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crop debris because undecayed roots harbor nematodes, protect them 

 from the fumigant, and interfere with fumigant application. It 

 should be in excellent tilth and soil moisture should approach that 

 desirable for seeding. Dry soils permit rapid escape of fumigants 

 whereas dispersion of fumigants in excessively wet soil is poor. 

 Fumigants do not volatilize and disperse properly at soil tempera- 

 tures below 50°F and escape too rapidly from soils when the tempera- 

 ture is above 80°F. Spring treatment usually delays planting so 

 late summer or early autumn is usually best for the application of 

 soil fumigants in Michigan. 



Soil fumigation is the primary treatment being utilized by 

 Michigan orchardists. The fumigant is chiseled 6-10 inches deep 

 into the soil with the chisels space 8-10 inches apart along the 

 tool bar. The soil is smoothed with a drag or cultipacker immedi- 

 ately after application to prevent the chemical from escaping. The 

 most widely utilized soil fumigants are Vorlex*, DowFume W-85*, 

 Telone* and Shell D-D*. Methyl Bromide also has been utilized to 

 treat individual tree sites with an injecting soil auger in the fall 

 prior to planting. When fumigating orchardists normally treat a 

 7-foot strip where the tree row will be located rather than treating 

 the entire field. 



Research with granular nematicides applied with fertilizer appli- 

 cators and rotatilled into the soil is encouraging. There also is 

 much interest in foliar application of nematicides. Vydate-L* is a 

 foliar nematicide that can be applied to non-bearing trees. However, 

 2 to 3 applications per year are necessary. Furthermore, we do not 

 consider it an alternative to soil fumigation, although yearly appli- 

 cations until a tree comes into bearing may help suppress nematode 

 difficulties . 



Nemagon* or Fumazone* can be applied as a post-plant row appli- 

 cation. It must be chiseled into the soil about 8 inches deep along 

 the tree row. However, it is usually a less effective method than 

 pre-plant soil fumigation. 



Orchard Replant Problems 



Another difficulty encountered in establishing fruit plantings 

 is frequently referred to as the Specific Apple Replant Disease. 

 This is observed where an apple orchard is replanted to apples. 

 Young trees planted where the old trees stood may make poor growth, 

 thus tree growth on the site is variable. 



A specific disease has been identified as the cause of this 

 difficulty in cherry, and work continues to identify the difficulty 

 in Apple. Chloropicrin is beneficial as a soil treatment for the 

 Specific Apple Replant Disease. The Dutch have found that using a 

 potting mixture in the planting hole is useful in preventing poor 

 vigor because of the disease. 



* Trade name 



