Bugs for Growers — Heterohabditis bacteriophora Nematodes

What are Japanese beetles?

As name implies Japanese beetles, Popillia japonica are native to Japan but in the United States, they were first accidentally introduced into New Jersey in 1916. Currently, Japanese beetles have been distributed throughout the United State and causing economic loss to many agricultural and horticultural crops, and reducing aesthetic values of many ornamental plants. Japanese beetle adults are shiny and attractive metallic-green in color, oval shaped and about 1.5 inch long (Fig. 1.). These beetles cause a severe damage to leaves (Fig. 1), flowers (Fig.2) and ripening fruits of different plant species.  In case of severe infestation, adult Japanese beetles can completely skeletonize all the leaves (Fig. 3) and eventually defoliate the whole plants.  Larvae (also called grubs) of Japanese beetle make C- shape when they are disturbed (Fig. 4) and they possess three pairs of thoracic legs. They are whitish in color with yellowish-brown colored head capsule. Japanese beetle grubs generally feed on the roots of turf grass and many ornamental plants. The damage caused by Japanese beetle grubs to turf grass is easily recognized.   [caption id="attachment_483" align="aligncenter" width="179" caption="Fig.1. Japanese Beetles feeding on rose leaves"][/caption] [caption id="attachment_485" align="aligncenter" width="179" caption="Fig. 2. Adult Japanese beetles are feeding on the rose flowers"][/caption] [caption id="attachment_484" align="aligncenter" width="179" caption="Fig.3. Rose leaves are completely skeletonized by Japanese beetle adults"][/caption] [caption id="attachment_486" align="aligncenter" width="300" caption="Fig. 4. Japanese beetle larvae or grubs feed on the turfgrass roots."][/caption]

Signs of Japanese beetle infestation and damage to lawns and golf courses.

• At the beginning of infestation in your lawn, you will notice localized patches of dead turf grass, which is always confused with the symptoms of water stress.
• As the feeding activity of grubs on turf roots increases, small patches of dead turf are enlarged and joined together to form the large areas of dead turf.
• This dead turf is generally loose and can be easily picked up with hand like a piece of carpet.
• The most important sign of presence of Japanese beetle grubs in your lawn is that the infested areas of lawn is destroyed by digging animals such as raccoons and skunks or by birds that are looking for grubs to feast on them.

Life cycle of Japanese beetle:

For Japanese beetles, it takes about one year to complete egg to egg life cycle.  For example, adults of Japanese beetles emerge from pupae in the late June through July and start feeding on leaves, flowers and fruits. While feeding they mate and lay eggs in the soil near grass root zone at the depth of 1-2 inches. The eggs hatch within 1-2 weeks (i.e. in August) and first instar grub immediately starts feeding on grass roots and organic matter.  Grubs develop into two more instars August through October by continuously feeding on grass roots. In September and October they start moving deep into soil for overwintering.  When weather warms in April, grubs move back into the turf root-zone, start feeding on turf roots again and continue to develop and early in the June they pupate into the soil.  Then adults of Japanese beetles emerge from pupae in the late June, then they mate, lay eggs and life cycle continues.

What are entomopathogenic nematodes?

Entomopathogenic nematode are also called as insect-parasitic nematodes, which are defined as thread-like microscopic, colorless and un-segmented round worms. These round worms are the members of both Steinernematidae and Heterorhabditidae families and currently used as an excellent biological control agents against many soil dwelling insect pests of many economically important insect pests including Japanese beetles.  Entomopathogenic nematodes are sold when they are in the infective juvenile stage that also called as dauer juveniles. These infective juveniles always carry mutualistically associated symbiotic bacterial cells in their gut. Since these bacteria are pathogenic and capable of causing a disease to a variety of insect hosts, they are called as entomopathogenic nematodes.

Which species of entomopathogenic nematodes are effective against Japanese beetles?

Following species of entomopathogenic nematodes have been considered to be the most effective species against Japanese beetle grubs (see below for the optimum rates of nematodes).

• Heterorhabditis bacteriophora nematodes
• Heterorhabditis zealandica
• Heterorhabditis indica nematodes
• Steinernema scarabaei
• Steinernema carpocapsae nematodes
• Steinernema rivobrave

Why fall is the time to apply nematodes and reduce existing populations to prevent future outbreaks of Japanese beetles.

As we know that Japanese beetles overwinter in their larval stages. To do this, they will start moving deep into the soil in September and October (depending on the temperature). In some places the temperature has already started declining, which is an important cue for Japanese beetle larvae to get ready for winter weather.  Therefore, it is time to apply entompopathogenic nematodes which can target the Japanese beetle larvae that start going deep into the soil for overwintering.

What stages of Japanese Beetles can be targeted?

• All the immature stages of Japanese beetles are susceptible to entomopathogenic nematodes.
• Adults of Japanese beetles are also susceptible to entomopathogenic nematodes.

How can Entomopathogenic Nematodes kill Japanese beetle larvae?

When the infective juveniles of entomopathogenic nematodes are applied to the soil surface or thatch layer, they start looking for their hosts including Japanese beetle grubs. Once a grub has been located, the nematode infective juveniles penetrate into the Japanese beetle grub body cavity via natural openings such as mouth, anus and spiracles. Then these infective juveniles enter grub’s body cavity where they release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae and Photorhabdus spp. for Heterorhabditidae) from their gut in grub blood. When in the grub’s blood, multiplying nematode-bacterium complex causes septicemia and kills Japanese beetle grubs usually within 48 h after infection.  Nematodes generally feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the cadaver to seek new Japanese beetle grubs or other insect host that present in the soil.

When, how and how many entomopathogenic nematodes should be applied for the effective control of Japanese beetles?

For details read our blog

Literature:

Grewal, P.S., Koppenhofer, A.M., and Choo, H.Y., 2005.  Lawn, turfgrass and Pasture applications. In: Nematodes As Biocontrol Agents. Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon. Pp 147-166. Koppenhofer, A.M., Fuzy, E.M., Crocker, R.L., Gelernter, W.D. and Polavarapu, S. 2004. Pathogenicity of Heterorhabditis bacteriophora, Steinernema glaseri, and S. scarabaei (Rhabditida : Heterorhabditidae, Steinernematidae) against 12 white grub species (Coleoptera : Scarabaeidae). Biocontrol Science and Technology. 14: 87-92. Maneesakorn, P., An, R., Grewal, P.S.and Chandrapatya, A. 2010. Virulence of our new strains of entomopathogenic nematodes from Thailand against second instar larva of the Japanese Beetle, Popillia japonica (Coleoptera: Scarabaeidae). Thai Journal of Agricultural Science.43: 61-66. Mannion, C.M., McLane, W., Klein, M.G., Moyseenko, J., Oliver, J.B. and Cowan D. 2001. Management of early-instar Japanese beetle (Coleoptera : Scarabaeidae) in field-grown nursery crops. Journal of Economic Entomology. 94: 1151-1161.

In my last blog post, I demonstrated the cutworms were susceptible to beneficial entomopathogenic Steinernema carpocapsae nematodes. These results are confirmed by a recent finding of Ebssa and Koppenhofer (2012), who also demonstrated that the Steinernema carpocapsae nematodes were highly effective against cutworm Agrotis ipsilon.  These researchers also demonstrated that the other species of beneficial nematodes including Heterorhabditis bacteriophora, Heterorhabditis megidis and Steinernema riobrave were effective in killing larval stages of cutworms.

Literature

Ebssa, L. and Koppenhofer, A.M. 2012. Entomopathogenic nematodes for the management of Agrotis ipsilon: effect of instar, nematode species and nematode production method.Pest Management Science 68: 947-957.

Sod webworms: One of the most damaging pests of turfgrass foliage

How to identify Sod webworms?

Full grown larvae/caterpillars of sod webworms are easy to identify as they are about 1 inch long having 4 parallel rows of distinct dark spots along the length of their body and coarse hair distributed all over the body. Also, depending upon species, caterpillars can be gray, brown or greenish in color. Adult sod webworm moths are light, brown or dull ash gray in color.

Life cycle of sod webworms:

Sod webworms develop through four different stages including egg, caterpillar/larva, pupa and adult moth. Sod webworms over-winter as caterpillar in silk-lined tunnels prepared in thatch and/or soil. In the spring, overwintering caterpillars resume feeding on new turfgrass growth, while feeding molts (shed its cuticle) 5-9 times and go through 6-10 stages (instars) of development. Last instar larva pupates inside the cocoons built from soil particles and plant debris in May through June. After 10-15 days of pupation, adult moths emerge from pupae and begin mating. After mating, female moths generally start laying their eggs individually while they are flying and dropping them randomly into the grass. Each moth lays up to 500 eggs during a life span of usually 10 to 15 days. Under optimal environmental temperatures, eggs hatch within 7-15 days. After hatching from egg, larval stage starts immediately feeding on grass foliage. These second generation caterpillars of sod webworms feed through September then overwinter and life cycle continues.

Damaging stages of sod webworms:

All six – ten stages/ instars of sod webworm caterpillars also called larvae cause damage to different grass species or other host plants. Adult moths do not cause any type of damage to any grass species.

How damage is caused?

All the stages of sod webworm caterpillars feed on a variety of grasses. Caterpillars generally chew leaves and stems at the crown of turfgrass causing thinning of grass in small areas. As the infestation progresses, these damaged small areas turn into large brown patches.  When infestation of sod webworms is very high, the damage caused by them is easily noticed as large and irregular brown patches are seen throughout lawns or golf course.  Sod webworm caterpillars feed at night but hide in the silk-lined tunnels prepared by them in thatch and/or soil during day time. The presence of irregular brown patches of dead grass caused by feeding of sod webworm in the middle of a lawn or golf course can reduce its aesthetic value.

Biological control of sod webworms:

Biological control agents including Bacillus thuringiensis (a bacterium which produces a toxin and paralyzes the gut of the caterpillar) and entomopathogenic nematodes also recognized as beneficial nematodes have a potential to manage sod webworms. However, beneficial nematodes have showed promising results in controlling sod webworms.

Why we should use beneficial nematodes?

Beneficial nematodes can kill sod webworm caterpillar with 48 hours after application. They are commercially available and easy to apply. Beneficial nematodes are not harmful to children, dogs, cats, personnel involved in its application and beneficial insects like honeybees. Beneficial nematodes do not need a special permission to apply because they are exempted by EPA.

Which species of beneficial nematodes are effective against sod webworms (see literature below)?

• Steinernema carpocapsae
• Heterorhabdtis bacteriophora

 What stages of Sod webworms can be targeted?

All the stages of caterpillars/ larvae and pupae can be targeted because both larvae and pupae are susceptible to beneficial nematodes. 

What is a recommended rate of beneficial nematodes required to control sod webworms?

For the successful control most of the soil dwelling insect pests, the optimal rate of 1 billion infective juveniles of beneficial nematodes in 100 to 260 gallons of water per acre is generally recommended (See Table for appropriate amounts of nematodes required for different sizes of sod webworm infested areas to be treated).

Where you can buy beneficial nematodes?

• Both Steinernema carpocapsae and Heterorhabdtis bacteriophora nematodes are sold in our store.
• Steinernema carpocapsae nematodes available both in liquid (sponge-water suspension) and granulated formulations
• Heterorhabdtis bacteriophora nematodes available only in liquid (sponge- water suspension) formulations

How long it takes to deliver nematodes?

We can directly deliver beneficial nematodes at your facility in person (service available only in Athens,Georgia) or by UPS throughout US within 3 days after receiving order.

When to apply beneficial nematodes

• To target sod webworms, beneficial nematodes should be applied starting from early spring through late summer i.e. when young larval (caterpillars) stages (instars) of sod webworms are already hatched from eggs and started feeding on grass leaves.
• 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.
• Another advantage of applying nematodes late in the evening is that sod webworm caterpillars can be easily targeted because they are generally active and searching for food during night and easily found by Steinernema carpocapsae nematodes that uses sit and wait (ambush) strategy to attack its passing by host.  Since sod webworm caterpillars are moving actively during night in search of food, they can easily come across to Heterorhabdits bacteriophora nematodes that uses cruising strategy to finds its host. Heterorhabdits bacteriophora nematodes can also find caterpillars that are hiding under thatch during day time.

How beneficial nematodes kill sod webworms?

After application of either Steinernema spp. or Heterorhabditis spp. on the lawns, their their infective juveniles find sod webworm larva or pupa and enter into its body cavity through natural openings such as mouth, anus and spiracles. Once infective juveniles of both Steinernema spp. and Heterorhabditis spp are in the insect body cavity, they release several cells of symbiotic bacteria, Xenorhabdus spp. and Photorhabdus spp., respectively from their gut via anus in the sod webworm blood, which is conducive for the multiplication of symbiotic bacteria. In the blood, multiplying nematode-bacterium complex causes septicemia and kill sod webworm caterpillar also called larvae usually within 48 h after infection.

Literature:

Grewal, P.S. Koppenhofer, A.M. and Choo, H.Y. 2005. Lawn, turfgrass and pasture applications. In: Nematodes As Biocontrol Agents. Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon. Pp 115-146.

How many nematodes should be applied?

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

Table1. Showing the number of nematodes required to treat different sizes [area in sq ft (sq M)] of lawns or fields

Nematode species	Area in sq ft (sq meter)
	1 (0.093)	10.76 (1)	108 (10)	1076 (100)	2500 (233)	5000 (465)	10000 (930)	43560 (4047) (an acre)
Heterorhabdtis bacteriophora	22.9 thousand	229.6 thousand	2.3 million	22.6 million	57.4 million	114.8 million	229.6 million	1.0 billion
Heterorhabdtis indica	22.9 thousand	229.6 thousand	2.3 million	22.6 million	57.4 million	114.8 million	229.6 million	1.0 billion
Steinernema carpocapsae	22.9 thousand	229.6 thousand	2.3 million	22.6 million	57.4 million	114.8 million	229.6 million	1.0 billion
Steinernema feltiae	22.9 thousand	229.6 thousand	2.3 million	22.6 million	57.4 million	114.8 million	229.6 million	1.0 billion

 

Armyworms: The important insect pest of turfgrass foliage

How to identify armyworms?

Armyworms are easy to identify. Adult moths are light reddish brown in color whereas their full grown larvae/caterpillars are brown in color and having several stripes on their body, and a distinctive "Y" shape mark on the head.

• [caption id="attachment_184" align="alignnone" width="293" caption="Adult armyworm moth"][/caption]

[caption id="attachment_217" align="alignnone" width="252" caption="A full grown caterpillar or larva of armyworm"][/caption]

Life cycle of armyworms:

Armyworms develop through four different stages: Moth, egg, caterpillar (larva) and pupa. Adult moths of armyworm begin emerging from over-wintering pupae early June through early August and start mating. After mating, each female moth lays about 500 eggs in a cluster on the lower surface of the leaves. Under optimal environmental conditions, eggs hatch within one week. After hatching from egg, larval stages starts feeding on grass foliage. While feeding, larvae molts (shed its cuticle) five times, and go through six stages (instars) of development. In the late summer mature, larva falls off the leaves and burrow into ground to form pupa, which survive during winter and life cycle continues. 

Damaging stages of armyworms:

• All the six stages/ instars of caterpillars/larvae of armyworms cause damage to grass or other host plants.
• Adult moths do not cause any type of damage to grasses or other plants.

  [caption id="attachment_213" align="alignnone" width="300" caption="Armyworm caterpillars or larvae cause a serious damage to the foliage of several grass species"][/caption]

How damage is caused?

All the larval stages cause damage by chewing margins of leaves of all kinds of grasses during night but hide under thatch during day time. Under sever infestation, caterpillars can skeletonize turf plant and reduce the aesthetic value of turfgrass.

Biological control of armyworms:

• Biological control agents including Nucleopolyhedrovirus, parasitoids (Braconid wasps, Apanteles spp. and Tachinid flies) and entomopathogenic nematodes have a potential to manage armyworms.

Why we should use entomopathoegnic nematodes?

• They can kill armyworm larvae with 48 hours after application.
• They are commercially available and easy to apply.
• They are not harmful to children, dogs, cats, personnel involved in its application and beneficial insects like honeybees.
• They do not need a special permission to apply because they are exempted by EPA.

Which species of entomopathogenic nematodes are effective against Armyworms (see literature below)?

• Steinernema carpocapsae
• Heterorhabdtis indica
• Heterorhabdtis bacteriophora

 What stages of armyworms can be targeted?

All the six stages of caterpillars/ larvae are susceptible to entomopathogenic nematodes. Pupae are also susceptible to entomopathogenic nematodes.

What is a recommended dosage of entomopathogenic nematodes required to control armyworms?

•  For the successful control of most of the soil dwelling insect pests, the optimal rate of 1 billion infective juvenile nematodes in 100 to 260 gallons of water per acre is generally recommended (See Table1).

Where you can buy entomopathogenic nematodes?

• All three entomopathogenic nematodes including Steinernema carpocapsae, Heterorhabdtis bacteriophora and Heterorhabdtis indica are sold in our store.
• Steinernema carpocapsae nematodes available both in liquid (sponge-water suspension) and granulated formulations.
• Heterorhabdtis indica and Heterorhabdtis bacteriophora nematodes available only in liquid (sponge- water suspension) formulations.

How long it takes to deliver nematodes?

We can directly deliver entomopathogenic nematodes at your facility in person (service available only in Athens,Georgia) or by UPS throughout US within 3 days after receiving order.

When to apply nematodes

• To target armyworms caterpillars, entomopathogenic nematodes should be applied starting from late June through late August i.e. when young larval (caterpillars) stages (instars) of armyworms are already hatched from eggs (laid in early June) and started feeding on grass leaves.
• To target especially armyworm pupae (to suppress the armyworm moth emergence in the next spring), entomopathogenic nematodes should be applied in late summer when caterpillars starting to fall off from leaves on the ground for pupation.
• 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.
• Another advantage of applying nematodes late in the evening is that armyworm caterpillars can be easily targeted because they are generally active and searching for food during night and easily found by entomopathogenic nematodes like Steinernema carpocapsae that uses sit and wait (ambush) strategy to attack its passing by host.  Since armyworm caterpillars are moving actively during night in search of food, they can easily come across to entomopathogenic nematodes like Heterorhabdits bacteriophora and Heterorhabdits indica that uses cruising strategy to finds its host. Because of cruising strategy, both Heterorhabdits bacteriophora and Heterorhabdits indica nematodes can also find caterpillars that are hiding under thatch during day time.

How entomopathogenic nematodes kill armyworms?

After application of either Steinernema spp. or Heterorhabditis spp. on the lawns, their their infective juveniles find armyworm larva or pupa and enter into its body cavity through natural openings such as mouth, anus and spiracles. Once infective juveniles of both Steinernema spp. and Heterorhabditis spp are in the insect body cavity, they release several cells of symbiotic bacteria, Xenorhabdus spp. and Photorhabdus spp., respectively from their gut via anus in the insect blood. Insect blood is conducive for the multiplication of symbiotic bacteria. In the blood, multiplying nematode-bacterium complex causes septicemia and kill their insect host usually within 48 h after infection.

Literature:

• Andalo, V., Santos, V., Moreira, G.F., Moreira, C., Freire, M. and Moino, A. 2012.   Movement of Heterorhabditis amazonensis and Steinernema arenarium in search of corn fall armyworm larvae in artificial conditions.  Scientia Agricola 69: 226-230.
• Ansari, M.A., Waeyenberge, L. and Moens, M. 2007.  Natural occurrence of Steinernema carpocapsae, Weiser, 1955 (Rhabditida: Steinernematidae) in Belgian turf and its virulence to Spodoptera exigua (Lepidoptera: Noctuidae). Russian Journal of Nematology 15: 21-24.
• Kim, J. and Kim, Y. 2011.  Three metabolites from an entomopathogenic bacterium, Xenorhabdus nematophila, inhibit larval development of Spodoptera exigua (Lepidoptera: Noctuidae) by inhibiting a digestive enzyme, phospholipase A (2). Insect Science 18: 282-288.
• Negrisoli, A.S., Garcia, M.S., Negrisoli, C.R.C.B., Bernardi, D. and da Silva, A. 2010.  Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops. Crop Protection 29: 677-683.