Previous PageTable Of ContentsNext Page

Herbicide resistance in littleseed canarygrass (Phalaris minor) and its management

RS Chhokar, RK Sharma, RK Singh and SC Gill

Directorate of Wheat Research, Karnal-132001, India, Email rs_chhokar@yahoo.co.in

Abstract

Littleseed canarygrass (Phalaris minor) is a serious weed of irrigated wheat in India that developed resistance to photosystem II- inhibiting herbicide (isoproturon) during the early 1990s. Isoproturon resistance is now common throughout the Indo-Gangetic Plains of India covering more than one million ha. Recently, some of the populations have evolved multiple resistances to 3 modes of action (Photosynthesis at photosystem II site A, ACCase and ALS inhibitor). However, these multiple resistant populations are sensitive to triazine (metribuzin and terbutryn) and dinitroaniline (pendimethalin) herbicides. The dependence on herbicides has contributed to the rapid evolution of multiple herbicide resistance and integrated weed management strategies must be developed to ensure the long term sustainability of wheat production in India. Early sowing, zero tillage and bed planting technique reduce the incidence of P. minor. The long term strategies comprising crop rotation, herbicide rotation and sanitation practices (weed free crop seeds and manure) along with other agronomic tactics (competitive variety, early sowing, higher seed rate, zero tillage, stale seed bed etc.) need to be integrated for effective management of herbicide resistant P. minor in wheat.

Key Words

Multiple herbicide resistance, zero tillage, crop rotation and early sowing

Introduction

Littleseed canarygrass (Phalaris minor) is the most troublesome winter season grass weed of wheat under rice-wheat sequence in India. This weed was not a problem until the mid 1970’s when new, less competitive dwarf wheat varieties were adopted and fertilizer applications increased. The weed thrived in this new agro-environment (Singh et al. 1999). Isoproturon was recommended for control in the late 1970s and was widely used as it was cost effective, had a wide application window, flexible method of application, offered broad spectrum weed kill along with its selectivity under wheat and mustard intercropping (Gill et al. 1978). However, during early 1990s the situation degraded as P. minor populations escaping isoproturon treatment were selected as resistant biotypes (Malik and Singh 1995). After isoproturon resistance evolution there were instances of complete wheat crop failure in absence of effective alternate herbicides (Malik and Singh 1995). The isoproturon resistance affected area is about 1.0 m ha. For the control of isoproturon resistant P. minor, four herbicides (sulfosulfuron, clodinafop, fenoxaprop and tralkoxydim) were recommended but farmers mainly used sulfosulfuron and clodinafop (Chhokar and Malik, 2002) because of their better efficacy and compatibility with metsulfuron. However, weed populations have also developed herbicide resistance to these modes of action (Chhokar and Sharma, 2008). The multiple resistance problems at few locations are so severe that it is causing huge grain yield reductions (Chhokar and Sharma, 2008). If the problem of resistance is not tackled, it may lead to serious consequences leading to decreased wheat production in the rice-wheat sequence. The present study was carried out with the aim to identify the effective herbicides and other non chemical weed control options against this serious weed for the sustainability of wheat production.

Methods

Herbicide resistance profile study.

Six populations of P. minor showing differential response to herbicides in field conditions were selected for a herbicide resistance profile study. The 6 populations were P1 (Directorate of Wheat Research Farm, Karnal, India); P2 (Uchana, Karnal), P3 (Kachhawa, Karnal); P4 (Sagga-1, Karnal); P5 (Sagga-2); P6 (Kamalpur, Nilokheri). P1 population was susceptible (S) to herbicides. The pots were filled with soil and well-rotted farm yard manure (FYM) in 6:1 ratio by volume after passing through a 2 mm sieve. Fifty seeds in each pot of P. minor populations were sown during the rabi season (winter) of 2007-08. Each treatment was replicated thrice. Plants were thinned two weeks after emergence, to 10 plants/ pot. Thirty days after sowing, isoproturon, metribuzin clodinafop, fenoxaprop, sulfosulfuron, mesosulfuron, pinoxaden, terbutryn, glyphosate, paraquat, quazilofop ethyl and pendimethalin were sprayed with a knapsack sprayer fitted with flat fan nozzles (Table 1). Surfactants, Leader Mix (polyethylene amine) at a conc. of 0.35 % (v/v) in sulfosulfuron and Puma activator at 500 ml/ha in fenoxaprop treatment were used. The spraying was done using 350 L/ ha of water at three-leaf stage of P. minor. Biomass cuts were taken 4 weeks after spraying and fresh weight was measured and expressed as a percentage of the control. Differences amongst treatment means were determined using ANOVA and when the F test was significant means were compared with LSD test at 5% level of significance.

Effect of tillage on P. minor

The effect of tillage in wheat under rice-wheat system on P. minor was evaluated on four farmer’s fields during 2 consecutive crop seasons (2005-06 and 2006-07). Wheat cv. PBW 343 was sown under zero tillage (ZT) and conventional tillage (CT) with similar package of practices except time of sowing. The crop in ZT was sown during the last week of October, whereas crop in CT was sown during second week of November. Fields were 4000 m2 in size and each field was divided in to 2 equal parts for sowing under ZT and CT. Sowing under ZT was done with zero till drill in a single operation, sowing in CT was done by same drill after conventional field preparation. For conventional tillage field preparation, 4, 2 and 3 passes of harrow, cultivator and plank, respectively were performed. Glyphosate @ 0.5% spray solution was applied using 300 l water/ha in ZT fields. Herbicide combinations, sulfosulfuron + metsulfuron 30 + 2 g/ha was applied at around 30-35 DAS, by leaving an area of 3 3 m2 as untreated at three places each in ZT and CT to examine the effect of tillage on P. minor. The P. minor fresh weight was recorded at 120 DAS under ZT and CT from each quadrat. Fischer t test was used for comparing the significance of two treatments means.

Effect of cropping sequence on P. minor

In an another study, to identify the effect of cropping sequence on P. minor, observations from 9 farmer’s field were taken under rice-wheat and rice-pea/potato-wheat cropping system. After rice harvest the short duration vegetable pea or potato were grown and after their harvest late wheat was sown during second fortnight of January. The P. minor populations in each field were recorded at 3 places just before the second irrigation. The two cropping systems were compared using Fischer t test.

Results

Herbicide resistance profile:

The response of 6 populations of P. minor to various herbicides are given in Table 1. The population P1 was susceptible to all the herbicides tested (isoproturon, clodinafop, fenoxaproip, pinoxaden, quazilofop, terbutryn, metribuzin, mesosulfuron, glyphosate, paraquat and pendimethalin). Where as, biotype P2 was resistant to isoproturon only. It means the isoproturon resistant biotype can be controlled with the rest of the herbicides. Three populations (P4, P5, P6) were resistant to 2 groups of herbicides ALS inhibitor (sulfosulfuron and mesosulfuron) and photosystem II (PS II) inhibiting herbicide (isoproturon). These populations were sensitive to ACCase–inhibiting herbicidal chemistries (clodinafop, fenoxaprop, quazilofop and pinoxaden). The P3 population was resistant to PS II and ACCase-inhibitor but was sensitive to sulfonyl ureas (sulfosulfuron and mesosulfuron), triazines (terbutryn and metribuzin), pendimethalin, glyphosate and paraquat. None of the populations showed resistance to pendimethalin, glyphosate, paraquat, terbutryn and metribuzin. One biotype has evolved multiple resistances against 3 modes of action (PS II site A, ACCase and ALS inhibitor). For control of such populations, dintroaniline (pendimethalin) and triazines (terbutryn and metribuzin) as pre or post-emergence treatment and glyphosate and paraquat as pre-seeding treatment can be used. However, sole dependence on herbicide will lead to herbicide resistance of these modes of actions. The continuous usage of a herbicide or herbicides belonging to the same group will increase the evolutionary rate of herbicide resistant weed populations (Beckie, 2006). Low levels of herbicides were used continuously in the wheat – rice rotations and this practice contributed to the prevalence of herbicide resistance in P. minor throughout India.

Effect of cropping sequence on P. minor

The inclusion of short duration crop like, potato and pea, in between rice-wheat system resulted in significant reduction in population of P. minor (Fig. 1). Its population in rice-pea/potato-wheat system was 46 plants/m2 whereas in rice-wheat system was 589 plants/m2. Adoption of such a sequence will reduce the seed bank of this weed over time. Besides reducing the P. minor population this intensified system will also improve the profitability and sustainability of the system. Similarly Malik and Singh (1995) also reported the beneficial effect of crop rotation in reducing the incidence of P. minor and herbicide resistance. Crop rotation and herbicide rotation helps in lowering the selection pressure (Gressel and Segel 1990). Crop rotations do not merely delay resistance by allowing use of different management options, but they also restore diversity in weed flora. Some crop rotations [growing Egyptian clover (Trifolium alexandrinum) for two years] may even be able to exhaust the soil seed bank of P. minor, thus providing a long term solution (Malik and Singh, 1995).

Table 1. Response of Phalaris minor populations to different herbicides.

Herbicide

P. minor populations

 

P1

P2

P3

P4

P5

P6

Mean A

 

% control

Control

0.0

0.0

0.0

0.0

0.0

0.0

0.0

Sulfosulfuron 12.5 g/ha

100.0

100.0

100.0

26.5

2.8

59.9

64.9

Sulfosulfuron 25 g/ha

100.0

100.0

100.0

47.8

8.8

97.8

75.7

Mesosulfuron + iodosulfuron 12 + 2.24 g/ha

100.0

100.0

100.0

54.9

92.4

99.3

91.1

Terbutryn 1000 g/ha

100.0

100.0

100.0

100.0

100.0

99.9

100.0

Metribuzin 300 g/ha

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Clodinafop 60 g/ha

100.0

100.0

3.7

91.9

99.4

23.7

69.8

Fenoxaprop 100 g/ha

100.0

100.0

7.4

91.2

96.8

11.8

67.9

Pinoxaden 30 g/ha

100.0

100.0

49.7

93.3

99.5

48.5

81.8

Quazilofop 50 g/ha

100.0

100.0

29.8

90.7

89.5

32.5

73.7

Isoproturon 1000 g/ha

100.0

8.2

15.2

16.7

9.4

7.7

26.2

Paraquat 500 g/ha

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Glyphosate 0.5%

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Pendimethalin 1000 g/ha

98.3

99.3

96.7

95.7

98.7

98.0

97.8

Mean B

92.7

86.3

64.5

72.1

71.2

62.8

 
   

Factor(A)

Factor(B)

Factor(A X B)

     

LSD (P=0.05)

2.830

1.852

6.931

     

Fig 1. Effect of cropping system on P. minor density. Vertical bars represent SEM. Means are significantly different at P=0.01 using "Fischer's t test"

Effect of tillage on weeds and wheat productivity

In wheat, the P. minor fresh biomass was lower in ZT (1330 g/m2) compared to CT (3579 g/m2) (Fig. 2). The lower dry weight in ZT might be due lower emergence levels associated with higher soil strength (Chhokar et al, 2007) and less favourable temperature during early sowing (Chhokar and Malik, 1999). The population of P. minor may be further reduced if encouraged to germinate through pre sowing irrigation and killed with non-selective herbicides (glyphosate/paraquat) followed by seeding under ZT conditions. These practices would suppress the seed bank and reduce soil disturbance. Therefore, an integrated approach consisting of ZT with slightly advanced sowing (last week of Oct.) with higher seed rate and narrow row spacing of competitive cultivars can drastically reduce P. minor population. Further if ZT is practised with residue retention then weed infestation may be further reduced due to mulch and allelopathy effect (Crutchfield et al, 1986).

Fig 2. Effect of tillage on P. minor biomass Vertical bars represent SEM. Means are significantly different at P=0.10 using "Fischer's t test"

Conclusions

The evolution of multiple herbicide resistance in P. minor is a major threat to wheat production in India. Management strategies must be developed to prevent selection and spread of herbicide resistant populations. The development of herbicide resistance in P. minor can be minimized if a range of integrated weed management strategies are used including alternative herbicide, crop rotation and other agronomic practices such as zero tillage, early sowing, competitive crop cultivars, higher crop density and sanitation practices (weed-free crop seeds and manure). Substituting short duration crops, such as potato and pea in between rice and wheat sequence can also help in P. minor management. The integration of all these approaches will likely to minimize the impact of herbicide resistance on crop production and farmers income.

References

Beckie HJ (2006). Herbicide resistant weeds: Management tactics and practices. Weed Technology 20, 793-814.

Chhokar RS and Malik RK (1999). Effect of temperature on the germination of Phalaris minor Retz. Indian Journal of Weed Science 31, 73-74.

Chhokar RS and Malik RK (2002). Isoproturon resistant Phalaris minor and its response to alternate herbicides. Weed Technology 16, 116-123

Chhokar RS, Sharma RK, Jat GR, Pundir AK and Gathala MK (2007). Effect of tillage and herbicides on weeds and productivity of wheat under rice-wheat growing system. Crop Protection 26, 1689-1696.

Chhokar RS and Sharma RK. (2008). Multiple herbicide resistance in littleseed canarygrass (Phalaris minor); A threat to wheat production in India. Weed Biology and Management 8, 112-123.

Crutchfield DA, Wicks GA and Burnside OC (1986). Effect of winter wheat (Triticum aestivum) straw mulch level on weed control. Weed Science 34, 110-114.

Gill HS, Walia US and Brar LS (1978). Control of Phalaris minor Retz. and wild oat in wheat with new herbicieds. Pesticides 12(3), 53-56.

Gressel J and Segal LA (1990). Modelling the effectiveness of herbicide rotations and mixtures as strategies to delay or preclude resistance. Weed Technol. 4, 186-198.

Malik RK and Singh S (1995). Littleseed canarygrass (Phalaris minor Retz.) resistance to isoproturon in India. Weed Technology 9, 419-425.

Singh S, Kirkwood RC and Marshall G (1999). Biology and control of Phalaris minor Retz. (littleseed canarygrass) in wheat. Crop Proection 18, 1–16.

Previous PageTop Of PageNext Page