agent against horse purslane weed.

No abstract