Agriculture Reference
In-Depth Information
3.
Chemical Name: 2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2 meth-
oxy-1-methylethyl) acetamide
Common Name: Dimethenamid
Family Name: Amide or substituted amide
Trade Name: Frontier
IV. INSECTICIDES
Pesticides are often classified according to their deposition or distribution
on or in treated plants; however, the following differentiation may be made:
Insecticides with local action
. These affect the pest directly, or they have
to be distributed as evenly as possible on the plant's surface, where uptake by
the insect occurs. Many insecticides show a good depth of action, penetrating
into the leaf and reaching even hidden insects on the underside of the leaf not
directly touched by the insecticide. Depth of action is important, particularly
in the control of mining developmental stages of the insects, as for example
the maggots of the beet leaf miner
(Pegomyia hyoscyami).
Insecticides with a
predominantly local action are to be found primarily in the chlorinated hydro-
carbons, many organic phosphoric acid esters, and carbamates displaying an
effective penetrating action.
Insecticides with systemic action
are taken up relatively quickly by the
plants and transported into the vascular system. According to the type of ap-
plication, uptake occurs through the roots or the parts of the plant above
ground. Distribution is chiefly by the xylem, but is also possible by the
phloem and by diffusion from cell to cell. The persistence of activity is de-
pendent on the type of substance, the intensity of breakdown in the plant or
the soil, and environmental conditions. A much longer period of protection
can be maintained if, by application of granulates at drilling or planting out, a
depot of the substance is created in the soil from which the active substance is
released slowly and taken up by the plants.
The following particularly important advantages of using systemic insec-
ticides should be mentioned:
•
Rapid uptake through the plants minimizes the degree of danger to
beneficial insects. A few hours after application, only the insects
which suck or feed on the plants are affected, whereas their natural
enemies, for example, bees are not.
•
Good distribution in the plants reaches even hidden pests, whereas lo-
cally acting agents affect them only slightly or not at all.
•
Requirements with respect to even distribution and weather resistance
are less stringent for systemic plant protection agents. Due to their
