It has been demonstrated that the virulence of Heterorhabditis indica and Heterorhabditis bacteriophora against the pupae of mustard beetle, Phaedon cochleariae was high at 30^oC but the virulence of Steinernema carpocapsae and Steinernema feltiae was high at 25^oC (Mahar et al., 2012).

Literature:

Mahar, A.N., Jan, N.D. and Mahar, A.Q. 2012.  Comparative effectiveness of entomopathogenic nematodes against the pupae of mustard beetle, Phaedon cochleariae F. (Chrysomelidae: Coleoptera). Pakistan Journal of Zoology 44: 517-523.

All the larval (caterpillar) stages of armywormfeed on turfgrass leaves but their adult moths are not harmful to any plant species. Generally caterpillars feed on grass leaves during night time but during day time, they hide under thatch.

Armyworm moth

You will start noticing the presence of larvae of armyworm in your laws from June through August as they hatch from eggs during that period.

Armyworm larva found on grass leaf

This is a right time to adopt effective control measures to target larval stages of armyworms. The effective control measures for armyworms can be chemical insecticides or biological control agents. However, most of the chemical insecticides have been restricted to use on home lawns, recreational parks and golf courses because of their deleterious effects on humans, both pet and wild animals, and the environment.

Biological control agents:

Therefore, the biological control agents including Nucleopolyhedrovirus, parasitoids (Braconid wasps, Apanteles spp. or Tachinid flies) and entomopathogenic nematodes (also called as beneficial nematodes) can serve as an alternative to chemical pesticides in controlling armyworms. Beneficial nematodes are also not harmful to animals, kids, pets, beneficial insects such as honeybees or the environment.

Beneficial Nematodes:

Three species of entomopathogenic nematodes including Steinernema carpocapsae, Heterorhabdtis indica and Heterorhabdtis bacteriophorahave showed a potential to manage armyworm infestation in the yards, parks and golf courses.

Entomopathogenic nematode, Steinernema carpocapsae infected cadaver of armyworm is kept in a white trap

To protect from harmful UV light, it is advisable that the nematodes should applied early in the morning or late in the evening using Knapsack/backpack sprayers for the area over 5000 square feet and watering cans for the area less than 5000 square feet.

For the ideal control of armyworm larvae, Steinernema carpocapsae, Heterorhabdtis indica and Heterorhabdtis bacteriophora nematodes should be applied at the optimal rate of 1 billion infective juveniles/ acre in 100 to 260 gallons of water.

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.

Cutworms are foliage feeding pest of turfgrass.  Moths of turfgrass cutworms emerge from overwintering pupae early in the spring and after mating they start laying about 1000-1200 eggs at tip of grass blades. Depending upon the temperature, eggs hatch within 10-12 days. After hatching from eggs, caterpillars (see photo of caterpillar) start feeding on turfgrass leaves and stems at night and hide under thatch during day time. During development all the stages (six instars) of caterpillars cause damage by cutting and chewing leaves and stems at the crown of turfgrasss until late summer completing 3-6 generations.

Entomopathogenic nematodes including Steinernema carpocapsae and Heterorhabditis bacteriophora have been proved to be effective when applied at rate of one billion nematode per acre. It is always advised to apply nematodes late in the evening to avoid exposure to UV light, which is detrimental to nematodes.

Entomopathogenic nematodes can kill turfgrass cutworms

Last year a new species of entomopathogenic nematode was isolated by Nguyen and Buss (2011) from a white grub (Phyllophaga sp.) and based on morphological and molecular characteristics, it was named as Steinernema phyllophagae.

Literature

Nguyen, K.B., and Buss, E.A. 2011. Steinernema phyllophagae n. sp (Rhabditida: Steinernematidae), a new entomopathogenic nematode from Florida, USA. Nematology 13: 425-442.

In a laboratory assay, when entomopathogenic nematodes including Steinernema carpocapsae and Heterorhabditis bacteriophora  are in direct contact, the can cause over 94% mortality of strawberry crown moth (Synanthedon bibionipennis) larvae  but when applied in the field, these nematodes are not in direct contact with insects therefore, they can cause up to 51% insect mortality (Bruck et al., 2008).

Bruck, D.J., Edwards, D.L. and Donahue, K.M.  2008.   Susceptibility of the strawberry crown moth (Lepidoptera : Sesiidae) to entomopathogenic nematodes. Journal of Economic Entomology 101: 251-255.

Today, I read a paper published in Journal of Pest Science by Khatri-Chhetri et al. (2011), who tested the efficacy of two newly isolated entomopathogenic nematode species from Nepal against white grub, Holotrichia longipennis.  This white grub is a very serious pest of many crops including black gram, cabbage, chilies, maize, millet, paddy soybean and tomato. Khatri-Chhetri et al. (2011) compared the efficacies of Nepalese strains of entomopathogenic nematodes including Steinernema lamjungense LMT5, S. lamjungense SS4, S. everestense DKP4 with other nematode species including S. abbasi CS1, S. sp. KL1, Heterorhabditis indica CK2 and H. indica CK6) and with an insecticide, chlorpyrifos against second third stages of white grub, Holotrichia longipennis. These researchers reported that when Nepalese entomopathogenic nematodes were applied at the rate of 2.5 billion nematodes per hectare, they were able to reduce over 73% larval populations of white grubs and these results were comparable with efficacy of traditional insecticide, Chlorpyrifos 19 weeks after nematode application. I found that these findings are very exciting because it is always difficult get over 50% mortality of any insect host when entomopathogenic nematodes are applied under field conditions. I think these researchers could have compared 3 and 9 week % corrected mortality data using repeated measure analysis, which would have gave them a better understanding about the nematode efficacy differences between two nematode application time intervals.

Publication:

Khatri-Chhetri, H.B., Timsina, G.P., Manandhar, H.K. and Moens, M. 2011. Potential of Nepalese entomopathogenic nematodes as biocontrol agents against Holotrichia longipennis Blanch. (Coleoptera: Scarabaeidae). Journal of Pest Science 84: 457-469.

Galleria-baiting technique (Bedding and Akhurst, 1975), was used to isolate an entomopathogenic nematode from the soil collected from a citrus orchard in South Africa. Based on molecular characteristics, this new nematode was named as Steinernema citrae that  found to be closely related Stienernema feltiae group.

For detail information read following original paper

Bedding, R.A. and R.J. Akhurst. 1975. A simple technique for detection of insect parasitic rhabditid nematodes in soil. Nematologica. 21: 109-110.

Stokwe, N.F., Malan, A.P., Nguyen, K.B., Knoetze, R. and Tiedt, L. 2011. Steinernema citrae n. sp. (Rhabditida: Steinernematidae), a new entomopathogenic nematode from South Africa. Nematology 13: 569-587.

New entomopathogenic nematode species was found in the soil collected from Atacama Desert in Chile and was named after Atacama Desert as Heterorhabditis atacamensis. I like the way nematode taxonomists (Edgington et al., 2011) used individual morphological characteristics to differentiate this new species from other morphologically similar species of entomopathogenic nematodes. For example, these researchers showed that the H. atacamensis differed from H. marelatus, H. downesi and H. amazonensis based on position of hemizonid (a nematode sensory organ), position of excretory pore and female tail terminus shape, and number and position of genital papillae, respectively.  Using molecular techniques, Edgington et al. (2011) were also able to distinguish H. atacamensis from closely related entomopathogenic nematode species, H. safricana.

 Research Paper

Edgington, S., Buddie, A. G., Moore, D., France, A., Merino, L. and Hunt, D. J. 2011. Heterorhabditis atacamensis n. sp (Nematoda: Heterorhabditidae), a new entomopathogenic nematode from the Atacama Desert, Chile. Journal of Helminthology 85: 381-394.

Based on morphological and molecular characteristics, the nematode isolated from vermicompost using Galleria bait method (Bedding and Akhurst, 1975) has been described as a new entomopathogenic nematode species, Oscheius carolinensis (Ye et al., 2010).  This nematode is also pathogenic to cabbage butterfly (Pieris rapae) and mealworms (Tenebrio molitor).

 Literature

Bedding, R.A. and R.J. Akhurst. 1975. A simple technique for detection of insect parasitic rhabditid nematodes in soil. Nematologica. 21: 109-110.

Ye, W., Torres-Barragan, A. and Cardoza, Y.J. 2010. Oscheius carolinensis n. sp. (Nematoda: Rhabditidae), a potential entomopathogenic nematode from vermicompost. Nematology 12: 121-135.

It is well known fact that the infective juveniles of both Steinernema spp. and Heterorhabditis spp. enter their insect host through natural openings such as mouth, anus and spiracles and eventually reach in the insect body cavity.  As insects do not have a closed circulatory system like animals, their body cavity acts as an open circulatory system, which is filled with the blood that is technically called as hemolymph.  The infective juveniles of Steinernema spp. carry in their gut species specific symbiotic bacteria of the genus, Xenorhabdus whereas the infective juveniles of Heterorhabditis spp. carry in their gut species specific symbiotic bacteria of the genus, Photorhabdus. 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.  Based on color of insect cadaver, we can easily determine which entomopathogenic nematode-symbiotic bacterium complex was responsible for killing the insect pests. For example, as shown in a picture below, infection by entomopathogenic nematode, Steinernema spp. and symbiotic bacteria, Xenorhabdus spp. complex gives beige color to wax worm cadavers whereas infection by entomopathogenic nematode, Heterorhabditis spp. and symbiotic bacteria Photorhabdus spp. complex gives red color to wax worm cadavers.

To enlarge, click the photo 

Wax worms infected with entomopathogenic nematodes, Steinernema sp and Heterorhabditis sp: Photo by Ganpati Jagdale