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out the state. The root-knot nematode species that attacks straw- 

 berries in areas south o£ Massachusetts does not overwinter here 

 and the root-knot species that attacks our carrots will not live 

 on strawberries. 



The soil fungi that cause the diseases Red Stele and Verticil- 

 lium Wilt are not generally controlled by fumigation, although con- 

 trol is possible under some conditions by using large amounts of 

 chemical. Nematode control will often reduce the amount of injury 

 from these fungi that enter the plant through the roots. More com- 

 monly, soil fumigation brings about a response spoken of as the 

 "I.G.R." effect. The I.G.R. effect, or Increased Growth Response, 

 is presumed to occur because secondary pests are killed at higher 

 rates of fumigation and plants simply grow more vigorously in their 

 absence. 



Should I fumigate ? Fumigation is expensive. In most cases, 

 however, a 10-151 increase in yield will make the treatment profit- 

 able. Each field has its own set of conditions, and whether or not 

 disease organisms build up to a point where they cause trouble is 

 largely a matter of crop sequence, temperature, moisture, organic 

 matter, and a host of unknowns. Many of these unknowns will also 

 determine whether or not a chemical treatment will work. Poor growth 

 of plants will lead you to suspect a problem, a soil test may con- . 

 firm that a nematode problem is present, and a trial application of 

 chemical may lead to a better growth. 



What can be used ? Listed below are fumigants registered for 

 use in Massachusetts. All are liquids that are injected into soil 

 before planting. They become gases that diffuse through all parts 

 of the soil mass. There are a number of factors that can influence 

 their effectiveness: organic matter absorbs these fumes; soil water 

 fills air spaces and prevents their spread: and at low temperatures 

 disease organisms are very resistant to toxic fumes. More than any 

 other group of pesticides, fumigants must be applied precisely ac- 

 cording to directions. Unless the soil temperature, texture, mois- 

 ture, and organic matter are right, and the proper amount of chemi- 

 cal is deposited at the right depth and is sealed in properly, the 

 entire treatment may be useless. 



Companies which manufacture soil chemicals can supply detailed 

 information on application equipment. In addition, custom applica- 

 tors are available who will not only apply treatments, but can give 

 advice based on their rather wide experience. 



The chemicals listed below are those generally in use. In ad- 

 dition, your regional specialist can supply you with the names of 

 others that may be of use under special conditions. One of these 

 is DBCP (Nemagon*, Fumazone*) , a fumigant which does not injure 

 strawberries at low rates and can be used on growing plants. 

 Methyl bromide mixtures (Dowfume MC-2*, MC-33*, Brozonel* require 



*Trade name 



