Plants respond to insect attack by releasing blends of volatile chemicals that attract their herbivores’ specific natural enemies, while insect herbivores may carry endosymbiotic microorganisms that directly improve herbivore survival after natural enemy attack. Here we demonstrate that the two phenomena can be linked. Plants fed upon by pea aphids release volatiles that attract parasitic wasps, and the pea aphid can carry facultative endosymbiotic bacteria that prevent the development of the parasitic wasp larva and thus markedly improve aphid survival after wasp attack. We show that these endosymbionts also attenuate the systemic release of volatiles by plants after aphid attack, reducing parasitic wasp recruitment and increasing aphid fitness. Our results reveal a novel mechanism through which symbionts can benefit their hosts and emphasise the importance of considering the microbiome in understanding insect ecological interactions.

Enhancement of natural enemies through habitat management developed sustainable pest management systems. Landscape composition; especially complex and permanent habitat mainly woody vegetation increased the abundance of natural enemies of crop pest. Alternatively, temporary vegetation like horticultural systems decreased the abundance of natural enemies as for monocropping. The rate of parasitism is higher in diverse ecosystems than in non-diverse ecosystems due to the availability of food source, provision of nectar and sugar, as well as alternative hosts. The intensification of agricultural practices disturbed the diversity of ecosystem and ultimately reduced the abundance of natural enemies and consequently diminished the efficacy of biological control of pests in a particular ecosystem. Moreover, plant characteristics especially in long blooming period, larger floral area, maximum flower height, narrow and deepest corolla and higher number of open flower increase the accessibility of nectar or pollen for natural enemies. As a result, the fecundity and longevity of predator and parasitoid are increased. Manipulation of food sources for natural enemies especially honey dew and artificial food spray like sucrose with the supplement of protein helps to enhance the activities of natural enemies, predators and parasitoids. For example, the widely applicable shelter habitats such as beetle banks are suitable over wintering sites for predatory beetles especially for Carabidae, Staphylinidae and spiders. Increase of non-crop habitats for instance, field margins, fallow land, hedgerows etc. might improve the shelters for natural enemies. Apart from the plants in that habitat under attack from herbivore, they make responses towards natural enemies by producing Herbivore Induced Plant Volatiles (HIPVs) known as indirect plant defense. The habitat with abundant natural enemies makes such continuous support for plant by means of plant indirect defense. In a nutshell, habitat management not only conserves biological control but also provides other indirect services like increasing biodiversity, photosynthesis, the activity of soil biota, and reduced soil erosion. Besides, it can also ultimately maximize the yield and profitability of crops for the farmers and stabilize the sustainable pest management system.

Experiments were carried out in the Field Laboratory of Entomology, Bangladesh Agricultural University, Mymensingh, during February to May, 2008 to investigate the population abundance and to determine the efficacy of three botanical oils (Neem, Mahogani, Karanja) and one synthetic insecticide (Admire 200 SL) against Okra Jassid, Amrasca devastans. The Jassid was first noticed in early March just 7 days after germination and attacked the crop seriously. The highest mean number of Jassid leaf-1 (34) was found in April, 2008. In evaluating the effectiveness of the insecticide and botanical oils to control Okra Jassid, three times applications were made at 7 days interval. The Jassid population varied significantly with the application of insecticide and botanicals. Admire 200 SL give the best result among the treatment. Out of three botanicals Karanja repelled 93.33%, where as Mahogoni and Neem repelled 86.66 and 63.33%.The effectivity of botanicals and synthetic insecticides was found in the following order: Admire 200 SL> Karajan oil >Mahogani oil >Neem oil.DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16743 Progress. Agric. 21(1 & 2): 1 – 7, 2010

Traditional there are two strategies to handle pest problems in crop production, either dependence on non-chemical agricultural practices (such as cultural, mechanical, biological practices etc.) or reliance on existing natural pest control mechanisms. Intercropping is a cultural non-chemical agricultural practice where two or more crops are grown on the same field in a year with different cropping patterns. In this multiple cropping system, biodiversity and pest suppression are increased. Biodiversity can restore the natural elements of agro ecosystem because almost all favorable elements of natural enemies are available in diversified agro ecosystem. Energy intensive modern technology in agriculture is one of the vital causes for loss of biodiversity. In intercropping system biological pest control method can be ensured with higher level of crop diversity instead of energy intensive agriculture. Intercropping provides different benefits on pest management with two available hypotheses or mechanism. One of the hypotheses is the ‘resource concentration hypothesis’ and another is the ‘natural enemies hypothesis’. Intercropping, directly and indirectly, influences to increase biodiversity which results in reduction of pest densities in crop fields. As a result, less expense for use of pesticide is required and finally higher yield also add some financial benefits. Intercropping system utilizes inherent ability of plant to protect pests. Therefore further knowledge about genotypic crop diversity, diversity of natural enemies, chemically-mediated mechanisms of Volatile Organic Compounds (VOCs) will be effective for further improvement of intercropping system for greater benefits.

The parasite, Plasmodium needs an insect vector (mosquito) and a vertebrate host (human) to successful malaria transmission. The parasite use the vertebrate hosts for their asexual reproduction and insect host for sexual multiplication. In order to know the mechanism of disease transmission, knowledge about the possible interactions causes by the three components, vector, parasite and host is important. The mosquito feeding behaviour greatly contributes in the rate of malaria transmission. To assist the rate of transmission of malaria, the parasite, Plasmodium completes a complex developmental stage in the mosquito. In the mosquito the parasite, passes complex developmental stages and ensuing changes into three important forms of their life cycle: ookinete, oocyst and sporozoites. This review study concludes that, the interactions among vector, parasite and host in terms of reproductive behaviour and blood-feeding behaviour helps in transmitting malaria to the vertebrate hosts mainly, human being.Progressive Agriculture 27 (2): 168-174, 2016