-8- 



TRENDS OF MICHIGAN TREE FRUIT INDUSTRY (PART III)^ 



Jerome Hull, Jr. 

 Department of Horticulture 

 Michigan State University 



Nematodes and Soil Fumigation 



Parasitic nematodes have become o£ increased concern to Michi- 

 gan fruit growers. Many orchards are planted on light-textured 

 soils and on these soils damaging nematode populations are being 

 detected in an increasing number of young orchards and orchard 

 sites. Peach trees are most susceptible to nematode injury in 

 Michigan. However, cherry trees also are susceptible and nematodes 

 can be a problem in apple and pear plantings, especially in orchard 

 replantings . 



The root-lesion nematode is of primary concern, although the 

 dagger, rootknot and lance nematodes may also be present. The usual 

 nematode damage symptoms are stunted trees with poor vigor. Nema- 

 tode numbers vary within a field; therefore, tree vigor on the site 

 is variable. 



Some feeding nematodes will induce gall formations on plant 

 roots. Root cells destroyed by nematode-feeding become dark dis- 

 colored areas in the root system. These root-lesions increase with 

 continued feeding and secondary invasion by other soil microorganisms 

 occurs. Some nematodes feed on young roots and alter the traditional 

 root branching structure. They may also devitalize or kill roottips. 



Soil fumigation prior to planting on old orchard sites is often 

 essential to produce vigorous healthy orchards. Thus, a laboratory 

 analysis of soil and root tissue is suggested to detect nematode 

 problems. The soil and root samples are usually collected about 2 

 months after the initiation of tree growth in the spring and before 

 frost in the fall (usually mid-July to mid-September) . 



Many fruit crops respond to soil fumigation with nematicides. 

 This is readily apparent by improved tree growth. A long-term study 

 in New York has demonstrated a definite financial advantage from 

 fumigating an apple orchard. In Michigan, increased growth and 

 winter survival of young peach trees has occurred following fumiga- 

 tion. Furthermore, fumigation also seems to be associated with 

 improved weed control in new fruit plantings. 



Nematode control is not simple. Proper soil preparation prior 

 to soil fumigation is essential for maximum nematode control. The 

 soil must be cultivated to promote thorough decomposition of previous 



Part III of Talk presented at the Annual Summer Meeting of the 

 Massachusetts Fruit Growers' Association on July 13, 1977. 



