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How to apply nematodes

Insect-parasitic nematodes can be easily applied using conventional pesticide and fertilizer sprayers that have up to 300 PSI pressures.  However, nematodes will be easily damaged, if they are agitated through excessive recirculation of spray mix or if the temperature in the tank increases beyond 86 degrees F. Nematodes can also be applied through different types of irrigation systems but pumps should have proper pressure to avoid damage to nematodes and screen sizes should be larger than 50 mesh so that nematodes will pass through them live. Watering cans are used to apply nematodes in small areas including vegetable and ornamental gardens.

How many nematodes should be applied

For the suscessful control most of the soil dweling insect pests, the optimal rate of 1 billion infective juvenile nematodes in 100 to 260 gallons of water per acre is generally recommended.

Optimal soil and environmental condtions to apply nematodes

All nematodes require proper soil moisture for their optimal movement and infectivity. The activity and infectivity of nematodes can be enhanced by maintaining optimum moisture levels in the soil before and after their application.  In case of nematode application in turf, turf should be irrigated immediately after applicationwith at least 1/2 inch of water to rinse off nematodes from the folliage and move them into the soil and thatch. As nematodes are very sensitiv to heat and cold, their infectivity will be reduced if soil temperature is below 4 degrees C and above 35 degrees C. Soil temperatures between 20 to 30 degrees C are considered favourable for application of majority of nematode species and their virulence.  Nematode survival and activity also influenced by soil type.  Both survival and activity of nematodes is higher in sandy-loam soils than in heavy clay soils.

When to apply nematodes

Since nematodes are very sensitive to UV light, they will die within a minute or two when exposed to full sun. Therefore, nematodes should be applied early in the morning or late in the evening to avoid exposure to UV light.

The citrus root weevil also called as Diaprepes root weevil (Diaprepes abbreviatus) is one of the major insect pests of citrus and many ornamental plants in Florida and California. Several researchers have demonstrated that the application of an insect-parasitic nematode can supress the populations of root weevils in citrus orchards. For example, Steinernema riobrave infective juveniles when applied in citrus orchards or greenhouses can provide 50 to 90% reduction in populations of D. abbreviatus (Bullock et al., 1999; Duncan and McCoy, 1996; Duncan et al., 1996; Shapiro and McCoy, 2000ab).  Applications of S. carpocapsae (All strain), Heterorhabditis bacteriophora (HP-88 strain) or H. bacteriophora (Florida strain) in the citrus grove can also reduce 50-70% adult emergence of D. abbreviatus (Duncan et al., 1996; Schroeder, 1992).  According to Shapiro et al. (1999), S. riobrave, H. bacteriophora and H. indica were highly virulent against younger (50-day-old) than older (100-day-old) D. abbreviatus larvae at 24 or 27 degrees C temperature. Heterorhabditis indica was more virulent than H. bacteriophora in 50-day-old D. abbreviatus larvae at all temperatures. However, H. bacteriophora was more virulent than S. riobrave in 20-day-old larvae at 24 degrees C but it was less virulent than S. riobrave in 50-day-old larvae at 21 degrees C.

Please Read following literature for detailed information on interaction between insect-parasitic nematodes and citrus root weevil.

Bullock, R.C., Pelosi, R.R. and Killer, E.E. 1999. Management of citrus root weevils (Coleoptera : Curculionidae) on Florida citrus with soil-applied entomopathogenic nematodes (Nematoda : Rhabditida). Florida Entomologist. 82: 1-7.

Duncan, L.W and McCoy, C.W. 1996 Vertical distribution in soil, persistence, and efficacy against citrus root weevil (Coleoptera: Curculionidae) of two species of entomogenous nematodes (Rhabditida: Steinernematidae; Heterorhabditidae). Environmental Entomology. 25: 174-178.

Duncan, L.W. McCoy, C.W. and Terranova, A.C. 1996. Estimating sample size and persistence of entomogenous nematodes in sandy soils and their efficacy against the larvae of Diaprepes abbreviatus in Florida. Journal of Nematology. 28: 56-67.

Schroeder, W.J. 1992. Entomopathogenic nematodes for control of root weevils of citrus. Florida Entomologist 75: 563-567.

Shapiro, D.I. and McCoy, C.W. 2000a. Susceptibility of Diaprepes abbreviatus (Coleoptera : Curculionidae) larvae to different rates of entomopathogenic nematodes in the greenhouse. Florida Entomologist. 83: 1-9.

Shapiro, D.I. and McCoy, C.W. 2000b. Effects of culture method and formulation on the virulence of Steinernema riobrave (Rhabditida: Steinernematidae) to Diaprepes abbreviatus (Coleoptera: Curculionidae). Journal of Nematology 32: 281-288.

Shapiro, D.I., Cate, J. R., Pena, J., Hunsberger, A. and McCoy, C.W. 1999. Effects of temperature and host age on suppression of Diaprepes abbreviatus (Coleoptera : Curculionidae) by entomopathogenic nematodes. Journal of Economic Entomology. 92: 1086-1092.

Before starting to write about this topic, I would like to make it clear that taxonomically all bugs are insects but all the insects are not bugs. As far as I know, both in the USA and Canada, almost all people except entomologists call each and every insect as a bug.  Even extension entomologists when they are giving extension seminars to farmers/growers about insect pests of different crops, they often refer them as bad bugs for the understanding of growers. “True” bugs are mainly belong to two insect orders including Hemiptera and Homoptera.

All natural enemies of insect pests are considered as good bugs because they can kill and feed on insect pests that cause tremendous yield losses to many economically important crops. Since many of these natural enemies are commercially produced and used in the integrated pest management program (IPM), they are called as biological control agents. These biological control agents can be parasitic or predatory insects.  In addition to these predators and parasites (good bugs), there are some microorganisms such as bacteria, fungi, protozoa and viruses that can cause diseases and kill insect pests.  These microorganisms are termed as insect pathogens and also considered as biological control agents. Nematodes belonging to two families, Steinernematidae and Heterorhabditidae are also considered as insect parasites or pathogens and used as biological agents in controlling many soil dwelling insect pests of many economically important crops (in this blog, please read several posts that are devoted to insect- parasitic nematodes). Furthermore, mites are closely related to spiders but not considered as insects. Some species of mites are predatory in nature but others are serious pests of many plant species.

Predators: Although, there are many kinds of vertebrate predators including birds, amphibians, reptiles, fish and mammals that feed on insects, in this blog I am going to focus on the predatory insects that are generally used in biological control programs. These insects are called predators because they feed and complete their entire life cycle by remaining outside of their prey host as opposed to parasites that complete at least part of their life cycle inside their hosts.  Predators are generally larger than their prey, they kill and feed on both immature and adult stages of many different kinds of hosts.

Following are the examples of insect predators that can be used as biological control agents against many kinds of insect pests.

Aphid midge (Aphidoletes aphidimyza): This predatory midge fly often found in many vegetable crops (potatoes, cabbage and cauliflower), fruit orchards (apple, blueberries and peaches) and many ornamental plants throughout North America. The larval stages of this midge fly are mainly predators of aphids. This midge fly is commercially available and widely used as biocontrol agents in the greenhouses against over 60 species of aphids infesting both vegetable and ornamental plants.

Bigeyed bug (Geocoris spp.): There are four most common species of bigeyed bug (G. punctipes, G. pallens, G. bullatus and G. uliginosus) found in almost all cropping systems in North America.  Bigeyed bugs generally feed on many small insects including aphids, mites and whiteflies, eggs and nymphs of many plant bugs. They can also feed on eggs and small larval stages of cotton ballworms, pink ballworms and tobacco budworms. Since this bug is very susceptible to broad spectrum pesticides, care should be taken to avoid killing of this important biocontrol agent.  This predator is commercially available from insectories in the USA.

Brown lacewings (Hemerobius stigma): These lacewings found throughout North American forests and are mainly predators of aphids and many other soft-bodied small insects including balsam woolly adelgis (Adelges piceae), pine bark adelgid (Pineus strobi) and Cooley’s spruce gall adelgid (Adelges cooleyi). These lacewings are not commercially available.

Deraeocoris bug (Deraeocoris nebulosus): This is a very important predator of many insect and mite pests different agricultural, horticultural and landscape plants in the Canada and USA. This is a true predatory bug, which is generally found in many fruit orchards including apple, peach and pecan.  They also found in cotton fields and many landscape settings.  These bugs are natural enemies of many small insects including aphids, lace bugs, psyllids, scales and whiteflies. They also feed on mites. These bugs are not commercially available.

Dragon and damselflies: Adult dragon and damsel flies generally feed on small flying small adult insects including midge flies, mayflies, mosquitoes, ants and termites in the air where as dragon/damsel fly nymphs feed on mosquito larvae in the water.

Green lacewing (Chrysoperla carnea, C. rufilabris): Lacewings adults are not predatory in nature but mainly feed on nectar, honeydew and pollens.  However, larvae of lacewings are predatory in nature and feed on insect pests of many crops including apples, asparagus, cotton, corn, cole crops, eggplants, leafy vegetables, potatoes, tomatoes, peppers and strawberries. Lacewing larvae generally prey on aphids, leafhopper eggs, eggs of butterflies and moths, mealybugs, mites, thrips, small larvae of beetles and moths. Both species of lacewings are commercially available and sold in all stages (eggs, larvae and adults).

Ladybird beetles (Hippodamia parenthesis and Harmonia axyridis): These beetles are also recognized as lady beetles or ladybugs and more than 450 of this beetles have been reported from North America. Both larval and adult stages of this predator found on many agricultural and ornamental plants and they primarily feed on aphids. In addition, they can feed on small insects, mites, scales, thrips and eggs of many moths and beetles. they can eat nectar or pollen if insect hosts are not around. These predators are now commercially available to use against many crop pests, especially aphids.

Lebia beetles (Lebia grandis): These beetles are natural enemies of Colorado potato beetle, Leptinotarsa decemlineata. Adults of the predatory insect can feed on all immature stages of colorado potato beetle. Larval stages of Labia beetles are generally parasitic in nature and therefore, they are considered as ectoparasites of larval and pupal stages of colorado potato beetles. These predators are not commercially produced.

Pirate bugs (Orius spp.): Both adults and nymphs of these predatory insects have a sharp, needle-like beak that they use to suck body content of their prey. These insects found in many crops including alfalfa, corn, cotton, pea, peanuts, and strawberries. These are predators of aphids, mites, thrips, small larval stages of many insects, eggs of many different kinds of insects. These insect predators are commercially available in the USA and most often suscessfully used as biocontrol agents in controlling greenhouse pests.

Rove beetles (Aleochara bilineata): These beetles naturally found in many vegetable crops including onions, different cole crops, turnip, radish and sweet corn.  Rove beetle adults are predatory in nature but their larval stages are parasitic in nature. Rove beetles generally feed on egg, larval and pupal stages of onion and cabbage maggots. These insects are not commercially available.

Soldier beetles (Chauliognathus marginatus and C. pennsylvanicus): These beetles are also called leatherwing beetle because of texture of their wings. Larvae of this insect mainly feed on grasshopper eggs, both adult and nymphal stages of aphids, soft bodied larvae of many insects (cutworms, gypsy moths) whereas adults mainly feed on adult aphids and other soft bodied insects. These predators also feed on snails and slugs. These insects are not pest any plant species but they can eat nector or pollen if insect hosts are not around.

Spined soldier bug (Podisus maculiventris): This is a “true bug” that also named as a stink bug because it emits a strong stinky odour when disturbed. Like Pirate bugs, this bug also uses its sharp beak to suck the body content of its prey. This predator feeds on immature stages of many insect pests including beet armyworm, cabbage loopers, cabbageworm, colorado potato beetle, corn earworm, diamond backmoth, Eropean corn borer, fall armyworms, flea beetles, Mexican bean beetle and velvetbean caterpillars. These insect predators are commercially available.

Colorado potato beetle, Leptinotarsa decemlineata: This is an economically important pest of potatoes with more than 40 species have been reported from North America.  The larvae of this beetle are voracious feeder of potato leaves costing hundreds of millions of dollars for pesticide control and yield loss each year in the United States. Entomopathogenic nematodes as biological control agents could provide an alternative to chemical pesticides in management of this noxious pest.

In a laboratory bioassay, four species of entomopathogenic nematodes including Steinernema carpocapsae, S. feltiae, Heterorhabditis bacteriophora, and H. megidis showed highest virulence against both larval and adult stages of the Colorado potato beetle, Leptinotarsa decemlineata at temperatures higher than 15oC when tested at the rate of 200 -2000 infective juveniles per individual of Colorado potato beetle (Trdan et al., 2009).

In another laboratory study, entomopathogenic nematode, H. marelata can cause 100% mortality of Colorado potato beetle larvae (Berry et al., 1997) but in the field, this nematode when applied twice in potato growing season can reduce only 50% population of adult Colorado potato beetles (Armer et al., 2004).

The efficacy of pesta-pelletized Steinernema carpocapsae All strain was tested against prepupal stages of Colorado potato beetle in a greenhouse (Nickle et al., 1994).  Infective juveniles of S. carpocapsae were able to survive the pesta-pellet process and able to reduce over 90% emergence of adults of Colorado potato beetle.

It has been also reported that prepupal stages of Colorado potato beetle were very susceptible to different species/strains of entomopathogenic nematodes including S. carpocapsae All strain; S. carpocapsae Mexican strain; S. feltiae strain #27; S. feltiae strain #980 and Heterorhabditis bacteriophora.  All these nematode species caused 100% mortality of beetle prepupae when applied in the soil at the concentration of 165 infective juveniles/cm2 (Cantelo and Nickle, 1992).

For more information, read following literature on interaction between entomopathogenic nematodes and Colorado potato beetle.

Armer, C.A., Berry, R.E., Reed, G.L. and Jepsen, S.J. 2004.  Colorado potato beetle control by application of the entomopathogenic nematode Heterorhabditis marelata and potato plant alkaloid manipulation. Entomologia Experimentalis et Applicata. 111: 47-58.

Berry, R.E., Liu, J. and Reed, G. 1997.  Comparison of endemic and exotic entomopathogenic nematode species for control of Colorado potato beetle (Coleoptera : Chrysomelidae). Journal of Economic Entomology. 90: 1528-1533.

Cantelo, W.W. and Nickle, W.R. 1992. Susceptibility of prepupae of the Colorado potato beetle (coleoptera, chrysomelidae) to entomopathogenic nematodes (Rhabditida, Steinernematidae, Heterorhabditidae). Journal of Entomological Science. 27: 37-43.

Nickle, W.R., Connick, W.J. and Cantelo, W.W. 1994. Effects of pesta-pelletized steinernema-carpocapsae (all) on western corn rootworms and colorado potato beetles. Journal of Nematology. 26: 249-250.

Trdan, S., Vidrih, M., Andjus, L. and Laznik, Z. 2009. Activity of four entomopathogenic nematode species against different developmental stages of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera, Chrysomelidae. Helminthologia. 46: 14-20.

• Apopka weevil (Diaprepes abbreviatus): This insect was named as Apopka weevil (Snout beetles) because it was first reported from Apopka, Florida. This is also recognized as a Diaprepes root weevil and considered as a very damaging pests of Citrus, many agricultural crops and ornamental plants throughout the United States.

• Armyworm (Heliothis armigera): This insect belongs to order Lepidoptera. These insect are called armyworms because their caterpilars (larvae) accumulated in large numbers and crawl in masses across fields defoliating everything in their path. These insect have wide host range but commonly cause a serious damage to cotton, maize, tobacco and chickpeas throughout the world. All larval stages of this insect are susceptible to S. carpocapsae. Read paper entitledle “Glazer I, Klein M, Navon A, et al. 1992 Comparison of efficacy of entomopathogenic nematodes combined with antidesiccants applied by canopy sprays against 3 cotton pests (lepidoptera, noctuidae). Journal of Economic Entomology. 85: 1636-1641″

• Billbugs (Sphenophorus purvulus): These weevils (Snout beetles) are also called the bluegrass billbugs because they prefer to feed on Kentucky blue- grass. This insect is also a serious pest of perennial rygrass, hybrid bermudagrass, bahiagrass, centipedegrass, St. Augustinegrass and fine-leaf fescue. Larval stages of this insect are susceptible to S. carpocapsae
• Black vine weevil (Otiorhynchus salcatus): This is a British native weevil and currently considered as the most serious garden pest, causing the most damage on evergreen trees and shrubs in the Europe and North America. All larval stages of this insect are susceptible to S. carpocapsae.
• Blue grass weevil (Listronotus maculicollis): Blue grass weevil is prevalent in the northeastern part of the US and primarily feeds on annual bluegrass. This insect has also been found to feed on perennial ryegrass and creeping bentgrass. The insect larvae feed inside the stem whereas adults feed on foliage. The damaged turf turns yellow and symptoms resemble drought stress. All larval stages of this insect are susceptible to S. carpocapsae.
• Codling moth (Cydia pomonella): Codling moth is a major pest of apples but it can also cause a serious damage to pears, walnut, crabapples, hawthorn, apricots and stone fruits. Insect larvae cause damage feeding on tissue and making tunnels in the fruits. This tunnels also serves as entry points for other disease causing organisms. All larval stages of this insect are susceptible to S. carpocapsae.
• Crane flies (Tipula spp.): The larvae of these European crane flies are called as leatherjackets. These leatherjackets generally feed on the roots and crowns. This direct damage cause yellowing and patchy appearance of turf on the golf courses and home lawns. These insects also cause serious damage to many cereals and forage crops. Larval stages of this insect are susceptible to S. carpocapsae.
• Cutworms (Agrotis ipsilon, A. segetum): The common cutworm (Agrotis segetum) and the black cutworm (A. ipsilon) are serious soil pests of many vegetable and field crops all over the world. These insects are called cutworms because their larva (caterpillar) cut off seedlings at ground level while feeding. The caterpillars are generally dark green, brown or yellow and voracious feeders of leaves, buds and stems of plants. Since theses spend most of their time in the soil environment, they are easy target of entomopathogenic nematodes. All larval stages of this insect are susceptible to S. carpocapsae.

Insect Species: Entomopathogenic nematode species

Ø Apopka weevil (Diaprepes abbreviatus): S. carpocapsae All strain

Ø Armyworm (Heliothis armigera): S. carpocapsae All strain

Ø Billbugs (Sphenophorus purvulus): H. bacteriophora & S. carpocapsae All strain

Ø Black vine weevil (Otiorhynchus salcatus): S. carpocapsae All & UK strains, S. feltiae, S. glaseri & H. megidis UK 211 strain

Ø Blue grass weevil (Listronotus maculicollis): H. bacteriophora & S. carpocapsae

Ø Carpenter worms (Cossus cossus): S. carpocapsae

Ø Carrot weevil (Listronotus oregonensis): S. feltiae

Ø Cat fleas (Ctenocephalides felis): S. carpocapsae

Ø Citrus root weevil (Pachnaeus litus): S. carpocapsae All strain

Ø Clover root weevil (Sitona hispidulus): S. feltiae & H. bacteriophora

Ø Codling moth (Cydia pomonella): S. carpocapsae

Ø Crane flies (Tipula spp.): S. carpocapsae & H. megidis

Ø Cutworms (Agrotis ipsilon, A. segetum): S. carpocapsae All strain

Ø Dog fleas (Ctenocephalides cannis): S. carpocapsae

Ø Face fly (Musca autumnalis): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Fall web worms (Hyphantria cunea): S. carpocapsae

Ø Flea beetles (Phyllotreta spp.): S. carpocapsae

Ø Fungus gnats (Bradysis spp.): H. bacteriophora, H. indica, H. zealandica, S. anomali, S. carpocapsae, S. feltiae SN strain & S. riobrave

Ø House flies (Musca domestica): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Hunting billbug (Sphenophorus venatus venatus): S. carpocapsae All strain

Ø Japanese beetle (Popillia japonica): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. anomali, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave, S. scapterisci & S. scarabae

Ø Leaf minors (Liriomyza trifolii): S. carpocapsae & S. feltiae

Ø Leopard moth (Zeuzera pyrina): S. carpocapsae

Ø Mole crickets (Gryllotapla gryllotapla): S. riobravis & S. scapterisci

Ø Peach borer moth (Synanthedon exitiosa): S. carpocapsae

Ø Pecan weevil (Curculio caryae): H. bacteriophora

Ø Pine weevil (Hylobius abietis): S. carpocapsae, S. feltiae & H. downesi

Ø Plum weevil (Conotrachelus nenuphar): S. riobrave 355 strain

Ø Shore flies (Scatella stagnalis): H. megidis, S. carpocapsae, S. feltiae & S. anomaly

Ø Sod webworm (Herpetogramma phaeopteralis): S. carpocapsae All strain

Ø Stable fly (Stomoxys calcitrans): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Strawberry root borer (Nemocestes incomptus): S. carpocapsae

Ø Sugarcane borer (Diaprepes abbreviatus): S. carpocapsae All strain

Ø Sweet potato weevil (Cylasformicarius elegantulus): S. carpocapsae All strain & H. bacteriophora HP88 strain

Ø Western flower thrips (Frankliniella occidentalis): H. bacteriophora, H. indica, H. marelata, S. abassi, S. arenarium, S. bicornutum, S. carpocapsae, S. feltiae

Ø White grubs (Amphimallon solstitiale): S. glaseri

Ø White grubs (Anomala orientalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. glaseri, S. longicaudum, S. scarabae

Ø White grubs (Ataenius spretulus): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Costelytra zealandica): H. bacteriophora & S. glaseri

Ø White grubs (Cotinus nitida): H. bacteriophora, S. carpocapsae, S. feltiae, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala borealis): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala hirta): H. bacteriophora, H. megidis, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave & S. scarabae

Ø White grubs (Cyclocephala lurida): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala pasadenae): H. bacteriophora, S. glaseri, S. kushidai & S. scarabae

Ø White grubs (Hoplia philanthus): H. megidis, S. feltiae & S. glaseri

Ø White grubs (Maladera castanea): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Melolontha melolontha): H. bacteriophora, H. marelata, H. megidis, S. arenaria, S. feltiae, S. glaseri & S. riobrave

Ø White grubs (Phyllophaga congrua): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Phyllophaga crinita): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Phyllophaga georgiana): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Rhizotrogus majalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. feltiae, S. glaseri & S. scarabae

For more information on insect pathogenic nematodes read following books:

Ø Nematodes As Biocontrol Agents by Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon.

Ø Entomopathogenic Nematodes in Biological Control by Gaugler, R. and Kaya, H. K. (eds.), CRC Press, Boca Raton

Ø Entomopathogenic Nematology by Gaugler, R. (Ed.), CABI