Journal of Research in Weed Science
Volume:5 Issue: 1, Mar 2022

Quizalofop ethyl applied regularly in broad leaved field crops as post emergence to control annual and perennial grass weeds. The experiment was carried out to determine the harvest time residues of quizalofop ethyl in soil and ground nut plant using ultra sonic bath extraction and HPLC-DADin Randomized block design. The quizalofop ethyl (5% EC) was applied at four rates along with control treatment. Standardized methodology supported by recovery studies was adopted to estimate quizalofop ethyl residues on groundnut and soil. The recoveries at different spiking level ranged from 74.0 to 99.3 % with the quantification limit of 0.01 μg g-1. The quizalofop ethyl residue in soil was ranged from 0.012 to 0.038 mg/kg at harvest. The residues were below the quantification limit (0.01 mg/kg) and maximum residue limit (MRL) in groundnut haulm and kernels. The study established that quizalofop ethyl at 50 g/ha can be used safely to control grass weeds with the pre harvest interval of 110 days.

A study was conducted in the net house of Department of Agronomy, Bangladesh Agricultural University as well as in farmers’ fields at Digarkanda village of Mymensingh district to evaluate the in situ and ex situ floristic diversity of the weed seed bank in rice. Five fields were surveyed for in situ evaluation with four replications and soil samples (1.5 kg soil) were collected and placed in plastic pots in the net house for ex situ study. Diversity was computed by the Shannon index (H’). a total of 33 weed species belonging to 17 families were found under in situ whereas, 37 species belonging to 22 families germinated under ex situ condition. The family Cyperaceae had the highest species richness and density under both conditions. Based on importance value, the five most dominant species under in situ condition were Eleocharis atroperpurea,Cyperus difformis, Alternanthera philoxeroides, Azolla pinnata and Echinochloa crusgalli. Whereas, under ex situ condition, two new weed species i.e. Fimbristylis miliaceae and Lindernia antipoda were found dominant instead of Alternanthera philoxeroides and Azolla pinnata and rest of the three species remained the same with slightly different rank and order. Weed density and diversity were also higher under ex situ condition than in situ condition. Ex situ condition had higher H’ index (H’=2.396) than in situ condition (H’=2.230). The highest percentage of weed emergence was observed within the first month of commencement of germination trial under both in situ and ex situ conditions. The information obtained from the study would help to determine the infestation potential of identified weed species and predict the upcoming threat which could lead to construct and improve successful weed management strategies.

The objective of this work was to assess the photosynthetic efficiency of sugarcane crop, in pre-emergency application, of two herbicides inhibiting photosynthesis. For sugar cane cuttings planting (variety SP80-3280), pots with a capacity of 8 dm3 were used. Atrazine and tebuthiuron application was performed by using a stationary spray installed in laboratory conditions and after treatment application, plants were transported to a green house where were kept until the end of the trial.  The reading of transport rate (ETR) was conducted in the middle portion of the youngest leaves of sugarcane with a portable fluorometer, with intervals for ETR assessment constituted by: 16, 17, 19, 25 and 30 days after herbicide application. It was also realized visual analysis of phytotoxiciy performed 30 days after application. The results showed that tebuthiuron herbicide caused greater reduction in the rate of electron transport than atrazine. In relation to herbicide symptoms, there was no significant difference between the studied herbicides. At the end of the work it could be verified that the chosen method using fluorometer to measure the rate of electron transport after herbicide application was adequate, allowing verifying sugar cane crop intoxication, even before any visual detection of herbicides performance in plants.

Rice is an important staple food crop of India. Several factors are responsible for reducing the yield of Kharif rice. However, weed infestation is the major threat to productivity of Kharif rice. Weeds by the virtue of their high adaptability and faster growth dominate the crop habitat and reduce the yield potential of the crop. These weeds could be controlled through various methods. Manual method is though very common but cost intensive. Herbicides when applied alone are although economical but may have limitation of resistance development and shift in weed flora etc. Therefore, presently there is a need to use high efficacy herbicides in combination coupled with broad spectrum nature to control the complex weed flora in Kharif rice.

Ryegrass (Lolium rigidum Gaudin) is a most prevalent weed in Bizerte region and caused losses in yield. Farmers used herbicides to control ryegrass in cereal crops. Thirteen herbicides (ALS inhibitors, ACCase inhibitors and PSII inhibitors) were used in the field experiment to evaluate their efficacy and their effect on yields of wheat and of ryegrass. The trial was installed in Randomized Complete Block Design (RCBD) in Bizerte. Seeds of ryegrass collected from Bizerte during surveys were the subject of the resistance detection to the ALS inhibitor herbicides [AmilcarWG® (mesosulfuron+iodosulfuron)] and to the ACCase inhibitor herbicides [Topik® (clodinafop-propagyl)] by a pot experiment method. The results of the field experiment showed that only Tolurex® [Chlortoluron (PSII inhibitor)] has the best efficacy (83.6%), but all other herbicides (ALS and ACCase inhibitors) have insufficient efficacy on ryegrass. Then, over 60% of ryegrass populations were escaped to treatments ACCase and ALS-inhibiting herbicides that are not statistically different. The low efficacy of herbicides (ALS and ACCase inhibitors) was not explained by a high density of ryegrass, but by the presence of herbicide resistance in ryegrass populations in Bizerte. These results were confirmed by the pot experiment method. The count of the surviving plants of ryegrass (30 DAT) in pot experiment method revealed that 70% of ryegrass populations are resistant to both herbicides inhibitors (ACCase and ALS). Similarly, the percentage of reduction in fresh weight of ryegrass, compared to untreated control, showed over 80% of the ryegrass populations was resistant to ACCase inhibitor herbicides and to ALS inhibitor herbicides.

A field experiment was conducted at Cotton Research Scheme Farm, VNMKV, Parbhani during kharif season 2015-16 and 2016-17 in randomized block design with seven treatments in three replicates. Sowing was done by dibbling with spacing 120 cm x 30 cm for Bt.cotton and for soybean 60cm x 5cm. The result indicated that, spraying of pre emergence application of Oxyflurofen 23.5% EC at 0.1 kg/ha ai followed by hand weeding and hoeing at 6 week after sowing (WAS) recorded significantly highest seed cotton equivalent yield (1868 kg ha-1), gross monetary returns (8159 Rs/ha) and net monetary returns (39024 Rs/ha) over rest of the treatment except it was on par with application of pre emergence application of Pendimethalin 30% EC at 0.75 kg/ha ai with hand weeding and hoeing at 6 WAS and Alachlor 50 % EC at 2.0 kg/ha ai followed by hand weeding and hoeing at 6 WAS. The treatment Spraying of pre emergence application of Oxyflurofen 23.5% EC at 0.1kg/ha ai followed by hand weeding and hoeing at 6 WAS was found productive and profitable followed by Pendimethalin 30% EC at 0.75 kg/ha ai with hand weeding and hoeing at 6 WAS and Alachlor 50 % EC at 2.0 kg/ha ai followed by hand weeding and hoeing at 6 WAS.