Sweet Potato

Sweet Potato otank Wed, 05/22/2024 - 10:59

Sweet Potato Disease Control Sweet Potato Insect Control Sweet Potato Weed Control

Introduction

Despite its name, the sweet potato (Ipomoea batatas) is not related to Irish or white potato. Sweet potato belongs to the morningglory family (Convolvulaceae). Sweet potato originated in South America and is one of the most important food crops in the developing world. Sweet potatoes are not the same as yam, although they are often marketed as such. True yams are in the family Dioscoreaceae, and are grown in tropical regions such as Africa and the Caribbean. Sweet potato is a frost-sensitive crop that needs a frost-free growing season ranging from 90-150 days (depending on variety) to produce harvestable roots.

Types and Varieties

New varieties come on the market and older varieties fall out of favor or become available over time. The information below is updated every 2 years, but with any questions, please contact your local Extension staff.

The skin of sweet potatoes can be yellow, orange, copper, red, or purple; the flesh can be white, yellow, orange, or purple. Varieties with copper-colored skin with moist orange-colored flesh (e.g. Beauregard, Covington) are the most common in New England. However, some markets prefer the starchier white-fleshed varieties and purple-skinned/purple-fleshed varieties are also available.

Types	Varieties
Orange-fleshed	Beauregard Covington Carolina Ruby - deep red, thick skin Orleans Bayou Belle Bellevue Evangeline
White-fleshed	O'Henry Murasaki - purple skin Bonita - white skin
Purple-fleshed	Purple Splendor - purple skin

Types

Varieties

Orange-fleshed

Beauregard

Covington

Carolina Ruby - deep red, thick skin

Orleans

Bayou Belle

Bellevue

Evangeline

White-fleshed

O'Henry

Murasaki - purple skin

Bonita - white skin

Purple-fleshed

Purple Splendor - purple skin

Soil Fertility

Sweet potato will grow at a soil pH of 4.5-7.5, but 5.8-6.2 is optimal. Well-drained, loam soils result in large and well-shaped roots. When grown in heavy clay soils, or in soils with high soil organic matter, sweet potato may produce rough, irregular roots.

Sweet potato does not need high levels of nitrogen (N), and yields may be reduced if N exceeds 75 lb/A. If manure or compost is added, be careful not to add excessive fertilizer-N. Nutrients should be applied according to soil tests. See fertilizer table below. Sweet potato needs high levels of phosphorous (P, up to 200 lbs/A) and potassium (K, up to 300 lbs/A). Both P and K can be applied at planting and N can be split between application at planting and before plants begin to run. Drip irrigation can be used to apply supplemental N under plastic mulch. Alternatively, all N can be applied at planting and covered with plastic mulch to prevent leaching.

Sweet potato requires more boron (B) than many vegetables. On B-deficient soils, 0.5 lb B/A (5 pounds Borax or 2.6 pounds Solubor) should be added to prevent a disorder called blister. This disorder is characterized by small, raised bumps on the root surfaces and plant stunting.

Plant Nutrient Recommendations According to Soil Test Results for Sweet Potato

SOIL TEST RESULTS	NITROGEN (N) - LBS PER ACRE	PHOSPHORUS (P) - LBS P₂O₅ PER ACRE				POTASSIUM (K) - LBS K₂O PER ACRE
SOIL TEST RESULTS	NITROGEN (N) - LBS PER ACRE	VERY LOW	LOW	OPTIMUM	ABOVE OPTIMUM	VERY LOW	LOW	OPTIMUM	ABOVE OPTIMUM
Broadcast and incorporate	25	200	120	30-60	0-30	300	200	50-100	0-50
Sidedress when vines start to run	25-50	0	0	0	0	0	0	0	0
Sidedress 6-8 weeks after planting	0	0	0	0	0	0	0	0	0
TOTAL RECOMMENDED	50-75	200	120	30-60	0-30	300	200	50-100	0-50

Planting

Sweet potatoes are grown from rooted sweet potato sprouts (slips) or vine cuttings. Slips can be produced by placing roots in warm (75-80ºF) moist sand or soilless media until sprouts are produced (about 1 month or longer). Slips are then pulled from the bedded roots and planted. In southern areas of the US, larger growers produce their own slips. It is recommended for New England that slips be purchased from companies that provide certified disease-free slips.

Field planting begins when all chance of frost has passed. Soil temperature in the production field should reach at least 65ºF at a 4" depth for 4 consecutive days before transplanting.

Rows are 32-42" apart with in-row spacing 8-12", depending on cultivar. Slips are transplanted into the rows at a depth of 3" with no less than 2 plant nodes in the ground and leaving 2 leaves or more above the ground. If slips do not have good root development, transplanting during cloudy weather and maintaining adequate field moisture just after transplanting will help ensure success.

Field Culture

Because of their vulnerability to wireworms, sweet potatoes should not be grown the first year after incorporating sod.

Research in New England has shown that yields are increased, particularly during cooler summers, by using raised beds covered with black plastic mulch.

Harvest and Storage

Sweet potato roots continue to grow until the leaves are killed by frost or until soil temperatures fall consistently below 65ºF, whichever comes first. Time of harvest is often determined by digging up a few representative plants and determining the percentage of roots in the size classes. When tops of the plants turn black after the first frost, it is imperative to harvest as quickly as possible regardless of root size.

Sweet potato roots are very susceptible to damage at harvest. The roots do not have a thick protective outer layer of cells such as that on white potato tubers. Abrasions and wounds can lead to rots in storage. Studies have shown that mowing vines 10-14 days before harvest can help increase skin toughness and minimize harvest damage.

Curing immediately after harvesting is recommended. This minimizes damage and loss during storage by healing harvest wounds. To cure, maintain roots in temperatures between 80-86ºF and a high relative humidity (85-95%) for 4-7 days. This forms a corky periderm layer below the damaged areas which limits microbial invasion and water loss. A freshly harvested sweet potato is more starchy than sweet. During curing and storage, starches in the sweet potato are converted to sugars, improving flavor. Wait at least 3 weeks after harvest before consuming the roots to permit the starches to convert to sugars for maximum eating quality.

Sweet potatoes can maintain excellent quality for up to a year in proper storage conditions. The ideal storage conditions for sweet potato are the same as for winter squash; moderately warm (55-60ºF) and 60-75% relative humidity. Storage temperatures that drop below 55ºF can cause chilling injury which will render tubers unmarketable.

Sweet Potato Disease Control

Sweet Potato Disease Control otank Tue, 05/28/2024 - 10:51

Sweet Potato - General Sweet Potato Insect Control Sweet Potato Weed Control

NOTES: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 26 and Fungicides and Bactericides Alphabetically Listed by Trade Name for more information on products with the same active ingredients.

The symbol ^OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Prevention is essential for disease control in sweet potato. The most important diseases are root diseases which become systemic; once infected it is not possible to cure the plant. Vegetative propagation is an ideal vehicle for disease perpetuation. Start with healthy propagating stock and inspect frequently in the production cycle. Planting stock should be produced and stored separately from commercial sweet potatoes. Careful handling and proper curing at harvest are primary disease prevention measures. Application of fungicides and bactericides are not as effective as proper curing in controlling post-harvest diseases. Practice good sanitation of farm equipment, storage bins, and storage rooms.

Rhizoctonia Root Rot and Stem Canker

azoxystrobin (Abound aka Quadris F): 0.4 to 0.8 fl oz/1000 row feet; PHI 14d, REI 4h, Group 11. Apply in-furrow or as banded applications over row. Rotate with a fungicide from a different FRAC Group. See label for rates and directions for postharvest rots.
Bacillus subtilis strain QST 713 (Minuet^OG):12.0 to 24.0 oz/A; PHI 0d, REI 4h, Group BM02. Soil application.
laminarin (Vacciplant): 14.0 to 22.0 fl oz/A; PHI 0d, REI 4h, Group P04.
Reynoutria sachalinensis extract (Regalia CG^OG): See label for rates; PHI 0d, REI 4h, Group P05.
Trichoderma harzianum strain T-22 [KRL-AG2] (Rootshield WP): See label for rates; REI 4h, Group BM02. For seed treatment and transplant and field production.

Black Rot (Ceratocystis fimbriata)

One of the most significant diseases of sweet potato, black rot is the common name for the decay of fleshy roots and symptoms on sprouts and vines. Successful control of black rot depends on selection of healthy seed roots, fungicide treatment, crop rotation, proper curing, and effective sanitation.

thiabendazole (Mertect 340F): 107.0 fl oz/100 gal water or 8.0 fl oz/7.5 gal water; REI 12h, Group 1. Dip the seed roots in the suspension for 1-2 minutes and plant immediately. Do not use treated roots as food or feed. See label for additional information on postharvest treatment for black rot.

Soft Rot (Rhizopus spp.)

Careful handling and proper curing at harvest are primary disease prevention measures. Application of fungicides and bactericides are not as effective as proper curing in controlling postharvest diseases. Practice good sanitation of farm equipment, storage bins, and storage rooms.

fludioxonil (Scholar SC): 16.0 to 32.0 fl oz/100 gal; Group 12. Postharvest dip/drench. See label for application methods. (Not for use in Maine).

Disease Control

Sweet Potato Insect Control

Sweet Potato Insect Control otank Tue, 05/28/2024 - 11:02

Sweet Potato - General Sweet Potato Disease Control Sweet Potato Weed Control

NOTES: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 27 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol ^OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Aphids, primarily Green Peach Aphid (Myzus persicae)

For more information see green peach aphid in the Pepper section.

acetamiprid (Assail 30SG): 2.5 to 4 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.
alpha-cypermethrin (Fastac* EC): 3.2 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
azadirachtin (Azatin O^OG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.
Beauveria bassiana (Mycotrol ESO^OG): 8 to 32 oz/A; PHI 0d, REI 4h, Bee: L, Group UN. Treat when populations are low and thoroughly cover foliage. Takes 7-10 days after the first spray to see control. Repeat applications may be needed.
chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.
Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.
clothianidin (Belay): 2 to 3 oz/A foliar, 9 to 12 oz/A soil, 0.4 to 0.6 oz/100 lbs seed; PHI 14d, REI 12h, Bee: H, Group 4A. Soil application maybe at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil).
cyantraniliprole (Verimark): 13.5 oz/A; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting. Suppression of green peach aphid only.
flonicamid (Beleaf 50SG): 2 to 2.8 oz/A; PHI 7d, REI 12h, Bee: L, Group 9C.
flupyradifurone (Sivanto): 10.5 to 14 oz/A green peach aphid, 7 to 14 oz/A other aphids; PHI 7d, REI 4h, Bee: L, Group 4D.
gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.
imidacloprid (Admire Pro): 1.2 oz/A for foliar application, 4.4 to 10.5 oz/A for soil application; PHI 7d foliar, PHI 125d soil, REI 12h, Bee: H, Group 4A.
lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.
petroleum oil (Suffoil X^OG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L.
pymetrozine (Fulfill): 2.75 to 5.5 oz/A; PHI 14d, REI 12h, Bee: L, Group 9A. Selective control of aphids. Translaminar. Apply before populations build up.
pyrethrin (PyGanic EC5.0^OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
spirotetramat (Movento): 4 to 5 oz/A; PHI 7d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity. Don't use sticker adjuvants. Controls immature stages; may also reduce adult fertility.
sulfoxaflor (Closer SC): 1.5 to 2.75 oz/A; PHI 7d, REI 12h, Bee: H, Group 4C.
thiamethoxam (Actara): 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4A.
thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4A. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer before or during planting, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. Do not apply as a foliar spray.

Cutworms

See cutworms in the Pepper and Tomato (Outdoor) sections for more information on black and variegated cutworms.

alpha-cypermethrin (Fastac* EC): 1.3 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 1.5 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt kurstaki products (Dipel).
Bacillus thuringiensis kurstaki (Dipel DF^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt aizawai products (XenTari).
beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.
carbaryl (10% Sevin Granules): 20 lb/A; PHI 7d, REI 12h, Bee: H, Group 1A. Apply evenly over soil surface.
chlorantraniliprole & lambda-cyhalothrin (Besiege*): 5 to 8 oz/A; PHI 14d, REI 24h, Bee:H, Groups 28 & 3A.
deltamethrin (Delta Gold*): 1 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
gamma-cyhalothrin (Declare*): 0.77 to 1.28 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.
lambda-cyhalothrin (Warrior* II): 0.96 to 1.6 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.
methoxyfenozide (Intrepid 2F): 6 to 10 oz/A; PHI 7d, REI 4h, Bee: L, Group 18. Suppression only.
spinosad (Seduce^OG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft.; PHI 7d, REI 4h, Bee: M, Group 5. Spread bait on soil around plants.
zeta-cypermethrin (Mustang*): 1.28 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Flea Beetle, Sweet Potato (Chaetocnema confinis)

Sweet potato flea beetles feed only on the plant family that includes sweet potato, bindweed (Convolvus spp.), morning glory (Ipomea spp.), and also the Asian leafy green crop known as water spinach (Ipomea aquatica) which is grown only with a state permit in MA because it is a noxious weed in southern states. Adults are small (1.5-1.8 mm) black flea beetles with a bronze cast. Like many flea beetles, they overwinter as adults and become active in spring. They lay eggs primarily in bindweed, where larvae feed on roots, and pupate in the soil. There is 1 generation per year. In sweet potato, adults cause damage primarily to young plants, feeding in long narrow strips on the foliage, parallel to veins, rather than the small round holes that are characteristic of most flea beetle species. Damage is rarely severe enough to require controls. Larvae rarely feed on sweet potato, but may damage fibrous roots or etch channels into the surface of tubers. Some sweet potato varieties have greater resistance to root injury. Because sweet potato acreage is increasing in New England, cultural practices such as crop rotation and eliminating bindweed are especially important to prevent insects that feed on sweet potato and related plants from building up and becoming significant pests.

acetamiprid (Assail 30SG): 1.5 to 2.5 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.
alpha-cypermethrin (Fastac* EC): 1.8 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.
bifenthrin (Brigade* 2EC): 3.2 to 9.6 oz/A at cultivation or lay-by, 2.1 to 6.4 oz/A foliar; PHI 21d, REI 12h, Bee: H, Group 3A. May be applied as a soil-incorporated broadcast, bed or T-band spray into planting furrow to control sweet potato flea beetle only. May be applied as foliar spray to control all adult flea beetles.
carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 7d, REI 12h, Bee: H, Group 1A.
chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.
clothianidin (Belay): 2 to 3 oz/A foliar, 9 to 12 oz/A soil; PHI 14d, REI 12h, Bee: H, Group 4A. Soil application maybe at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil).
cyantraniliprole (Verimark): 10 to 13.5 oz/A; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting. Suppression of potato flea beetle only.
deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A. Adults only.
imidacloprid (Admire Pro): 1.2 oz/A foliar, 4.4 to 10.5 oz/A soil; PHI 7d foliar, PHI 125d soil, REI 12h, Bee: H, Group 4A.
kaolin (Surround WP^OG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Generally compatible as a tank mix with other insecticides.
lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A. Adults only.
pyrethrin (PyGanic EC5.0^OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
thiamethoxam (Actara): 1.5 to 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4A.
thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4A. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer before or during planting, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. Do not apply as a foliar spray.
zeta-cypermethrin (Mustang*): 1.76 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Tortoise Beetle

There are several species of tortoise beetles which feed on sweet potato and related plants in the morning glory (Convulvulaceae) family and have a broad geographic range. These leaf-feeding beetles cause foliar damage in both adult and larval stages. Adults have a distinctive rounded shape, with their head and thorax covered and flattened often translucent margins on their wings and thorax, giving them the appearance of a turtle shell. Coloration is often bright and metallic, especially in the golden tortoise beetle (Charidotella bicolor). Adults overwinter and lay eggs in late spring and early summer; larvae feed on underside of leaves, and when full grown, pupate attached to the leaf. Larvae are flattened, adorned with branched spines, and construct a protective dried mass of cast skin and feces attached to their posterior end, which is held over their back. Their distinctive feeding holes are round, irregular, and scattered across the leaf. There is 1 generation per year. Unless the numbers are very high, sweet potato outgrows the damage without yield loss.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.
gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.
lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

Slugs

Damage appears as shredded foliage. Look for silvery slime trails on leaves or turn over soil clods or debris to find slugs during daylight hours. Grow plants away from moist, shaded habitats, use clean cultivation, control weeds, hand pick/crush slugs or scatter baits on the ground near infested plants. See the Cabbage, Broccoli, Cauliflower, and Other Brassica Crops section for more information on slugs.

iron phosphate (Sluggo: Snail and Slug Bait^OG): 20 to 44 lb/A; PHI 0d, REI 0h, Bee: L, Group 9B. Apply around perimeter, scatter around base of plants, or band down rows. Apply to moist soil in the evening.

Whiteflies

For more information see whiteflies in the Tomato section.

Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.
flupyradifurone (Sivanto): 10.5 to 14 oz/A; PHI 7d, REI 4h, Bee: L, Group 4D.
gamma-cyhalothrin (Declare*): 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A. Suppression only.
imidacloprid (Admire Pro): 1.2 oz/A foliar, 4.4 to 10.5 oz/A soil; PHI 7d foliar, PHI 125d soil, REI 12h, Bee: H, Group 4A.
novaluron (Rimon 0.83EC): 12 oz/A; PHI 14d, REI 12h, Bee: L, Group 16B. Most effective on immature stages. Do not apply more than 2 applications per year for whitefly control.
petroleum oil (Suffoil X^OG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L.
pyrethrin (PyGanic EC5.0^OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
spiromesifen (Oberon 2SC): 8 to 16 oz/A; PHI 7d, REI 12h, Bee: M, Group 23. Immature whiteflies only.
spirotetramat (Movento): 4 to 5 oz/A; PHI 7d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity. Don't use sticker adjuvants. Controls immature stages; may also reduce adult fertility.
sulfoxaflor (Closer SC): 4.5 oz/A; PHI 7d, REI 12h, Bee: H, Group 4C. Silverleaf and sweet potato whiteflies only.

Wireworms and White Grubs

See the Potato section for more information on wireworms. These root pests are favored by low, heavy soils that have been in sod or pasture. Delay planting susceptible crops, such as corn, potatoes or sweet potatoes, on such land for at least 2 years after the sod has been broken.

bifenthrin (Brigade* 2EC): 9.6 to 19.2 oz/A at-plant for corn and tobacco wireworms only, 3.2 to 9.6 oz/A at cultivation or lay-by, or 2.1 to 6.4 oz/A foliar for southern potato wireworm only; PHI 21d, REI 12h, Bee: H, Group 3A. May be applied as soil-incorporated broadcast, bed, or T-band spray into planting furrow or soil-directed and incorporated spray at cultivation or lay-by for wireworms and white grubs. May be applied as foliar spray for click beetle (adult wireworm) and May/June beetles (adult white grubs).
Burkholderia spp. strain A396 (Majestene^OG): 4 to 16 qt/A at planting; PHI 0d, REI 4h, Bee: M, Group UN. Apply in furrow at planting or during cultivation.
ethoprop (Mocap* 15G): 20 to 26 lb/A, 1.6 to 2.1 lb/1,000 row feet; REI 48h, Bee: H, Group 1B. Apply in a 12"- 15"-wide band, 2-3 weeks prior to planting. Mix in top 2-4" of soil right after application. Apply only once during the growing season.
Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDG^OG): 1 to 2 lb/A soil drench; PHI 0d, REI 4h, Bee: M, Group UN.

Insect Control

Sweet Potato Weed Control

Sweet Potato Weed Control otank Tue, 05/28/2024 - 11:08

Sweet Potato - General Sweet Potato Disease Control Sweet Potato Insect Control

NOTES: For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases, there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using.

Plastic mulch is recommended for sweet potato culture. It is important to maintain good weed control between the mulched rows before the plants run because once they do run access will be limited. Also, weedy areas between rows may harbor voles and wireworms.

Stale Seedbed

See Stale Seedbed Technique in the Weed Management section.

glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
paraquat (Gramoxone SL 2.0*): REI 12h or 24h, Group 22. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

clomazone (Command 3ME): PHI 95d, 125d above 53.3 oz/A, REI 12h, Group 13. Apply 21.3-64 oz/A per application, only 1 application per year. Apply in a minimum of 10 gal/A of spray. Use the lower rate on sandy soils and the higher rate on silt and clay soils. Can be applied after transplanting, before weed emergence. Some temporary crop injury (partial whitening of leaf or stem tissue) may be visible after crop emergence. Complete recovery will occur from minor early injury without affecting yield or earliness.
flumioxazin (Valor SX): REI 12h, Group 14. Apply up to 3 oz/A per application, only 1 application per year. Apply to soil before transplanting sweet potato slips. Do not use on any sweet potato variety other than “Beauregard”, unless varietal tolerance has been tested.
napropamide (Devrinol 2-XT): REI 24h, Group 0. Apply 2-4 qt/A per application, only 1 application per year. Use the lower rate on sandy soils and the higher rate on silt and clay soils. Apply after transplanting to a weed-free soil surface. Activate and incorporate 2-4" into the soil with water through irrigation or rainfall within 24-72 hours of application. Can be applied and incorporated 1-2’’ into the soil through shallow cultivation.
dimethenamid (Outlook): PHI 40d, REI 12h, Group 15. Apply 7-21 oz/A per application, only 1 application allowed per year. Apply after planting or drag-off. Can cause delayed emergence or temporary stunting in cold and wet conditions. Can cause crop injury to sweet potatoes, so be careful not to allow herbicide to come into contact with tubers. Apply when the potential for loss due to weeds is higher than potential loss due to herbicide injury.

Postemergent Herbicides (after weeds germinate)

carfentrazone (Aim EC): PHI 7d, REI 12h, Group 14. Apply up to 2 oz/A per application, multiple applications allowed per year. Do not exceed 6.1 oz/A per year. Can also be applied to row middles of emerged crops with hooded sprayers to control emerged weeds, including crops grown on mulch or plastic. Prevent any spray from contacting the crop, or injury will occur. For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across. Can use up to 5.8 oz/A as a harvest aid, but do not exceed the maximum of 6.1 oz/A per year. Adequate desiccation is achieved within 14 days after application.
clethodim (Select Max): PHI 30d, 24hr REI, Group 1. Apply 6-32 oz/A per application, up to 4 applications allowed per year, a minimum of 14 days apart. Do not exceed 64 oz/A per year. Apply to actively growing grasses. Add 0.25% v:v nonionic surfactant (1 qt/100 gal of spray). Can also be applied as a spot-spray by mixing 0.33-0.66% (0.44-0.85 oz/gal) Select Max and 0.25% v:v nonionic surfactant (0.33 oz/gal). Spray to wet, but do not allow runoff of spray solution.
fluazifop (Fusilade DX): PHI 14d, REI 12h, Group 1. Apply up to 12 oz/A per application, up to 4 applications allowed per year, a minimum of 14 days apart. Do not exceed 48 oz/A per year. Apply to actively growing grasses (see product label for susceptible stage). Add either crop oil concentrate (0.5-1%, 0.5-1 gal/100 gal of spray) or nonionic surfactant (0.25-0.5%, 1-2 qt/100 gal of spray).
glyphosate (Roundup PowerMax): PHI 14d, REI 4h, Group 9. Apply 10 oz to 3.1 qts/A per application, multiple applications allowed per year. Do not exceed 5 qts/A per year. Rate based on target weed species. Can be applied during fallow intervals, prior to planting or transplanting, at planting, or before crop has emerged. Could cause injury when applied prior to transplanting or direct-seeding into plastic mulch. Remove residual product from plastic mulch with a 0.5” of water through irrigation or rainfall prior to planting. Can also be applied with the wiper method using a 33% solution by volume. A maximum of 5 wiper applications allowed per year, a minimum of 14 days apart and 7 days prior to harvest.
paraquat (Gramozone SL 3.0*): REI 12h or 24h application type, Group 22. Apply 0.7-1.3 pts/A per application, up to 3 applications allowed per year, a minimum of 7 days apart. Do not exceed 4 pts/A per year. Can be applied before, during, or after planting but before emergence (up until ground cracking). Apply in a minimum of 10 gal/A of spray. May be fatal if swallowed or inhaled. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
pelargonic acid (Scythe): PHI 24h, REI 12h, Group 0. Apply a 3-10% solution (3-10 gal/100 gal of spray). Apply in 75-200 gal/A of spray. Can use preplant, or as a directed and shielded spray during crop growth. Avoid contact with foliage or crop damage may occur. Spray to wet, but do not allow runoff of spray solution.

Weed Control