Puja Ray

Evaluation of Indigenous Fungal Pathogens from Horse Purslane (Trianthema portulacastrum) for Their Relative Virulence and Host Range Assessments to Select a Potential Mycoherbicidal Agent

Abstract Periodic surveys were conducted to seek potential indigenous fungal agents for development as mycoherbicides against horse purslane, a major weed of agricultural fields in India. Pathogenic fungal species were isolated and identified from naturally infected horse purslane. The biocontrol potential of these pathogens for horse purslane was evaluated by studying their host range and virulence under growth chamber and greenhouse conditions. Three candidates, Alternaria alternata, Fusarium oxysporum, and Phoma herbarum, were identified as potential candidates for biological control of horse purslane. Preliminary host-range tests and pathogenicity studies, conducted using 45 crop and weed plants belonging to 18 families, demonstrated that P. herbarum provided effective weed control and was safe to most of the plant species tested. Further mycoherbicidal application of P. herbarum as plant spray under field condition caused mortality of horse purslane 60 d after application of the inoculums. Phoma herbarum is a good mycoherbicide candidate against horse purslane. Nomenclature: Alternaria alternata (Fr.) Keissler, Fusarium oxysporum Schltdl., Phoma herbarum Westendorp, horse purslane, Trianthema portulacastrum L. TRTPO.

Deleterious effect of herbicides on waterhyacinth biocontrol agents Neochetina bruchi and Alternaria alternata

Abstract The integration of biological and herbicidal methods is advocated to manage waterhyacinth, but this can only be achieved when herbicides are nontoxic to the biocontrol agent. Therefore, laboratory experiments were conducted to determine the toxic effect of herbicides on the insect biocontrol agent, the waterhyacinth weevil, Neochetina bruchi Hustache, and phytopathogen, Alternaria alternata, with two commonly used herbicides, glyphosate and 2,4-dichlorophenoxy acetic acid at three recommended doses. The herbicides were sprayed on the waterhyacinth weevils and added to the nutrient media of A. alternata. 2,4-D caused higher weevil mortality (6.7, 13.3 and 15.6%) as compared to glyphosate (3.3, 5.6 and 11.1%), at three doses over 72 h. There was also a decrease in feeding in the herbicide treated leaves. When the weevils were allowed to move freely between the herbicide treated and untreated plants, higher orientation of the weevils was found on the untreated waterhyacinth than on the treated ones. Neither of the two herbicides actually killed the fungus but both inhibited its growth. Glyphosate though, delayed mycelial growth yet stimulated sporulation while 2,4-D inhibited both growth and sporulation. Glyphosate at low concentration did not affect the virulence of A. alternata, while fungi grown on 2,4-D amended plates lost their virulence.

Fungi associated with Eichhornia crassipes in South Africa and their pathogenicity under controlled conditions.

Eichhornia crassipes Mart. Solms-Laubach (Pontederiaceae), water hyacinth, continues to be the worlds worst aquatic weed. In South Africa, considerable research has been conducted on biological control agents associated with water hyacinth, with the release of six arthropods and one fungus, but little is known about the occurrence and impacts of native phytopathogenic fungi. Nation-wide surveys were conducted in 2010 and 2011 on various aquatic bodies of South Africa to identify the fungal pathogens associated with water hyacinth. Diseased plant parts were collected and fungi were isolated and identified. Some 250 isolates belonging to more than 25 genera were collected. Some of these represent new host records, as well as undescribed taxa. Isolates of Acremonium zonatum (Sawada) Gams, Alternaria eichhorniae Nag Raj and Ponnappa, Bipolaris hawaiiensis (M.B. Ellis) Uchida and Aragaki, Fusarium Link, Myrothecium roridum Tode ex Fr. and Ulocladium sp., showed the highest pathogenicity and have the potential to be useful in complementing the ongoing biocontrol programme on water hyacinth in South Africa.

Activity enhancement of Zygogramma bicolorata, a biocontrol agent of Parthenium hysterophorus, by temperature regulated diapause aversion

Abstract Diapause is a unique strategy of dormancy in insects to avoid unfavourable conditions. The exotic beetle Zygogramma bicolorata, is an effective biological control agent of Parthenium hysterophorus in India, Adults diapause in soil during December to May. As a result, there is delay in its effectiveness on the plant that reaches to flowering and seed production by the time the beetle is able to build up its population after emerging from diapause. Therefore, a study was conducted to explore possibilities of diapause aversion by temperature regulation. Results indicated that exposure of newly emerged adults to heat treatment of 35°C and to low temperature of 10°C could reduce diapause in Z. bicolorata. The low temperature can also be used as a medium for the storage of the mass reared beetles for a long time without having negative effect on their longevity and fecundity.

Microbial agents for control of aquatic weeds and their role in integrated management

Aquatic ecosystems throughout the world are threatened by the presence of invasive aquatic plants, both floating and submerged. Some of the aquatic species, such as water hyacinth (Eichhornia crassipes [Mart.] Solms), alligator weed, Alternanthera philoxeroides (Mart.), giant salvinia, Salvinia molesta D.S. Mitchell and water lettuce (Pistia stratiotes L.), Griseb. despite being relatively minor problems in their native range, have become major invaders of aquatic habitats in other parts of the world after having escaped from their natural enemies. Unchecked growth of aquatic vegetation is generally undesirable and reduces the value of the water resource. Despite adopting all control options including manual, mechanical, chemical and classical biological, the problem persists. The current weed management is oriented towards finding approaches that are effective in controlling the weed and reducing environmental contamination from herbicides. Plant pathogens have been gaining increasing attention and interest among those concerned with developing environmentally friendly, effective and compatible approaches for integrated management of the noxious weeds. This paper discusses some of the major microbial agents associated with aquatic weeds and their increasing role in integrated weed management.

A Report on Intergeneric Mating Among Butterfly Species in Nature

A rare sight of intergeneric mating of two lycaenid butterfly species, Rathinda amor Fabricius (Monkey Puzzle) and Anthene emolus Godart (Common Ciliate Blue) is being reported for the first time from Chintamani Kar Bird Sanctuary, Kolkata, India.