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    A Symposium on Entomopathogenic Nematodes and Multitrophic interactions in the Rhizosphere

    A Symposium entitled “Entomopathogenic Nematodes and Multitrophic interactions in the Rhizosphere” has been organized by Raquel Campos-Herrera, Claudia Dolinski and Ganpati B. Jagdale at the Society of Nematologists 51st Annual meeting, which would be held in Savannah, Georgia from August 12th to 15th 2012. Following topics by various authors/speakers on interactions among entomopathogenic nematodes and multitrophic groups in the rhizosphere will be discussed between 8.0- 10.0 am on Tuesday August 14, 2012 in Marriot Riverfront hotel, Savanna, GA.   Topics with authors:

    1. Multitrophic interactions involving entomopathogenic nematodes applied against pine weevils in a forest ecosystem by Christine T. Griffin, A.M. Dillon, C.D. Harvey and C.D. Williams.
    2. Entomophathogenic nematodes: Effects of the soil agroecosystem on biological control potential by David I. Shapiro-Ilan, T.C. Leskey, S.E. Wright, I. Brown, and L. Fall.
    3. Interactions among entomopathogenic nematodes and other nematode trophic groups and plants in agroecosystems by Somasekhar Nethi, G.B. Jagdale and P.S. Grewal.
    4. Herbivore induced plants volatiles and entomopathogenic nematodes as agents of plant indirect defense by Jared G. Ali, H.T. Alborn, R. Campos-Herrera, F. Kaplan, L.W. Duncan, C. Rodriguez-Saona, A.M. Koppenhöfer, and L.L. Stelinski.

    Heavy infestation of organically grown Chinese long beans by Kudzu bugs

    Incidence of Kudzu bugs on Chinese long beans- bugsforgrowers

    For the last couple of years, I have been growing Chinese long beans (Vigna unguiculata subsp. sesquipedalis) in my organic garden. Although this year (2012) I did not plant these beans in my garden, I noticed early in the spring that a few number of Chinese long bean seeds were voluntarily germinated. This means these seeds from last years crop were overwintered in the soil and germinated early in the spring when there was enough moisture in the ground and optimum temperature for their germination. So I let these voluntarily germinated vines/plants to grow in my organic garden. Over the growing season, these plants grew very well and healthy without the infestation of any insect pests. For the last few weeks these plants are producing a lot of pods that we have been harvesting at their maturity and shelling from them beans (grains) and preparing delicious curries. However, two weeks ago, I noticed that the vines of my Chinese long beans were heavily infested with Kudzu bug, Megacopta cribraria (Fig. 1). [caption id="attachment_387" align="aligncenter" width="300" caption="Fig.1. Chinese long bean vine is heavily infested with Kudzu bugs- Click on the image for its enlargement"]"Chinese long beans infested by Kudzu bugs"[/caption] Last year, I did not see any infestation of Kudzu bugs on long beans but as shown in pictures, they are now feeding on the pods (Fig. 2), leaves and stem (Fig. 3) of my Chinese long beans.   [caption id="attachment_388" align="aligncenter" width="300" caption="Fig. 2. Several adult of kudzu bugs are feeding and causing severe damage to my organically grown Chinese long bean pods- Click on the image for its enlargement"]"Kudzu bugs on Chinese long bean pods"[/caption] [caption id="attachment_389" align="aligncenter" width="300" caption="Fig. 3. Several nymphs of kudzu bugs are congregated and feeding on leaves and stem of Chinese long bean in my organic garden- Click on the image for its enlargement"]"Several greenish looking Kudzu bug nymphs"[/caption] The immature and mature stages of Kudzu bugs are dark brown (Fig. 2) and greenish brown (Fig. 3) in color, respectively. Both mature and immature stages of Kudzu bugs feed on the long bean vine/plant. Since these Kudzu bugs have sucking type of mouthparts, they suck cell sap from leaves, stem and pods. The intensive feeding by these bugs can cause leaves, stem and pods to dry and eventually cause the death of vines/plants.

    Possible organic control measures

    • Although I don’t know how to control these Kudzu bugs organically, I have decided to spray garlic extract (prepared by grinding garlic in water) as a repellent. I will let you know the effects of garlic extract on the Kudzu bugs in my next blog.
    • Meanwhile, I have also exposed both nymphs and adults of Kudzu bugs to entomopathogenic Steinernema carpocapsae nematodes in a petri dish. I will also communicate with you the results of this experiment in my next blog.

    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:

    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.

    Susceptibility of black cutworms to beneficial nematodes

    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.