4 MASS. EXPERIMENT STATION BULLETIN 353 



is the case with grubs of the elm leaf beetle), then care must be taken to direct 

 the spray to that side of the leaves. Dry, powdered lead arsenate is the chief 

 poison used. Because weathering action is apt to wash this material off the 

 foliage in a short time, flour or calcium caseinate may be added to the liquid 

 spray to make it spread better and stick to the foliage longer. Spreaders also 

 tend to reduce the danger of arsenical injury to the tender foliage of susceptible 

 plants. On especially tender foliage it may be advisable to reduce the amount of 

 lead arsenate. Sometimes raw linseed oil or fish oil is used as a sticker for lead 

 arsenate. These oils, however, have little value as spreaders; neither will they 

 lessen the burning action of the lead arsenate. The fish oil, moreover, is objec- 

 tionable for use near dwellings because of its unpleasant odor. If soap or sprays 

 containing soap are used with lead arsenate, injur\- to the foliage may result. 

 After a spray has been applied, the spray tank should be carefully cleaned before 

 another spray is prepared. 



The usual method of controlling leaf miners, or insects which feed in the tissues 

 between the surfaces of the leaves, is to apply a contact spray that will kill the 

 insects in the leaves without harming the leaf tissue itself. For this purpose 

 nicotine sulfate, with or without soap, or some similar material is usually applied. 

 Best results are obtained when the insect is young and the leaf mine is small. 

 Later the larvae are more resistant to the spray. The thickness of the leaf tissue 

 also influences the effectiveness of the spray. 



In the discussion of the various insects, recommendations for dilution arc made 

 for large amounts of spray. The accompanying dilution table gives amounts 

 of the various materials for small quantities of spray of equal concentrations. 



Dilution Table for Use of Insecticides 



Avoirdupois Weight 



Large Quantities Small Quantities 



1 pound in 100 gallons 1/6 ounce in 1 gallon 



2 pounds in 100 gallons 1/3 ounce in 1 gallon 



3 pounds in 100 gallons 1/2 ounce in 1 gallon 



5 pounds in 100 gallons 4/5 ounce in 1 gallon 



Liquid Measure 



3/4 pint in 100 gallons 1 teaspoonful in 1 gallon 



1 pint in 100 gallons 1 1/4 teaspoonfuls in 1 gallon 



1 1/4 pints in 100 gallons 1 1/2 teaspoonfuls in 1 gallon 



11/3 pints in 100 gallons 1 2/3 teaspoonfuls in 1 gallon 



11/2 pints in 100 gallons 1 9/10 teaspoonfuls in 1 gallon 



1 3/5 pints in 100 gallons 2 teaspoonfuls in 1 gallon 



1 quart in 100 gallons 2 1/2 teaspoonfuls in 1 gallon 



Sprays must be applied when the particular stage of the insect to be controlled 

 is present; otherwise effective results cannot be expected. The experienced 

 operator is fully aware of the importance of this fact but very often the layman 

 is not. The actual date of application, however, may change from year to ^ear, 

 varying with the earliness or lateness of the season. Insect pests are very often 

 not noticed until the damage is almost completed, when it is too late for control 

 measures to do any good. If a pest is known to be present, preparations should 

 be made to control it either in a succeeding generation or in the following season, 

 depending on the species involved and the locality. 



