Learn effective weed management techniques for tomato crops. Discover common weeds, safe herbicides, and proven strategies to protect yield and ensure a healthy harvest.
Weed management is a crucial factor in tomato cultivation, especially for Tomato (Lycopersicon esculentum) production in Brazil, where it constitutes a major portion of crop expenses. Effective weed control is essential for achieving high yields and premium-quality fruit. This discussion explores the negative impact of weed interference on tomato crops, whether grown from transplanted seedlings or directly sown in the field.
Weed control is essential in tomato farming, as weeds compete for vital resources like space, light, water, and nutrients, ultimately reducing yields and weakening the crop stand. They can also hinder harvest efficiency and serve as hosts for pests, including insects, diseases, and nematodes.
Weeds are most competitive when they emerge before or around tomato planting, particularly during the first 6 to 8 weeks after crop emergence (fewer weeks for transplants). After this period, tomato plants become more resilient, though late-germinating weeds can still impact harvesting and contribute to future weed infestations by producing seeds.
A well-rounded approach to weed control includes:
Choosing the right herbicide depends on the weed species, farming practices, and crop rotation plans. Herbicides fall into two main categories:
Weed control is essential for maintaining tomato crop health and maximizing yields. A successful strategy requires identifying common weeds by their scientific names and implementing integrated weed management (IWM) techniques.
Tomato crops are often affected by various weeds, including:
These weeds compete for essential resources such as nutrients, water, space, and light, while also serving as hosts for pests and diseases.
An effective weed control plan includes:
✅ Cultural practices – Proper field preparation, mulching, and intercropping.
✅ Herbicide application – Selecting preemergence or postemergence herbicides based on weed susceptibility.
✅ Crop rotation – Disrupting weed growth cycles to minimize infestation.
Dodder (Cuscuta spp.) is a parasitic weed that depends on host plants like tomatoes, safflower, and sugarbeets for survival. It lacks chlorophyll, extracting nutrients directly from the host, leading to stunted growth and reduced yields.
✅ Early Detection & Removal – Host tomato plants should be removed as soon as dodder is identified.
✅ Prevent Seed Spread – If dodder is flowering, infected plants must be removed and burned to prevent seed dispersal.
✅ Preemergence Herbicides – Pendimethalin (Prowl H2O) application before emergence can reduce dodder germination by 80%.
✅ Resistant Tomato Varieties – Certain tomato cultivars, like Heinz 9492 and 9553, show resistance to dodder infestation.
Dodder germinates primarily between March 1 and May 20. Delayed planting can help reduce the risk of infestation by avoiding peak germination periods.
A proactive integrated approach, combining timely removal, chemical control, and resistant varieties, is essential for effectively managing dodder in tomato fields.
Field bindweed (Convolvulus arvensis) is a deep-rooted perennial weed that is difficult to control once established. It competes aggressively with tomato plants for nutrients, water, and sunlight, reducing crop yields.
✅ Chemical Control – Trifluralin (Treflan) layby treatment effectively controls seedling field bindweed. Seedlings can be identified by their cotyledons, which differ from the leaves of mature plants.
✅ Cultivation – In drip-irrigated fields, established bindweed plants require mechanical cultivation for effective control.
✅ Crop Rotation – Rotating tomatoes with a cereal crop followed by glyphosate application in the fall can help suppress field bindweed populations.
✅ Summer Blading – In heavily infested fields, using a reclamation blade during the summer can sever and dehydrate bindweed rhizomes, especially after a crop that depletes soil moisture to 18–20 inches.
Common Nightshade Weeds includes:
These weeds are resistant to many herbicides commonly used in tomato farming, making their control challenging.
✅ Pre-Plant Soil Treatment – Soil fumigation with metam sodium (Vapam) effectively suppresses nightshade populations before planting.
✅ Herbicide Application – Rimsulfuron (Matrix) provides preemergence control when applied post-seeding or after transplanting and incorporated with water within 5–7 days. It also controls cotyledon-stage nightshade postemergence.
✅ Crop Rotation – Planting Roundup Ready corn or cotton allows for the use of effective herbicides like glyphosate, which helps reduce nightshade seed banks in the soil.
✅ Deep Plowing – Using specialized deep plows can bury nightshade seeds deep enough to prevent their emergence, significantly lowering weed infestations.
Nutsedge (Cyperus spp.) is a persistent perennial weed that primarily reproduces through underground tubers, which can remain viable in the soil for years, making control difficult.
✅ Tuber Suppression – S-metolachlor (Dual Magnum) applied at layby can partially suppress yellow nutsedge, while Halosulfuron (Sandea) is effective for postemergence control.
✅ Preplant Treatment – Metam sodium application before planting helps control yellow nutsedge in the tomato seedline.
✅ Timely Cultivation – Cultivation should occur at the 5- to 6-leaf stage to prevent the formation of new tubers, reducing future infestations.
✅ Crop Rotation – Rotating with crops like corn or beans, which allow for herbicide applications that suppress nutsedge, helps reduce its spread.
✅ Specialized Plowing – Using deep inversion plows to bury tubers at least 12 inches deep minimizes nutsedge emergence in tomato fields.
Weeds compete with tomato plants for essential resources like space, light, water, and nutrients, which weakens crop growth and reduces harvest efficiency. Some weeds also serve as hosts for pests and diseases, further threatening yield and plant health.
Weeds are most competitive if they emerge before or around tomato planting and continue growing for 6 to 8 weeks after crop emergence (a shorter period when using transplants). Effective weed control during this critical window is essential for maximizing yields.
✅ Crop Rotation – Helps break weed life cycles and reduce persistent weed infestations.
✅ Cultivation & Field Preparation – Mechanically removes weeds before planting.
✅ Sanitation & Irrigation Management – Prevents weed establishment and spread.
✅ Herbicide Selection – Choosing the right herbicide based on weed species and growth stage.
Herbicides work best with adequate soil moisture but should be applied only when the soil is moderately wet to prevent compaction and uneven distribution.
Conduct weed surveys at key stages:
Keep detailed records of weed species, location, and seed-producing weeds for targeted future control.
Pay special attention to perennial weeds and other potential sources of reinfestation.
Rotating crops disrupts weed growth cycles by altering environmental conditions and enabling alternative control methods. Ideal rotational crops for tomatoes include:
✅ Corn
✅ Alfalfa hay
✅ Wheat
✅ Cotton
✅ Rice
✅ Dry beans
✅ Onions
✅ Carrots
✅ Safflower
Avoid monocropping and crops like potatoes, peppers, and eggplants, as they share similar herbicides and genetic traits with tomatoes, limiting weed control options.
✔ Select fields with minimal weed infestations to reduce initial competition.
✔ Keep canal banks weed-free and clean equipment to prevent weed seed transfer.
✔ Deep plowing (at least 12 inches) with a specialized moldboard plow helps bury seeds and tubers, reducing populations of nightshade and nutsedge.
Soil Solarization – Effective for controlling soilborne diseases, nematodes, and weeds when applied in June–August for 4 to 6 weeks.
Soil Fumigation – Using metam sodium, metam potassium, 1,3-D, or 1,3-D plus chloropicrin can effectively control weeds and soilborne pests. Ensure sufficient time between fumigation and transplanting to prevent crop damage.
✔ Fall/Winter Herbicide Applications – Allow early planting in fields with wet soil conditions. Some fall-applied herbicides require adequate rainfall for breakdown.
✔ Postharvest Weed Control – After harvest, irrigate fields and apply contact herbicides to control perennial weeds like field bindweed and little mallow.
✔ Apply herbicides before planting and incorporate them into the soil to control early weeds.
✔ Band treatments reduce costs, require sprinkler irrigation, and lower herbicide carryover risks.
✔ Postemergence herbicides may be needed for already-emerged weeds before planting.
✔ Herbicide mixtures improve weed control, extend residual activity, and ensure tomato crop safety.
✔ Crop Rotation – Disrupts weed cycles; ideal rotational crops include corn, wheat, cotton, and safflower. Avoid monocropping and genetically similar crops like potatoes and peppers.
✔ Field Preparation – Select weed-free fields, maintain clean canal banks, and use specialized plows to control nightshade and nutsedge.
✔ Soil Solarization & Fumigation – Applied in summer, solarization controls soilborne pests and weeds. Fumigation with chemicals like metam sodium and chloropicrin enhances weed suppression.
✔ Herbicide Management – Fall and winter herbicide applications enable early planting. Pre-plant band treatments reduce costs, and postemergence herbicides target emerging weeds.
✔ Crop Rotation – Disrupts weed cycles; avoid monocropping and related crops like potatoes and peppers.
✔ Field Preparation – Start with minimal weed infestations, maintain clean canal banks, and use specialized plows to control nightshade and nutsedge.
✔ Soil Solarization & Fumigation – Summer solarization controls soilborne pests and weeds; fumigation with metam sodium and chloropicrin enhances weed suppression.
✔ Herbicide Application –
Tomato preplant weed control options include various herbicides that help manage weed infestations before planting. These include
Tomato postemergent weed control options include DCPA (Dacthal), Halosulfuron-Methyl (Profine 75, Sandea), Metribuzin (TriCor DF, Metribuzin), Rimsulfuron (Matrix), Clethodim (Arrow, Clethodim, Intensity, Select), Sethoxydim (Poast), Trifloxysulfuron-Sodium (Envoke), Carfentrazone-Ethyl (Aim), Napropamide (Devrinol, Devrinol DF-XT, Devrinol 2-XT), Pendimethalin (Prowl H2O), and Paraquat (Firestorm, Parazone, Gramoxone SL). These herbicides help control annual grasses, small-seeded broadleaf weeds, yellow and purple nutsedge, and certain other broadleaf weeds.
Effective weed management is essential for maximizing tomato yields and promoting healthy plant growth. Weeds compete for nutrients, water, and sunlight, potentially reducing crop productivity. A variety of herbicides with specific modes of action are available to control common weeds in tomato fields. Selecting the right herbicide and applying it correctly ensures effective weed suppression while maintaining crop safety. Proper weed management strategies contribute to a successful and thriving tomato harvest.
In case you missed it: The Ultimate Guide to Tomato Farming: From Seed to Harvest Success
Edited by Gayathri
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