Management of cross resistance in P. minor against recommended herbicides in wheat
AAU, Jorhat
Taxonomic and Phyto-geographic assessment of invasive and other problem weeds
In the year 2018, the genus Acmella L.C Richard (1807) belonging to the family Asteraceae is taken in to account for this study. Most of the species of this genus occurring in India are weeds in crop fields as well as in crop fallow lands. Many a times the genus is confused with another Asteraceaen herbaceous genus Spilanthes. Looking towards the existing difficulties in recognizing Acmella species in the field, the present study was undertaken to review the taxa taxonomically and to record their phytogeographic distribution in the country.
Acmella v/s Spilanthes: The members of Acmella were characterized by the presence of shallow rooted decumbent (or erect) broadleaved herbaceous habit, opposite and petiolated leaves, capitula with usually yellow (rarely white) flowers and dimorphic cypsela (fruit) with or without bristle like pappus. The differences between Acmella and Spilanthes as per the most recent taxonomic revisionary works are as follows-
| Spilanthes | Acmella | |
| Leaves | Sessile | Petiolate |
| Capitula | Discoid | Radiate & discoid |
| Corolla | White to purplish white | Yellow (rarely white) |
| Cypsela | Monomorphic; rhombic in cross section; with a massive, stramineous cork-like margin at maturity | Dimorphic- ray cypsela triangular and disc cypsella 2-angular in cross section; with or without a stramineous cork-like margin at maturity |
| Pappus | Of stiff awns | Of soft bristles or lacking |
Enumeration and Phyto grographic distribution:
Altogether ten taxa of species and variety ranks have been recognized so far in the country, out of which only one species (Acmella oleracea) is known only under cultivation state and rarely in escaping state from cultivation in certain location in and around Haflong of Dima Hasa district of Assam. Rest of the taxa has been found as facultative weed of a member of field crops. Phytogeographic distribution of seven interesting taxa are also shown in Fig. 2.3.1.
The list of the recognized task is given below:-
- Acmella brachyglossa Cassini, Dict. Sci. Nat. 50: 258.1827.
Synonyms: Spilanthes caespitosa DC; Ceratocephalus caespitosus (DC) Kuntze; Spilanthes arrayana Gardner; Spilanthes eggersii Hieronymus; Spilanthes limonica A. H. Moore; Spilanthes ocymifolia f. radiifera A. H. Moore. A South American herb newly migrated to India. An erect herbaceous facultative weed grows in marshy croplands of Jorhat and Majuli districts of Assam. It is also known to occur in Kerala.
- Acmella calva(DC in wight) R.K.Jansen, Syst. Bot. Monog. 8:41. 1885.
Synonyms: Spilanthes calva DC in Wight; Spilanthes acmella var. calva (DC in Wight) Clarke ex Hook. f.; Spilanthes rugosa Blume ex DC; Spilanthes javanica Schultz-Bipontinus ex Miquel; Spilanthes rugosa var. truncata Miquel; Spilanthes callimorpha A.H.Moore; Colobogyne langbianensis Gangnepain; Spilanthes langbianensis (Gagnepain) Stuessy. A native to Indian subcontinent grows in moist places; common along the hilly tracts from NE India mto South India.
- Acmella ciliata(Humboldt, Bonpland & Kunth) Cassini, Dict. Sci. Nat. 24: 331.1822.
Synonyms: Spilanthes ciliata Humboldt, Bonpland & Kunth; Ceratocephalus ciliatus (Humboldt, Bonpland & Kunth) Kuntze; Spilanthes fimbriata Humboldt, Bonpland & Kunth; Acmella fimbriata (Humboldt, Bonpland & Kunth) Cassini; Ceratocephalus fimbriatus (Humboldt, Bonpland & Kunth) Kuntze; Spilanthes poeppigii DC; Ceratocephalus poeppigii (DC) Kuntze; Spilanthes melampodioides Gardner; Spilanthes popayanensis Hieronymus. A weed of fertile soil, occurs both in croplnd and crop fallow land situations. Native to South America, appreared as one of the most common weeds in India, mostly along the rice belt of the country.
- Acmella oleracea(Linnaeus) R.K.Jansen, Syst. Bot. Monog. 8:65. 1885.
Synonyms: Spilanthus oleracea Linnaeus; Spilanthes acmella var. oleracea (Linnaeus) C. B. Clarke ex Hooker f.; Ctula pyrethraria Linnaeus; Isocarpha pyrethraria (Linnaeeus) Cassini; Bidens fusca Lamarck; Spilanthes fusca Lamarck; Spilanthes radicans Schrader ex DC. Nativity is unknown. Commonly cultivated as ornamental and medicinal herb; however, escaped and naturalized elsewhere including the Dima Hasao district of Assam.
- Acmella oppositifolla(Lamarck) R. K. Jansen, Syst. Bot. Monog. 8:30. 1985. var. oppositifolla.
Synonyms: Spilanthes beccabunga DC; Spilanthus beccabunga G. Gomez; Spilanthes subhirsuta DC; Spilanthes diffusa Poeppig & Endlicher; Ceratocephalus diffusus (Poeppig & Endlicher) Kuntze; Spilanthes ciliata var. diffusa (Poeppig & Endlicher) A.H. Moore. A Latin American species, recorded for the first time in India from Assam as a newly introduced cropland weed of upland situations.
- Acmella oppositifolia repens(Walter) R.K.Jansen, Syst. Bot. Monog. 8:34. 1885.
Synonyms: Anthemis repens Walter; Spilanthes repens (Walter) Michaux; Ceratocephalus repens (Walter) Kuntze; Spilanthes americana var .repens (Walter) A.H.Moore; Acmella occidentalis Nuttall; Acmella nuttaliana Rafinesque; Spilanthes nuttalli Torrey & Gray. A weed of Southern United States nativity. It was first recorded from Andhara Pradesh in 1999 in India and now extended towards the eastern Ghat.
- Acmella paniculata(Wall. ex DC) R. K. Jansen, Syst. Bot. Monog. 8:67. 1885.
Synonyms: Spilanthes paniculata Wall. ex DC; Spilanthes acmella var. paniculata (Wall. ex DC) C. B. Clarke ex Hooker f.; Spilanthes grandifolia Miquel; Spilanthes acmella var. albescentifolia A.H.Moore; Spilanthes paniculata f. bicolor Koster. A native to SE Asia; commonly grows in forest edges, roadsides and west places as well as a facultative weed in upland crops. Common in Kerala, MP, Andhra Pradsh to NE India.
- Acmella radicans(Jacquin) R. K. Jansen, Syst. Bot. Monog. 8:69. 1885.
Synonyms: Spilanthus radicans Jacquin; Spilanthes exasperatus Jacquin. A Central American weed, distributed to Kerala, Eastern Ghat to West Bengal.
- Acmella radicans debilis (Humboldt, Bonpland & Kunth) R. K. Jansen, Syst. Bot. Monog. 8:72.1885.
Synonyms: Spilanthes debilis Humboldt; Acmella debilis (Humboldt, Bonpland & Kunth) Cassini; Ceratocephalus debilis (Humboldt, Bonpland & Kunth) Kuntze. A native to Central America; in India it was first reported in 2015 and known to occur in Maharastra, Karnataka and MP. The present investigation has confirmed its presence in Assam and Arunachal Pradesh since a long past, as the species is commonly used as vegetable by Mishing and Adi tribes. A naturalized herbaceous species ith weedy nature in NE India.
- Acmella uliginosa(Swartz) Cassini, Dict. Sci. Nat. 24: 331.1822.
Synonyms: Spilanthes uliginosa Swartz; Jaegeria uliginosa (Swartz) Sprengel; Spilanthes acmella var. uliginosa (Swartz) Baker in Martius; Ceratocephalus acmella var. uliginosa (Swartz) Kuntze; Coreopsis acmella var. uliginosa (Swartz) K. Krause; Spilanthes lundii DeCandolle; Spilanthes salzmanni DC; Ceratocephalus acmella var. depauperata Kuntze; Spilanthes iabadicensis A.H. Moore; Spilanthes charitopis A.H. Moore; Spilanthes uliginosa var. discoidea Aristeguieta.A Pan-tropical species and a common cropland weed of upland and marshland situations almost throughout the country.
A dichotomous key for identification is constructed for the Indian taxa with slight modification of Jansen’s (1985) work.
KEY FOR IDENTIFICATION OF TAXA BELONGED TO ACMELLA:
1a. Head discoid:
2a. Corolla white, greenish white or with purple tinge. (Pappus of 2 or 3 sub-equal bristles; cypsela moderately to densely ciliate with hairs having straight tips; leaves attenuate at base; erect annuals) … …. …. …. … … … A. radicans var. radicans
2b. Corolla pale yellow, yellow, or orange-yellow:
3a. Pappus absent; cypsela usually glabrous or if ciliate hairs having strongly recurved tips; perennials; stems decumbent or repent and rooting at nodes …… … A. calva
3b. Pappus of 2 or 3 sub- or unequal bristles; cypsela moderately to densely ciliate with hairs having straight tips; annuals or perennials; stems erect and usually lacking nodal roots:
4a. Mature cypsela with evident cork-like margins, surfaces sparsely to densely tuberculate …………….. ………. …….. ………….. ………… ………. A. paniculata
4b. Mature cypsela without cork-like margins, surfaces not tuberculate:
5a. Corolla 4-merous; phyllaries 5-6, uniseriate; heads 5.7-8.1mm high, 4-6mm in diameter; receptacle 3-6mm high ……………………………………… A. uliginosa
5b. Corolla 5-merous; phyllaries 8-18, biseriate to triseriate; leaves broadly ovate to deltate, truncate to short attenuate at the base; known only from cultivation … .….. …. ……. … … …. ……… …. ……. … … …. ……. … … …. ……. … … A. oleracea
1b. Heads radiate:
6a. Ray florets slightly shorter to only slightly exceeding the phyllaries, often inconspicuous:
7a. Cypsela glabrous and epappose …. ……. … … A. oppositifolia var. oppositifolia
7b. Cypsela moderately to densely ciliate, usually with a well developed pappus of 2 or 3 bristles:
8a. Mature cypsela with evident, straminous, cork-like margins:
9a. Corolla orange-yellow; disc corollas 5-merous; perennials with stem rooting at nodes …….. ………….. ………….. ………….. ……………… …… ….. …….……. A. ciliata
9b. Corolla white or greenish white; disc corolla 4-merous; erect annuals ….. … …. ……. … ……. ……. … ……. ……. … ……. ……. … ……. … … A. radicans var. debilis
8b. Mature cypsela lacking evident, straminous, cork-like margins:
10a. Phyllaries 7-11, biseriate; leaves ovate; corollas pale yellow, 4-5-merous; disc florets 107-222; cypsela 1.8-2.3mm long, 0.5-0.9mm wide … … … A. brachyglossa
10b. Phyllaries 5-6, uniseriate; leaves lanceolate to narrowly ovate; corollas yellow to orange-yellow, 4-merous; disc florests 68-148; disc cypsela 1.2-1.8mm long, 0.4-0.6mm wide ….. ….. ……… ………… ………….. … …. … … ..…. A. uliginosa
6b. Ray florets 3-10 times longer than the phyllaries, conspicuous. (Leaves narrowly or broadly ovate, never linear-lanceolate) :
11a. Cypsella with pappus of bristles and moderately to densely ciliate …… ……… …………. …… ……… …… …. … ………… A. oppositifolia var. oppositifolia
11b. Cypsela epappose or pappose poorly developed and then the cypsela glabrous:
12a. Phyllaries lanceolate, acuminate at apex; cypsela sparsely to densely ciliate with very short straight-tipped hairs; pappus absent …. …. A. oppositifolia var. repens
12b. Phyllaries narrowly to broadly ovate, rounded to acute at apex; cypsella glabrous to densely ciliate with long straight-tipped hairs … A. oppositifolia var. oppositifolia
Fig. 2.3.1. Phyto-geographic distribution of some species of Acmella in India
(Map is not in scale)
Management of cross resistance in P. minor against recommended herbicides in wheat through use of pre and post emergence herbicides used
HAU, Hisar
Phalaris minor is the dominant and troublesome grass weed of wheat in rice-wheat cropping system in the north-western Indo-Gangetic plains of India. To study the efficacy of different herbicides against P. minor with poor control by clodinafop, sulfosulfuron and pinoxaden since last 3-4 years, a field experiment was conducted during rabi 2017-18 at Agronomy research area CCS HAU Hisar. The experiment was laid out in a randomized block design. Herbicides were sprayed with knapsack sprayer fitted with flat fan nozzle using water volume of 375 L/ha. Phyto-toxicity in terms of chlorosis, stunting, leaf burning and epinasty was recorded at 10 and 20 DAT (days after treatment).
All herbicide treatments caused significant reduction in density of P. minor at 30 and 60 DAT. Pre-emergence application of pendimethalin or metribuzin was not much effective against resistant population of P.minor with only 33-35% control. Although pre-emergence application of pendimethalin + metribuzin (TM) at 1500+175 g/ha increased control of P. minor but was not sufficient to control second flush of weeds appeared after first irrigation to satisfactory level with only 53.3 % control. Pre-emergence application of pendimethalin + pyroxasulfone (RM) at 1500 + 102 g/ha either alone or followed by sequential use of pinoxaden 60 g/ha/, meso + iodosulfuron(RM) 14.4 g/ha at 35 DAS caused significant reduction in density of P. minor and provided 83-93 % control. Pre-emergence use of pendimethalin + metribuzin in conjunction with post emergence herbicides provided 60-68.3% control. None of herbicide treatment except tank mixture of pinoxaden and metribuzin at 50 + 120/150 g/ha and pendimethalin + metribuzin (before sowing) at 1500 + 175 g/ha caused any phytotoxicity on wheat. Toxicity up to 5% in form of chlorosis and yellowing was observed with tank mixture of pinoxaden and metribuzin at 50 + 120/150 g/ha up to 10 DAT which mitigated up to 20 DAT and this mixture was not much effective with only 51.7% control of P. minor. Pre-emergence application of pendimethalin + metribuzin (before sowing) at 1500 +175 g/ha (before sowing) caused 5% reduction in wheat germination affecting no. of tillers/m2 and significant reduction in grain yield. WCE also varied among treatments due to varying control of P. minor. Maximum WCE (83-93% at 30 DAT and 87-88 % at 60 DAT) was obtained with pyroxasulfone treatments which had a reflection on number of tillers/m2 and grain yield of wheat. Recommended herbicide pinoxaden and meso + iodosulfuron at 14.4 g/ha provided only 51.7% control of weeds at 60 DAT. Effect of different treatments on weed density, dry weight of weeds, visual control and grain yield of wheat was also evaluated. Maximum grain yield (5.82 t/ha) was obtained with pendimethalin + pyroxasulfone at 1500+102 g/ha fb sequential use of pinoxaden 60 g/ha with 88.7% control of P. minor which was at par with weed free check, pendimethalin + pyroxasulfone at 1500+102 g/ha fb sequential use of meso +iodosulfuron (14.4 g/ha) and pendimethalin + pyroxasulfone at 1500+102 g/ha
Monitoring and management of herbicide resistance to different herbicides in P. minor biotypes from farmers’ fields (Pot-culture)
HAU, Hisar
There are reports of reduced efficacy of the recommended herbicides against P. minor in wheat at farmers’ fields in Haryana. The reason might be the wrong method of application, dose or development of cross-resistance in P. minor. The seeds of uncontrolled P. minor were collected from farmers’ fields in different districts of Haryana during Rabi 2016-17. Twelve such biotypes were collected from different parts of Haryana. The herbicidal treatments along with untreated check were laid out in completely randomized block design (CRD) with three replications. The observations on control of weeds were taken at 30 days after herbicide application.
The pot-culture studies with 12 populations of P. minor, viz. P1 Hisar (HAU), P2. Khedar (Hisar), P3. Khedi (Kaithal), P4 Keorak (Kaithal), P5 Kalwan (Jind), P6 Rasidan (Hisar), P7 Ludas (Hisar), P8 Lamba Kheri (Kaithal), P9 Dhos (Kaithal), P10 Ujhana (Jind), P11 Lehrawali Dhani (Sirsa), P12 Nangla (Fatehabad) from different parts of Haryana indicated the decrease in efficacy of one or two out of 12 populations of P. minor evaluated; 10 populations were resistant to recommended dose of clodinafop, 9 populations to sulfosulfuron and 7 populations to meso + iodosulfuron (RM) and pinoxaden each. Even 10 populations (P1, P3, P4, P5, P6, P7, P8, P9, P10, P12) were found tolerant to 2X dose of clodinafop. Populations from P1, P3, P4, P5, P6, P7, P8, P9, and P12 were resistant to 2X dose of sulfosulfuron. Biotypes P3, P4, P5, P6, P8, P10, P12 were not controlled satisfactorily by recommended dose of pinoxaden. Less than 50% control of populations P6, P7, P8 and P9 was achieved when treated with 2X dose of sulfosulfuron. Two populations P6 (50% control)) and P8 (65% control) have poor control when treated with 2 X dose of meso + iodosulfuron (RM) at 28.8 g/ha. Only 20% control of population P6 was achieved when treated with 2X dose of pinoxaden (Fig. 2.3.2).
Development of cross-resistance against clodinafop in majority of areas was observed (Fig. 2.3.3). Pinoxaden and mesosulfruon + iodosulfuron (RM) could also play an important role in management of resistant populations.
Fig. 2.3.2 Efficacy (≥80%) of different herbicides against P. minor biotypes in pot studies
Fig. 2.3.3 Resistant populations of P. minor treated with different doses of clodinafop
Survey on status of herbicide resistance in Phalaris minor Retz. in wheat at farmers’ fields of Haryana
HAU, Hisar
Information about spray pattern
Many field surveys were conducted to assess the status of resistance in P. minor but these were random in nature. Hence, an extensive survey with systematic approach was conducted in Rabi 2018 in five districts (Yamunanagar, Kaithal, Karnal, Fatehabad and Rohtak) of Haryana. Two blocks were selected from each district and three villages from each block and a total of 300 farmers were covered from 30 villages involving 10 farmers from each village.
Farmers are mainly using knapsack sprayer for herbicides application but recently have also started using the power sprayer to reduce the drudgery. Overall 76.3% farmers use knapsack sprayer and 23.7% use power sprayer in surveyed districts. Almost all famers reported that they use single nozzle and apply the herbicides in clear weather. In case of nozzle 49.3% farmer use flood jet/cut nozzle followed by hollow cone nozzle by 45.3% farmers; only 6.3% famers use the flat fan nozzle (Table 2.3.4). Farmers in the Karnal, Kaithal and Bilaspur block of Yamunagar district mainly use the cut nozzle it is mainly rice-wheat growing area. Farmers in Fatehabad, Rohtak and Radaur block use the hollow cone nozzle in this belt diversification is there farmers also take cotton, sugarcane, sorghum and pear millet along with rice in Kharif. Very few farmers are using flat fan nozzle for herbicides application. Farmers are not using right nozzle for herbicides application due to ignorance, casual approach (same nozzle for pesticides and herbicides) and flat fan nozzle takes more time than other nozzle. In case of water volume used for herbicides spray less than <2% use the standard recommended amount of water 200 L acre. Around 90% farmers are using water volume from 90-120 L acre (51.7 and 39.3% using 120 and 90 L acre, respectively) (Table 22). Farmers not use standard water volume due to cost factor and some farmers also have misconception perceived by pesticides dealer that concentrated spray gave better result so higher water volume dilute the herbicides and reduce the efficacy. Farmers have tendency to use more and more concentred spray as they face more resistance problem.
Table 2.3.4 Information about spray pattern
| Name of sprayer used | ||||||||
| Knapsack | 229 (76.3%) | |||||||
| Power | 71 (23.7%) | |||||||
| Boom | ||||||||
| Single Nozzle | 294 (98.0%) | |||||||
| Double nozzle | ||||||||
| Three nozzle | 6 (2.0%) | |||||||
| Nozzle | ||||||||
| Flood jet/cut nozzle | 148 (49.3%) | |||||||
| Hollow cone | 136 (45.3%) | |||||||
| Flat fan | 19 (6.3%) | |||||||
| Weather at spray time | ||||||||
| Foggy | – | |||||||
| Clear | 300 (100.0%) | |||||||
| Water volume used for spray (liters/acre) | 60 | 90 | 120 | 150 | 180 | 200 | >200 | |
| 0 (0.0%) | 118 (39.3%) | 155 (51.7%) | 21 (7.0%) | 1 (0.3%) | 3 (1.0%) | 2 (0.7%) | ||
Maximum numbers of farmers 48.3% go for first herbicide application at 2-3 leaf stage (40-45 DAS), only <2% farmers apply herbicides at recommended time 30-35 DAS. Nowadays farmers have started using pre and post emergence herbicides combination to get desirable control and few farmers also reported that application of sulfosulfuron at 20 DAS before first irrigation in dry field also gave satisfactory control that why in table it showing that 20% farmers applying first spray up to 25 DAS. Overall three-fourth farmers 74.6% are applying first herbicides after 35 DAS. In case of second spray highest number of farmers is applying herbicides >50 DAS (71.8%), almost all farmers go for second spray after 40 DAS (Table 2.3.5). Field takes time to come in wapsa condition is the one of the prime reason for delay in herbicides application other than this some farmers also have perception that application of herbicides at later stage 4-5 leaf stage of P. minor gives better control. Farmers also have tendency to apply fertilizers (mainly urea) and irrigation within one week of herbicides application
Table 2.3.5 Time of spray and P. minor growth stage
| Time of spray | H1 (First spray) | H2 (Second spray) | |
| 0 DAS | Pre emergence | 14 (4.7%) | 0 (0%) |
| 20-25 DAS | Not germinated | 50 (16.7%) | 1 (0.7%) |
| 25-30 DAS | Germination <50% | 5 (1.7%) | 0 (0%) |
| 30-35 DAS | Germination >50% | 5 (1.7%) | 0 (0%) |
| 35-40 DAS | 1-2 leaf stage | 29 (9.7%) | 1 (0.7%) |
| 40-45 DAS | 2-3 leaf stage | 145 (48.3%) | 13 (9.1%) |
| 45-50 DAS | 3-4 leaf stage | 37 (12.3%) | 25 (17.6%) |
| >50 DAS | >4 leaf stage | 13 (4.3%) | 102 (71.8%) |
Information about the herbicide use pattern X-dose against P. minor
In 2017-18 overall farmers applied 2.91 X-dose of total herbicides to control P. minor highest in case of Karnal district 4.13 and lowest in Rohtak 1.80 X-dose. Still only get 69.1 to 80.8% control lowest in Karnal and highest in Yamuna Nagar district. Overall 23.6% regeneration reported lowest in Yamuna Nagar (19.1%) and highest in Karnal (27.7%). Farmers accept that clodinafop is not showing any result but still it is contributing about half (48.48%) of the total herbicide use. Whereas, sulfosulfuron and pinoxaden contributed one-fifth 21.62 and 19.23%, respectively of the total herbicide use. Mesosulfuron + iodosulfuron (ready-mix) contributed very less (<5%) to total herbicide use.
Every year farmers need to apply more and more herbicides to deal with P. minor but in 2017-18 they were faced more problem and herbicides consumption raise by 25% than 2016-17, instead only 13% rise in 2016-17 over 2015-16 base year. It also observed that year by year desirable control getting low 87.3% in 2015-16 to 75.7% in 2017-18 and farmers are facing more regeneration problem 12.1% in 2015-16 to 23.6% in 2017-18. Farmers are raising the herbicides dose to get desirable control and also shifting towards the diversification use of herbicides. Recently, they have started using pendimethalin (750-1000 g/ha) as pre-emergence and metribuzin as post tank-mix (50-140 g/ha) with alternate herbicides to get desirable results. But not diversifying the crop. Farmers accept that clodinafop not showing any result but still it leading in the total herbicides use because it is one of the cheapest, safest herbicides, no phytotoxicity at higher dose, wider window of application and no residual effect on succeeding crop. Pinoxaden is one of the favorite herbicides among farmers in those area where resistance developed against clodinafop and sulfosulfuron or farmers facing more problem, Karnal leading with use of 26.53% followed by Kaithal 24.05%. Maximum number of farmers (mainly in Fatehabad districts) are using clodinafop and sulfosulfuron as tank mix as per their perception sulfosulfuron work on 2-3 leaf stage of P. minor and clodinafop work on 4-5 leaf stage so it gave total control, none of the farmers challenge this theory all of them agree with this point. Mesosulfuron + iodosulfuron provided good control, but farmers are afraid of it due to phyto-toxicity in wet conditions or overlapped repeat spraying. Few farmers reported that they applied metribuzin (175-350 g/ha) at first irrigation by mixing with urea and found satisfactory control. Farmers also reported that application of sulfosulfuron before first irrigation at 20 DAS in dry field gave good control of P. minor.
Farmer, Malkhan Singh left wheat cultivation and shifted to mustard due to P. minor problem. Lowest problem faced by Radaur block of Yamuna Nagar farmers only using clodinafop with 1.12 times dose and get good control. Radaur block farmers given credit to sugarcane cultivation as they facing lowest or no herbicides resistance problem against P. minor. They reported that some time they need not to apply any herbicides for P. minor still get satisfactory control.
Management of cross resistance in P. minor against recommended herbicides in wheat
GBPUAT, Pantnagar
An experiment was conducted to mange cross resistance in P. minor against recommended herbicides in wheat. The experiment was laid out in RBD with three replications. Data on weed density and biomass as well as yield and yield attributes of wheat were recorded. Weed density of P. minor was recorded at 30, 60 and 90 DAS At 30 DAS, the density was highest in Weedy plot (134.67 /m2) followed by clodinafop + metsulfuron-methyl (102.7/m2) and mesosulfuron + idosulfuron (64 /m2). There was no weed recorded in pendimethalin followed by clodinafop-propargyl treatment at 60 DAS. At 90 DAS, the density was highest in Weedy plot (249.3 /m2) followed by mesosulfuron + idosulfuron (70.67 /m2) and pendimethalin (25.3/m2) treatment (Fig 2.3.5).
Fig. 2.3.5 Effect of herbicides on P. minor density at 30, 60 and 90 DAS
Whereas weed biomass was recorded at different growth stages, viz. 30, 60 and 90 DAS. At 30 DAS, weed biomass was maximum in weedy plot (3.60g/m2) followed by clodinafop + metsulfuron-methyl (3.50g/m2) and mesosulfuron + idosulfuron (2.12 g/m2) treatment. The biomass was gradually increased in weedy plot and mesosulfuron + idosulfuron till 90 DAS. At 90 DAS, weed biomass was maximum in weedy plot (201.6 g/m2) followed by pendimethalin (21.4 g/m2). The few herbicide treatments, pendimethalin + metribuzin, pendimethalin + metribuzin followed by mesosulfuron + idosulfuron, pendimethalin + metribuzin followed by clodinafop + metsulfuron-methyl, pendimethalin followed by clodinafop-propargyl, pendimethalin followed by mesosulfuron + idosulfuron) and clodinafop + metsulfuron-methyl were effective to control the weed successfully (Fig. 2.3.6).
Fig. 2.3.6 Effect of herbicides on biomass of P. minor at 30, 60 and 90 DAS
Number of shoots was recorded at 30 and 60 DAS (Fig. 2.3.7). There was no significant difference in number of shoots at different growth stages. At 30 DAS, pendimethalin followed by clodinafop-propargyl and pendimethalin + metribuzin followed by mesosulfuron + idosulfuron treatment had highest number of tillers whereas, lowest in weedy plot. At 60 DAS, the herbicides treatments Pendimethalin, endimethalin + metribuzin, pendimethalin + metribuzin followed by mesosulfuron + idosulfuron and clodinafop + metsulfuron-methyl had comparable number of shoots.
Fig. 2.3.7 Effect of herbicides on tiller number of wheat at 30 and 60 DAS
The biological yield (kg/m2) of wheat was maximum in pendimethalin + metribuzin followed by clodinafop + metsulfuron-methyl treatment (1.48 kg/m2) whereas, lowest biological yield was found in weedy plot (1.2kg/m2). The biological yield of pendimethalin followed by clodinafop-propargyl was at par with clodinafop + metsulfuron-methyl treatment.
Grain yield was also highest in pendimethalin + metribuzin followed by clodinafop + metsulfuron-methyl treatment (0.53 kg/m2) whereas, lowest grain yield was achieved in weedy condition (0.30 kg/m2).
PAU, Ludhiana
To study the bio-efficacy of combination of herbicides against cross resistant p. minor, a study was carried out as per details given below:
| Sr. No. | Treatment | Dose (g/ha) | Application time |
| T1 | Pendimethalin | 750 | PRE |
| T2 | Pendimethalin + metribuzin | 750 + 210 | PRE |
| T3 | Pendimethalin + metribuzin fb mesosulfuron + iodosulfuron (RM) | 750 + 210 fb 12 + 2.4 | PRE fb POST |
| T4 | Pendimethalin + metribuzin fb clodinafop-propargyl + metsulfuron-methyl (RM) | 750+210 fb 60+4 | PRE fb POST |
| T5 | Pendimethalin + pyroxasulfone (TM) | 750+102 | PRE |
| T6 | Pendimethalin + pyroxasulfone (TM) fb clodinafop-propargyl + metsulfuron-methyl (RM) | 750+102 fb 60+4 | PRE fb POST |
| T7 | Pendimethalin + pyroxasulfone (TM) fb mesosulfuron + iodosulfuron(RM) | 750+102 fb 12 + 2.4 | PRE fb POST |
| T8 | Clodinafop-propargyl + metsulfuron-methyl (RM) | 60+4 | POST |
| T9 | Mesosulfuron + iodosulfuron(RM) | 12 + 2.4 | POST |
| T10 | Weedy | – | – |
| *Pendimethalin | |||
Pre-emergence application of pendimethalin 750 g and tank-mix of pendimethalin 750 g + metribuzin 210 g/ha significantly (>75%) reduced P. minor density as compared to unsprayed control at 20 DAS (Table 2.3.9). At 40 and 90 DAS, all weed control treatments significantly reduced P. minor density and biomass as compared to unsprayed control. Pendimethalin + pyroxasulfone herbicide resulted in weed control after first irrigation and sequential application of pendimethalin 750 g + pyroxasulfone 102 g/ha as pre-emergence followed by either clodinafop propargyl 60 g + metsuflruon methyl 4.0 g/ha or mesosulfuron 12 g + iodosulfuron 2.4 g/ha as post-emergence gave >90% control of P. minor (Table 2.3.1). All herbicides did not show any significant influence on crop plant height, tiller production and biomass indicating safety of these chemical combinations for wheat. All weed control treatments gave significantly higher wheat grain yield than unsprayed check and were at par among each other. Weed control with these chemicals increased net returns from wheat by Rs. 19000 to Rs. 24000 /ha as compared to unsprayed check (Table 2.3.1).
Table 2.3.1Effect of different pre-emergence herbicides on weed density, visual weed control and crop phytotoxicity at 20 DAS (2017-18).
| Treatments | Dose (g/ha) | P. minor (No./m2) | Weed control efficiency (%) | Crop phytotoxicity (0-10 scale) |
| Pendimethalin | 750 | 5.1 (25) | 86 | 0 |
| Pendimethalin+metribuzin | 750 + 210 | 4.9 (23) | 86 | 0 |
| Pendimethalin+pyroxasulfone | 750+102 | 9.1 (83) | 50 | 0 |
| Unweeded control | – | 12.9 (166) | – | – |
| SEm± | – | 0.3 | – | – |
| LSD (P=0.05) | – | 1.1 | – | – |
Visual weed control was taken with respect to unweeded control
Table 2.3.10 Effect of different weed control treatments on density and biomass of Phalaris minor (Rabi 2017-18).
| Treatments | Dose (g/ha) | P. minor population (No./m2) | Weed biomass (g/m2) | Weed Control Efficiency (%) | |||
| 40 DAS | 90 DAS | 40 DAS | 90 DAS | 40 DAS | 90 DAS | ||
| Pendimethalin | 750 | 5.1 (26) | 6.1 (36) | 4.3 (17) | 13.6 (185) | 69.7 | 50.6 |
| Pendimethalin + metribuzin | 750 + 210 | 4.2 (17) | 5.6 (30) | 3.7 (12) | 13.1 (171) | 78.2 | 54.1 |
| Pendimethalin + metribuzin fb mesosulfuron + iodosulfuron (RM) | 750 + 210 fb 12 + 2.4 | 4.4 (19) | 2.9(7) | 2.4 (5) | 8.8 (78) | 91.4 | 79.1 |
| Pendimethalin + metribuzin fb clodinafop-propargyl + metsulfuron-methyl (RM) | 750+210 fb 60+4 | 4.8 (22) | 2.6 (6) | 5.5 (5) | 9.4 (87) | 90.6 | 76.7 |
| Pendimethalin + pyroxasulfone (TM) | 750+102 | 2.0 (4) | 2.6 (6) | 2.4 (5) | 6.6 (43) | 91.2 | 88.6 |
| Pendimethalin + pyroxasulfone (TM) fb clodinafop-propargyl + metsulfuron-methyl (RM) | 750+102 fb 60+4 | 2.0 (4) | 2.0 (3) | 2.0 (3) | 5.5 (29) | 94.7 | 92.1 |
| Pendimethalin + pyroxasulfone (TM) fb mesosulfuron + iodosulfuron(RM) | 750+102 fb 12 + 2.4 | 1.5 (2) | 1.7 (2) | 1.7 (2) | 4.7(21) | 96.5 | 94.4 |
| Clodinafop-propargyl + metsulfuron-methyl (RM) | 60+4 | 10.1 (102) | 4.5 (19) | 3.8 (13) | 10.8 (115) | 76.5 | 69.2 |
| Mesosulfuron + iodosulfuron(RM) | 12 + 2.4 | 9.2 (84) | 3.4 (11) | 3.5 (11) | 9.8 (95) | 80.0 | 74.6 |
| Weedy check | – | 15.6(243) | 15.6 (243) | 7.6 (57) | 19.3 (373) | – | – |
| SEm± | 0.5 | 0.1 | 0.1 | 0.4 | – | – | |
| LSD (P=0.05) | 1.6 | 0.3 | 0.3 | 1.1 | – | – | |
Data is subjected to square root transformation. Figures within parenthesis are means of original values
Table 2.3.11 Wheat growth at 40 DAS, yield attributes at harvest and yields under different weed control treatments (Rabi 2017-18).
| Treatments | Dose (g/ha) | Plant height (cm) | Tillers (No./m2) | Crop biomass (g/m2) | Effective tillers (No./m2) | Final plant height (cm) | Grain yield (t/ha) | Biological yield (t/ha) |
| Pendimethalin | 750 | 48.4 | 605.0 | 303.3 | 293.3 | 84.8 | 5.08 | 12.3 |
| Pendimethalin + metribuzin | 750 + 210 | 48.1 | 605.0 | 306.7 | 302.0 | 86.3 | 5.37 | 12.6 |
| Pendimethalin + metribuzin fb mesosulfuron + iodosulfuron (RM) | 750 + 210 fb 12 + 2.4 | 48.6 | 608.3 | 308.3 | 305.0 | 86.0 | 5.79 | 13.5 |
| Pendimethalin + metribuzin fb clodinafop + metsulfuron (RM) | 750+210 fb 60+4 | 48.2 | 608.3 | 311.7 | 305.0 | 86.3 | 5.72 | 13.5 |
| Pendimethalin + pyroxasulfone (TM) | 750+102 | 48.0 | 609.0 | 310.0 | 300.0 | 86.0 | 5.58 | 13.0 |
| Pendimethalin + pyroxasulfone (TM) fb clodinafop + metsulfuron (RM) | 750+102 fb 60+4 | 48.3 | 610.0 | 311.5 | 309.0 | 86.3 | 5.74 | 13.7 |
| Pendimethalin + pyroxasulfone (TM) fb mesosulfuron + iodosulfuron(RM) | 750+102 fb 12 + 2.4 | 47.0 | 608.3 | 311.3 | 306.0 | 86.3 | 5.797 | 13.7 |
| Clodinafop-propargyl + metsulfuron-methyl (RM) | 60+4 | 48.7 | 600.0 | 301.7 | 293.3 | 86.1 | 5.59 | 12.6 |
| Mesosulfuron + iodosulfuron(RM) | 12 + 2.4 | 47.9 | 608.3 | 304.6 | 301.7 | 86.0 | 5.60 | 13.1 |
| Weedy | – | 47.4 | 535.0 | 200.0 | 225.0 | 83.4 | 4.00 | 9.93 |
| SEm± | – | 0.8 | 9.5 | 8.0 | 4.7 | 0.9 | 0.07 | 0.45 |
| LSD (P=0.05) | – | NS | 28.3 | 23.7 | 14.0 | NS | 0.27 | 1.43 |
WP 2.4 Threshold of Phalaris minor in wheat
PAU, Ludhiana
In wheat threshold level of P. minor was studied in variety PBW 677. Seven densities, viz. 0, 1, 2, 4, 6, 8 and 10 plants per m2 were maintained in wheat field. The weeds other than P. minor were uprooted at weekly intervals. The yield and yield attributes of all treatments were at par indicating that P. minor at densities upto 10 plants /m2 were not competitive with wheat (Tables 2.4.1 and 2.4.2).
Table 2.4.1 Phenological stages of wheat and P. minor
| Phenological stage of rice | Days after transplanting (DAT) |
| Tillering | 52 |
| Jointing | 71 |
| Anthesis | 100 |
| Physiological maturity | 150 |
| Harvest maturity | 164 |
| Phenological stage of P. minor | |
| Flowering initiation | 78 |
| Completion of flowering | 96 |
| Maturity | 128 |
Table 2.4.2 Effect of P. minor density (No./m2) on yield and yield attributes of rice.
| Density of P. minor (No./m2) | Plant height (cm) | Effective tillers (No./m2) | Biological yield (t/ha) | Grain yield (t/ha) |
| 0 | 113 | 409 | 15.1 | 5.41 |
| 1 | 115 | 416 | 15.1 | 5.53 |
| 2 | 116 | 416 | 15.2 | 5.47 |
| 4 | 112 | 408 | 15.4 | 5.46 |
| 6 | 111 | 411 | 15.3 | 5.49 |
| 8 | 114 | 398 | 15.0 | 5.51 |
| 10 | 112 | 407 | 14.9 | 5.47 |
| SEm± | 1.7 | 10.5 | 0.20 | 0.13 |
| LSD (P=0.05) | NS | NS | NS | NS |