Control of weeds in maize and wheat – Part 4: Devil’s thorn

    1440
    Young seedling still actively growing.
    Mature Devil’s thorn plant.

     

    Fruiting bodies containing seed.
    Flowering and developing fruiting bodies.

     

    Scientific name: Tribulus terrestris
    Afrikaans names: Dubbeltjie, platdubbeltjie, volstruisdoring
    English name: Devil’s thorn, common dubbeltjie, burnut

    Short description 

    Devil’s thorn is a pesky, annual endemic, creeping, prostrate weed that can spread up to 1 m in diameter.

    The weed is multi-branched, with sturdy, long taproots. Stems are finely corrugate, greenish-brown and white felty haired. Leaves are opposite, once pinnately compound, with one of the pair shorter than the other.

    The upper (adaxial) surface of the leaves is bright shiny green, the lower (abaxial) surface is dull green to white because of dense hairs. Flowers are axillary, solitary, bright yellow, on hairy pedicels and are up to 1 cm in diameter.

    Young fruits in which seeds are borne, are green, fleshy but become woody, each with two long and two shorter, sharp spines. Seed fruits’ spines are very sharp and hook onto animals’ wool, coat and feet, as well as onto shoe soles and tractor tyres. This is how they are distributed.

    Devil’s thorn only propagate by means of seed. The plant causes “geeldikkop” disease or tribulosis in sheep, especially when wilted plants are eaten (hot, dry conditions).

    Distribution 

    Widespread in southern Africa. They are a problem on sandy soils, especially in parts of the North West Province and can be a strong competitor for moisture. Devil’s thorn seeds have the ability to still emerge and grow successfully, even in very dry conditions.

    Control

    Cultivation
    Because of its prominent tap roots, devil’s thorn can be easily controlled mechanically by severing its tap roots beneath the soil.

    Chemical
    Control with pre-emergence herbicides is precarious where devil’s thorn is a serious problem (high levels of infestation). Enough soil moisture is necessary to activate the pre-emergence herbicides in the soil and to give effective control.

    Post-emergence herbicides gives better control, but then devil’s thorn has to be controlled as early as possible – before it reaches the six leaf stadium. Because it is a prostrate and creepy weed, it has to be controlled before it branches. The control of bigger devil’s thorn will be less successful. Herbicides registered for the control of devil’s thorn in maize and wheat are summarised in Tables 1 and Table 2.

    TABLE 1: Herbicides registered on maize for the control of Devil’s thorn.

    Active ingredient Formula Time of application
    2,4-D

    480 g/litre

    Only post-emergence when crop is 30 cm tall, drop-arms should be used for directed application
    2,4-D/dicamba240/80 g/litrePost-emergence when weed is actively growing, five to six leaf stage

    acetochlor/atrazine/simazine160/165/165 g/litrePre-emergence or just after planting
    acetochlor/atrazine/terbuthylazine
    125/187,5/87,5 g/litre
    Pre-emergence with plant or within three days after planting
    acetochlor/atrazine/terbuthylazine (with and without safener)150/225/225 g/litre

    200/150/150 g/litre

    250/225/225 g/litre

    350/175/175 g/litre
    Early post-emergence, but not later than the four leaf stage of the weed
    atrazine500 g/litrePre-emergence on well-prepared seedbed.

    Early post-emergence at two leaf stage of the weed
    atrazine/cyanazine167/333 g/litre

    250/250 g/litre
    Pre-emergence or early post-emergence
    atrazine/mesotrione/s-metolachlor208,5/26,8/208,5 g/litrePre-emergence
    atrazine/metazachlor/terbuthylazine210/60/210 g/litrePre-emergence or within three days after planting.

    Can be followed-up with an early post-emergence application
    atrazine/sulcotrione
    300/125 g/litre
    Pre- or post-emergence application
    atrazine/terbuthylazine250/250 g/litre

    300/300 g/litre

    450/450 g/kg
    Pre-emergence or post-emergence, but before four leaf stage of weed
    atrazine/terbutryn250/250 g/litrePre-emergence with planting or just after planting
    bendioxide480 g/litrePost-emergence application
    bromoxynil225 g/litre

    400 g/litre

    450 g/litre

    500 g/litre
    Post-emergence application when weed is still between the four to six leaf stage
    bromoxynil/terbuthylazine150/333 g/litrePost-emergence application
    dicamba700 g/kgPost-emergence application before crop is 30 cm tall
    dicamba/topramezone160/50 g/litreEarly post-emergence before the six leaf stage.

    Apply with tank mix of atrazine or atrazine/terbuthylazine
    flumetsulam200 g/litre

    800 g/kg
    Pre-emergence, apply with tank mix of metolachlor or s-metolachlor
    glyphosate/mesotrione/s-metolachlor250/25/250 g/litrePost-emergence, only on glyphosate-resistant cultivars
    halosulfuron750 g/kgPost-emergence application
    MCPA400 g/litre

    700 g/kg
    Pre-emergence application within five to six days of planting
    Post-emergence until crop is 30 cm tall
    mesotrione480 g/litrePre- or post-emergence.
    Apply only in tank mix with atrazine, terbuthylazine or s-metolachlor
    s-metolachlor960 g/litrePre-emergence application within three days after planting

    s-metolachlor/terbuthylazine102,8/497,2 g/litre
    312,5/187,5 g/litre
    Pre-emergence application Early post-emergence application with tank mix of mesotrione
    metribuzin480 g/litrePost-emergence application between four and six leaf stage of weed in tank mix with 2,4-D or bromoxynil
    nicosulfuron240 g/litre

    40 g/litre

    750 g/kg

    Post-emergence application between two and six leaf stage of crop
    tembotrione/isoxadifen-ethyl420/120 g/litre

    Post-emergence application in tank mix with atrazine
    topramezone/dicamba

    50/160 g/litreEarly post-emergence before six leaf stage apply in tank mix with atrazine or atrazine/terbuthylazine

    TABLE 2: Herbicides registered on wheat for the control of Devil’s thorn.

    Active ingredient Formula Time of application
    2,4-D480 g/litrePost-emergence application when crop is between seven and 13 growth stage
    2,4-D/dicamba
    240/80 g/litre
    Post-emergence application when crop is between seven and 13 growth stage
    bendioxide480 g/litre

    Post-emergence application when weed is still actively growing
    bromoxynil225 g/litre

    400 g/litre

    450 g/litre

    500 g/litre
    Post-emergence application before the six leaf stage of the weed and the three leaf stage and the end of stooling stage
    chlorsulfuron750 g/kgPost-emergence application when crop is between two and five leaf stage
    chlorsulfuron/metsulfuron-methyl/

    tribenuron-methyl
    119/79/222 g/kg

    Post-emergence application when crop is between four and six leaf stage
    dicamba700 g/kgPost-emergence application in tank mix with Enhancer (10 - 12 g) and Reaper (10 g)
    halosulfuron
    750 g/kg

    Post-emergence application
    MCPA400 g/litre

    700 g/kg
    Post-emergence application when crop is between seven and 13 growth stage
    metsulfuron-methyl200 g/kg

    600 g/kg
    Post-emergence when crop is between three to five leaf growth stage

    metsulfuron- methyl/thifensulfuron68/680 g/kgPost-emergence application before five leaf stage of weed

    trifluralin480 g/litreApply before planting

    For effective control, post-emergence herbicides have to be mixed with an additive that improves the penetration of the herbicide. See product labels for specifications and tank mixtures that are registered. Always contact a reliable chemical advisor before using any chemicals to adhere to the correct dosages and specifications on the label.

    Contact the writers at elbe.hugo@syngenta.com (Elbe Hugo) and deweth@arc.agric.za (Hestia Nienaber).