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    Bugs for Growers — Heterorhabditis indica Nematodes

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    Nine important things about the damage caused by flea beetles and their control

    Interaction between flea beetles and entomopathogenic nematodes
    1. Flea beetles are called as flea beetles because they jump like fleas. Flea beetles are metallic black, blue, bronze or brown in color and about 1/16-1/8th inch long.
    2. Life cycle of flea beetles is very simple containing egg, larval and adult stages.  Flea beetles overwinter as adults by hiding under shelters including dry debris of plants (leaves and stems) left over from your garden crops or weeds. Early in the spring when temperature rises to about 50 F, the overwintering beetles become active and start feeding on the leaves of young plants. While feeding, they mate and lay eggs in the soil cracks around the root system of host plants or weeds in your garden or surrounding areas . Eggs hatch within 1-2 weeks and immediately larvae starts feeding on the roots of young host plants (see below) or weed hosts until they become mature. Then mature larvae pupate in the soil for 1-2 weeks; then emerge as adults and the life cycle continues. Generally this insect completes 2-3 generations in a year.
    3. Flea beetles are known to cause economic damage to many different vegetable crops including beans, broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collards, corn, eggplant, kale, lettuce, melons, mustard,  peppers, potatoes, radishes, red Russian kale, rutabaga, spinach, squash, sunflowers, tomatoes, turnips and several species of weeds.
    4. Adults are the most damaging stage of flea beetles. They generally feed on foliage by chewing small holes through leaves and their heavy infestation gives a sieve-like appearance to the plant leaves thus reducing their marketable value especially leafy vegetables. Also, the heavy infestation of flea beetles can kill young seedlings.
    5. Flea beetle larvae feed on the plant roots but they do not cause a considerable economic damage to crop.
    6.  As temperature starts declining in the fall, adult flea beetles start looking for a shelter to hide and overwinter. Therefore, the process of management of flea beetles should begin in the fall to target overwintering beetles to reduce their incidence and outbreak in the next spring. The management of flea beetles should include both cultural and biological methods. Although the chemical insecticides could be more effective than other methods in controlling flea beetles, their use in the organic gardens should be avoided due to their detrimental effects on the human/animal health and environmental pollution.
    7. As a cultural control practice, keep your garden and its surrounding clean in the fall by removing all the plant debris including dry leaves and stems of harvested crops, weeds and other trash that may serve as the possible shelter for overwintering beetles.
    8.  Biological control method includes use of entomopathogenic nematodes (also called as insect-parasitic or beneficial nematodes) to target and kill larval and pupal stages of flea beetles in the spring.  Entomopathogenic nematodes can also attack and kill flea beetle adults if they come in contact in the soil.  Application of entomopathogenic nematodes such as Steinernema carpocapsae, Heterorhabditis bacteriophora and Heterorhabditis indica in the mid-late spring in your garden can kill both larval and pupal stages of flea beetles and thus reduce the emergence second generation adults, which are the most damaging to your crop.
    9. For the optimal rates and appropriate methods of application of entomopathogenic nematodes, read our blog at http://blog.bugsforgrowers.com/natural-predators/entomopathogenic-nematodes/beneficial-nematodes/how-to-deploy-your-nematode-army-and-kill-insect-pests/

    Target Japanese beetle larvae with entomopathogenic nematodes in the fall

    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"]"The Japanese beetles"[/caption] [caption id="attachment_485" align="aligncenter" width="179" caption="Fig. 2. Adult Japanese beetles are feeding on the rose flowers"]"The Japanese beetles feeding on roses"[/caption] [caption id="attachment_484" align="aligncenter" width="179" caption="Fig.3. Rose leaves are completely skeletonized by Japanese beetle adults"]"The severely skeletonized rose leaves"[/caption] [caption id="attachment_486" align="aligncenter" width="300" caption="Fig. 4. Japanese beetle larvae or grubs feed on the turfgrass roots."]"The Japanese beetle larvae or grub"[/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


    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.

    Apply Heterorhabditis indica nematodes to kill small hive beetles

    Why entomopathoegnic Heterorhabditis indica nematodes should be used to kill small hive beetles?

    • They are not harmful to honeybees and honeybee brood but can kill larvae or pupae of honeybee hive insect pest called small hive beetle within 48 hours of application.
    • They are commercially available and easy to apply using water cans or traditional knapsack sprayes.
    • They are not harmful to children, dogs, cats and personnel involved in its application.
    • Since they are exempted by EPA, no special permission need to apply them around honeybee hives against small hive beetles.

    How do entomopathogenic nematodes kill small hive beetles?

    When the infective juveniles of entomopathogenic nematodes are applied to the soil surface around bee hives, they start searching for their insect hosts such as larvae (grubs) or pupae of small hive beetles that are already present in the soil. Once larva and/or pupa has been located, the nematode infective juveniles penetrate into the body cavity of larva or pupa via natural openings such as mouth, anus and spiracles (breathing pores). Infective juveniles of Heterorhabditis nematodes can also enter by puncturing the inter-segmental membranes of the host cuticle. Once in the body cavity, infective juveniles of Steinernematid and Heterorhabditid nematodes release symbiotic bacteria, Xenorhabdus spp. and Photorhabdus spp., respectively from their gut in the blood of small hive beetle larva/pupae. In the blood, multiplying nematode-bacterium complex causes septicemia and kill mature larvae and/or pupae of small hive beetles usually within 48 hours after infection. Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the small hive beetle larval or pupal cadavers to seek new larvae small hive beetle that are already moved from bee hives in the soil for pupation.    

    Protect honey bee hives from small hive beetle with Heterorhabditis indica


    Honeybees are the insects that are members of the genus Aphis belonging to an insect order, Hymenoptera, family, Aphidae and class, Insecta. These bees are well known for collection (Fig. 1) and storage of honey in the combs constructed by bees out of wax. Since honeybees visit hundreds of different kinds beautiful flowers to collect honey and pollen (Fig. 2), they are also very good pollinators of different plant species including crops grown in organic vegetable gardens. [caption id="attachment_384" align="aligncenter" width="179" caption="Fig. 1. A honey bee collecting honey"]"Honeybee"[/caption] [caption id="attachment_385" align="aligncenter" width="179" caption="Fig. 2. Honeybee visiting flowers for honey and pollen"]"A honeybee on flowers"[/caption]

    What is a beekeeping?

    Beekeeping is the practice in which beekeepers who raise honey bee colonies for the production of honey for their personal use or commercial purpose (i.e. selling honey, bee wax, royal jelly etc). Beekeepers also use these bees to pollinate crops.

    What are bee hives?

    Bee hives are the enclosed structures that are generally made out of wood by beekeepers for raising colonies of honey bees for the production and storage of honey. The active honey bee hives are also placed in the fields or near to organic gardens to use bees for the pollination of crops.

    What are small hive beetles?

    Small hive beetlesAethina tumida Murray (Coleoptera: Nitidulidae) are a destructive pest of honey bees, Aphis mellifera L. (Ellis and Delaplane, 2008). Although this insect pest is native to South Africa, its been around in North America since 1996 and responsible for causing serious economic damage to Apiculture (Beekeeping) industry in the United Sates.

    How to identify small hive beetles?

    Newly emerged young adults are light brown to red in color whereas mature adults are dark black in color and very active. Fully grown larvae (also called grubs) of small hive beetles are about 9-10 mm in length, 1.5- 2.0 mm wide and whitish in color. Pre-pupal stages are creamy white in color but mature pupae are dark brown in color. Both larval and adult stages found in active bee hives but pupal stages found about 3 feet away from bee hive and 10 - 20 cm deep in the soil.

    Life cycle of small hive beetles

    Under optimal climatic conditions, small hive beetles can complete their life cycle from egg to adult stage within 4-6 weeks and go through 5-6 generations in a year. Briefly, adult beetles immediately after emerging from pupae invade active honey bee colonies.  They find honey bee hives by using their olfactory system to detect smells released from their favorite foods such as honey, pollen or honey bee alarm pheromones. After locating hives, beetles enter into the bee colony and hide from bee attacks in the cracks and crevices of colony boxes.  In these cracks beetles mate and females lay over 1000 eggs in their life-time. Depending on the temperature, eggs hatch within 2-3 days after laying. Right after hatching from eggs, grubs enter into the comb and start feeding on honey, pollen and broods and matures in a couple of weeks. After maturation, larvae move into soil for pupation.  Generally, pupal stage lasts for 3-4 weeks and and life cycle begins again when new adults emerged from pupae.

    How do small hive beetle cause damage to honey bee hives?

    Immediately after hatching from eggs, small hive beetle larvae begin feeding on honey, pollen collected by bees and especially brood. During this feeding process they destroy honey combs. In case of heavy infestation of small hive beetles, bees will leave the colony. In addition, both adults and larvae of small hive beetles carry yeast (Scientific name: Kodamaea ohmeri) on their bodies into the colony (Benda et al., 2008). This yeast grows on honey combs and that ferments all honey in the comb and the compounds secreted by this yeast also attracts beetles to bee hives. This fermented honey becomes useless as food for honey bees as well as for human consumption. Small hive beetles can also damage stored honey as described above.

    What options are available for the control of small hive beetles?

    Following options are available for beekeepers to control small hive beetles. Chemical control: Although there are two chemical insecticides (including GuardStar and Checkmite) available to kill pupae and adults, respectively, extra care is needed as they may be toxic to humans, pets and the environment. Biological Control: Entomopathogenic nematodes can be used as biological control agents against small hive beetles (see below). These nematodes are commercially available and not harmful to animals, honeybees and humans. They are easy to apply using water cans or any traditional sprayers. According to USDA scientist Dr. Shapiri-Ilan and his colleagues, Heterorhabditis indica nematodes have a potential to suppress the population of small hive beetles (Shapiro-Ilan et al., 2010). These researchers also reported that H. indica can cause over 78% mortality of small hive beetles.

    What stages of small hive beetles can be targeted with entomopathogenic nematodes?

    • Both mature larvae (grubs) and pupae are the best targets of entomopathogenic nematodes.
    • When mature grubs of small hive beetle moves in the soil for pupation, entomopathogenic nematodes should be applied to the soil surface within 3 feet area around honey bee hives to target and kill both mature grubs and pupae.

    When to apply nematodes

    • As mature larvae of small beetles move away from bee hives and enter the soil to pupate, entomopathogenic nematodes should be applied on the soil surface.
    • Since entomopathogenic nematodes are very sensitive to UV light, they will die within a minute or two when exposed to direct sunlight. Therefore, nematodes should be applied early in the morning or late in the evening to avoid exposure to UV light.
    • Another advantage of applying entomopathogenic nematodes late in the evening around the bee hives is that these nematodes will be ready to attack the mature grubs/larvae of small hive beetles that generally move during night time to the soil to pupate.
    • In addition, these moving grubs will be easily found by cruiser entomopathogenic nematode like Heterorhabditis indica to attack mature larvae that are already entered in the soil (at 10-20 cm depth) to pupae and those larvae already pupated.

    How many nematodes should be applied to obtain good control of small hive beetles?

    See our table for the right dosages of each entomopathogenic nematode species to be applied for optimum control of small hive beetles.   Read following papers for detailed information on effect of entomopathogenic nematodes on the small hive beetles. Cabanillas, H.E. and Elzen, P.J. 2006.  Infectivity of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) against the small hive beetle Aethina tumida (Coleoptera : Nitidulidae) . Journal of Apicultural Research 45: 49-50. Ellis, J.D., Spiewok, S., Delaplane, K.S., Buchholz, S., Neumann, P. and Tedders, W.L. 2010.  Susceptibility of Aethina tumida (Coleoptera: Nitidulidae) larvae and pupae to entomopathogenic nematodes. Journal of Economic Entomology. 103: 1-9. Shapiro-Ilan, D.I., Morales-Ramos, J.A., Rojas, M.G. and Tedders, W.L. 2010.  Effects of a novel entomopathogenic nematode-infected host formulation on cadaver integrity, nematode yield, and suppression of Diaprepes abbreviatus and Aethina tumida. Journal of Invertebrate Pathology. 103: 103-108.

    Optimal rates of beneficial nematodes required to treat different sizes of area

    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