Bio-control agents and Bio pesticides in Grapes IPM

Introduction Biological control is an important component of IPM where deliberate use of bioagents /biopesticides (predators, parasitoids and pathogens) are made in the crops to maintain pest population at a level below that causing economic loss either by introducing them into the environment of pest or by increasing the effectiveness of those already present in the field. Crop ecosystems are replete with natural enemies but these needs to be conserved against harmful effect of pesticides.

Bio control agents Bio-control agents: Important bio control agents commercially available are species of Parasitoids like Trichogramma, Bracon, predators like Chrysoperla,, Coccinellids etc., With a view to regulate manufacture, use and quality, these bio-pesticides have been brought under the preview of Insecticides Act, 1968.

Bio-pesticides Biopesticides (also known as microbial biological pesticides) are pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals to control plant diseases and arthropod pests”. Among bio-pesticides, different species of Trichoderma, Nuclear polyhedrosis virus (NPV), Paecilomyces, Metarrhizium, Beauveria, Pseudomonas, Verticillium, Bacillus and plant products like neem are notable ones.

Advantages of biocontrol agents and biopesticides They are inherently less harmful than conventional pesticides. They generally affect only the target pest and closely related organisms, in contrast to broad-spectrum conventional pesticides that may affect organisms as different as birds, insects, and mammals. They often are effective in very small quantities and often decompose quickly, thereby resulting in lower exposures and largely avoiding the pollution problems caused by conventional pesticides.

Biopesticides of plant origin Biopesticides of plant origin like, Neem, Symbopogam, etc. are being popularized as a component of Integrated Pest Management approach for Pest Control to preserve the agro-eco-system, development of resistance, pest resurgence etc. Foliar spray of Azadirachtin 1% @ 2 ml/l or 5% @ 1 ml/l after pruning to deter sucking pests feeding tender tissues.

For insect pests: Mealy bugs: Release of Australian lady beetle/grub Cryptolaemus montrouzeri (also known as mealy bug destroyer) @ 10,000 per ha. Both adults and larvae kill mealybugs. Single grub can feed 900-1500 eggs or 300 nymphs or 30 adults in its lifetime. Spray of insecticides should be avoided during and after the release of beetles / grubs. Release should be done during evening hours. Predator grub feeding on mealy bug Predator adult feeding on mealy bug

Other predators like Green lace wing, Chrysoperla carnea, Lepidoptera predator, Spalgius epius are found effective. Parasitoids like Anagyrus dactylopii found parasitizing mealy bug up to 70%. Biological control involves identification of the predators, their rearing and field release. Eggs of Chrysoperla A third-instar green lacewing attacks a grape mealybug, a female Anagyrus sp. near a vine mealybug mummy showing the round parasitoid exit hole Spalgius adult and its larva feeding on mealybugs http://californiaagriculture.ucanr.org

Mealy bugs and Thrips: Foliar spray of fungal BCA, Verticillium lecanii or Beauveria bassiana (2x108 cfu/ml ) @ 5 g/ ml/l is advised whenever there is a lapse of 15 days after fungicides spray and whenever temperatures are between 25-30oC and RH > 90%. Mealybug infected with V. lecanii

For Disease causing pathogens: Commonly these are microbial biological insecticides, but there are also examples of fungal control agents, including Trichoderma spp., Bacillus subtilis and Ampelomyces quisqualis (a control agent for grape powdery mildew) are used to control plant pathogens. Soil application / spray of Trichoderma during monsoon or rainy periods during Sep/Oct also be given for reducing the inoculum of pathogens like Alternaria, Cladosporium, Botryodiplodia etc. These sprays can also be given in combination with safe fungicides.

Ampelomyces quisqualis (a control agent for grape powdery mildew) The fungus Ampelomyces quisqualis is a naturally occurring hyperparasite of powdery mildews. It infects and forms pycnidia within powdery mildew hyphae, conidiophores, and cleistothecia. This parasitism reduces growth and may eventually kill the mildew colony. Grape cluster infected with powdery mildew Electron micrograph of powdery mildew colony on grape leaf showing pycnidium of A.quisqualis PHOTO: D.Gadoury

Biological control/ Bio-control agents Against post harvest pathogens: BCA, Trichoderma harzianum can be used in grapes especially for the control of post harvest pathogens. In the grapes meant for export, two sprays of this stain given at 20th and 3 or 5 days before harvest can provide very good control of post-harvest diseases at reduced dose of Sodium metabisulphite (Grape guard). In case of enhanced rotting of grapes due to raisins occurring few days before harvest,spray of Trichoderma has effectively prevented the spoilage of fruits.

Fungal bio control agents Spray formulations of Trichoderma @ 2-5 ml/l to control infection of Alternaria, Cladosporium on leaves to delay leaf fall. 1 or 2 sprays at 10 days interval may be given when high humidity prevails during Sep - Oct.

Let’s sum up Use of Biocontrol agents or Bio-pesticides is usually compatible with most other tactics of pest management except the use of broad spectrum synthetic organic pesticides. Chemical ecology of the host plant-insect pest - Natural enemy interactions needs to be studied to identify the factors favouring colonization by the NES. With increasing concerns regarding the impact of conventional insecticides, parasitoids and predators appear poised for greater role in future environmentally- benign IPM programmes.