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Sondhia S.,National Research Center for Weed Science
Environmental Monitoring and Assessment

A field study was conducted to determine persistence and bioaccumulation of oxyflorfen residues in onion crop at two growth stages. Oxyfluorfen (23.5% EC) was sprayed at 250 and 500 g ai/ha on the crop (variety, N53). Mature onion and soil samples were collected at harvest. Green onion were collected at 55 days from each treated and control plot and analyzed for oxyfluorfen residues by a validated high-performance liquid chromatography method with an accepted recovery of 78-92% at the minimum detectable concentration of 0.003 μg g -1. Analysis showed 0.015 and 0.005 μg g-1 residues of oxyfluorfen at 250 g a.i. ha-1 rate in green and mature onion samples, respectively; however, at 500 g a.i.ha-1 rates, 0.025 and 0.011 μg g-1 of oxyfluorfen residues were detected in green and mature onion samples, respectively. Soil samples collected at harvest showed 0.003 and 0.003 μg g-1 of oxyfluorfen residues at the doses 250 and 500 g a.i. ha-1, respectively. From the study, a pre-harvest interval of 118 days for onion crop after the herbicide application is suggested. © 2009 Springer Science+Business Media B.V. Source

Sushilkumar,National Research Center for Weed Science | Ray P.,National Research Center for Weed Science
Crop Protection

Augmentative release of biocontrol agents has been largely successful for the management of insect pests but it has not been a common approach for weed management. Augmentation methods need to be developed for weed management, especially for pernicious weeds like Parthenium hysterophorus L., commonly known as pathenium or carrot weed. The leaf beetle Zygogramma bicolorata is a potential biocontrol agent of P hysterophorus. Initial release of biocontrol agents is subject to uncertainties as to whether timely population built-up will take place in sufficient numbers. Several augmentative releases may be required to ensure early establishment of the biocontrol agents, for successful biological control of noxious weeds including pathenium. We made augmentative releases of larvae or adults of Z. bicolorata each to three sites, severely infested with pathenium at Jabalpur, India consecutively for a period of three years. Initially 10 larvae or adults per sq m were released in each plot, followed by a second, third and fourth release of 3, 1.5 and 1.5 larvae or adults per sq m at an intervals of 3, 7 and 14 days after the first augmentation. The pathenium at augmented sites were completely defoliated in 45 and 60 days by larvae and adults respectively. There was also a reduction in the pathenium density and plant height in the augmented sites as compared to the non-augmented sites. Over a period of 3 years augmentation resulted in a noteworthy negative effect on the weed. © 2011 Elsevier Ltd. Source

Sushilkumar,National Research Center for Weed Science | Ray P.,National Research Center for Weed Science
Biocontrol Science and Technology

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. © 2010 Taylor & Francis. Source

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