Plant Parasitic Nematode Diversity in Pome, Stone and Nut Fruits

Abstract

Plant parasitic nematodes such as Pratylenchus, Meloidogyne, Paratylenchus, Criconemoides and Heliocotylenchus represent a worldwide concern for pome, stone and nut fruit growers. This chapter contains lists of nematodes in apple, peach, pear, plum, cherry, almond, apricot, walnut, pecan and walnut. Nematodes have various attack strategies, feeding ectoparasitically and endoparasitically caus- ing necrosis and galls on the roots, stunted plant growth, varying degree of chlorosis, wilting of foliage and sometimes death of the plants. Other parasitic nematodes such as Xiphinema, Longidorus, Trichodorus and Paratrichodorus are also vectors of transmission of viruses to plants. The plant roots weakened and damaged by nematodes are easy prey to many types of pathogenic fungi and bacteria which invade the roots and accelerate root decay. The negative effects on plant growth decrease yields and plant growth. Annual yield loss of 13.54% has been estimated to world’s major horticultural crops due to damage caused by plant parasitic nema- todes. Studies reveal a 16% yield suppression of peach due to single nematode spe- cies Pratylenchus vulnus. Growth suppression of apple can be caused by 15 Pratylenchus penetrans/100 g soil, 30/100 g for pear, 80/100 g for cherry and 320/100 g for plum. Similarly 5,000 and 4,200 Criconemella xenoplax/100 g soil can suppress the growth of peach and walnut, respectively. The great loss of some fruits are due to increased rates of tree mortality due to disease complex such as cherry decline and peach tree short life syndrome where stress caused by nematode parasitism results in an increase in susceptibility of the tree to other pathogens. This ultimately leads to a reduction in agricultural sustainability. Nematode management therefore becomes a priority for the security of food supply. Hot water treatment of planting materials, soil manipulation, use of certified planting materials, dipping the planting materials in systemic chemicals having nematicidal properties, pre and post planting treatment of nurseries with nematicides, soil fumigation, soil treat- ment with chemical nematicides, application of oil seed cakes in tree basins, use of bioagents and of course, the identification of nematode resistant rootstocks/cultivars are some of the management strategies which need to be applied in an effective manner for their inclusion in integrated nematode management programme.