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HETP does not keep well after it has been diluted, and it has no persistent action, whereas E605 may be stored indefinitely in diluted form, and remains effective on the plant for at least two weeks. Systemic sprays are absorbed by the leaves, rendering the sap poisonous to sucking insects, such as aphides and harlequin bugs; they are also ovicidal. In this last respect they are not as potent as tar distillate, but have the great compensation of being harmless to young foliage. They are compatible with copper oxychloride, and colloidal and wettable sulphur preparations. All alkaline preparations, such as lime sulphur, Bordeaux mixture, and alkalinized white oils accelerate greatly the breaking down of E605, and systematic sprays, - and so destroy their persistent action.

HETP is available in Australia and New Zealand under several trade names, including Hexone, Vallo HETP, Tephos, Tetraphos, and Demite, as well as under the name of HETP, which is an abbreviation for hexaethyl tetraphosphate. E605 or parathion, chemically known as para nitrophenyl diethyl thiosulphate, is available as Phosfone 20, E605 Folidol, Para-phos, and Parathion. Systox and Sytam are two examples of systemic sprays. Neither marks foliage.

DDT (dichloro-diphenyl-trichloroethane) is one of the most powerful of all insecticides. It is a contact poison, acting on the insect's nervous system, and is absorbed through the footpads. DDT is useful against thrips, aphides, and Rutherglen bugs when applied in a white-oil or wax base. If any is allowed on open flowers it will kill the bees that visit those flowers. It is only slightly toxic when swallowed, and is almost useless if not mixed with a white-oil or mayonnaise emulsion (as in Pes-pruf-20), or with some other base (as in Rucide). Rucide needs to be warmed, but not boiled, and adheres to the foliage better than the white-oil emulsion preparations. DDT preparations are cheap and easy to apply. They have persistent action lasting two to three weeks, but, of course, a good unbroken film cannot be maintained without more frequent spraying on young flower-buds that are swelling rapidly and are ready for invasion by thrips. The film is torn apart by the enlarging surface. In the spring aphides sometimes seem to breed faster than DDT can kill the older generations. E605 and Lindane act more quickly, while with systemic sprays the maintenance of an unbroken cover is unnecessary.

Spraying with white-oil suspensions of DDT causes white spots to remain on the foliage of plants. These can be wiped off easily with an oily rag if the flowers are cut for indoor use, but should be left on the leaves that remain on the plant. DDT loses its potency when mixed with TMTD sprays, whereas Lindane remains effective, as also do organic phosphates.

Benzene hexachloride (BHC) is a compound which was discovered first by Michael Faraday in 1825. It can exist in four forms, known as the alpha, beta, gamma, and delta isomers of BHC; each has the same molecular formula, but different properties. In 1943 it was found that the gamma isomer had insecticidal properties which in many respects are the most potent ever discovered; yet it is almost entirely harmless to men and animals. DDT appeared before the gamma isomer of BHC was offered commercially, and the organic phosphates followed before the BHC products had been publicized widely. The phosphates were so amazingly efficient that BHC was temporarily overlooked. However, now that the phosphates are virtually disqualified in some States many people have come to realize the superiority of the gamma isomer of BHC over DDT. It acts more quickly and with much greater certainty. The two products are combined in Pespruf-4G, making a very useful preparation. They are combined with Chlorparacide in Spraymate.