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Herbicide damage guide for cotton - PDF by benbenzhou


									                           Herbicide damage guide for cotton
Photographs & material by:                                    Graham Charles
                                                          NSW Dept. Primary Industries
Herbicide:                        dicamba                            Damage key:
Rate:                             140 g a.i./ha                 Leaf loss
% of typical field rate           50%                           Leaf distortion           x
Date of exposure:                 5th Dec                       Petiole distortion        x
                                  (9 weeks post-emergence)      Plant stunting            x
Growth stage at exposure:         11 nodes                      Square shedding           x
                                                                Boll shedding             x
                                    Herbicidal action
Herbicide group:           I
Translocation:     readily absorbed by leaves
Mode of action:    an auxin-type herbicide that affects plant growth, nitrogen metabolism
                   and enzyme production
Residual activity: limited
Soil half-life:    4 – 14 days

                                                 Kamba 500 applied broadcast at 280 ml/ha
                                                 to 11 node cotton. Photo taken on 14th Dec, 9
                                                 days after exposure.
                                                 The only symptoms of dicamba damage
                                                 apparent 9 days after exposure were cupping
                                                 of the new leaves, with reddening around the

                                                 Kamba 500 applied broadcast at 280 ml/ha
                                                 to 11 node cotton. Photo taken on 21st Dec,
                                                 16 days after exposure.
                                                 By 16 days, distorted growth was becoming
                                                 apparent on the new leaves, a symptom
                                                 typical of Group I damage. Many of the
                                                 emerging new leaves were “wedge” shaped,
                                                 ending in multiple “fingers”. Cupping and
                                                 reddening of the newer leaves was still

                                                 Kamba 500 applied broadcast at 280 ml/ha
                                                 to 11 node cotton. Photo taken on 2nd Jan, 28
                                                 days after exposure.
                                                 Plants were beginning to resume normal
                                                 growth on the laterals, but new growth on the
                                                 main stem was showing symptoms typical of
                                                 Group I damage. Distortion ranged from
                                                 almost normal leaves with a leathery
                                                 appearance and heavy venation, to cupped
                                                 leaves and more typical “wedge” shaped
                                                 leaves ending in multiple “fingers”.

       Revised Sept 2011                                                                 [J3.16.4]
                                                                                            Kamba 500 applied broadcast at 280 ml/ha
                                                                                            to 11 node cotton. Photo taken on 14th Jan,
                                                                                            40 days after exposure.
                                                                                            Symptoms of damage were disappearing as
                                                                                            new ‘normal’ growth developed. Distorted
                                                                                            growth could still be found in the centre of
                                                                                            the plant.

 1400        Undamaged crop
                                                                                                    Impact on plant growth

 1200                                                                  Open      160
                                                                                            Plants: exposure to a 50% rate of dicamba at
                                                                       bolls                   11 nodes caused stunting and symptoms
 1000                                                                                          typical of Group I damage. Plants
                                                                                               remained 17 cm and 7 nodes shorter at
                                                                                               picking and were 28% smaller by weight.
  600                                                                            80
                                                                                            Leaves: plants compensated for the herbicide
  400                                                                                          damage by producing a mass of vegetative
                                                                                               growth, resulting in 25% more leaves and
            Leaves                                                               20            19% more leaf area mid-season.
    0                                                                             0
        0     30      60     90   120    150     180     210    240   270      300          Squares: the damage delayed peak square
                                  Days since planting                                          production by around 30 days and
                                                                                 200           reduced peak squaring by around 30%.
 1400       Kamba 500 @ 280 ml/ ha at 11 nodes
                                                                                 180        Bolls: the herbicide exposure delayed boll
 1200                                                                            160           production by around 30 days. Early bolls
                                                                                 140           were shed from the first 3 fruiting
                                                                                               positions, with 68% of bolls retained on
  800                                                                                          outer positions. Boll weight was down by
                                      Leaves                           Open
                                                                                               16% and final boll retention by 38%. Boll
                                                                                               maturity was delayed by 39 days.
  400                                Green
                                                                                            Lint: ginning turnout was unaffected by the
  200                                                                                          herbicide damage, but the cotton was
                                                                                               immature, with low micronare (3.0) and
        0     30      60     90   120    150     180     210    240   270      300
                                                                                               lint yield was reduced by 59%.
                                  Days since planting

                                                                                                     Exposure to 50% of a typical field
                             Final plant count data
                                                                                                     rate of dicamba at 11 nodes caused
                                                        undamaged                 dicamba            moderate damage to emerging leaves
                                                                                                     with symptoms typical of a Group I
             Nodes/plant                                       27.8                    20.9          herbicide. Plants responded to the
               Leaves/m*                                       342                     647           damage by producing additional
                                                                                                     leaves and leaf area.
        Leaf area (cm2/m)*                                 13541                      16064
                                                                                                     Many early bolls were shed, changing
  Reduction in leaf area*                                                               -            the pattern of boll retention and boll
                   Bolls/m                                     200                     123           size, with few bolls retained on the
                                                                                                     main stem. Crop maturity was
 Boll weight (g/open boll)                                     4.2                     3.6           delayed, with many bolls still
                                                                                                     immature at picking, reducing fibre
 Retention in posit’s 1-3^                                     88%                     32%
                                                                                                     quality. Lint yield was down by 59%.
Nodes carrying >80% bolls#                                 6 - 22                     4 - 20
                                                                                                     Note* These parameters were last
        Days to 50% open                                       187                     226           recorded 119 days after planting.
   Maturity delay (days)                                                               39            Note^ Percentage of bolls retained on
                                                                                                     positions 1 – 3.
 % Open bolls at picking                                       86%                     80%
                                                                                                     Note# The spread of nodes carrying
             Lint yield/ha                                     2246                    923           more than 80% of open bolls.

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