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Carrots

Last updated on July 5, 2024

Carrots

Growing Carrots

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Varieties

Fresh Market Bunching

Mokum, Nelson, Austria, Yaya, Tendersnax.

Fresh Market Packaging

Maverick, Appache, Enterprise, Six Shooter, Sweet Bites.

Nantes Types

Bolero, Magnum, Nevis, Napa, Nelson, Vitana.

See your seed dealer for the most recent variety recommendations.

 

Soils

Deep well-drained, sandy loam and muck soils of pH 5.5 to 7.0 are desirable. A chisel plow is recommended to work these soils to a depth of 30 to 40 cm for good root penetration.

 

Seeding

Seed Treatment

Purchase treated seed if possible. For control of damping off and seedling blight caused by Pythium spp., Fusarium spp. and Rhizoctonia spp., use seed treated with Apron MAXX RTA.  See the Carrots Insect Management section below for information on a seed treatment option for suppression of carrot rust fly.

Lower Mainland

Drainage permitting, the first fields are seeded mid-March and the last about the first of July. Raised beds of at least 10 cm height on 1.8 m centres should be used throughout the season.

Some growers have shifted from 4 rows 36 cm apart per bed to 3 rows 46 – 48 cm apart per bed. Seeding with a precision seeder is recommended. With a special shoe, 3 lines are seeded per row with belts punched to allow 6 to 7 seeds per 30 cm of line evenly spaced in a triangular pattern. Use the lower rate when reported germination is over 90%.

With normal coating and spacing, approximately 7 kg/ha (2.8 kg/acre) of coated seed are required, resulting in a final population of about 1,000,000 plants/ha (400,000 plants/acre). For cut’n’peel production, where long, slender carrots are cut into 3 equal pieces, use appropriate varieties at 2 to 3 times the above seeding rate. More rows per bed may be seeded for the production of baby-whole carrots (see below).

Baby-Whole Carrots

To obtain a uniform size and shape of baby-whole carrots, seed should be sown at high density and distributed evenly in wide bands or solid beds. The raw seed should be size-graded by the supplier. Rows should be 22 to 30 cm apart. Planting at 22 cm results in a solid bed.

 

Fertilizer

A soil test is necessary to determine phosphate and potash requirements. Use the Vegetable Production Guide: Nutrient Management (PDF) for recommendations based on soil test results.

Apply 70 kg/ha (28 kg/acre) nitrogen.

For the early crop, broadcast and disc in all the required phosphate but only half the nitrogen and potash. Band the balance after the crop has germinated. For the later seedings, broadcast all the fertilizer before seeding.

An additional sidedressing of 40 to 70 kg/ha (16 to 28 kg/acre) nitrogen may be required on sandy soils or on muck if early crops have been subjected to heavy rainfall.

 

Carrot Weed Management

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Pre-plant Incorporation

Pre-plant Incorporation: Herbicide Application Rates
Product Rate PHI* Comments

Bonanza 480

(trifluralin)

Group 3
 1.25 to 2.3 L/ha
(500 to 900 mL/acre)

Apply in a minimum of 100 L/ha (40 L/acre) of water at 275 kPa 		N/A
  • Rates vary with soil type, see label for detail.
  • Controls seedling grasses and some broadleaved weeds.
  • Lady’s-thumb, nightshades, groundsel, shepherd’s-purse, cudweed and mustards are not controlled.
  • Use the lower rate on sandy soil, the higher rate on heavier soils.
  • Apply treatment from 3 weeks before planting and incorporate thoroughly within 24 hours to 8 to 10 cm deep.
  • Effectiveness is reduced on cold, wet soils or on mineral soils with less than 2% or greater than 15% organic matter.
  • If manure is spread prior to application, ensure it has been thoroughly mixed into soil with at least 2 tillage operations prior to application.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Stale Seed Bed

Stale Seed Bed: Herbicide Application Rates
Product Rate PHI* Comments

Ignite 15 SN

(glufosinate ammonium)

Group 10
 2.7 to 5.0 L/ha
(1.1 to 2.0 L/acre)

Apply in 110 to 330 L/ha (45 to 135 L/acre) of water at 275 to 310 kPa 		N/A
  • May be used for annual grasses and broad leaf weeds.
  • Do not handle with bare hands or with leather or cloth gloves.
  • Rainfall within 4 hours may reduce effectiveness.
  • For more information on stale seed bed technique, consult the corresponding section of the Vegetable Production Guide: Pest Management (PDF, 1.2 MB).
  • Do not enter treated area for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Pre-emergence

Pre-emergence: Herbicide Application Rates
Product Rate PHI* Comments

Prowl H2O


(pendimethalin)

Group 3
Muck soils:
6.6 L/ha
(2.7 L/acre)

Mineral soils:
3.7 L/ha
(1.5 L/acre)
 
Apply in 200 L/ha (80 L/acre) of water at 138 to 276 kPa.
 90
All soils:
  • Apply as a single broadcast spray to the soil surface as a post-plant treatment within 2 days after planting and prior to emergence of crop and weeds.
  • Rain or irrigation within 7 days of application improves control.
  • Do not apply more than once per season per field.
  • Do not apply more than once in 2 consecutive years.
  • Do not enter treated area for 24 hours.
  • Muck soils: 
  • Controls barnyard grass, crab grass, green and yellow foxtail, chickweed, lamb’s-quarters and pigweed.
  • Should weeds develop, a shallow cultivation or rotary hoeing will generally result in better weed control.
  • In case of crop failure, treated land can be reseeded with dry bulb onions.
  • Carrots, direct-seeded lettuce and dry bulb onions may be planted into soil treated the previous year.
  • Mineral soils:
  • Controls barnyard grass, green foxtail, lamb’s quarters and suppresses redroot pigweed.
  • Field corn and dry bulb onions can be grown as rotational crops the year following treatment.
  • Do not plant fall seeded crops such as winter wheat, winter barley, winter rapeseed on land treated the previous spring.
  • In the event of a crop failure after application, corn may be reseeded the same year.  See label for planting directions.

Gesagard 480SC

(prometryne)

Group 5
Sandy Soils:
3.75 L/ha
(1.5 L/acre)

Loams:
4.58 L/ha
(1.85 L/acre)

Muck Soils:
7.08 L/ha
(2.86 L/acre)
 85
  • Controls many annual broadleaved weeds and seedling grasses, but not atrazine-resistant pigweed, lamb’s-quarters and groundsel.
  • For best results use on moist soils.
  • One application per season.
  • Only replant treated areas with crops on the label if planting in the same season.
  • Apply soon after planting and before emergence.
  • Do not apply at or near the time of emergence.
  • Apply in 200 to 1000 L/ha (80 to 405 L/acre) of water at 200 to 300 kPa.
  • Do not enter treated area for 12 hours.

Pardner

(bromoxynil)

Group 6
1.0 to 1.2 L/ha
(400 to 480 mL/acre)
 
Apply in 200 to 300 L/ha (80 120 L/acre) of water at 275 kPa
 45
  • Use only on mucks soils containing greater than 10% organic matter.
  • Apply 3 to 4 days prior to crop emergence.
  • Do not irrigate for 2 days following application or 3 days of crop emergence.
  • Controls the following weed seedlings up to the 4 leaf stage:  smartweed, lady's-thumb, wild mustard, pigweed and American nightshade.
  • Controls the following weed seedlings up to the 8-leaf stage:  wild buckwheat, common groundsel and lamb's-quarters.
  • Do not re-enter treated area for 24 hours.  

Lorox L

(linuron)

Group 7
 1.1 to 2.25 L/ha
(0.4 to 0.9 L/acre)

Apply in 225 to 335 L/ha (90 to 135 L/acre) of water 		N/A
  • Closed mixing/loading systems are required.
  • May be applied once per year as a pre-emergent application or in combination with a post-emergence application of Lorox L.
  • Apply as a single broadcast spray at least 1 cm deep after planting but before emergence.
  • If applying once as a pre-emergent application in the year, do not apply more than 2.25 L/ha (0.9 L/ac) per year.
  • Do not apply more than 1.25 L/ha (0.5 L/acre) if following with a post-emergence treatment of Lorox L.  Check label for pre-emergence plus post-emergence use directions.
  • Severe damage may result if pre-emergence application is followed by unusually heavy rains.
  • Crop injury may result from pre-emergence application of the higher rate.
  • Do not use on coarse-textured soils, containing 2% or less organic matter.
  • Do not replant treated areas to other crops within 4 months after last application.
  • Will not control atrazine resistant weeds.
  • Apply using a closed cab.
  • Limit the amount of product handled per day to 77 kg a.i. per person when mixing, loading and applying.
  • Do not re-enter treated area for 8 days for scouting, and for 2 days for all other tasks. 

Dual II Magnum

(S - metolachlor)

Group 15
Mineral soils:
1.2 to 1.5 L/ ha
(500 mL to 600 mL/ acre)
 
Muck soils (>20% OM):
 1.5 to 1.75 L/ ha
(600 to 708 mL/ acre)
 
Apply in 150 to 300 L/ha (60 to 120 L/acre) of water at 200 to 300 kPa
 30
  • Apply by groundspray or banded spray prior to emergence of crop and weeds.
  • Use lower rates on medium-textured soils and higher rates on fine-textured soils.
  • For mineral soils, controls nightshade, foxtail and barnyard grass and suppresses redroot pigweed.
  • For muck soils, suppression only of listed weeds.
  • Make only one application per year.
  • Do not follow with a post-emergent spray of Dual II Magnum later in the season (see Post-emergence section of this chapter).
  • Do not apply in areas where water is likely to pool.
  • May cause significant injury to carrots resuting in reduced yields.
  • Rain is required within 10 days of application, or a shallow cultivation.
  • Do not apply to soils with less than 1% organic matter.
  • Do not re-enter for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Post-emergence

Post-emergence: Herbicide Application Rates
Product Rate PHI* Comments

Select

(clethodim)
Group 1

0.19 to 0.38 L/ha

(75 to 155 mL/acre)  

Apply in 110 L/ha (45 L/acre) of water at 275 kPa

 30
  • Apply post-emergence of weeds and crop.
  • Controls annual grasses and suppresses quackgrass at the 2 to 6 leaf stage.
  • Use only with the adjuvant Amigo at 0.5 to 1.0% v/v.
  • Apply early, prior to tillering.
  • Repeat using a 14 day interval.
  • Maximum of 2 applications per year.
  • Do not apply more than 0.38 L/ha (155 mL/acre) per crop season.
  • Allow 4 days after treatment before applying any chemical not listed on this label.
  • Do not enter treated area for 12 hours.

Centurion

(clethodim)
Group 1

0.19 to 0.38 L/ha

(75 to 155 mL/acre)

Apply in 110 L/ha (45 L/acre) of water at 275 kPa

 30
  • Apply post-emergence of weeds and crop.
  • Controls annual grasses and suppresses quackgrass at the 2 to 6 leaf stage.
  • Use only with the adjuvant Amigo at 0.5 to 1.0% v/v.
  • Apply early, prior to tillering.
  • Repeat using a 14 day interval.
  • Maximum of 2 applications per year.
  • Do not apply more than 0.38 L/ha (155 mL/acre) per crop season.
  • Allow 4 days after treatment before applying any chemical not listed on this label.
  • Do not enter treated area for 12 hours.

Excel Super

(fenoxaprop-p-ethyl)

Group 1
 670 mL/ha
(270 mL/acre)

Apply in at least 110 L/ha (45 L/acre) of water at 275 kPa 		38
  • Apply at the 1 to 6 leaf stage of seedling grasses.
  • Controls foxtail, barnyard grass, crabgrass, fall panicum, Proso millet and old witch grass.
  • Do not apply any other pesticide, or chemical 4 days before or after applying Excel Super.
  • Does not control quackgrass, sedges, or other pernnial grasses.

Venture L

(fluazifop-P-buty & S-isomerl)

Group 1
Barnyard Grass (2 to 5 leaf):
0.8 L/ha (320 mL/acre)

Proso Millet (2 to 5 leaf):
1.0 L/ha (400 mL/acre)

Foxtails (2 to 4 leaf):
1.4 L/ha (560 mL/acre)

Quackgrass (3 to 5 leaf):
2.0 L/ha (800 mL/acre)
 50
  • Annual bluegrass and broadleaved weeds are not controlled.
  • Apply when crop is 10 cm in height or less.
  • Apply in 50 to 200 L/ha (20 to 80 L/acre) of water at 200 to 300 kPa.
  • Warning: Women capable of bearing children should avoid exposure to Venture.
  • Do not handle more than 50 kg a.i. (400 L product) per day.
  • Use a closed cab when applying more than 33 kg a.i. (264 L product) per day.
  • Observe a plantback interval of 12 months for crops not listed.
  • Do not re-enter treated area for 12 hours.

Poast Ultra

(sethoxydim)

Group 1

Note:  No longer produced

Annual grasses (incl. volunteer cereals):

320 mL/ha (130 mL/ac)

Annual grasses & quackgrass suppression:

470 mL/ha (190 mL/ac)

Quackgrass:

1.1 L/ha (445 mL/ac)

 49
  • For control of annual grasses and quackgrass suppression, add Merge adjuvant using a rate of 0.5 - 1.0 L/ha (0.2 - 0.4 L/ac).
  • For control of quackgrass, add Merge adjuvant using a rate of 1.0 - 2.0 l/ha (0.4 - 0.8 L/ac).
  • Does not control annual bluegrass.
  • Apply in 50 to 100 L/ha (20 to 40 L/acre) of water at 240 kPa pressure.
  • See label for water volume and pressure when weed infestations or crop canopies are dense.
  • Apply when annual weeds are in the 1 to 6 leaf stage, and when quackgrass is in the 1 to 3 leaf stage.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not enter treated area for 12 hours.

Sencor 75 DF

(metribuzin)

Group 5
 190 g/ ha
(77 g/ acre)

Apply in 150 to 300 L/ha (60 to 120 L/acre) of water at 150 to 275 kPa 		 60
  • Use only on carrots treated pre-emerge with linuron herbicide.
  • Controls annual broadleaf weeds less than 4 cm in height including common chickweed, lamb's quarters and wild mustard.
  • Does not control triazine resistant weed biotypes.
  • Apply when the 4th leaf is paritially expanded for most of the carrot plants.
  • Repeat application can be made when the 5th leaf of most of the carrot plants is partially expanded.
  • Do not tank mix with fluid fertilizers, oils, oil concentrates or surfactants.
  • May be applied when crop is wet with dew, but control is reduced if applied within 6 hours of a rainfall.
  • To improve coverage, spray boom may be rotated forward by 45°.
  • First use should be applied to a limited area of each cultivar to determine crop tolerance before adoption as a field practice.
  • It may be necessary to delay harvest of sensitive cultivars treated with Sencor 75 DF.
  • Do not apply to stressed plants.
  • 3 days of sunny weather should follow cloudy, cool weather before applying. 
  • On sunny days, application should be made in the afternoon or early evening.
  • Do not apply on coarse soils with less than 2%organic matter.
  • Rotation crops including onions, celery, peppers, cole crops, lettuce, spinach, table beets, turnips, pumpkin, squash, cucumbers and melons may be injured if planted into soil treated with Sencor 75 DF during the year of application or the following crop year. 
  • Fall-seeded cover crops including wheat, oats and rye may be injured when planted within the same season as the application of Sencor 75 DF. 
  • Do not re-enter for 12 hours.

Lorox L

(linuron)

Group 7
 2.25 L/ha
(0.9 L/acre)

Apply in 225 to 335 L/ha (90 to 135 L/acre) of water at 175 to 275 kPa 		N/A
  • Closed mixing/loading systems are required.
  • For carrots not treated with Lorox L pre-emergence, apply once when crop has two or more fully developed true leaves (8 to 15 cm tall).
  • For carrots treated with Lorox L pre-emergence, follow once with a post-emergence application provided treatments are at least two weeks apart (Check label for pre-emergence plus post-emergence use directions). 
  • Do not apply more than 2.25 L/ha (0.9 L/ac) per year.
  • Controls annual grasses and broadleaf weeds.
  • Will not control atrazine resistant weeds.
  • Use the lower rate on small seedling weeds and the higher rate on larger established weeds.
  • Apply before annual grasses are 5 cm tall and before broadleaved weeds reach 15 cm.
  • To avoid crop injury, temperature should be below 32 C and spray pressure should not exceed 275 kPa
  • If unusually heavy rains follow application, severe injury may result.
  • Do not use on sandy soils with less than 2% organic matter.
  • Do not replant treated areas to other crops within 4 months after last application.
  • Allow 2 weeks between oil application and Lorox.
  • Apply using a closed cab.
  • Limit the amount of product handled per day to 77 kg a.i. per person when mixing, loading and applying.
  • Do not re-enter treated area for 8 days for scouting, and for 2 days for all other tasks. 

Aim EC

(carfentrazone-ethyl)
Group 14
 37 to 117 mL/ha
(15 to 47 mL/acre)

Apply in 100 L/ha (40 L/acre) of water		 1
  • Controls annual weeds.
  • Must be applied using hooded sprayers to weeds between the rows of the emerged crop.
  •  Use an adjuvant such as Agral 90 or Agral-Surf at 0.25% v/v (0.25 L/100 L of spray solution) or Merge at 1% v/v (1 L/100 L of spray solution).
  • Precaution:  crop injury will occur when spray drift is allowed to come in contact with green stem tissue or leaves.
  • Apply only once per growing season.

Dual II Magnum

(S - metolachlor)

Group 15
 1.2 to 1.5 L/ ha
(500 mL to 600 mL/ acre)

Apply in 150 to 300 L/ha (60 to 120 L/acre) of water at 200 to 300 kPa		 30
  • Apply to crop at 3 to 5 leaf stage and weeds prior to 2-leaf stage.
  • Controls labelled weeds including nightshade, foxtail and barnyard grass.
  • Make only one application per year.
  • Do not follow a pre-emergent application of Dual II Magnum in the same season with this post-emergent treatment (see Pre-emergence section of this chapter).
  • Do not apply in areas where water is likely to pool.
  • May cause significant injury to carrots resuting in reduced yields.
  • Do not tank mix with fluid fertilizers, oils, oil concentrates or surfactants.
  • Rain is required within 10 days of application, or a shallow cultivation.
  • Do not apply to soils with less than 1% or more than 10% organic matter.
  • Do not re-enter for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Carrot Insect Management

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Carrot Rust Fly (Carrot Maggot)

Small (6mm long), shiny black fly with yellowish legs and a yellow-brown head, lays eggs in soil near plants. Yellowish-white legless maggots feed on roots of carrots, parsley, parsnips and celery, leaving rust-coloured tunnels. Plants may be killed. Older plants may be stunted and the roots deformed.

Monitoring

Monitoring with yellow sticky traps is effective at detecting carrot rust flies early and allows for achieving control with fewer sprays. If a commercial scouting service is operating in your area, it would be advisable to subscribe to it.

If this service is not available, the following information will enable you to do your own monitoring.

Monitoring enables you to determine if and when carrot rust flies are present and allows you to adjust your spray program accordingly. If no carrot rust flies are caught on the traps, no sprays need be applied.

The traps are set in the outside beds and in each corner around the field at a rate of one per hectare. Fields smaller than one hectare should have one trap at each corner. The traps, 14 cm X 11 cm, are attached to a stake with a clip and should face north and south. The bottom of the traps should be just above the top of the plants. The first carrot rust flies usually come out of the overwintering pupae between the end of April and early May and are present until late May. Any carrots that were seeded early and are up by that time should have traps. Carrots seeded later should have traps set at the time of emergence of the crop. The next generation of flies appears from early to late June and the last generation is present from about mid-July to freeze-up.

The traps are replaced twice per week and examined for the presence of carrot rust flies. When the count reaches 0.2 carrot rust flies per trap per day (about one fly/trap per week), there are enough of them out in the field to cause damage to the crop. Sprays to control them must be applied within three days to avoid losses at harvest. Growers who want to do their own monitoring can Contact US  for further details.

Suppression

Purchase seed treated with Sepresto 75 WS (clothianidin/imidacloprid).  Note:  Toxic to bees.  Bees may be exposed to Sepresto 75 WS residues in flowers, leaves, pollen and/or nectar resulting from seed treatment applications.

Control

The suggested spray schedule in the table below need only be followed if the carrot field is not monitored for carrot rust flies. Monitoring can eliminate or substantially reduce the number of sprays per season. When sprays are required, they can be applied exactly when needed.

Sprays are most effective when applied in the early evening (4:00 to 9:00 pm), when flies are active in the field. Flies are not generally present in the field at other times.

Spraying of weeds immediately surrounding carrot fields will give additional protection against the carrot rust fly.

Caution: Do not spray headland areas where water may become contaminated.

Carrot fields near shady, wooded areas or alongside buildings generally have higher levels of carrot rust flies and associated maggot damage. In these high hazard locations, particularly if damage has been observed in recent years, growers should carefully follow one of the appropriate spray programs in Table 2 to avoid serious damage.

Note: When harvesting, sprays are sometimes withheld from fields due to the 10 – 15 day pre-harvest interval required. During slack marketing periods, however, untreated fields are open to rust fly attack. Since rust flies and damage are always most pronounced at the field edges, it is advised whenever possible to harvest from the outer rows inward. If harvesting from the middle outwards, spray all outside rows that will not be harvested within the pre-harvest interval of the pesticide used.

When carrots are approaching maturity, the tops should be partially mowed to permit better pesticide coverage. Increased foliage aeration also discourages blight build-up, and rust fly populations appear to decline in these fields after clipping.

Serious rust fly damage can occur in September.

Carrots Seeded After April 15

Spray 30 days after seeding with any of the following:

Chemical Control of Carrot Rust Fly
Product Rate PHI* Comments

Mako

(cypermethrin)

Group 3

175 mL/ha
(70 mL/acre)

Apply in 550 L/ha (220 L/acre) of water

 35
  • Controls adult flies.
  • Repeat using 7 day intervals.
  • Do not apply more than 3 times per season.
  • May kill beneficials.
  • Mako also controls cutworms, see label for details.
  • If the field slopes downward to water, construct and maintain a vegetative filter strip.  Check label for details.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not re-enter treated area for 12 hours.

Up-Cyde 2.5 EC

(cypermethrin)

280 mL/ha
(115 mL/acre)

Apply in 550 L/ha (220 L/acre) of water

 35
  • Controls adult flies.
  • Repeat using 7 day intervals.
  • Do not apply more than 3 times per season.
  • May kill beneficials.
  • Up-Cyde 2.5 EC also controls cutworms, see label for details.
  • If the field slopes downward to water, construct and maintain a vegetative filter strip.  Check label for details.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not re-enter treated area for 12 hours.

Matador 120 EC / Silencer 120 EC

(lambda-cyhalothrin)

Group 3

83 mL/ ha
(34 mL/ acre)

Apply in 100 L/ha (40 L/acre) of water

Matador: 14

Silencer: 7
  • Controls adult flies.
  • Repeat using a 7 day interval.
  • Do not apply more than 3 times per season.
  • Toxic to bees. Avoid spraying when bees are foraging.
  • If the field slopes downward to water, construct and maintain a vegetative filter strip.  Check label for details.
  • Check label for personal protective equipment requirements.
  • Note:  check label for PHI.
  • Do not re-enter treated area for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Carrot Disease Management

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Aster Yellows

This is a virus-like disease spread by leafhoppers from nearby weeds, forage crops, etc. Leaves of infected carrots become feathery and yellowish to purplish in colour. Roots become hairy, coarse and woody. It is most common in the Interior of B.C.

Control

Isolate carrot plantings from forage legume fields and rough weedy areas where leafhoppers are common. Avoid planting carrots close to other susceptible crops such as lettuce.

 

Black Root Rot

The fungus, Thielaviopsis (Chalara), is present in most muck soils in the Fraser Valley, especially those cropped continuously to vegetables. It has a wide host range including many weeds and can survive in soil for extended periods. The fungus seldom causes disease in the field, but can be a severe postharvest problem. Contamination of carrots with infested soil and wounding during washing and grading enhance disease in storage and transit.

Control

  • Wash and cool carrots as quickly as possible after harvest.
  • Use clean water chlorinated at 50–100 ppm available chlorine for washing or hydrocooling or at 100-200 ppm as a surface spray. The chlorinated water must be buffered to pH 6.5 to 7.5 to be effective.
  • Hydrocool promptly to reduce core temperature below 7°C in the largest carrots.
  • Avoid build-up of organic debris on grading or packing lines by thorough cleaning.
  • Minimize wounding during grading.
 

Cavity Spot (Pythium)

The symptoms are seen at harvest as sunken, elliptical, horizontal lesions on the root. The cavities may be light tan in colour to dark brown and corky. They develop over the entire root surface. The problem is widespread, but is brought on by cool, wet springs and excessive soil moisture. Low lying spots in the field and heavy soils frequently yield severely infected roots.

Control

Pythium spp. can also cause lateral root dieback (rusty root). Similar control measures are recommended. In particular:

  • Avoid fields with a past history of cavity spot.
  • Avoid seeding early in cool, wet soils.
  • Improve drainage (i.e. grow on raised beds) and avoid heavy irrigations which might cause temporary water-logging of soil during warm weather.
  • If carrots are to be left in the field late in the fall, select only the best drained fields for this purpose.
  • The varieties Eagle, Carochoice, Panther, Six Pak and Nathalie are worthy of trial in fields prone to cavity spot.
  • Apply Ridomil Gold 1G (metalaxyl-m) as an in-furrow treatment at seeding. Use 2.5 g per cm of planter shoe width per 100 m of row length (25 kg per treated ha or 10.1 kg/treated acre). It is suggested that only a few hectares be treated to compare with untreated seedings. The treatment is costly and may not prove to be economic in average situations. However, the treatment will probably also help to reduce the incidence of damping-off and rusty root in the event that heavy rains create saturated soil conditions following seeding.
  • Torrent 400SC (cyazofamid), applied once per season either as a post-plant or pre-emergence treatment, is also registered for suppression of Pythium spp. See table below for details.

Suppression

When applied after sowing, Trianum P (Trichoderma harzianum Rifai strain T22) protects plants against infection by soil-borne pathogens via the root system.  It is a biological fungicide that out-competes plant pathogenic fungi for space and nutrients, colonizing plant roots ahead of pathogens.

  • Suspend 1 volume of Trianum P in 5 volumes of water and mix thoroughly. 
  • Add suspension to required amount of water to make up final drench volume.
  • Apply immediately after sowing.
  • In furrows: use 1.5 kg/ha (0.6 kg/acre) in 50 to 200 L/ha (20 to 80 L/acre) of water.
  • In beds:  use 2.5 kg/ha (1.0 kg/acre) in 50 to 200 L/ha (20 to 80 L/acre) of water.
  • Becomes active when soil temperatures are above 10 degrees C and is not effective while soils remain cold.
  • More effective in neutral or acidic soils.  
  • Use within 6 months of the date of manufacture.  

Chemical Control of Cavity Spot (Pythium spp.)
Product Rate PHI* Comments

Torrent 400 SC

 

(cyazofamid)
 
Group 21
 440 mL/ha
(180 mL/acre)		 30
  • Suppression only.
  • Also suppresses root dieback and forking.
  • Do not make more than one application per year.
  • Apply as either a post-plant, pre-emergent within 3 days of seeding or as a soil-directed spray 14 days after planting.

Post-plant, pre-emergent application:

  • Apply before plant emergence within 3 days of seeding.
  • Use sufficient water to ensure full coverage and follow with sprinkler irrigation of 1.25 to 2.5 cm of water.

Surface application (broadcast or band):

  • Apply as a soil directed spray, 14 days after seeding.
  • Use sufficient water to ensure penetration into the soil or irrigate with 1.25 to 2.5 cm of water.
  • For banded applications, use a 15.2 to 20.3 cm band.  See label to calculate amount of product required in the band.

Reason 500SC

(fenamidone)

 

Group 11

600 mL/ha
(240 mL/acre)

Apply in 300 to 750 L/ha (120 to 300 L/acre) of water

 14
  • Also controls damping off caused by Pythium spp.
  • Make the first application within 7 days after planting.
  • Direct spray to the base of the plant.
  • Repeat at 7 day intervals.
  • Do not make more than 2 applications per growing season.
  • Observe a plantback interval of 30 days.

Serenade Soil

(QST 713 strain of dried Bacillus subtilis)
 
Used in organics.
 2.7 to 14 L/ha (1.1 to 5.7 L/acre)  
  • Suppression only.
  • Serenade Soil (PCP# 30647) is OMRI-Canada listed.  Check with your certification body before using in an organic operation.  

Surface Application:

  • Apply as a 15 cm band over the top of the seed row as a broadcast spray after planting.
  • Ensure incorporation into the seed zone within 24 hours of application via rainfall or overhead irrigation.

Post-plant applications:

  • After crop germination, additional applications may be made to the soil as a drench or spray directed towards the base of the plant.
  • Irrigate to move material into the seed or root zone within 24 hours.
  • Repeat at 21 to 28 day intervals.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

OMRI-Canada = Organic Materials Review Institute of Canada

 

Foliar Blights

There are several fungi and bacteria which can cause foliar blights. In B.C., Alternaria blight is most common and is often seen in the fall in the Cloverdale area. Cercospora blight is sometimes seen earlier in the summer, especially in the Sumas Prairie area. Occasionally, the tops are badly damaged making the harvesting operation difficult and reducing yields.

Control

  • Use fungicide-treated seed as the pathogens may be seed-borne.
  • If possible, bury crop refuse after harvest to hasten breakdown of foliage. Infected tops from the previous crop are the main source of overwintering for both Alternaria and Cercospora.
  • Rotate with alternate vegetable crops.
  • When the crop is to be left in the field until late fall or in unusually wet summers, a spray program may be warranted. See table below.

Chemical Control of Foliar Blights
Product Rate PHI* Comments

Bravo 720

(chlorothalonil)

Group M5

    
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than 7 times per season.
  • A closed transfer system must be used when mixing and loading.
  • For PPE requirements while mixing and handling, check the label.    
  • Do not re-enter treated area for 22 days for hand harvesting; 7 days for scouting and 12 hours for all other activities.

Bravo ZN

(chlorothalonil)

Group M5

 2.4 to 3.2 L/ha
(1.0 to 1.3 L/acre)		 2
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than 7 times per season.
  • A closed transfer system must be used when mixing and loading Bravo ZN.
  • When using Bravo ZNC, mixers and loaders cannot handle more than 680 L of product per day.
  • For PPE requirements while mixing and handling Bravo products, check the labels.    
  • Do not re-enter treated area for 22 days for hand harvesting; 7 days for scouting and 12 hours for all other activities.

Bravo ZNC

(chlorothalonil)

Group M5

Echo 720

(chlorothalonil)

Group M5

 1.7 to 2.2 L/ha
(700 to 900 mL/acre)		 1
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than 7 times per year.
  • Do not apply within 10 days before or after an oil application.
  • If handling more than 340 kg a.i. in one day, mixers and loaders must use a closed system.
  • Do not re-enter treated area for 22 days for hand harvesting; 7 days for scouting and 12 hours for all other activities.

Lance WDG

(boscalid)

Group 7		 315 g/ha
(126 g/acre)

Apply in 100 L/ha (40 L/acre) of water 		0
  • For control of Alternaria only.
  • Repeat at 7 to 14 day intervals.
  • Apply before disease develops.
  • Do not make more than 5 applications per season.
  • No more than 2 consecutive applications before alternating with a fungicide with a different mode of action.
  • Do not enter treated area for 12 hours.
  • For crops not on the label, observe a plant back interval of 14 days.

Cantus WDG

(boscalid)

Group 7		 315 g/ha
(126 g/acre)

Apply in 100 L/ha (40 L/acre) of water 		0
  • For control of Alternaria only.
  • Repeat at 7 to 14 day intervals.
  • Apply before disease develops.
  • Do not make more than 5 applications per season.
  • No more than 2 consecutive applications before alternating with a fungicide with a different mode of action.
  • Do not enter treated area for 12 hours.
  • For crops not on the label, observe a plant back interval of 14 days.

Sercadis

(fluxapyroxad)

Group 7		 250 to 333 mL/ha
(101 to 135 mL/acre)

Apply in 100 L/ha (40 L/acre) of water		 7
  • For control of Alternaria only.
  • Repeat at 7 to 14 day intervals.
  • Do not make more than 3 applications per season.
  • Do not apply more than 1.0 L/ha (405 mL/acre) per season
  • No more than 2 consecutive applications before alternating with a fungicide with a different mode of action.
  • Do not enter treated area for 12 hours.
  • For crops not listed, observe a plant back interval of 1 year.

Fontelis

(penthiopyrad)

Group 7		 1.25 to 2.25 L/ha
(505 to 910 mL/acre)

Apply in 110 L/ha (45 L/acre) of water		 0
  • Controls Alternaria blight
  • Repeat at 7 to 14 day intervals.
  • Do not apply more than 45 L/ha (1.8 L/acre) per season.
  • Do not make more than 2 sequential applications before switching to a fungicide with a different mode of action.
  • Do not re-enter for 12 hours.

Miravis Duo

(pydiflumetofen & difenoconazole)

Group 7 & 3

1.0 L/ha (405 mL/ac)

 

Apply in 150 L/ha (60 L/ac) of water		 7
  • Provides control of Alternaria Leaf Blight and suppression only of white mould (Sclerotinia sclerotiorum)
  • Repeat using a 7 to 14 day interval.
  • Do not make more than 2 consecutive applications before switching to a non-Group 7 & 3 fungicide.
  • Do not apply more than 4.0 L/ha (1.6 L/ac) per season.
  • See label for details on plantback interval.
  • Do not re-enter treated area for 12 hours.

Cabrio EG

(pyraclostrobin)

Group 11		 Alternaria:
0.56 to 1.1kg/ha
(220 to 440 g/acre)

Cercospora:
560 to 840 g/ha
220 to 340 g/acre)		 3
  • Maximum of 3 applications per season.
  • Repeat at 7 to 14 day intervals.
  • No more than 2 consecutive applications before alternating with a fungicide with a different mode of action.
  • Do not enter treated area for hand-harvesting for 3 days and for all other activities, do not enter for 12 hours.
  • Do not use treated crop for feed.
  • Apply in 225 L/ha (90 L/acre) of water.

Flint

(trifloxystrobin)

Group 11

140 to 210 g/ha ( 57 to 85 g/acre)

Apply in 100 L/ha (40 L/acre) of water at 241.5 kPa

 7
  • Control or suppression of Alternaria Leaf blight.
  • Repeat at 14 day intervals.
  • Do not apply more than 840 g/ha (340 g/acre) of product per season.
  • Do not make more than 4 applications per season.
  • Observe a plantback interval of 30 days for crops not listed.

Quadris Top

(azoxystrobin/ difenoconazole)

Group 11 & 3

566 to 1000 mL/ha
(229 to 405 mL/acre)

Apply in 150 L/ha (60 L/acre) of water

 7
  • Controls Alternaria blight.
  • Repeat at 7 to 14 day intervals.
  • Do not make more than 3 applications per year.
  • Do not re-enter treated areas for 12 hours.
  • Observe a plant back interval of 60 days for all crops not registered on this label or the Inspire label.

Pristine WG

(boscalid & pyraclostrobin)

Group 7 & 11		 580 to 735 g/ha
(235 to 297 g/acre)		 0
  • Begin applications prior to disease development and continue on a 7 to 14 day schedule.
  • Do not apply more than 6 times per season.
  • Do not re-enter for hand-harvesting for 3 days after applying. For all other activities, do not re-enter until residues have dried.

Switch 62.5 WG

(cyprodinil & fludioxonil)

Group 9 & 12		 775 to 975 g/ha
(314 to 395 g /acre)

Apply in 200 L/ha (80L/acre) of water 		7
  • Repeat at a 7 to 10 day interval.
  • Do not make more than 2 sequential applications of Switch or other fungicides in the same group (9 or 12) in a season.
  • Do not apply more than 2.9 kg of product/ha/year.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not enter treated area for 12 hours.

Allegro 500 F

(fluazinam)

Group 29		 1.16 L/ha
(469 mL/acre)

Apply in 200 to 600 L/ha (80 to 240 L/acre) 		7
  • Controls white mold and Alternaria leaf blight.  Check label.
  • Repeat using a 7 day application interval.
  • Maximum 4 applications per year.
  • See label details for plantback intervals.
  • Do not enter treated area for 24 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Lateral Root Dieback (Rusty Root)

In fields where carrots have been grown repeatedly, infection of the fine feeder roots by Pythium may occur during prolonged wet periods. The fine roots turn orange to brown and die back to the tap-root. Later, a proliferation of feeder roots may occur as the carrots resume growth. The crop may be much reduced both in yield and grade.

Control

  • Avoid seeding carrots repeatedly in the same field; rotate with onions or crops other than carrots and parsnips.
  • Avoid heavy seeding rates; precision seeding at a spacing of 3 cm is ideal.
  • In fields with a history of disease, seed on raised beds particularly for the early crop when periods of prolonged wet weather can be expected.
 

Root-Knot Nematode

This nematode causes roots to become misshapen or abnormally bumpy. Samples of suspect roots should be sent to the Plant Health Laboratory or other nematode laboratories for confirmation. Soil counts of root knot nematodes should be done in August or September since most of the nematodes are in the roots in June and July and are not detected in soil samples. For nematode testing, consult the Plant Health Laboratory or your local agriculture consultant.

Control

  • Prevent root-knot nematodes from increasing by: (a) rotating with onions, radishes, lettuce, oats, wheat, rye or timothy; (b) avoiding such crops as potatoes, tomatoes, peppers, celery, carrots or beans, which are highly susceptible; (c) following recommended weed-control practices; and (d) removing or destroying crop refuse promptly after harvest.
  • Fallowing fields will also reduce nematode populations.
  • If nematode counts are high, fumigate infested areas in the fall or before planting when soil temperatures are above 10°C at injection depth. For more information, consult the “Nematodes” section in the Vegetable Guide: Pest Management (PDF, 1.2 MB) and the “Sterilization and Fumigation” section in the Vegetable Guide: Planting (PDF).  
 

Rhizoctonia Crown Rot

Chemical Control of Rhizoctonia Crown Rot

Product

Rate

PHI*

 Comments

Quadris

(azoxystrobin)

Group 11		 4 to 6 mL of product per 100m of row

Apply in 50 to 100 L/ha (20 to 40 L/acre) of water 		40
  • Apply either in-furrow at seeding or as a banded application over the row soon after emergence or within 30 days of emergence.
  • Do not make more than one application per year.
  • A plant back interval of 30 days is required for broadleaf and root crops.
  • A plant back interval of 45 days is required for cereals.
  • Do not enter treated area until residues have dried.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

OMRI-Canada = Organic Materials Review Institute of Canada

 

Post-Harvest White Mold/Sclerotinia Rot (Sclerotinia sclerotiorum)

The rotted area is soft and watery and is covered with a loose, white fungal growth. Later, round, black, hard sclerotia are present.

Control

Rotate with resistant crops such as beets, onions, spinach, cereals, corn, or grasses for at least two years before planting susceptible crops such as beans, lettuce, parsnips, cole crops, cucumbers, or celery.

Rapid cooling of the crop at harvest and maintaining a storage temperature of 0°C will reduce post-harvest storage rot. Contans WG (Coniothyrium minitans) is a soil treatment registered for suppression. It must be applied to the soil and incorporated as thoroughly and uniformly as possible at least 3 months prior to an anticipated Sclerotinia outbreak.

Chemical Control of Post-Harvest White Mold/Sclerotinia Rot (Sclerotinia sclerotiorum)
Product Rate PHI* Comments

Scholar 230SC

(fludioxonil)

Group 12

N.B.  For domestic use only.  Do not use on product intended for export.

 Mix 498 mL of product in 378 L of water. N/A
  • Apply as a post-harvest dip or drench immediately before storage.
  • Dip for approximately 30 seconds and allow carrots to drain.
  • Maximum of one application.
  • Do not store treated carrots in direct sunlight.
  • Replenish the suspension when the volume is too low or when it becomes dirty.
  • Runoff and wastes from dipping operation should not be discarded in a drainage which could enter public water systems.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

OMRI-Canada = Organic Materials Review Institute of Canada

 

Other Related Problems

Expand All | Collapse All
 

Ribbing

Carrots have a corrugated or “washboard-like” appearance. This appears to be a physiological disorder which commonly occurs in shallow muck soils having clay subsoil mixed in. It does not occur in sandy soils in the Fraser Valley.

Control

  • Avoid degraded mucks with clay ridges if more suitable soil is available.
  • There is some indication that regular, light irrigation produces a smoother crop than alternating wet and dry soil conditions.