Track 2-2-1: Plant Diseases, Insect Pests and Weed Management

Description

Lucerne or Alfalfa (Medicago sativa L) is the world’s most important forage legume and a key component of many crop rotation systems (Osborn et. al., 1997). Alfalfa is considered an insectary due to the large number of insects it attracts. Some pests, such as alfalfa weevil, aphids, armyworms, and the potato leafhopper, can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest. Chemical controls are sometimes used to prevent this. As a perennial crop, lucerne has a lifespan approaching 5 years, but in some areas of the world fields may remain productive for considerably longer. Such a long stand life affords ample time for the establishment and development of a diverse community structure by an abundance of organisms. In spite of system perturbations caused by frequent harvests and occasional pesticide applications, a lucerne field provides a temporal stability which is uncommon among field crops. As a result of this stability, lucerne supports an immense diversity of flora and fauna which, at times, exceeds that of riparian ecosystems. While most of lucerne’s inhabitants have little or no impact on it as a crop, a few are capable of causing extensive damage. Arthropods, plant pathogens, weeds, vertebrates, and plant parasitic nematodes can all cause significant yield and/or quality reductions and frequently contribute to shortening the productive life of the stand. On the other hand large number of beneficial fauna like predators and parasites helps in reducing the aphis population. Pollinators also have a vital role in pollinating the lucerne crop. Cross- pollination in lucerne contributes to 89% seed yield (Somerville, 2002). In the present study, important insect pests of lucerne, their seasonal incidence, their economic threshold level were studied. Role of pollinator fauna and their impact on the seed yield was studied.

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Studies on Insect Fauna of Lucerne Medicago sativa and Their Impact on Seed and Forage Yield in Lucerne Medicago sativa

Lucerne or Alfalfa (Medicago sativa L) is the world’s most important forage legume and a key component of many crop rotation systems (Osborn et. al., 1997). Alfalfa is considered an insectary due to the large number of insects it attracts. Some pests, such as alfalfa weevil, aphids, armyworms, and the potato leafhopper, can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest. Chemical controls are sometimes used to prevent this. As a perennial crop, lucerne has a lifespan approaching 5 years, but in some areas of the world fields may remain productive for considerably longer. Such a long stand life affords ample time for the establishment and development of a diverse community structure by an abundance of organisms. In spite of system perturbations caused by frequent harvests and occasional pesticide applications, a lucerne field provides a temporal stability which is uncommon among field crops. As a result of this stability, lucerne supports an immense diversity of flora and fauna which, at times, exceeds that of riparian ecosystems. While most of lucerne’s inhabitants have little or no impact on it as a crop, a few are capable of causing extensive damage. Arthropods, plant pathogens, weeds, vertebrates, and plant parasitic nematodes can all cause significant yield and/or quality reductions and frequently contribute to shortening the productive life of the stand. On the other hand large number of beneficial fauna like predators and parasites helps in reducing the aphis population. Pollinators also have a vital role in pollinating the lucerne crop. Cross- pollination in lucerne contributes to 89% seed yield (Somerville, 2002). In the present study, important insect pests of lucerne, their seasonal incidence, their economic threshold level were studied. Role of pollinator fauna and their impact on the seed yield was studied.