6. 



The Root lesion (meadow) nematodes, Pratylenchus species 



The root lesion nematodes are represented in Europe by at least 

 six species. However, only two of these cause damage. Pratyipochus 

 penetrans causes serious damage to a wide vari'?ty of plants, an un- 

 descnbed species causes root rot in Convallaria majalis . 



Pratylenchus penetrans 



The hosts of P. penetrans can be divided into three groups: 

 (see also SLOOTWEG 1956) 



I. Plants which only sufferr at very heavy attacks and show 

 little secondary root rot (cereals, peas, etc.). 



II. Plants which suffer when attacked by mediimi numbers 

 (potatoes, apples, tulips, hyacinths). 



III. Plants which suffer at low or very low degrees of infestation 

 of the soil (daffodils, strawberries, lilies). In this group 

 the damage is largely done by secondary root rot caused by 

 several fungi to winch the roots become susceptible even 

 When attacked by only a few specimens of this nematode. 



The third group is the most important one as damage in these plants 

 is found over a much larger area than in the other two groups. Some 

 host plants belonging to the first two groups run a risk of being dam- 

 aged because either they stay for many years in the same place so that 

 the nematodes can build uo a large population (apples) or they are re- 

 planted in the same field a few times in succession (nurseries). 



Although P. penetrans is a dangerous parasite of some plants 

 where it occurs, its distribution in Western Europe seems to be lim- 

 ited. This definitely is not due to lack of host plants in non- in- 

 fested areas, but most probably to the soil type being unfavorable to 

 this nematode. Also in infested areas there are great differences in 

 the all over degree of infestation. It is low in the sandy soil in 

 the western part of the Netherlands, although in this vegetable grow- 

 ing area there are host plants on the fields most of the time. How- 

 ever, serious damage only occurs in daffodils (root rot results wtien 

 1 or more specimens of P. penetrans are present in 500 g. of soil) and 

 strawberries vJhich build up a high eelworm population. Tulips and 

 hyacinths are only attacked occasionally. 



Fortunately, soils where P. penetrans occurs are very suitable 

 for the use of nematicides, and generally the cost of treatment is no 

 objection. 



