Pests of farm crops

Abstract Animal pests are responsible for millions of pounds of damage to agricultural crops every year, although only a relatively small number of species in the animal kingdom are responsible. This chapter describes the structure of some common pests, identification characteristics, life-cycles and the type of damage that they can cause. There is a discussion on the various methods used to control pests as well as issues with pesticide resistance. Finally, there is a summary of the main pests found in UK crops, their symptoms and methods of control. 

Key words pests of farm crops, symptoms of pest damage, pest life-cycles, pest identification, methods of pest control. 

Before discussing the various methods used to control pests, it is important to understand something of the stracture of the pest, identification characteristics, life-cycles and type of damage that they can cause. 

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Insect pests of farm crops are difficult to control when necessary activities such as tillage weeding irrigation and harvesting increase the pest population and decrease the numbers of its natural enemies. 

Bayer CropScience, Pest Spotter, A Guide to Common Pests of Farm Crops, Bayer CropScience, 2011. 

HCH, sometimes misleadingly termed benzene hexachloride (BHC), exists in a number of different isomeric forms of which the gamma isomer has valuable insecticidal properties. These were discovered during the 1940s, and HCH came to be widely used as an insecticide to control crop pests and certain ectoparasites of farm animals after the Second World War. Crude technical BHC, a mixture of isomers, was the first form of HCH to be marketed. In time, it was largely replaced by a refined product called lindane, containing 99% or more of the insecticidal gamma isomer. 

Pesticides are considered a necessary evil however, it has been estimated that without their use food expenditure for western families would more than double (Zilberman et al. 1991) and, much worse, food shortage would be more acute in many third world countries about 40% crop production would be lost, according to FAO. Pest and pesticide control is probably the sector where a really integrated view of farm management is most required certainly, pest treatments by calendar as largely in use till a few years ago and still in use today here and there are unsustainable. The principles of targeting interventions according to real need as advocated... 

Many definitions of sustainable agriculture are reported by literature, but all are related to the basic concept of a profitable crop production with no environmental pollution and depletion of farm and natural resources, including effects on soil, water, and biodiversity (Doran 2002 Francis et al. 2006). Soil solarization seems to fit the fundaments of sustainable agriculture as providing an effective and environmentally safe control of many soilbome pests and more competitive market positions and higher prices to pesticide-free products. 

Perennial farming systems with tree, bush or vine crops also provide niches for short and longer term intercropping. In addition to the use of cover crops on the orchard floor of many crops including apples (Hartley ef al. 2000) and wine grapes (Bugg ef al. 1996), plantings of commercially and environmentally valuable species within or around the orchard have also been used for pollination, disease and pest control (Finckh and Wolfe 1998, Altieri 1999) in crops such as such as leeks (Baumann ef al. 2001) and carrots (Brandsseter and Riley 2002). 

Yield is not the only indicator of farm productivity. Inputs used to deliver those yields should also be considered, and can be in the form of materials, as discussed below, but they may also be in different forms. For example, one way to manage soil fertility and pest problems on organic farms is to employ a different rotation from that on conventional farms where synthetic fertilisers and pesticides can perform those tasks. Because of the difference in rotation, which may also mean a larger diversity of crops, the whole farm needs to be considered when determining productivity and profitability. 

Natural products can occasionally be used for crop protection purposes in their own right. The natural pyrethrins, such as pyrethrin I (Figure 1), are insecticidal compounds produced in the flowers of the plant Chrysanthemum cinerariaefoUum, and are well-known examples. They are used to control insect pests on various crops and on farm and domestic animals, but their use outdoors is limited by their poor stability in sunlight. Incidentally, this example is highly appropriate for this conference held at the University of Nairobi, because much of the world s supply of pyrethrins is produced in Kenya. 

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