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    Bugs for Growers — Beneficial insects

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    Ladybugs can control of aphids, mealybugs, mites, scales and thrips

    Now is the right time to use ladybugs to control aphids, mealybugs, mites, scales and thrips- Bugsforgrowers.com

    Watch YouTube video about using ladybugs for the control of aphids: "

    https://youtu.be/UH9jPIUEheo

     Description: Ladybird beetles are also called as ladybugs and scientifically known as Hypodamia convergens. Both larvae and adults of ladybugs are active predators of many soft bodied insects including aphids, mealy bugs, mites and scale insects. Adult ladybugs are hemispherical shaped and bright orange to red in color with 6 black spots on each wing (Fig. 1) whereas larvae have appearance like an alligator with yellow stripes and reddish dark brown color (Fig. 2).  Since adults of ladybugs are very active predators, they can move very fast after their release and find their prey in the garden. Each adult of ladybug is capable of eating over 5000 aphids whereas each larva in its life-span can eat over 400 aphids (Fig. 3).  Use of ladybugs as biological control agents in the organic gardens is a good choice because released ladybug adults can continuously reproduce and maintain their populations as long as they find their food in the garden.  For example, once ladybugs are released in the garden, they immediately start feeding on their prey.  While feeding they mate and lay up to 1,500 tiny yellow eggs on foliage. Eggs hatch within a week into blackish brown alligator like larvae, which are very mobile. After hatching, these larvae immediately start feeding on the available insect hosts in the garden.  While feeding, larvae molts 3 times before pupation.  The pupae are orange to black in color and attached to any substrate in the garden. Young adults emerge from pupae within 1-2 weeks and life cycle continues.  Ladybugs generally complete several generations in a year and they hibernate as adults during winter. [caption id="attachment_1288" align="aligncenter" width="201" caption="Fig. 1. An adult ladybug"]Ladybugs are predators of aphids[/caption]   [caption id="attachment_1299" align="aligncenter" width="300" caption="Fig.2. A ladybug larva was feeding on okra aphids"]Ladybug larva feeding on aphids[/caption]   [caption id="attachment_1300" align="aligncenter" width="300" caption="Fig. 3. Red aphids feeding on underside of a tomato leaf"]Red aphids are pests of tomatoes[/caption]  

    Ladybugs are effective against following insect pests

    • Aphids
    • Mealy bugs
    • Mites
    • Scale insects
    • Thrips

    How ladybugs are applied in the organic garden?

    Ladybugs are commercially available and they sold about 1500 adults in a bag and one such bag is enough to treat about 900 square foot area of garden. After purchasing, if it is possible, release adults immediately at dusk in watered garden near plants infested with aphids or other host insect pests. If it is not possible to release ladybugs immediately after arrival, they can be stored in the refrigerator at 38o F (4oC) until you are ready to release them in the garden. However, for their highest survival rate in the refrigerator, it is recommended that the bags containing lady bird beetles should be pre-conditioned upon arrival by rinsing bags under cold water and then transfer them into the refrigerator at 4oC (38o F).

    Are ladybugs safe to use as biological control agent?

    Yes, as they are not harmful to humans, children and pets.

    Research Papers: Dreistadt, S.H. and Flint, M.L 1996. Melon aphid (Homoptera: Aphididae) control by inundative convergent lady beetle (Coleoptera: Coccinellidae) release on Chrysanthemum. Environmental Entomology 25:688-697. Eigenbrode, S.D., White, C., Rohde, M. and Simon, C.J. 1998. Behavior and effectiveness of adult Hippodamia convergens (Coleoptera: Coccinellidae) as a predator of Acyrthosiphon pisum (Homoptera: Aphididae) on a Wax Mutant of Pisum sativum. Environmental Entomology 27: 902-909.

    Employ three biological control agents to manage imported cabbageworms

    Biological and Cultural methods to control imported cabbageworms

    The cabbage butterfly is commonly called as imported cabbageworm, Artogeia rapae (Pieris rapae). This is one of the most important pests of many Cole crops including broccoli, cabbage, collard greens, cauliflower, kale and turnip.  Butterflies are easy to identify as they have whitish colored fore-and hind-wings with one and two black spots on the top of each of fore wings of males and females, respectively.  Also, both males and females have a black spot on the outer front margin of each hind wing.  Females lay singly yellow colored and oblong eggs on the either side of the leaves and depending on the temperature eggs hatch within a week. Mature larvae are velvety green in color with a narrow orange stripe down the middle of the back and a yellowish stripe along each side of the body (Fig. 1.)  The pupae are green to light brown in color, attached to bottom leaves and adults generally emerge from these pupae within 2 weeks of pupation. Cabbage butterflies overwinter as pupae in previous crop plant debris in the garden. [caption id="attachment_644" align="aligncenter" width="300" caption="Fig. 1. Severe damage caused by Imported Cabbageworms near growing point of a collard green plant"]"The Damage by imported cabbageworms"[/caption] Generally cabbage butterfly larvae feed voraciously near to the growing point of the host plants (Fig. 2) but they can also feed indiscriminately by chewing large irregular holes on both young and mature leaves of different host plants including broccoli, cabbage, cauliflower, collard greens, kale and turnip (Figs. 1 and 2). [caption id="attachment_645" align="aligncenter" width="200" caption="Fig. 2. Larva of an imported cabbageworm feeding by chewing large irregular holes on a collard green mature leaf"]"The imported Cabbageworm"[/caption] Since chemical insecticides cannot be used in organic vegetable gardens, growers have to rely on the cultural and biological methods to manage populations of imported cabbageworm.

    Cultural Methods

    For small or large vegetable gardens, best cultural practice is hand picking and killing of all the larval stages of imported cabbageworm. Although this practice is laborious and time consuming, it works and reduces the damage caused by this economically important insect pest. Also, at the end of the fall season remove all the previous crop plant debris so that there will be less protected areas available for overwintering imported cabbage worms, which in turn will reduce the populations of adults in the next spring.  This low number of adult emergence means there will be less numbers of eggs to hatch into larvae meaning there will be less larval incidence to cause the damage to the crop in the spring.

    Biological Methods

    Biological methods include use of natural enemies/biological control agents to control cabbage butterflies. Three well known biological control agents including Bacillus thuringiensis (Bt), entomopathogenic nematodes and wasps have a potential to manage imported cabbageworm population in the vegetable gardens.

    Bacillus thuringiensis kurstaki (Bt):

    This bacterium is recognized as a bacterial insecticide but it is not harmful to the humans, animals or the environment. This is a very effective biopesticide on young larval stages as compared to the mature larval stages of cabbage butterflies.  This microbial biocontrol agent is commercially available and can be applied using traditional sprayers. For the effective control of imported cabbageworms, Bacillus thuringiensis kurstaki should be applied at every seven day interval after noticing the first incidence of pest.

    Entomopathogenic nematodes:

    Currently, entomopathogenic nematodes are used as effective biological control agents against many different kinds of soil-dwelling insect pests of many economically important crops and turfgrasses. These nematodes are commercially available and are not harmful to humans, animals and even beneficial insects like honeybees. Canadian researchers have demonstrated that the entomopathogenic nematodes including Steinernema carpocapsae, S. feltiae and S. riobrave can cause 76 to 100% mortality of imported cabbageworms Artogeia rapae if applied at temperatures ranging from 25 to 30 °C and their LC50 values were ranged from 4 to 18 infective juveniles (Bélair et al., 2003). Mahar et al (2005) also reported that in addition to the above stated species of entomopathogenic nematodes, Heterorhabditis bacteriophora and H. indica nematodes can infect and kill both larvae and pupae of cabbage butterflies. Recently, another insect-parasitic nematode, Rhabditis blumi also been shown to be effective against imported cabbageworm (Park et al., 2012).

    Wasps:

    Following four species of parasitic wasps can serves as effective biological control agents against imported cabbage worm.
    1. The egg parasitic wasp, Trichogramma spp.: This is a very tiny parasitic wasp known for parasitizing eggs of imported cabbageworms. These wasps are commercially available and can be mass released when lots of adult butterflies are present in the garden and already started laying eggs on the leaves.  This will prevent the hatching of eggs into larvae thus preventing damage caused by imported cabbageworm larvae to Cole crops (Oatman et al., 1968).
    2. The brachonid wasp, Cotesia glomerata: This gregarious wasp parasitizes the larvae of the imported cabbageworms. This wasp species is not commercially available but it can naturally occur (Herlihy et al., 2012) and capable of suppressing the populations of cabbage butterflies in the vegetable gardens and fields. This wasp lays eggs inside the young caterpillars of imported cabbageworms. The eggs hatch and the larvae develop inside the developing imported cabbageworm larvae, then emerge as mature larvae and pupate in yellow silken cocoons outside the host, which dies during the process of the emergence of wasp larvae. If this wasp is present in the fields, which are infested with imported cabbageworms or other insect hosts, it can parasitize and kill over 60% of their insect host larvae.
    3. The solitary wasp, Cotesia rubecula:  This naturally occurring parasitic wasp is known to its specificity to the members of genus Pieris especially imported cabbageworms. Although C. rubecula wasp parasitizes all the stages of imported cabbageworms, it prefers last instar of imported cabbageworms, which is the most damaging stage. This is the most studied parasitic wasp of imported cabbageworms and found to be distributed throughout the US (Herlihy et al., 2012).
    4. The pteromalid wasp, Pteromalus puparum: This tiny wasp specifically parasitizes pupae of imported cabbageworms and other lepidopterous insects.  Since this wasp parasitoid kills only pupae of its insect host, it does not reduce the larval feeding damage caused before pupation but it certainly reduces the emergence of the next generation of adults. This means there are less number of egg laying females that results in the less number of eggs and therefore, less larval incidence to cause severe damage to the crop.
     
    Literature:
    Bélair, G., Fournier, C.Y. and Dauphinais, N. 2003. Efficacy of Steinernematid nematodes against three insect pests of Crucifers in Quebec.  Journal of Nematology 35: 259–265. Cai, J., Ye, G.Y. and Hu, C. 2004.  Parasitism of Pieris rapae (Lepidoptera: Pieridae) by a pupal endoparasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae): effects of parasitization and venom on host hemocytes. Journal of Insect Physiology 50:315-322. Cameron, P.J. and Walker, G.P. 1997.  Host specificity of Cotesia rubecula and Cotesia plutellae, parasitoids of white butterfly and diamondback moth. Proceedings of 50th N.Z. Plant Protection Conference: 236-241 Herlihy, M.V., Van Driesche, R.G., Abney, M.R., Brodeur, J., Bryant, A.B., Casagrande, R.A., Delaney, D.A., Elkner, T.E., Fleischer, S J., Groves, R.L., Gruner, D.S., Harmon, J.P., Heimpel, G.E., Hemady, K., Kuhar,T.P., Maund, C.M., Shelton, A.M., Seaman, A.J., Skinner, M., Weinzierl, R., Yeargan, KV. And Szendrei, Z. 2012. Distribution of Cotesia rubecula (Hymenoptera: Braconidae) and its displacement of Cotesia glomerata in Eastern North America.  Florida Entomologist, 95:461-467. Mahar, A.N., Jan, N.D., Chachar, Q.I., Markhand, G.S., Munir M. and Mahar, A.Q. 2005. Production and infectivity of some entomopathogenic nematodes against larvae and pupae of Cabbage Butterfly, Pieris brassicae L. (Lepidoptera:Pieridae). Journal of Entomology 2: 86-91. Oatman, E. R.; Platner, G. R.; Greany, P. D. 1968. Parasitization of imported cabbageworm and cabbage looper eggs on cabbage in Southern California, with notes on the colonization of Trichogramma evanescens. Journal of Economic Entomology 61: 724-730. Park, H.W., Kim, H.H., Youn, S.H., Shin, T.S., Bilgrami, A.L., Cho, M.R. and Shin, C.S. 2012. Biological control potentials of insect-parasitic nematode Rhabditis blumi (Nematoda: Rhabditida) for major cruciferous vegetable insect pests. Applied Entomology and Zoology 47: 389-397.