Plants and Their Environment

**159**

**Chapter 7**

**Abstract**

*Sarwan Kumar*

pest management strategies.

sieve elements

**1. Introduction**

Aphid-Plant Interactions:

Implications for Pest Management

Aphids are important herbivores and important pest of many field and forest crops. They have specialized long and flexible stylets which are adapted to feeding on phloem sap. To establish successful feeding on host plant, they need to counter a range of both physical and chemical defenses. The defenses employed by plants can have direct effect on the aphid species through difficulty in establishing successful feeding due to the presence of trichomes, thick cell wall, etc. or effect on their biology with lethal consequences in extreme cases (direct defenses). In contrast to this, plants can attract natural enemies of aphids through the release of volatile compounds (the so-called "cry or call for help") (indirect defense). The information on different defense strategies employed by plants can be utilized to enhance the level of resistance (R) to develop sustainable

**Keywords:** Aphidoidea, insect-plant interactions, phloem feeding, plant defense,

Aphids constitute a major group of crop pests that limit productivity of many crops and cause serious damage to plants both by direct feeding and indirectly as vectors of many diseases. Despite being a relatively small insect group (about 5000 known species) compared to 10,000 species of grasshoppers, 12,000 species of geometrid moths, and 60,000 species of weevils, aphids are a serious problem for agriculture [1–3]. Of the 5000 known species in family Aphididae, 450 are endemic on crop plants, and 100 have successfully exploited the agricultural environment to the extent that they are of significant economic importance [3]. They are the specialized phloem sap feeders resulting in significant yield losses in many crops. It is their ability to rapidly exploit the ephemeral habitats that makes them serious pests, and this ability results from (i) their high reproductive potential, (ii) their dispersal capacities, and (iii) their adaptability to local survival [2]. Unlike majority of insects, aphids exhibit parthenogenetic viviparity—phenomenon that limits the need for males to fertilize females and eliminates egg stage from their life cycle. Thus, aphids reproduce clonally and give birth to young ones, and embryonic development of an aphid begins before its mother's birth leading to telescoping of generations. All these traits allow aphids to exploit the periods of rapid plant growth, conserve energy, and allow for short generation times; nymphs of certain

aphid species can reach maturity in as little as 5 days [4].
