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Parathion 
Parathion, as an insecticide, was discovered by chemists and entomologists of the |. G. Farben 
Corp. in Germany during the war, as a result of preparing and testing over 300 phosphorus com- 
pounds, following’earlier work on phosphorus-fluorine compounds for war gases. 
This new insecticide shows promise of being the most important material yet discovered for green- 
house pest control. Parathion remains effective for a week or more both as a contact and stomach 
poison. This continued killing effect is very important in giving better control of many pests with 
fewer applications. 
Parathion aerosol is very effective against many of the pests attacking chrysanthemums and it is 
safe on all varieties listed in this manual. If moisture is present on the foliage or bloom, a burn 
certain. Parathion aerosol will give control of red spiders, mites, black aphids, green aphids and the 
straw colored aphids (thought to carry the virus Stunt), thrips, greenhouse leaf tyers, mealy bugs 
and the leaf miners. 
The Parathion aerosol is applied in the same manner as the HETP aerosol, through an applicator 
consisting of a flexible hose, brass rod and oil burner nozzle, directing the aerosol mist into the 
air above the plants. A gas mask and protective clothing should be used when applying this  in- 
secticide. 
Greatest effectiveness is obtained with temperatures of 75°F or above at the time of application 
and with vents kept closed for four hours, although excellent kills have been secured at temperatures 
as low as 65° and with vents closed for only two hours. Dr. Blauvelt, Cornell University, reports that 
parathion aerosol was applied with safety to many commercial greenhouse crops. 
Hexaethy! Tetraphosphate 
This new insecticide is available under trade names of Vapotone, Hexcide, Blot, Kill-Ex and Arbortox 
64 and very likely many more will be added within the year. HETP as it is commonly referred to in the 
trade is used as a spray or in aerosol dispensers. This new insecticide is extremely effective in killing 
the active stages of red spider, but little kill on the eggs. This material also gave good control for 
thrips, leaf tyers, aphids and mealy bugs. Follow the directions of the manufacturer and remember thig 
material kills on contact only so you will have to do a thorough spraying to get good results. 
HETP will decompose very rapidly after it is mixed with water, therefore is necessary to use the mixed 
spray very soon after mixing and never hold over any left over spray mixture. Precaution is to spray 
HEPT in the morning so the plants will dry off rapidly. In cloudy weather or when the humidity is ex- 
ceptionally high the foliage will stay moist for three to four hours after spraying and a spotting of the 
leaves will appear on chrysanthemums. 
Aerosol bombs are being carefully tried by the U.S.D.A. and excellent control of red spider may be 
expected by making four applications at three-day intervals. Allow the houses to stay closed for about 
1!/> hours after the application. The range of temperature is from 60-90 degrees. 
Sodium Selenate 
This material has been on the market for the past several years but is comparably new to a large num- 
ber of growers. This material is applied to the soil and is absorbed by the plant through the roots. It 
will kill foliar nematodes, red spider, mites, midge and aphids. Available as P-40 or as a powder, 
applications every 3 months are necessary as it leaches from the soil. 
P-40 is applied dry at the rate of 3 pounds per 100 square feet of area. Sodium selenate crystals are 
applied in liquid form and a stock solution is made by dissolving | pound in 4!/, gallons of water. 
For most crops the suggested dosage is !/4 gram sodium selenate per square foot (equal to | pound to 
1800 square feet.) Each quart of stock solution contains 25 grams and is therefore enough for 100 
square feet of bench surface. It must be diluted with additional water to get even application and 
good distribution in the soil. Full directions are available with the material. 
On chrysanthemums we recommend !/, gram sodium selenate per square foot. The safest method is to 
make two applications at the !/g gram rate a week or so apart. 
Follow the precautions and syringe off any solution which might get on the foliage. Do not treat plants 
until 2 or more weeks after transplanting. Be sure to apply the correct amount evenly. Sodium selenate 
is a poison and treat it as such. 
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