Several key insect and mite pests are known to attack watermelons grown in the Mid-Atlantic region. Certain species cause economic losses on an annual basis while others may only be occasional pests. The most important pests of watermelons include seed corn maggot, cucumber beetles, melon aphids and spider mites. Occasional pests include thrips and leafhoppers.
Seed corn maggot (Primary pest)
Seed corn maggot eggs are laid in freshly plowed fields as well as in greenhouse flats before transplanting into the field. Only a few maggots per seed or plant can significantly reduce stands. At the present time, there are no labeled materials for seed corn maggot on melons. However, broadcast applications of diazinon for other soil insect pests as well as at planting treatments of labeled neonicotinoid insecticides ( i.e. Admire and Platinum) and Furadan 4F ( 24 C label) have helped to reduce problems. However, in high risk fields, control levels have been variable.
A. Chemical
Pros and Cons:
Currently, there are no available seed treatments or soil insecticides available for seed corn maggot control in watermelons. As indicated above, the use of diazinon for other soil insecticide as well as the use of at planting applications of the neonicotinoids and Furadan 4F for cucumber beetle control have helped to reduce problems. However, these treatments provide only fair control, especially under heavy seed corn maggot pressure.
1. Organophosphates
Diazinon AG500 – REI = 24 hrs; 3 day PHI;
Currently, a broadcast application of diazinon is only labeled for wireworms and cutworms; however, the use for SCM is allowed under Section 2ee of FIFRA in Delaware. According to the current diazinon IRED, one soil application of diazinon should still be allowed under the new labels. Although the use of a broadcast application of diazinon before planting can reduce maggot populations, it is only effective if applied immediately before planting. Since it must be applied before plastic is layed, it is often applied weeks before planting resulting in reduced levels of control. No Resistance Issues
2. Carbamates
Furadan 4F (carbofuran) (24C label in Delaware, Maryland, VA) – REI – 48 hours; no PHI on 24C label
The only 24C label only states cucumber beetle control; however, the use for SCM control is allowed under Section 2ee of FIFRA in Delaware. Overall, SCM control has been fair, especially under heavy pressure. In addition, a notice was issued in 2006 by EPA regarding the potential cancellation of Furadan on numerous vegetables. In many cases, the use of Furadan has also been shown to flair spider mites. No resistance issues.
3. B2 Carcinogens – none
4. Other chemical pesticides
Admire 2F (imadacloprid, neonicotinoid) (VA , MD, DE) – REI – 12 hours; 21 day PHI
Currently, an at-planting application of Admire is only labeled for aphid and cucumber beetle control; however, the use for SCM is allowed under Section 2ee of FIFRA in Delaware. In general the use of Admire at planting to control aphids and cucumber beetles has helped reduce problems; however, it is not adequate under heavy population pressure. No resistance issues.
Platinum ( thiamethoxam, neonicotinoid) (VA,DE, MD) – REI – 12 hours; 30 day PHI
Currently, an at-planting application of Platinum is only labeled for aphid and cucumber beetle control; however, the use for SCM is allowed under Section 2ee of FIFRA in Delaware In general the use of Platinum at planting to control aphids and cucumber beetles has helped reduce problems; however, it is not adequate under heavy population pressure. No resistance issues.
B. Biological – none
C. Cultural
The use of cultural management practices before planting can help to reduce the potential for economic problems. A combination of the following cultural strategies can be used: (1) plow down cover crops at least 3-4 weeks before planting or transplanting, (2) completely bury cover crops or previous crop residue to reduce fly attraction to rotting organic matter on the soil surface, and (3) avoid the use of heavy manure applications close to planting. However, tillage must be done before seed corn maggots lay eggs early in the spring. Unfortunately, weather conditions are often not favorable for early tillage; therefore, this is often not a viable management option. Even if plowed down early SCM can still be pests.
Use clear plastic mulch or Infra red selective mulch to heat soil to 21.7O C which will reduce SCM infestations.
Heavier soils will remain cooler for a longer period than sandy soils and will take more time for plant material plowed down to decay.
D. Non-registered pipeline materials
Seed treatments in IR-4 pipeline include thiamethoxam (Cruiser) and fipronil (Regent)
Striped and spotted cucumber beetles (primary pests)
As soon as melons are planted in May, beetles migrate to the field and begin feeding on young seedlings. Although most watermelon cultivars have good bacterial wilt resistance, heavy beetle populations (greater than 5 per plant) can severely affect stand establishment during the cotyledon stage. Once the first three leaves are established, plants generally compensate for damage and growth delays before harvest. However, beetles can also damage mature fruit (rindworm damage). The use of at-planting insecticides or one-two properly timed foliar insecticides can provide effective control of overwintering beetles. Control of beetles late in the season to prevent rind damage is more difficult and inconsistent.
A. Chemical
1. Organophosphates – none
2. Carbamates
Furadan 4F (carbofuran) – Special Local-Needs label 24(C) in Delaware, MD and VA . REI – 48 hours; no PHI on 24C label.
In recent years, some producers have reported reduced efficacy with Furadan for cucumber beetle control. In addition, the use at planting has lead to spider mite outbreaks in season, but gives 2-3 weeks of protection from beetle feeding. No resistance issues.
Lannate LV (methomyl) – REI – 48 hours; 3 day PHI
Has provided effective control in Delaware and is most often used when both aphids and cucumber beetles are present early in the season; however, Maryland reports moderate to poor control of cucumber beetles. Under certain conditions ( i.e. exploded populations; heavy weed pressure; poor coverage), it has not provided effective late season control. No resistance issues.
Sevin 80S (carbaryl) – REI – 12 hours; 0 days PHIPros and cons – In recent years, growers have reported reduced efficacy. In addition, repeated use has been shown to flair two-spotted spider mite and aphid populations later in the season. Extremely harmful to bees. No resistance issues.
3. B2 Carcinogens – none
4. Other chemical pesticides
Asana XL (esfenvalerate; pyrethroid) – REI – 12 hours; 3 day PHI
– In general, it has provided good control. Repeated use of pyrethroids has been shown to flair aphids and mites in season. No resistance issues.
Baythroid XL – (new label for 2006; beta-cyfluthrin; pyrethroid) – REI – 12 hours; 3 day PHI
Limited experience with product on cucurbits in DE; however, should provide effective control. However, same concern over multiple use and aphid flairs like other pyrethroids. No resistance.
Permethrin 3.2EC (pyrethroid) – REI – 12 hours; 0 day PHIIn recent years, growers have reported poor control with permethrin. In addition, multiple applications have resulted in aphid flairs. No resistance. .
Capture 2EC (bifenthrin; pyrethroid) - REI - 24 hours; 3 day PHI. (Virginia, DE and MD)Has provided good cucumber beetle control and help control low-moderate mite populations. Repeated use has been shown to flair aphids in season. No resistance issues.
Admire ( imidacloprid; neonicotinoid) (NOTE –Provado does not have a federal label for cucurbits) (North Carolina, DE, MD.VA) - REI – 12 hours; 21 day PHI
The use of Admire at planting or through the drip system has provided good cucumber beetle control for 3-6 weeks depending on beetle population levels. It will not interfere with foliar natural enemy populations. No resistance.
Thionex (endosulfan chlorinated hydrocarbon; ) (North Carolina, DE and MD ? VA)- NOTE – Do not think trade names Phaser or Thiodan are available anywhere anymore; REI – 24 hours; 2 day PHI
Has provided good cucumber beetle control in DE; however, MD reports poor control. It has also provided good melon aphid control in DE so is often used when both insects are present. In addition, it is relatively safe when used around bees so can be used after flowering. No resistance
Platinum ( thiamethoxam, neonicotinoid) (VA,DE, MD) – REI – 12 hours; 30 day PHI
The use of Platinum at planting or through the drip system has provided good cucumber beetle control. No resistance. .
Venom ( dinotefuran, neonicotinoid) (VA, DE, MD) – REI – 12 hours; 21 day PHI (soil); 1 day PHI (foliar)
The use of Venom both as a soil application and foliar application has worked well in VA. Currently a 2ee label in all states for cucumber beetle control.
B. Biological - None Available
C. Cultural (Virginia)
Plant varieties resistant to bacterial wilt (there are a limited number of resistant cultivars that also have the desirable horticultural attributes that growers want). Always cultivate the soil thoroughly before planting. The use of plastic or straw as bedding for the developing watermelons may deter rindworm feeding (NOTE only useful for small plantings JW), but may also increase squash bug populations. Areas of the field near woods will be the first sections attached by overwintering beetle populations. In the fall, eliminating surrounding weeds will reduce the overwintering sites for the beetles ( Has this worked ?JW).
D. Non-registered pipeline materials
Assail ( acetamiprid; neonicotinoid)
Melon aphid (Primary pest)
Melon aphid is the predominant aphid species attacking watermelons grown in the Mid-Atlantic region. Infestations begin when winged forms fly to the fields in late May. They feed mainly on the undersides of the leaves resulting in cupping of leaves, leaf distortion, plant stunting, and a reduction in the quality and quantity of fruit. In addition to feeding damage, the melon aphid is one of the chief vectors of cucumber mosaic virus. A foliar treatment should be applied if beneficial insect populations are low and 20% or more of the runners are infested with 5 or more aphids per leaf.
A. Chemical
1. Organophosphate-
Diazinon; Spectracide (diazinon) (North Carolina) – not used in DE
Dimethoate (North Carolina) – not effective on melon aphid in DE so is not used for aphid control; however MD reports good control.
2. Carbamates
Lannate LV (methomyl) – REI – 48 hours; 3 day PHI
In Delaware and Maryland, Lannate has provided good early season control of aphids (MD reports moderate to poor control). In recent years, growers have experienced variable levels of control generally due to exploded populations at application and coverage issues. No documented resistance in DE.
3. B2 Carcinogens – none
4. Other chemical pesticides
Thionex 3 EC (endosulfan; chlorinated hydrocarbon; cyclodiene organochlorine)- REI – 24 hours; 2 day PHI
Has provided good – excellent melon aphid control, especially if populations have not exploded at the time of application. In addition, it is relatively safe when used around bees so can be used after flowering. No resistance.
Fullfill ( pymetrozine; triazine?; pyridine azomethine) – REI – 12 hours; 0 day PHI
Fulfill has provided good control of aphids, especially before populations explode. The use of penetrating type spray adjuvant is recommended to provide the most effective coverage and control. In general, it should not be applied with a “sticky fungicide” to provide effective control. Low toxicity to honey bees; however, should not be applied directly to bees that are actively foraging in the field. No resistance.
Venom ( dinotefuran, neonicotinoid) (VA, DE, MD) – REI – 12 hours; 21 day PHI (soil); 1 day PHI (foliar)
New label in 2006. Provides good control as a soil applied material. Still some questions on efficacy as a foliar product.
Beleaf (flonicomid; pyridine carboxamide) – Might have labels in 2007 – in December still no state label in DE
B. Biological
The level of natural controls (e.g. lady beetles, lacewings, and parasitized aphids) should also be considered when making a treatment decision. In general, chemical controls are not needed if you can find one beneficial insect for every 50 aphids per plant. But if you know that you have a potential for virus problems in your area, only a few aphids can vector enough virus to cause economic losses. In these cases, early detection and control of aphids is critical. Spraying to stop initial virus infection into a field is useless as viruses are transmitted within seconds and pesticide-use cannot stop this initial plant infection. You can slow down secondary spread (aphids
acquiring the virus from initially infected watermelon plants and spreading it to nearby plants) by early detection and control of aphids, but this results in only small reductions in the number of virus infected plants.
C. Cultural – (Virginia)
Many watermelon cultivars are resistant to plant viruses and should be considered in the pest management decision-making process for aphids. Know what viruses are most common for your growing area to be sure you are purchasing the correct virus resistant cultivars. Plant disease-free certified seed. Avoid planting fields immediately downwind of a barrier such as hedgerows or woodlots, which reduce wind velocity and increase the number of dispersing aphids falling into fields. These barriers can also cause over-fertilization with nitrogen, which results in lush growth attractive to aphids. Use of reflective mulch can give 2-4 weeks more time before initial virus infection takes place and reduces aphid populations in the field.
D. Non-registered pipeline materials
Spider mites (Primary pest)
Spider mites are a serious pest of watermelons, especially during hot, dry weather. Mites feed on the plant sap and can defoliate vines in a few weeks in hot, dry weather. Defoliated plants tend to yield small, poor quality fruit. A treatment should be applied when 10-15% of the crown leaves are infested with mites. Treatments should be applied before populations explode. Two applications spaced 4-5 days apart are needed in most years. The addition of crop oil or an organosilicone to most insecticides has improved control, especially with aerial application.
A. Chemical
1. Organophosphate
Dimethoate 4EC – REI – 48 hours; 3 day PHI
Pros and cons – In recent years, dimethoate has not provided effective spider mite control in Delaware.
Highlight general IPM and/or resistance management issues – Although not documented, spider mites may be resistant to dimethoate in our area. In addition, drought stressed plants and pH of the water could results in reduced efficacy.
2. Carbamates – none
3. B2 Carcinogens – none
4. Other chemical pesticides
Kelthane 50WP (dicofol; organocholirine) – REI – 48 hours; 2 day PHI
Pros and cons – MD reports that this product still gives excellent control of mites in most circumstances, but mite resistance has been observed. DE reports fair to poor control in many fields in recent years.
Highlight general IPM and/or resistance management issues – Although not officially document, it appears that mite resistance has been observed
Agri-Mek 0.15EC (abamectin; ? glycoside) – REI – 12 hours; 7 day PHI
Has provided good control when used at higher rates but is an expensive product to use. Reduced control observed when combined with “sticky fungicides”. Should not be applied directly to bees foraging in a field.
Highlight general IPM and/or resistance management issues – Good resistance management tool.
Capture 2EC (bifenthrin; pyrethroid) – REI – 24 hours; 3 day PHI; (Virginia, DE and MD)
Pros and cons – Provides effective control when applied before mites explode. In season, have seen reduced control on exploded populations. In addition, have see mite explosions if not timed correctly and over used. MD reports that at times its use can cause dispersion of mites so that it appears there is a reduction in numbers when in fact they have spread to other plants.
Danitol (fenpropathrin; pyrethroid) – REI – 24 hours; 7 day PHI
Pros and cons – Provides effective control when applied before mites explode. In season, have seen reduced control on exploded populations. In addition, have see mite explosions if not timed correctly and over used.
Oberon (spiromesifin;tetronic acid ) REI – 12 hours; 7 day PHI
Pros and Cons - Excellent new miticide – providing control of nymphs as well as has ovicidal properties. Excellent resistance management tool. Extremely safe on bees
B. Biological
Although predatory mites can be found in fields, populations rarely reach high enough levels to provide economic control.
C. Cultural (Virginia)
If possible, avoid mowing field margins and grassy areas until after midsummer since this forces mites in the crop.
D. Non-registered pipeline materials
Cabbage Looper (minor pests) (Virginia)
These insects feed on the underside of leaves, producing ragged holes of various sizes. Feeding begins in late July or early August and usually continues through harvest. Healthy plants can usually sustain feeding injury unless populations become exceedingly large. Loopers are not usually serious pests of watermelon in Virginia.
A. Chemical
1. Organophosphates -none
2. Carbamates
Lannate ( methomyl)--1.5-3 pt LV/A or OLF – REI – 48 hours; 3 day PHI- Provides effective control of cabbage loopers.
3. B2 Carcinogens - none
4. Other chemical pesticides
Asana XL ( esfenvalerate; pyrethroid) – REI – 12 hours; 3 day PHI
Starting to see reduced levels of control of cabbage looper in some fields treated with pyrethroids.
Bacillus thuringiensis – REI – 4 hours ; 0 day PHI
Only effective in small caterpillars
Baythroid XL( beta-cyfluthrin; pyrethroid) – REI – 12 hours; 0 day PHI
Starting to see reduced levels of control of cabbage looper in some fields treated with pyrethroids.
Capture (bifenthrin; pyrethroid)- REI 12 hours; 3 day PHI
Starting to see reduced levels of control of cabbage looper in some fields treated with pyrethroids
Entrust –(spinosad; naturalyte )– REI – 4 hours; 3 day PHI
Provide good cabbage looper control but need higher rates
Intrepid (methoxyfenozide; diacylhydrazine )–- REI – 4 hours; 3 day PHI
Provides good cabbage looper control
permethrin—(pyrethroid)– REI – 12 hours; 0 day PHI
Starting to see reduced levels of control of cabbage looper in some fields treated with pyrethroids
SpinTor—(spinosad;naturalyte ) - REI – 4 hours; 3 day PHI; Provides good cabbage looper control but need higher labeled rates
Highlight general IPM and/or resistance management issues: Although not documented have see reduced control of cabbage loopers with pyrethroids.
B. Biological Control
There are several parasitic wasps and predators that attack the cabbage looper. Also, a nuclear polyhedrosis virus (NPV) can substantially reduce population levels of larvae, especially after a period of precipitation.
C. Cultural Control - No current recommendations for commercial production.
D. Non-registered pipeline materials - none
Cutworms (Virginia) minor pest
Black cutworm, Agrotis ipsilon
Variegated cutworm, Peridroma saucia
Granulate cutworm, Feltia subterranea
Cutworms are sporadic pests of numerous crops. Several species of cutworm may be found in the mid-Atlantic. Newly hatched cutworm larvae feed on young plants at the soil line, often severing the stems. Later generations of cutworms feed on developing melons and in severe cases may tunnel completely through the fruit, greatly diminishing marketability. If cutworms are actively cutting plants, a postplanting contact treatment may be used. In Delaware, watermelon fields are rarely sprayed for cutworm.
A. Chemical
1. Organophosphates -none
2. Carbamates
Lannate (methomyl) (North Carolina) – – REI - 48 hours; 3 day PHI; not used in Delaware
Sevin (carbaryl) (North Carolina)- – REI – 12 hours; 0 days PHI not used in DE
3. B2 Carcinogens -none
4. Other chemical pesticides
Asana XL- ( esfenvalerate; pyrethroid)- REI – 12 hours; 3 day PHI
Baythroid XL (beta-cyfluthrin; pyrethroid) -– REI – 12 hours; 0 day PHI
Capture 2EC (bifenthrin; pyrethroid) - PHI - 3 days; REI - 24 hours. (Virginia and DE)
Ambush (permethrin) (North Carolina) – not available in DE as Ambush
Just as generic permethrin—(pyrethroid) )– REI – 12 hours; 0 day PHI
Pros and cons - In general – pyrethroids have provided very effective cutworm control. Reduced control is seen during drought conditions when cutworms feed below the soil surface.
B. Biological control
Cutworms are attacked by numerous ground-dwelling insect predators, especially carabid beetles. Also, pathogens such as Beauveria bassiana and entomopathogenic nematodes often will infect larvae.
C. Cultural Control
Proper tillage will help eliminate some species of cutworms that may move off of cover crops.
D. Non-registered pipeline materials -none
Leafminers (Virginia)
Serpentine Leafminer, Liriomyza brassicae
Leafminers cause injury to leaves primarily as a result of their mining of leaves, which results in the destruction of leaf mesophyll tissue. Leaf mining depresses the level of photosynthesis and may result in leaf droppage. Fewer leaves in the canopy can result in sun scalding of fruit. Many generations occur annually in Virginia, but the first is usually the most damaging. In Delaware , we have seen some damage but generally do not treat. Level of control has been questionable with available products – may be an issue of timing.
A. Chemical
1. Organophosphates
Dimethoate 4EC - PHI - 3 days. REI - 48 hours.
Pros and cons – This product has been used in DE and MD with limited success.
Diazinon (North Carolina) REI – 24 hours; 3 day PHI; not used in DE; poor control in MD
2. Carbamates
Vydate L-(oxamyl) REI – 48 hours; 1 day PHI- not used in DE for this pest
3. B2 Carcinogens -none
4. Other chemical pesticides
Agri-Mek 0.15EC (abamectin ? glycoside; ) -; REI 12 Hrs.; 7 day PHI
Pros and cons – Has been used in DE with some success; however, very expensive and control can be variable. MD reports excellent control of leafminers and is considered a reduced risk pesticide.
Thiodnex (endosulfan; – chlorinated hydrocarbon cyclodiene organochlorine)- REI – 24 hours; 2 day PHI (North Carolina) not used in DE
The following are listed in the Mid-Atlantic Guide – no knowledge of efficacy since we rarely spray for this pest
Entrust – –(spinosad; naturalyte )– REI – 4 hours; 3 day PHI
SpinTor—(spinosad;naturalyte ) - REI – 4 hours; 3 day PHI
Venom –( dinotefuran, neonicotinoid) – REI – 12 hours; 21 day PHI (soil); 1 day PHI (foliar)
B. Biological Control
Parasitoids often provide excellent suppression of leafminers if broad-spectrum insecticides are not applied to the crop. The level of control will often preclude the need for an insecticide in most cases.
C. Cultural Control: No current recommendations.
D. Non-registered pipeline materials -none
Pickleworm, Diaphania nitidalis (Virginia)
Melonworm, Diaphania hyalinata
The melonworm is generally a foliage feeder (unlike the pickleworm, which attacks the developing leaf and flower buds) but also causes damage to the vines and fruit. Although several generations can occur during a year, pickleworm and melonworm are rarely serious pests of watermelon in the mid-Atlantic. As soon as pickleworms or their damage appears, begin insecticide treatments.
Not aware of any melon fields sprayed in Delaware for these 2 insect pests.
A. Chemical
The following are all listed in mid-Atlantic Veg Reccs under these 2 insect pests: See above sections for REIs and PHIs
Asana XL—(esfenvalerate; pyrethroid) – (pickleworm only),
Baythroid XL – ( beta-cyfluthrin) –
Capture(bifenthrin; pyrethroid)
Entrust ( spinosad; naturalyte
Capture(bifenthrin; pyrethroid)
Intrepid –( methoxyfenozide; diacylhydrazine) -
Lannate-(methomyl; carbamate) -
permethrin—(pyrethroid)
Sevin-(carbaryl; carbamate)
SpinTor(spinosad; naturalyte)
Thionex-(endosulfan; chlorinated hydrocarbon)
1. Organophosphates
2. Carbamates
See above for Lannate
Sevin 80S (carbaryl) - PHI - 3 days; REI - 12 hours. Carbaryl is not used as extensively anymore because of its high toxicity to bees.
3. B2 Carcinogens -none
4. Other chemical pesticides -none
B. Biological Control - No current recommendations
C. Cultural Control
After harvest, remove all debris from the field, destroy vines and unused fruit, and control adjoining weeds. Also, plowing early in the fall will bury the pupae. In the spring, planting early will help the crop establish itself, thus preventing major damage. Resistant varieties are also available.
D. Non-registered pipeline materials -none
Rindworm (North Carolina)-DE and MD as well – Includes cucumber beetle larvae; beet armyworm
Damage to the rinds may result from a complex of insects including cucumber beetle, wireworms, and a number of “worm species, including but not limited to beet armyworm. Larvae of several insects attack the bottom of the fruit that contacts the soil. Management of adult cucumber beetles early in the season may help reduce damage. See cucumber beetle for labeled products.
The following are the labeled beet armyworm products:
1. Organophosphates -none
2. Carbamates- none
3. B2 Carcinogens -none
4. Other chemical pesticides
Entrust – (spinosad; naturalyte )– REI – 4 hours; 3 day PHI
Intrepid –(methoxyfenozide; diacylhydrazine )–- REI – 4 hours; 3 day PHI
SpinTor– (spinosad; naturalyte )– REI – 4 hours; 3 day PHI
All three provide good BAW control. High rates needed. To be effective, spray applications must reach the underside of the fruit, which necessitates adequate volumes (> or equal to 100 gals/a) of water be used.
Flower Thrips (North Carolina)
There are several species that can appear in watermelon flowers. Unless there are many individuals, they should pose no economic problem.
A. Chemical
1. Organophosphates
2. Carbamates
Vydate L-(oxamyl) REI – 48 hours; 1 day PHI- not used in DE for this pest
3. B2 Carcinogens -none
4. Other chemical pesticides
Entrust – (spinosad; naturalyte )– REI – 4 hours; 3 day PHI
SpinTor— (spinosad; naturalyte )– REI – 4 hours; 3 day PHI
Entrust and Spintor have provided effective thrips control
Venom– ( dinotefuran, neonicotinoid) – REI – 12 hours; 21 day PHI (soil); 1 day PHI (foliar) – New material in 2006
B. Biological Control - none
C. Cultural Control - none
D. Non-registered pipeline materials -none