Insect Management for Sweet Potatoes¹

S. E. Webb²

Sweet potatoes are widely grown in Florida. In addition to the traditional moist, orange-fleshed varieties, a dry, white-fleshed type, the boniato, is extensively grown in south Florida. Both types are the same species (Ipomoea batatas), however, and their pest problems are similar.

Foliar pests are generally not too difficult to manage and include agromyzid leafminers, sweetpotato whitefly, (also called silverleaf whitefly), and morningglory leafminer (a caterpillar). Armyworms will also feed on foliage. Natural enemies of these pests can be conserved by using pesticides specific for the pest and avoiding broad-spectrum insecticides, if at all possible.

The most serious pests are those whose immature stages feed on roots: sweetpotato weevil, wireworms, banded cucumber beetle, pale-striped and sweetpotato flea beetles, and in south Florida, Diaprepes weevil and Cuban May beetle. Other white grubs will also feed on sweet potato roots. There are very few soil insecticides available at this time. One of the two that remain (chlorpyrifos) has a 125 days-to-harvest interval which rules out its use with early-maturing varieties. Foliar insecticides aimed at the adult stage can give some control.

Sweetpotato weevil is the most serious pest of sweet potatoes (http://edis.ifas.ufl.edu/IN154). Sweet potatoes fed upon by weevil larvae become extremely bitter in taste so even minor feeding renders the potato unmarketable. Some varieties (Regal, for instance) of sweet potato have some resistance to the weevil as well as other beetle pests but the most popular orange-fleshed variety, Beauregard, is highly susceptible. Of varieties currently grown in Florida, Jewel is the only one with some resistance to insects (flea beetles).

In areas of the state where weevils are not common, it is very important to use only certified slips or transplants from weevil-free areas to avoid introducing weevils. The adult weevil does not have wings, and it and the larval stage are most often moved by transporting infested plants or storage roots (potatoes). During the growing season, keeping storage roots covered with soil helps reduce damage by preventing female weevils from laying eggs directly in roots.

Cultural practices can help reduce insect problems. Ideally, soil should be turned two to three months before planting. Crop rotation is also important. Avoid growing sweet potatoes in the same field two years in a row. New fields should be at least a mile from old fields. Destroy crop residues and culls immediately after harvest and for weevils, empty and clean potato storage areas thoroughly at least a month before harvesting the new crop.

The following table lists insecticides currently registered for use on sweet potatoes.

Tables

Table 1. Selected insecticides approved for use on insects attacking sweet potatoes.

Trade Name (Common Name)	Rate (product/acre)	REI (hours)	Days to Harvest	Insects	MOA Code1	Notes
Actara (thiamethoxam)	1.5-3.0 oz	12	14	potato leafhopper, may help control aphids and whiteflies	4A	Toxic to bees. Do not use after Platinum.
Admire 2F (imidacloprid)	10-24 fl oz	12	125	aphids	4A	Do not use if standing water is present in production area.
Admire Pro	4.4-10.5 fl oz
Agree WG (Bacillus thuringiensis subspecies aizawai)	0.5-2.0 lb	4	0	lepidopteran larvae (caterpillar pests)	11B1	Apply when larvae are small for best control. OMRI-listed2.
Assail 70 WP (acetamiprid)	0.6-1.7 oz	12	7	aphids, leafhoppers, flea beetles, whiteflies	4A	Whiteflies not on label for sweet potatoes but are for other crops on label! No more than 4 applications per season.
Assail 30 SG	1.5-4.0 oz
Aza-Direct (azadirachtin)	1-2 pts, up to 3.5 pts, if needed	4	0	aphids, beetles, caterpillars, leafhoppers, leafminers, mites, stink bugs, thrips, weevils, whiteflies	18B	Antifeedant, repellant, insect growth regulator. OMRI-listed2.
Azatin XL (azadirachtin)	5-21 fl oz	4	0	aphids, beetles, caterpillars, leafhoppers, leafminers, thrips, weevils, whiteflies	18B	Antifeedant, repellant, insect growth regulator.
*Baythroid 2 (cyfluthrin)	0.8-2.8 fl oz	12	0	cabbage looper, cutworms, flea beetles, potato leafhopper, potato leafhopper, sweetpotato weevil adults	3	No more than 6 applications.
*Baythroid XL (beta-cyfluthrin)
Biobit HP (Bacillus thuringiensis subspecies kurstaki)	0.5-2.0 lb	4	0	caterpillars (will not control large armyworms)	11B2	Treat when larvae are young. Good coverage is essential. Can be used in the greenhouse. OMRI-listed2.
BotaniGard 22 WP, ES (Beauveria bassiana)	WP: 0.5-2 lb/100 gal ES: 0.5-2 qts/100 gal	4	0	aphids, thrips, whiteflies	--	May be used in greenhouses. Contact dealer for recommendations if an adjuvant must be used. Not compatible in tank mix with fungicides.
*Capture 2 EC (bifenthrin)	19.2 oz at-plant (soil) 3.2-9.6 oz at lay-by (soil) 2.1-6.4 oz (foliar)	12	21	Wireworms (at-plant and lay-by), white grubs (lay-by), flea beetles, cucumber beetles, whitefringed beetle adults, wireworm adults, white grub adults, sweetpotato weevil adults (foliar)	3	No more than 2 foliar applications, at least 21days apart. Do not apply more than 0.5 lb active ingredient per acre per season, including soil applications.
*Capture LFR	See label for rates
Crymax WDG (Bacillus thuringiensis subspecies kurstaki)	0.5-2.0 lb	4	0	caterpillars	11B2	Use high rate for armyworms. Treat when larvae are young.
Deliver (Bacillus thuringiensis subspecies kurstaki)	0.25-1.5 lb	4	0	caterpillars	11B2	Use higher rates for armyworms. OMRI-listed2.
Diatect V; Diatect Multipurpose Insecticide II (diatomaceous earth + pyrethrins + piperonyl butoxide)	1-6 lb	12	0	aphids, armyworms, cabbage looper	3, --	Diatect V is OMRI-listed2 (no piperonyl butoxide)
DiPel DF (Bacillus thuringiensis subspecies kurstaki)	0.5-2.0 lb	4	0	caterpillars	11B2	Treat when larvae are young. Good coverage is essential.
Endosulfan 3 EC (endosulfan)	0.66-1.33 qt	24	1	sweetpotato flea beetle, sweetpotato weevil, whiteflies	2	Do not make more than 3 applications per year or exceed 3.0 lb active ingredient per acre per year.
Entrust (spinosad)	1-3 oz	4	7	armyworms, leafminers, Liriomyza, loopers, thrips	5	Do not make applications less than 7 days apart or apply more than 4 times per crop. Do not apply more than 6.5 oz/acre per crop.
Extinguish ((S)-methoprene)	1.0-1.5 lb	4	0	fireants	7A	Slow-acting IGR (Insect Growth Regulator), Best applied early spring and fall where crop will be grown. Colonies will be reduced after three weeks and eliminated after 8 to 10 weeks. May be applied by ground equipment or aerially.
Fulfill (pymetrozine)	2.75-5.5 oz	12	14	buckthorn aphid, green peach aphid, melon aphid, potato aphid	9B	Allow a minimum of 7 days between applications. Do not exceed 11 oz/acre/season.
Imidan 70 W (phosmet)	1.3 lb	24	7	banded cucumber beetle, sweetpotato weevil, whitefringed beetle, suppression of white grub and wireworm	1B	No more than 5 applications per season. Do not apply through irrigation system. Crop must be mechanically harvested.
Javelin WG (Bacillus thuringiensis subspecies kurstaki)	0.12-1.5 lb	4	0	most caterpillars, but not Spodoptera species (armyworms)	11B2	Treat when larvae are young. Thorough coverage is essential. OMRI-listed2.
Lepinox WDG (Bacillus thuringiensis subspecies kurstaki)	1.0-2.0 lb	12	0	for most caterpillars, including beet armyworm (see label)	11B2	Treat when larvae are small. Thorough coverage is essential.
Lorsban 15G; 75WG (chlorpyrifos)	See labels for rates	48	preplant broadcast treatment, 125 days before harvest	flea beetles, sweet potato flea beetle, wireworms (Conoderus)	1B	See label.
Malathion 8 F (malathion)	1-1.75 pt	12	3	leafhoppers, morning glory leafminer	1B
Mocap 10 G, *15 G (ethoprop)	See labels	48	preplant see label	cucumber beetles, flea beetles, white grubs, wireworms	1B
M-Pede 49%EC Soap Insecticidal	1-2% V/V	12	0	aphids	--	OMRI-listed2.
*Mustang Max (zeta-cypermethrin)	1.28-4.0 oz	12	1	cabbage looper, cucumber beetles, cutworms, flea beetles, grasshoppers, leafhoppers, tarnished plant bug, vegetable weevil, whitefringed beetle (adult), yellowstriped armyworm; aids in control of aphids and beet armyworm	3	A maximum of 0.15 lb ai/acre per season may be applied. Leaves cannot be used for food or feed.
Neemix 4.5 (azadirachtin)	4-16 fl oz	12	0	aphids, beetles, caterpillars, grasshoppers, leafhoppers, leafminers, thrips, weevils, whiteflies	18B	Does not kill adult insects. IGR and feeding repellant. OMRI-listed2.
Oil, insecticidal	1-2 gal/100 gal	12	Up to day of harvest	leafminers, mites, whiteflies	--
Platinum (thiamethoxam)	5-8 fl oz	12	Applied at planting	aphids, Colorado potato beetles, flea beetles, potato leafhoppers		For most crops that are not on the label, a 120-day plant-back interval must be observed. To manage resistance, avoid using Actara or Provado in conjunction with Platinum.
Provado 1.6F (imidacloprid)	3.5 oz	12	7	aphids, flea beetles, leafhoppers, whiteflies	4A	Limited to 3 applications.
Pyrellin EC (pyrethrin + rotenone)	1-2 pt	12	12 hours	aphids, cabbage looper, leafhoppers, mites, plant bugs, thrips	3, 21
Rimon 0.83 EC (novaluron)	9-12 fl oz	12	14	armyworms, loopers, other foliage feeding caterpillars, whiteflies (suppression)	15	Do not apply more than 24 oz per acre per season. Limited to two applications.
Sevin 80S; XLR; 4F (carbaryl)	80S: 1.25-2.5 lb XLR, 4F: 1-2 qt	12	7	corn earworm, cucumber beetles, flea beetles, sweetpotato hornworm, sweepotato weevil (preplant dip), totoise beetle, whitefringed beetle, yellowstriped armyworm	1A	Do not apply more than 10 lb (80S) per acre per crop or 8 qt (XLR, 4F). See label for preplant dip treatment.
SpinTor 25C (spinosad)	3-6 fl oz	4	7	armyworms, leafminers (Liriomyza spp.), loopers, thrips	5	Do not apply more than a total of 21 fl oz per acre per crop.
*Telone C-35 (dichloropropene + chloropicrin)	See label	5 days - See label	preplant	symphylans, wireworms	--	See supplemental label for use restrictions in south & central Florida.
*Telone II (dichloropropene)
Trilogy (extract of neem oil)	0.5-2.0% V/V	4	0	aphids, mites, suppression of thrips and whiteflies	18B	Apply morning or evening to reduce potential for leaf burn. Toxic to bees exposed to direct treatment. OMRI-listed2.
Xentari DF (Bacillus thuringiensis subspecies aizawai)	0.5-2.0 lb	4	0	caterpillars	11B1	Treat when larvae are young. Thorough coverage is essential. May be used in the greenhouse. Can be used in organic production.
The pesticide information presented in this table was current with federal and state regulations at the time of revision. The user is responsible for determining the intended use is consistent with the label of the product being used. Use pesticides safely. Read and follow label instructions.
1 Mode of Action codes for vegetable pest insecticides from the Insecticide Resistance Action Committee (IRAC) Mode of Action Classification v.5.2 December 2006. 1A. Acetylcholine esterase inhibitors, Carbamates 1B. Acetylcholine esterase inhibitors, Organophosphates 2A. GABA-gated chloride channel antagonists 3. Sodium channel modulators 4A. Nicotinic Acetylcholine receptor agonists/antagonists, Neonicotinoids 5. Nicotinic Acetylcholine receptor agonists (not group 4) 6. Chloride channel activators 7A. Juvenile hormone mimics, Juvenile hormone analogues 7C. Juvenile hormone mimics, Pyriproxifen 9A. Compounds of unknown or non-specific mode of action (selective feeding blockers), Cryolite 9B. Compounds of unknown or non-specific mode of action (selective feeding blockers), Pymetrozine 9C. Compounds of unknown or non-specific mode of action (flonicamid) 11B1. Microbial disruptors of insect midgut membranes, B.t. var aizawai 11B2. Microbial disruptors of insect midgut membranes, B.t. var kurstaki 12B. Inhibitors of oxidative phosphorylation, disruptors of ATP formation, Organotin miticide 15. Inhibitors of chitin biosynthesis, type 0, Lepidopteran 16. Inhibitors of chitin biosynthesis, type 1, Homopteran 17. Inhibitors of chitin biosynthesis, type 2, Dipteran 18A. Ecdysone agonist/disruptor 18B. Ecdysone agonist/disruptor (azadirachtin) 20. Site II electron transport inhibitors 21. Site I electron transport inhibitors 22. Voltage-dependent sodium channel blocker 23. Inhibitors of lipid biosynthesis 25. Neuronal inhibitors 2 OMRI-listed: Listed by the Organic Materials Review Institute for use in organic production.
* Restricted Use Only.

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Footnotes

1. This document is ENY-473 (IG159), one of a series of the Entomology & Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: August 2001. Revised: September 2007. For more publications related to horticulture/agriculture, please visit the EDIS Website at http://edis.ifas.ufl.edu/.

2. S. E. Webb, associate professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611-0640.

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The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.

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