Wild Radish Management and Control:

Wild Radish Management and Control:

Farm hygiene to prevent Wild Radish infesting clean areas is very important. Most infestations have been caused by the planting of contaminated crop seed or feeding of contaminated produce. Sheep that have been exposed to Wild Radish seed should not be allowed into clean paddocks for at least 2 weeks even though most seed is passed in the first 2-5 days (Heap and Honan, 1993).

Shallow cultivation early in the season will promote germination ⁹¹², ⁸⁹⁹.

In cereals, early control is required to gain the maximum yield benefits. Spraying at the 3 leaf stage of wheat normally returns 4-5 times more yield than spraying at tillering. Use of Diflufenican based products is preferred. Diflufenican will remain in the soil for some weeks and control later germinating seeds. Larger vegetative plants should be treated with Eclipse plus oil. Once the flowering stem has emerged Logran plus oil is preferred. At the hard dough stage of cereals 2,4-D may be used to reduce seed viability and twist radish plants down to the ground so the harvester may pass over the top of them. Just before harvest, green radish can be desiccated with diquat or the crop may be swathed.

Diuron plus MCPA is a useful alternative ³⁶ where resistance requires management.

Pre emergence mixtures of metribuzin plus pendimethalin have give good control of a range of grasses and broadleaved weeds including Wild Radish and Doublegee ⁹¹³

Canola also suffers significant yield losses from early competition from wild radish. Triazine tolerant varieties should be grown in infested paddocks and pre emergent atrazine application should be followed up with a post emergence application if wild radish survives to the 2 leaf stage.

In lupins, wild radish doesn't appear to be overly damaging to yield potential early in the season. Pre emergence simazine followed by a top-up application 2-5 weeks post planting usually provides good control ⁹¹⁴. Diflufenican should be used for early control and metosulam for later control in some varieties. Mixtures of the two products may be useful for controlling larger wild radish and providing residual control of late germinating seed. On some varieties mixtures of diflufenican plus metribuzin provide good control of Wild Radish.

In clover based pastures, spray grazing with 500 mL/ha of 2,4-D amine in early winter is cheap and effective. In medic and lucerne based pastures and 25 g/ha of Broadstrike may be used at the 3-4 leaf stage of the radish. In pastures, radish is not normally a problem and is only controlled to prevent it affecting future crops.

Black plastic and straw mulches can be used in horticultural situations for wild radish control. Soil solarisation, using clear plastic over cultivated, moist soil in summer for 30-50 days giving temperatures of 47.5 deg C at 5 cm deep gave 99% control ⁹¹⁵, ⁹¹⁶

Spectral imaging and textural analysis can be used to distinguish Wild Radish from crop plants ⁹¹⁷.

1-3 minute exposure to UHF radiation kills 78-100% of seed ⁹¹⁸.

⁹¹⁹ has a dielectric separator for removing Wild Radish from Sugar Beet seed.

Wild Radish grown under cool (5/10 deg C) conditions requires 7 times more glufosinate than plants grown under warm (20/25 deg C) conditions ⁹²⁰, ⁹²¹.

The ratio of dry weight of Wild Radish/Crop is better for determining weed control decisions than the soil seed bank ⁹²².

Flumetsulam and to a lesser extent metosulam are likely to fail at normal rates when the temperature is less than 5 deg C ⁹²³.

TCA increases the absorption of Pyramin in Wild Radish seeds ⁹²⁴

Flame weeders gave 93% control of 4-6 leaf Wild Radish and 21% control of 12 leaf plants ⁹²⁵

⁹²⁶ reviews methods of reducing the Wild Radish seed bank.

Multi species RIM is a bio-economic model to compare management strategies for Wild Radish and Annual Ryegrass ⁹²⁷, ⁹²⁸. ⁹²⁹, ¹¹² have yield loss data for WA.

Green and brown manuring are only profitable where Wild Radish numbers are very high or resistance is severe ⁹³⁰, generally a longer pasture followed by a long cropping phase is more profitable ⁹³¹.

Theory and practice of mechanical separation of Wild Radish from Buckwheat is presented in ⁹³², ⁹³³, ⁹³⁴ and ⁹³⁵ and ⁹³⁶ looks at the requirements for cleaning in sugar beet.

Thresholds:

In cereals, 10 plants/m² typically reduces cereal yields by 10% and 200/m² causes a 50% yield reduction in wheat ⁹²⁹, ⁹³⁷ and a decease in grain size resulting in increased levels of screenings ⁹³⁸. Less than 1 plant/m² will cause sufficient contamination to incur dockage. If there are more than 10 plants/m²spray early with Diflufenican based residual herbicides. If less, spray later with Eclipse or Logran based products.

In heavy infestations the cereal yield response to early spraying is often 4-5 times more than for late spraying. Applications after tillering generally give little response in cereal yield and are used to reduce grain contamination and reduce weed seed set.

⁹³⁹ has thresholds for wild radish in Australian cereals.

Competitive effects are proportional to seed weight and biomass in wheat ⁹⁴⁰ so increasing wheat planting rates reduces effects of competition but never solves the grain contamination problem ⁹²⁹.

Wild Radish emerging 4 weeks after wheat had no effect on yield in Victoria but seeds were produced on plants emerging up to 10 weeks after the cereal crop ⁹⁴¹.

In Turkey, economic thresholds are 1.8-2 plants/m² with 4 t/ha wheat crops ⁹⁴².

Economic threshold in Canada was 37 wild radish/m² in 250 barley/m² which is over double the Australian densities and the main effect was on tillering ⁹⁴³.

In Florida farms, yields of wheat were not reduced if Wild Radish was controlled within 6-8 weeks of emergence ⁹⁴⁴, However in WA, spraying at the 3-4 leaf stage usually gives greater wheat yields than later spraying ⁹⁰⁴.

In Canola, the response is greater with 5 plants/m² reducing yields by about 10% and 100 Wild Radish/m² causing a 50-75% yield reduction {Moore, 2002}. The time of emergence of the Wild Radish compared to the Canola has a big effect with 64 plants/m² emerging with the crop causing an 77-90% yield reduction and a 19% yield reduction when they emerged 7 weeks after the crop and no yield reduction when they emerged 10 weeks after the crop ⁷⁹⁰.

In Lupins and pulses the timing of spraying has little effect on yields providing it is done before the Wild Radish starts to compete for water or light late in the season. For each gram of Wild Radish grown, 0.67 g Lupin dry mass is lost. 2 Wild Radish/m² reduced Lupin yield by 4-15% and 20/m² reduced yield by 48-59% ⁹⁴⁵ and up to 92% is some situations ⁹³⁸.

Wild radish reduces lupin yields by decreasing pod number and grain size and also reduced germination percentage ⁹⁴⁶.

Increasing lupin density up to 50 lupins /m² doesn't affect the numbers of weeds but does reduce their effect and adding simazine pre plant reduces weed numbers and increases lupin yields by increasing pod numbers ⁹⁴⁷.

Eradication strategies:

Wild radish will be difficult if not impossible to eradicate once it has established in an area. Quarantining clean areas of the farm is advised. Drought feeding should be restricted to contaminated paddocks and careful monitoring of crop seeds and produce entering clean areas should be conducted. Odd plants can be removed by hand before seeding and an buffer area 5 m should be sprayed with 500 mL/ha (or 50 mL/100L for spot spraying) of Brodal.

On infested areas, plan to crop for at least 5 years.

The aim is to stop seed set completely. This usually requires 2 spays per year ⁹³⁷.

Burn or graze trash over summer. Shallow cultivate to 10 mm deep, 5 days after the first rains to stimulate emergence and desiccate the first germination. Apply 750 mL/ha Glyphosate plus 500 mL/ha of Tigrex 7 days after the second rains and plant wheat 5 days later. Apply 500 mL of Spray.Seed plus 40 g/ha Logran 5-7 days after planting before the wheat emerges. At the 3-4 leaf stage of the crop, apply 500 mL/ha of Tigrex. At stem elongation apply 15 g/ha Logran plus 1% spray oil. If any surviving radish look like they may set seed then 500 mL/ha of 2,4-D ester can be used at the firm dough stage of wheat. Before harvest, 2 L/ha diquat(200g/L) can be used if necessary to desiccate green plants. These may re shoot after harvest if there is sufficient soil moisture. These should be treated with 500 mL/ha glyphosate(450g/L) plus 10 g/ha of Logran plus 1% oil (i.e. 1 L of spray oil per 100 L of spray mix). Use a seed catcher, behind the harvester and dispose of seed by treating with diesel and burning or burying at least 500 mm deep. A salt scald is an ideal location providing water doesn't flow over the area to move seed.

If summer rains cause a germination of wild radish then spray with 750 mL/ha Tigrex when the plants are young and graze heavily with sheep that have not been exposed to wild radish seed for at least 2 weeks. If grazing is not an option then spray with 500 mL/ha of glyphosate(450g/L) plus 10g/ha of Eclipse plus 1% oil.

In the second year, shallow cultivate as above, then apply 750 mL/ha glyphosate(450g/L) plus 250 g/ha of Diuron(900g/kg) plus 500 mL/ha of Tigrex. 7 days later plant barley. Apply 500 mL/ha of Spray.Seed plus 50 mL/ha of Brodal 3-6 days after planting before the barley emerges. At the 4-5 leaf stage of the barley apply 500 mL/ha of Tigrex. At the elongation stage of the barley and wild radish, 15g/ha of Logran plus 1% oil can be applied if necessary. At the firm dough stage of the barley, 500 mL/ha of 2,4-D ester(800g/L) or at the hard dough stage 2000 mL/ha of Reglone may be used to prevent any survivors setting seed. Use a seed catcher to collect seed at harvest and dispose of as above.

In the third year, plant lupins because they are tolerant to both Brodal and Eclipse. If high levels of control have been achieved in the first two years then it is appropriate to consider reducing the level of tillage. This is because the negative effect of exposing dormant seed or burying surface seed and inducing dormancy could be greater than positive effect of improving germination. Apply 500 g/ha Atrazine(900g/kg) plus 1000 g/ha of Simazine(900g/kg) plus 100 mL/ha Brodal plus 1% oil just before the break of the season (add 750 mL/ha of Spray.Seed if any green plants are present). Dry seed or plant lupins just after the break with minimum surface soil disturbance. At the 2 leaf stage of the lupins apply 100 mL/ha of Brodal. At the 10-20 leaf stage of the lupins apply 7 g/ha of Eclipse plus 0.25% wetting agent if necessary. When the lupin seed on lateral pods has reached 75% of its mature size, 2000 mL/ha of paraquat(250g/L) may be used to desiccate any surviving wild radish. Use sheep or a follow up spray of 500 mL/ha of glyphosate(450g/L) plus 10g/ha Eclipse plus 1% oil to control re shooting if necessary after harvest. Use a seed catcher.

By now, there should be less than 1 plant/m² left to germinate. In the fourth year plant triazine tolerant canola. Apply 500 mL/ha Spray.Seed plus 1000 g/ha atrazine(900g/L) plus 1% oil 10 days after the break of the season. Plant triazine tolerant canola 2 days later. Apply 1000 g/ha atrazine(900g/L) plus 1% oil 4 weeks after planting. If radish appear close to harvest then desiccate the crop with 1000 mL/ha of glyphosate (450g/L) or 3000 mL/ha of Reglone. Otherwise, swath the crop.

When grazing stubbles, make sure the stock have been in areas free from wild radish seed for at least two weeks before introducing them into the wild radish control areas.

Always use absolutely clean seed when planting paddocks in the control program and don't feed hay or grain in these areas.

In areas that can't be cropped, apply 500 mL/ha of Tigrex in early winter and graze with 4-5 times the normal stocking rate 7 days after spraying. Use Jaguar on medic or lucerne based pastures. For summer germinations, apply a mixture of 500 mL/ha of glyphosate(450g/L) plus 500 mL/ha of Tigrex plus 1% oil on dried annual pastures (or 5 g/ha of Eclipse plus 50 mL/ha of Brodal plus 1% oil on perennial pastures) when the wild radish plants are young, and graze 7 days after spraying.

Areas that have been cut for hay often require special attention. Firstly, herbicides should be used to ensure there is no viable seed at the time of hay cutting. This ensures the hay does not become a source of contamination of clean areas. Secondly, wild radish sometimes grows prolifically after the haymaking process has removed competition. Eclipse at 10g/ha plus 1% oil is usually a good option for controlling wild radish regrowth.

Fence lines, firebreaks and unused areas may be treated with a mixture of 1000 mL/ha glyphosate(450g/L) plus 1000 mL/ha Tordon 75-D plus 1500 g/ha of atrazine(900g/kg) plus 1000 mL spray oil plus 1000 g of crystalline ammonium sulphate per 100 L of spray mix in autumn. This will provide season long weed control. In areas where it is desirable to maintain ground cover a mixture of 1500 mL/ha Tordon 75-D plus 200 mL/ha of Brodal plus 1% oil applied early in the season will control established plants and provide residual control of wild radish seedlings for the season with little effect on grasses. For spot spraying isolated plants, a mixture of 500 mL of Tordon 75-D plus 50 mL of Brodal plus 1000 mL spray oil per 100 L water is effective. A buffer area of 5-10 m around these plants should be sprayed until just wet to capture any seed that may germinate after spraying.

Herbicide resistance:

21% of wild radish populations in the northern, central and eastern wheat belt were resistant to chlorsulfuron in 1998 ⁹⁴⁸.

Populations resistant to the sulfonylurea (group B) herbicides and triazines ⁷⁵⁰ have been found.

⁹⁴⁹ has described the target site resistance mutation.

13% of populations of Wild Radish that were resistant to chlorsulfuron (Group B) showed low levels of cross resistance to the group B mixture of imazapic plus imazapyr (OnDuty®) used in IT tolerant Canola ⁹⁵⁰.

⁹⁵¹ have a seed soaking technique for testing group B resistance.

Triazine tolerance from Canola is not likely to be transferred to Wild Radish because it is not carried on the genes in the pollen.

The Syngenta Quick Test can be used to determine resistance status of Wild Radish to group B herbicides.

⁹⁵², ⁹⁵³ have determined the mutations in the wild radish ALS gene resulting in resistance to group B herbicides. The ALS gene is 1758 base pairs long.

Multiple resistance has been found to group C (metribuzin & atrazine), group F (diflufenican) and group I (2,4-D) and another population to group B (sulfonylureas), group I (2,4-D) and group F (diflufenican) ⁹⁵⁴.

Biological Control:

Redlegged Earth Mite, Cabbage Moth, Thrips, Rutherglen Bug and White Italian Snail attack Wild Radish but don't provide sufficient control. Downy Mildew infects it but rarely causes significant damage. Ants may eat seeds.

Because Wild Radish is in the Brassicaceae family that contains many important crops, introduction of biological control agents from overseas will be limited. There is currently CSIRO research projects are evaluating potential biocontrol agents in the Mediterranean region.

Responses by the plant to insect attack may increase or decrease it susceptibility to further attack or to attack by other insects ⁹⁵⁵.

It is relatively tolerant to Blackleg (Leptosphaeria maculans) ⁹⁵⁶.

Phytoplasmas have attacked Wild Radish in Italy and caused significant damage ⁹⁵⁷.

Mycoherbicides have been investigated for biocontrol of Wild Radish ⁹⁵⁸ but development in Australia has been suspended. ⁹⁵⁹ has reviewed biocontrol of Wild Radish.

⁹⁶⁰ lists insect of Wild Radish in the USSR.

Deleterious Rhizobacteria have some effect on wild radish ⁹⁶¹.