Recent Pre and Post emergence herbicides molecules for field crops with mode of action and its phytotoxicity

efficient use and proper knowledge of herbicide application makes it environment safe and minimizes ts residues in ecosystem.

1. WELCOME

2. Recent Pre and Post emergence herbicides molecules for field crops with mode of action and its phytotoxicity Presented In Doctoral Seminar BY Mr. Khedekar M. A. REG. NO. Ph.D. Post graduate Institute MAHATMA PHULE KRISHI VIDYAPEETH, RAHURI

3. CONTENT Introduction Herbicides Mode of Action Phytotoxic symptoms Case studies

4. Introduction What is hebicides ? Herbicide , an agent, usually chemical, for killing or inhibiting the growth of unwanted plants, such as residential or agricultural weeds and invasive species . Pre emergance :- Application of herbicides before a crop or weed has emerged. e.g . Atrazine, Pendimethalin .

5. Post Emergence :- Herbicide application after the emergence of crop or weed is referred as post-emergence application. When the weeds grow before the crop plants have emerged through the soil and are killed with a herbicide then it is called as early post-emergence.

6. What is Phytotoxicity ? It the ability of chemical substance to cause harmful or toxic effects on plants. Phytotoxic Symptoms :- Abnormal Growth . Certain parts such as the aerial roots or suckering, or perhaps the entire plant will experience excessive growth. Chlorosis . Spots or tip margin or leaf yellowing appears. Leaf Distortion . The leaf crinkles, curls, or appears to be cupping. Stunting . The plant in its entirety is reduced in size, or specific parts such as the fruit, roots, or flowers may look smaller in comparison to the rest of the plant.

7. Pre Emergence Herbicides Atrazine :- Atrazine is a herbicide that is used to stop pre- and post-emergence broadleaf and grassy weeds in crops such as sorghum, maize, sugarcane, lupins , pine, and eucalypt plantations Formulation Registerd :- a) 2,4-D sodium salt a.i . 80% w/w min. b) 2,4-D amine salt 58% SL 22.5% SL c) 2,4-D ethyl ester 38% EC, 4.5% Gr, 20% WP Atrazine is a herbicide of the triazine class IUPAC ID:  1-Chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine

8. Trade Names :- Atranex , Atratraf Avialable Formulation:- 50 % WP

9. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required kg ha 1 Dilution in water (L) Maize 0.5-1 1-2 500-700 Bajra , 1-2 2-4 500-600 Sugarcane 1-2 2-4 500-600 Sorghum 1-2 2-4 500-700 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

10. Mode Of action Like other triazine herbicides, atrazine functions by binding to the plastoquinone -binding protein in photosystem II, which animals lack starvation and oxidative damage caused by breakdown in the electron transport process. Oxidative damage is accelerated at high light intensity . Biodegradation Atrazine degrades in soil primarily by the action of microbes. The half-life of atrazine in soil ranges from 13 to 261 days. Atrazine biodegradation can occur by two known pathway

11. hydrolysis of the C-Cl bond is followed by the ethyl and isopropyl groups, catalyzed by the hydrolase enzymes called AtzA , AtzB , and AtzC . The end product of this process is cyanuric acid, itself unstable with respect to ammonia and carbon dioxide. The best characterized organisms that use this pathway are of Pseudomonas sp. strain ADP . Dealkylation of the amino groups gives 2-chloro-4-hydroxy-6-amino-1,3,5-triazine, the degradation of which is unknown. This path also occurs in Pseudomonas species, as well as a number of bacteria .

12. Phytotoxicity Symptoms phytotoxicity tests appear initially as marginal chlorosis or yellowing in mature leaves, followed by chlorosis. The leaf veins remain green unless extremely high rates are tested. Symptoms generally do not appear the following year and new foliage is not affected unless excessive rates are tested, causing new leaves to become necrotic. Clyde et al. 2008

13. Effect Of herbicides on Weed Density ( m 2 ) in winter Maize Treatment Chenopodium Spp. Convulses Arvensis Phalaris minor Parthenium Hysterophorus 40 DAS 90 DAS 40 DAS 90 DAS 40 DAS 90 DAS 40 DAS 90 DAS Control 6.52 6.68 3.81 3.81 4.14 4.21 00 7.60 Atrazine 0.25 kg ha 1 ( PE 1-3 DAS) 1.48 1.06 1.35 1.30 1.85 1.74 00 7.31 Atrazine 0.50 kg ha 1 ( PE 1-3 DAS) 0.71 0.71 1.17 1.35 1.77 1.68 00 5.80 Weeding 20 and 40 DAS 2.01 2.34 1.06 1.09 1.23 1.25 00 7.44 LSD ( P= 0.05) 0.17 0.16 0.13 0.57 0.17 0.15 00 4.14 Verma Et al . (2009)

14. Effect Of herbicides on Growth characters in winter Maize at Harvest Treatmenr Plant height (cm) Culm Girth (cm) LAI (cm 2 ) CGR ( g DM/day ) Control 168.17 5.84 3.50 3.13 Atrazine 0.25 kg ha 1 210.50 7.47 5.18 3.63 Atrazine 0.50 kg ha 1 215.87 7.86 5.91 3.88 Weeding 20 and 40 DAS 211.18 7.88 5.86 4.07 LSD ( P= 0.05) 4.92 0.28 0.27 0.17 Verma Et al . (2009)

15. Results The winter maize was predominated with abundant population of Chenopodium album which appeared to be very aggressive at initial growth and developmental stages of maize. The competition of C. album with other weed species in the experimental field, namely, P. minor and C. arvensis was quite obvius . The weed population decreased significantly by weed control measures (Tables 1). Atrazine 0.50 kg/ha registered 79.12% weed control efficiency followed by two weedings with 87.55% WCE and one weeding fb earthing treatment with maximum 93.88% WCE at 45 DAS indicating suppression of first flush of weeds successfully . ( Varma et al. 2009)

16. Pyroxasulfone IUPAC Name :- 3- [[5-( difluoromethoxy )- 1-methyl-3- ( trifluoromethyl )pyrazol-4-yl] methylsulfonyl ]- 5,5-dimethyl- 4H-1,2-oxazole. Group :- Pyrazole Formulation registerd :- Pyroxasulfone 85% WG Recommended dose :- 127.5 a.i g/ha Trade Names :- Zidua ( BASF ) Weeds Controlled :- Phalaris Minor.

17. Mode Of Action Cell Division Inhibitor It inhibits multiple eloangation steps to produce 20, 22, 26 and 28 chains fatty acids in VLCFAE production system. A pre-emergence, selective, translocated herbicide that inhibits meristematic growth. Weeds absorb the herbicide soon after germination and may grow for a few days or weeks before dying . Pyrazole , isoxazoline or chloroacetamide group of chemicals Inhibits very long chain fatty acid production which disrupts shoot elongation.

18. The injury symptoms of pyroxasulfone were growth inhibition and a slight twisting on corn and growth inhibition and leaf cupping on soybeans . Discoloration of leaves. Phytotoxicity Symptoms Yoshihiro Yamaji 2014

19. Effect of Pyroxasulfone weed density and biomass of P. minor in wheat at 70 DAS at Ludhiana Treatment Dose a.i g/ha Application time Weed Density Weed Biomass WCE Pyroxasulfone 85 PE 2.07 3.21 50.0 Pyroxasulfone 102 PE 1.24 2.18 72.2 Pyroxasulfone 127.5 PE 1.07 1.73 88.9 Pendimethalin 750 PE 1.30 2.20 72.2 Sulfosulfuron 25 PoE ( 25 DAS) 2.13 3.44 38.9 Clondofop 60 PoE ( 25 DAS) 3.89 3.69 27.8 Control - - 5.25 14.37 LSD P=0.05 - - 0..61 0.87 - Kaur et al. 2019

20. Pendimethalin Pendimethalin is an herbicide of the dinitroaniline class used in premergence and postemergence applications to control annual grasses and certain broadleaf weeds. IUPAC name :- 3,4-Dimethyl-2,6-dinitro-N-pentan-3-yl- aniline Trade names :- Stomp, Eraser, Pendimide , Pendin Available Formulation :- 30 % EC ( Liquid) Weeds Controlled :- Phalaris minor, Chenopodium album, Melilotus alba, Portulaca oleracea , Anagallis arvensis

21. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required (kg, ml, L) ha 1 Dilution in water (L) Wheat (pre- em , 0-3 DAS) Light soil- 1.0 kg 3.3 L 500-700 Medium soil- 1.25 kg 4.2 L Heavy soil- 1.5 kg 5.0 L Rice 30 EC (6-7 DAT) 1-1.5 kg 3.3-5 L 500-700 Rice 5% Gr (6-7 DAT) 1-1.5 kg 20-30 kg Cotton 30 EC (0-3 DAS) 0.75-1.25 kg 2.5-4.16 L 500-600 Soyabean Greengram Redgram 30 EC (0-3 DAS) 0.75-1 kg 2.5-3.3 L 500-600 Sorghum Bajara 30 EC (0-3 DAS) 0.75-1 kg 2.5-3.3 L 500-600 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

22. Mode of action Pendimethalin inhibits root and shoot growth . It controls the weed population and prevents weeds from emerging, particularly during the crucial development phase of the crop. Its primary mode of action is to prevent plant cell division and elongation in susceptible species . Cause mitotic cell abrasion. Disruption of nuclear cell division Types of formulations: Pendimethalin is available in granular, dispersible granular, and emulsifiable concentrate formulations Gupta et al. 2006

23. Effect of resource conservation techniques, cultivars and weed control treatments on weed dry matter (60 DAS), yield attributes and yield of durum wheat. Treatment Dry matter (g/m2 ) Spike length (cm) Grains/ spike Grain yield (t/ha) Grassy Weeds BLW RCTs Zero Tillage 13.3 14.2 9.4 47.3 5.28 Conservation Tillage 17.8 12.5 9.3 45.7 5.12 FIRBS 19.5 13.6 9.5 46.2 5.14 LSD (P=0.05) 1.1 1.0 NS NS NS Cultivars WH896 18 13.7 9.4 46 5.13 WH912 16.7 13.7 9.1 44.1 4.96 PWD291 16 13 9.7 49.2 5.46 LSD (P=0.05) 2.4 NS 0.5 2.4 0.27 Herbicide Pendimethalin ( PE 1.5 kg /ha) 7 6.8 9.7 50.3 5.76 Weedy check 26.8 20 9.1 42.5 4.60 LSD (P=0.05) 0.2 0.3 0.1 0.4 0.04 Jat et al. 2013 FIRBS- Furrow-irrigated raised-bed system

24. Post Emergence Herbicides Tembotroin ( Laudis ) Topramezon ( Tynzer ) Ametryn ( Tamar) 2, 4-D ( Weedmaar ) Oxyflurofen ( Goal ) Imazethapyr ( Persuit )

25. Tembotroin ( Laudis ) Tembotrione  is an aromatic ketone that is 2-benzoylcyclohexane-1,3-dione in which the phenyl group is substituted at positions 2, 3, and 4 by chlorine, ( 2,2,2 trifluoroethoxy ) methyl , It is from methylsulfonyl groups , respectively. Molecular Formula: C17 H1 6Cl F3 O6S IUPAC Name : 2- [ 2-chloro-4-methylsulfonyl-3- ( 2,2,2 trifluoroethoxymethyl )benzoyl]cyclohexane-1,3-dione Trade Names :- Laudis ( Buyer ) Available Formulation : 42 % SC

26. Mode Of Action 4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors (HPPD inhbitors ) are a class of herbicides that prevent plants by blocking 4-Hydroxyphenylpyruvate dioxygenase, an enzyme in plants that breaks down the amino acid tyrosine into molecules that are then used by plants to create other molecules that plants need. This process of breakdown, or catabolism, and making new molecules from the results, or biosynthesis, is something all living things do.

27. They were originally thought to be inhibitors of  protoporphyrinoges oxidase ( protox ). 4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an enzyme found in plants which catalyzes the catabolism of the  amino acid  tyrosine Preventing the breakdown of tyrosine has three negative consequences: the excess of tyrosine stunts growth; the plant suffers oxidative damage due to lack of tocopherols (vitamin E); and chlorophyll is destroyed due to lack of carotenoids that protect it .   Plants turn white without deformation due to a complete loss of chlorophyll, which has led compounds of this class to be classified as "bleaching herbicides", as are protox inhibitors.

28. More specifically, inhibition of HPPD prevents the formation of a breakdown product,  homogentisic acid, which in turn is a key precursor for the biosynthesis of both tocopherols and  plastoquinone . Plastoquinone is in turn a critical co-factor in the formation of carotenoids, which protect chlorophyll in plants from being destroyed by sunlight. Yadav et al . 2018, Buyer Crop Science 2020

29. Epinasty Hyponasty Necrotic Symptoms Stunted Growth Wilting There is no above effect of this herbicide on maize (Kumar et al. 2017) Phytotoxicity Symptoms

30. Effect of Tembotroin on Weeds Mitra e t al., 2018

31. Treatment Grasses (no./m 2 ) Sedges (no./m 2 ) Broad-leaves (no./m 2 ) 20 DAS 40 DAS 60 DAS 20 DAS 40 DAS 60 DAS 20 DAS 40 DAS 60 DAS Pre-emergence herbicides No PE 10.85 6.74 7.40 3.19 1.38 1.41 5.49 2.61 3.05 Pendimethalin 1 kg/ha 6.65 5.50 6.71 3.06 1.0 1.09 4.24 2.42 2.50 Atrazine 1 kg/ha 6.09 5.24 6.03 1.99 1.0 1.0 2.62 2.10 1.93 LSD (p=0.05) 0.18 0.14 0.16 0.15 0.04 0.03 0.16 0.07 0.08 Post-emergence herbicides No application 7.78 9.08 10.26 2.83 1.76 1.83 4.12 5.06 5.16 Tembotroin 120 g/ha 7.94 3.64 4.82 2.72 1.0 1.0 4.08 1.0 1.66 Halosulfuron 90 g/ha 7.94 8.24 8.39 2.70 1.00 1.0 4.18 4.22 4.56 LSD (p=0.05) NS 0.21 0.23 NS 0.05 0.05 NS 0.09 0.12 Weed population affected by Tembotroin Mitra et al. 2018

32. Phytotoxic Effect of Tembotroin on Weeds

33. Treatment Dose (g/ha) Application stage DAS No. of kernel per cob Kernal W.t per cob Grain yield (kg/ha) Tembotrione 100+S 15-20 408.6 107.3 4800 Tembotrione 110+S 15-20 417.6 112.7 5167 Tembotrione 120 + S 15-20 435.7 116.3 5333 Tembotrione 100 15-20 365.8 95.3 4283 Tembotrione 110 15-20 376.0 99.7 4492 Tembotrione 120 15-20 400.3 105.3 4533 Atrazine 1000 0-3 442.5 118.3 5267 Pendimethalin 1000 0-3 363.7 93.7 4667 2, 4-D Na Salt 800 20-25 348.2 88.3 4267 Hand Weeding - 20 & 40 439.5 116.0 5150 Control - - 280.6 65.3 2817 LSD (p=0.05) - - 27.5 6.8 244 By Singh et al. 2012 Following table shows the effect of tembotrion on yield attributes of maize

34. At 40 and 60 DAS, application of tembotrione alone as post-emergence with preemergence atrazine or pendimethalin also recorded lower weed dry weight. Tembotroin significantly controls the Grasses, sedges and Broad leave Weeds. Weed control treatments brought about significant increases in no. of kernels per cob, kernel weight per cob and 100 kernel weight as compared to the weedy check the highest cob yield was recorded with the application of Tembotrione at 120 g/ha along with surfactant which was at par with twice hand weeding and pre emergence application of atrazine.

35. Among the treatments, highest no. of kernel/cob was obtained with atrazine (422.5) in first year whereas in the second year, it was at par with Tembotrione along with surfactant. All the weed control treatments registered significantly higher kernel weight per cob and test weight over the weedy check.

36. 2, 4-D Sodium Salt 2,4-Dichlorophenoxyacetic acid IUPAC name:- (2,4-dichlorophenoxy)acetic acid Trade Names :- Fernoxone (Syngenta), Weedmar-80 ( Dhanuka Agritech ) Safaya ( Devidayal ), Weed Killer ( Okruti ). Group :- Phenoxyacetic Formulation registered :- 80 % w/w min Weeds Controlled :- Leucas aspera , Chenopodium album, Vicia sativa, Argemone mexicana , Fimbristylis miliacea , Anagallis arvensis , Amaranthus spinosus .

37. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required (kg, ml, L) ha 1 Dilution in water (L) Wheat 58% SL (30-35 DAS) 0.50-0.75 0.86-129 L 500-700 Wheat 80% WP (30-35 DAS) 0.50-0.84 0625-1.0 kg 500-700 Wheat 38% EC (30-35DAS) 0.45-0.75 1.32-2.20 L 500-700 Rice 38% EC (20-25DAT) 0.85 2.5 L 500-700 Rice 4% Gr (20-25 DAT) 1 25 - Maize 58% SL PE and PoE 0.5 0.86 L 500-600 Maize 80% WP 1 1.25 kg 500 Sugarcane 58% SL 3.5 6.3 L 500-700 Sugarcane 80% WP 2-2.6 3-3.25 kg 500-900 Sugarcane 38% EC 1.2-1.8 3.53-5.29 L 500-700 Sorghum 58% SL 1.8 3.1 L 500-700 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

38. Mode Of Action 2,4-D is a synthetic auxin, which is a class of plant hormones. It is absorbed through the leaves and is translocated to the meristems of the plant. Uncontrolled, unsustainable growth ensues, causing stem curl-over, leaf withering, and eventual plant death. 2,4-D is typically applied as an amine salt, but more potent ester versions exist, as well. It may dislocate the plant food supply in certain ways by which phloem cambium leaf cells may swells in response to 2 4-D and fill the intracellular spaces and check CO2 intake. Results in closer stomata and plants goes under starvation and leads in death It often induce Epinasty rolling and curling of leaves

39. Effect of 2,4- D in sugarcane

40. General and interveinal chlorosis Mottled chlorosis Yellow spotting Purpling of the leaves Necrosis Stem dieback Stem bending and downward curving of the leaves and leaf petioles. Phytotoxicity Symptoms Kassim Al- Khatib http://herbicidesymptoms.ipm.ucanr.edu/

41. Weed density influenced by 2, 4-D application in M aize crop Treatment ( 30-35 DAS) Dose (g/ha) Weed density (No./m2 at 60 days after treatment) C. album E. alba M. indica R. dentatus C. didymus C. arvense 2 4-D Na 500 2.73 1.86 2.34 2.34 1.58 2.34 2 4-D Na 750 2.34 1.86 1.86 1.86 1.56 1.86 Sulfoslfuron 25 4.30 3.23 3.86 2.91 2.34 2.73 Chlorosulfuron 10 3.38 2.73 2.73 1.86 1.86 2.34 Isoproturon 750 3.80 3.38 3.93 3.08 2.54 3.08 Weed Free 0.70 0.70 0.70 0.70 0.70 0.70 Control 6.20 4.29 4.94 3.23 2.91 2.91 LSD P= 0.05 0.93 0.47 0.56 0.59 0.41 0.39 Malik et al ., 2008

42. All the herbicidal treatments resulted in significant reduction in the density of weeds. There was considerable increase in the number of effective tillers and grain yield of wheat due to enhanced dose of each individual herbicide. 2, 4-D Na (500-750 g/ha) resulted in significantly higher yield compared to Weedy Check treatments and this could be obviously due to good control of weeds due to these treatments.

43. Topramezon IUPAC name :- [3-(4,5-dihydro-1,2-oxazol-3-yl)- 4-mesyl-o- tolyl ]( 5-hydroxy1-methylpyrazol-4-yl) methanone Trade Names :- Tynzer (BASF) Group :- P yrazole Subgroup :- Benzoylpyrazole Formulation registered :- a.i . 33.6% SC Weeds Controlled :- Cyprus rotundus , Cynadon spp., Chenopodium albu m

44. Mode of action They were originally thought to be inhibitors of protoporphyrinogen oxidase ( protox ) 4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an enzyme found in both plants and animals which catalyzes the catabolism of the  amino acid   tyrosine.   Preventing the breakdown of tyrosine has three negative consequences: the excess of tyrosine stunts growth; the plant suffers oxidative damage due to lack of tocopherols (vitamin E); and chlorophyll is destroyed due to lack of carotenoids that protect it .  Plants turn white without deformation due to a complete loss of chlorophyll, which has led compounds of this class to be classified as "bleaching herbicides", as are protox inhibitors.

45. More specifically, inhibition of HPPD prevents the formation of a breakdown product,  homogentisic acid, which in turn is a key precursor for the biosynthesis of both tocopherols and  plastoquinone . Plastoquinone is in turn a critical co-factor in the formation of carotenoids, which protect chlorophyll in plants from being destroyed by sunlight.

46. Effect of Topramezon on Commelina benghalensis in Maize

47. The damage was exhibited in the form of slightly delayed emergence , resulting in smaller plants, which were at times a slightly lighter green colour . All or portions of the true leaves will turn white. Phytotoxicity Symptoms Rahman et al. 2010 Peters et al. 2010

48. Treatment Weed Density ( 20DAS ) Total Weed Dry Matter (g) (20 DAS ) Grasses Sedges BLW Atrazine ( 1 kg a.i ha 1 ) PE 9.6 26.4 5.3 41.4 20.3 Topramezon ( 25.2 g a.i ha 1 ) PoE 13.7 28.6 7.6 49.9 28.3 Tembotroin ( 105 g a.i ha 1 ) PoE 12.7 29.5 8.9 51.1 28.3 Maize + cowpea and PE pendimethalin (1.0 kg a.i ha 1 ) 10.8 19.7 6.8 37.4 18.9 Hand Weedind 20 and 40 DAS 46.3 37.6 54.7 138.3 73.3 Unweeded Control 53.2 38.6 57.7 149.4 79.3 LSD ( P = 0.05 ) 0.52 0.54 0.695 0.84 0.4 Effect of different weed control treatments on weed density (no./m 2 ) and dry matter production (g/m 2 ) of weeds Swetha e t al . 2015

49. Weed control through various means significantly reduced the weed density over weedy check at 20 DAS. Lower density of sedges (19.72/m 2 ) was recorded in intercropping with cowpea and application of pendimethalin at 1.0 kg/ha as pre emergence, which was at par with topramezone + atrazine at 25.2 + 250 g/ha + MSO as post emergence (23.5/m 2 ).

50. Ametryn IUPAC NAME :- 2-( ethylamino )-4-( isopropylamino )-6( methylthio )-s- triazine Group :- Triazine Subgroup :- Methylthiotriazine Formulation registered :- 80 % WG, 50 SC Trade Names :- Tamar Weed Controlled :- BLW and grasses

51. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required (kg, ml, L) ha 1 Dilution in water (L) Sugarcane 80 WP (30 DAP) 2 2.5 kg 500 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

52. Mode Of action Like other triazines , ametryn inhibits photosynthesis and other enzymatic processes. It is a selective systemic herbicide, absorbed by the leaves and roots, with translocation acropetally in the xylem, and accumulation in the apical meristems. Their chief mode of action appears to involve carbohydrate metabolism. The chlorinated s- triazines inhibit starch accumulation by blocking the production of sugars. Similar behavior has been shown for the methoxy & methylthio -s- triazines .

53. S peed of appearance of symptoms will be more rapid with sunny days than with cloudy weather . Initial symptoms include browning of the cotyledonary leaves and yellowing of the true leaf margins. Browning of leaves will increase with time and total desiccation may result. Older and larger leaves are affected before younger leaves Phytotoxicity Symptoms Peters et al. 2010

54. Dry weight and weed control efficiency as influenced by different treatments in Sugarcane Treatment Dose a.i g ha 1 Dry Weight 15 DAA WCE % Dry Weight 45 DAA WCE % Ametryn + trifloxysulfuron 731.5+18.5 4.0 (52.1) 71.6 3.7 (40.1) 79.6 Ametryn + trifloxysulfuron 914.37+23.12 3.4 (29.9) 83.7 2.9 (18.4) 90.6 Trifloxysulfuron 30 4.4 (80.7) 56.0 5.0 (144.9) 26.4 Atrazine 1000 4.2 (63.9) 65.2 3.7 (41.2) 79.1 2,4- D dimethyl amine salt 3500 4.5 (91.7) 50 4.9 (139.8) 29.0 Hand Weeding Thrice 1.4 (4.2) 97.7 0.5 (0.7) 99.6 Weed free 100 100 Control 5.2 (183.6) 00.0 5.3 (196.8) 00 Figures in parentheses indicate original values which were transformed to loge x + 1 1/3 Singh et al. 2016 DAA :- Days After Application

55. Mesotrione IUPAC name :- 2- [4-( Methylsulfonyl )- 2- nitrobenzoyl ]cyclohexane-1,3- dione . Group :- Benzoylcyclohexanedione . Formulation Registerd :- 40 SC Trade Name :- Callisto (Syngenta) Weeds Controlled :- Annual broadleaf in sweetcorn

56. Mode Of Action It is a synthetic  analog  of  leptospermone  developed to mimic the effects of this natural herbicide .   Mesotrione is a member of the class of HPPD inhibitors, which all work by inhibiting the plant enzyme 4-hydroxyphenylpyruvate dioxygenase.  In plants, HPPD is necessary for carotenoid biosynthesis; carotenoids in turn protect chlorophyll from being degraded by sunlight .   When an HPPD inhibitor is sprayed on a plant, it prevents carotenoid from being made, chlorophyll degrades and the plant dies.

57. . Weed control efficiency and maize grain yield as influenced by herbicides Treatment Dose a.i . g /ha Time Of Application WCE Grain Yield t/ha Untreated check - - 0.0 4.76 Mesotrione + atrazine 68+682 15 DAS 94.5 7.55 Mesotrione + atrazine 80+795 15 DAS 97.5 7.74 Mesotrione + atrazine 91+909 15 DAS 98.7 7.76 Mesotrione 120 15 DAS 31.0 5.96 2,4-D- Na 1000 15 DAS 6.5 5.30 Atrazine 1000 0-3 DAS 66.7 6.70 p-Value - - - <0.0001 Chhokar et al. 2019

58. Oxyflurofen IUPAC Name :- 2-chloro-1-(3-ethoxy-4-nitrophenoxy)- 4- ( trifluoromethyl )benzene. Group :- Diphenyl ether Sub-group:- Nitrophenyl ether Formulation registered :- 23.5 % EC, 0.35% Gr Trade Names :- Goal (Buyer), Oxygold ( Indofil ), Oxykill ( Dhanuka Agritech Ltd.), Crall ( Krishi Rasayan ).

59. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required (kg, ml, L) ha 1 Dilution in water (L) Onion 23.5% EC PE 100-200 425-850 ml 600 Onion 23.5% EC PoE 200 850 600 Rice 23.5% EC PE 100-150 425-650 ml 500 Rice 0.35% Gr (0-3 DAT) 100-150 30-40 kg - Cotton 23.5% EC PE 0.15-0.25 0.6-1 L 600 Gram 23.5% EC PE 0.100-0.125 400-500 ml 400-500 Groundnut 23.5% EC PE 0.100-0.200 425-850 ml 500 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

60. Mode of action Diphenylether-type herbicides are extremely potent inhibitors of  protoporphyrinogen oxidase, a membrane-bound enzyme involved in the heme and chlorophyll biosynthesis pathways . The diphenyl-ether herbicides exert their phytotoxic activity in plants by preventing chlorophyll formation as a result of inhibition of protoporphyrinogen oxidase. This enzyme is the last step of the common pathway for chlorophyll and heme biosynthesis. Camadro et al. 1995

61. Necrotic Symptoms Scorching and burning Stunted Growth Wilting Phytotoxicity Symptoms

62. Effect of Oxyflurofen on weeds

63. Effect of different weed control treatments on weed density, weed dry matter, weed control efficiency and weed index in onion Treatment Total weed density (no./m2) Total weed dry matter (g/m2) WCE (%) Weed index (%) Oxyflurofen 0.30 kg/ha before planting and 30 DAT 5.75 (32.6) 9.08 (82.3) 41.2 28.1 Oxyflurofen + quizalofop -p-ethyl 0.30+0.05 kg/ha at planting and 30 DAT 5.54 (30.3) 8.93 (79.3) 43.3 18.2 Pendimethalin 1.0 kg/ha before planting and 30 DAT 5.73 (32.3) 9.24 (85.3) 39.0 28.0 Oxyflurofen fb one hand weeding 0.30 kg/ha before planting and 40-60 DAT 4.87 (23.3) 7.70 (59.5) 57.5 6.6 Pendimethalin + quizalofop -p-ethyl 1.0 + 0.05 kg/ha at planting and 30 DAT 4.95 (24.0) 7.85 (61.4) 56.1 9.4 Weed free 100 Weedy check 7.79 (60.6) 11.84 (139.9) 32.7 LSD (P=0.05) 0.69 .98 - - Singh et al . 2006 Figures in parentheses indicate original values which were transformed to loge x + 1 1/3

64. All the weed control treatments resulted significant reduction in total weed density and dry matter accumulation in comparison to weedy check Treatment oxyflurofen fb one hand weeding 0.30 kg/ha before planting and 40-60 DAT superior to control and at par with the weed free.

65. Imazethapyr IUPAC Name :- 5-ethyl-2-(4-methyl-5-oxo-4-propan-2-yl-1H-imidazol-2-yl)pyridine-3-carboxylic acid Group :- Imidazolinone . Formulation registerd :- 10 % SL. Trade Names :- Persuit (BASF), Inro (PI Ind.), Shikhor (Bharat Rasayan )

66. Crops Recomonded Dose a.i . ( g,kg ) kg ha 1 Orignal Formulation Required (kg, ml, L) ha 1 Dilution in water (L) Soyabean ( 10SL PE and EPoE ) 100 g 1 L 500-600 Groundnut ( 10SL PoE) 0.75-1000 g 750-1000 mL 500-600 Redgram ( 10SL PoE) 0.75-1000 g 750-1000 mL 500-600 Greengram ( 10SL PoE) 0.75-1000 g 750-100 mL 500-600 Krishidarshini 2019 Herbicide Use in Indian Agriculture ICAR Info. Bulletin No.22, 2016

67. Mode Of Action Absorbed by plant roots and foliage, being translocated to meristematic regions where it inhibits the biosynthesis of valine, leucine and isoleucine preventing cell division . their mode of action is to inhibit acetohydroxyacid synthase (AHAS), an enzyme involved in the biosynthesis of the amino acids leucine, isoleucine and valine. Fragiorge    et  al. 2008

68. Effect of treatments on growth attributes and weed control efficiency of Soyabean Treatment Plant height (cm) Leaf area index Dry matter production Kg ha1 WCE % 30 DAS 45 DAS 30 DAS 45 DAS 30 DAS 45 DAS 30 DAS 45 DAS 90 DAS EPOE imazethapyr 50 g/ha 36.3 69.0 0.61 1.73 611 1385 77.7 59.7 93.1 EPOE imazethapyr 75 g/ha 37.6 70.0 0.63 1.85 613 1413 81.6 60.6 94.8 EPOE imazethapyr 100 g/ha 41.7 77.5 0.76 1.98 763 1655 87.7 71.9 96.8 EPOE imazethapyr 200 g/ha 39.1 76.6 0.70 2.20 717 1529 91.1 78.3 98.1 PE pendimethalin 750 g/ha 36.1 68.5 0.61 1.79 632 1328 80.3 65.8 94.4 HW on 25 and 45 DAS 35.1 66.1 0.60 1.48 564 1055 81.4 50.9 53.5 Unweeded control 28.2 56.4 0.56 1.25 420 887 - - - LSD (P=0.05) 2.8 6.9 0.08 0.62 70 222 NA NA NA EPOE- Early post-emergence, PE- Pre-emergence, NA- Not analysed Sangeetha et al. 2012

69. Conclusion Herbicides gives quicker control of weed. It is more economic than conventional methods of weed managements. To increase the efficiency of herbicides it should be used with rotations to avoid weed resistance. Users must have known proper knowledge and information about herbicides used to avoid their phytotoxic effects on crop.

70. Thank-you