Active herbicides and pesticides

Press, 1 May 1981, Page 18

Active herbicides and pesticides

Contributed by Peter Bell, South Island technical officer for Ivon Watkins-Dow, Ltd.) During the early 19605, researchers at the Dow Chemical Company discovered a new active group of chemicals based on the pyridine ring structure.. The first of this group to be developed was Tordon herbicide and, since then, a range of pesticides including further herbicides and insecticides have been developed. One of the most recent herbicides to be screened and developed in New Zealand by Ivon Watkins-Dow, Ltd, is 3,6-DCPA, which is sold under the trademark Lontrel. Last season saw the introduction of Lontrel Cereal herbicide for the control of broadleaf weeds in cereal crops. It is a combination of 3,6-DCPA, bromoxynil and MCPA. In its first season in the market place, Lontrel Cereal herbicide performed extremely well. It is a product that exhibits a high degree of crop selectivity, while retaining the same excellent standards of weed control associated with the traditional trimix cereal herbicides.

It is now possible to treat weeds in cereal crops at a late growth stage without having to run the risk of

significant yield suppression. This property makes Lontrel Cereal . herbicide the preferred product for controlling Californian thistles in cereal crops. It is often difficult to obtain a high level of control of Californian thistle due to the long time taken for growth to emerge from the buried rhizomes.

In general terms, the greater the amount of top growth present at the time of treatment, the higher the level of thistle control. With Lontrel Cereal herbicide, it is now possible to delay the treatment of Californian thistles in cereal crops until full emergence without fear of significantly depressing crop yield.

Last season was a very good one for cereal growers with some very high yields being reported thanks to the weather and Lontrel Cereal herbicide.

Continuing work on 3,6DCPA by the I.W.D. Research Division has led to the introduction this year of Lontrel Pasture herbicide. Lontrel Pasture herbicide is especially recommended for the control of difficult-to-kill nodding and winged thistles where results with MCPA and 2,4-D may be variable and disappointing. Lontrel Pasture herbicide

contains 3,6-DCPA and MCPB ester. The 3,6-DCPA is readily translocated down into the root zone of actively growing thistles, preventing any root regrowth following spraying.

Because of this systemic action, Lontrel Pasture herbicide more readily controls large multicrown nodding thistles that have previously been not well controlled with MCPA and 2,4-D.

When applied during the autumn to late spring period (May-August), the degree of clover suppression with Lontrel Pasture herbicide is similar to MCPA with much improved thistle control.

To assist farmers In obtaining the maximum benefit from Lontrel Pasture herbicide, Ivon Watkin-Dow, Ltd, have introduced a new innovation on the product label that has its origin in many years of experience in thistle spraying. It has long been recognised that hard-to-kill thistles are not necessarily those that have large tops but rather those thistles that, due to any number of circumstances (grazing, mowing, ineffective spraying, two year old plants) have an extraordinary large root system. To assist the farmer in choosing the correct applica-. tion rate of Lontrel Pasture

herbicide, the rate varies according to the tap root ' diameter rather than the traditional rosette diameter. Those thistles with an unusually large tap root diameter qualify for the top rate.

Another new herbicide developed from the same chemical group is triclopyr, which is available under the trademark, Garlon. Garlon 520 herbicide is the result of five years research by Ivon Watkins-Dow, Ltd, and is specifically recommended for the control of blackberry. It contains a mixture of picloram and triclopyr. Garlon 520 herbicide is more effective for blackberry control than the traditional Tordon 520 brushkiller, yet like Tordon 520 brushkiller, it does not harm valuable pasture grasses.

The continuing presence of these grasses is essential for the suppression of re-colon-ising blackberry seedlings and other unwanted weed species. Garlon 520 herbicide does remove clover from the pasture but it can be reintroduced six to 12 months after treatment. Another chemical from this group which has very unique properties is nitrapyrin. the active ingredient of N-Serve nitrogen stabiliser.

This greatly reduces the ability of soil micro-organ-isms from converting nitrogen fertiliser into soluble nitrates which are readily, leached through the soil and out of reach of the growing crop.

In other words, N-Serve \ greatly increases the effi- * ciency with which the crop; utilises the applied nitrogen. . Liquid N-Serve is applied at. drilling at one to two litres, per hectare as a fine spray down the drill furrow.

Crop responses depend on' type of crop, soil type and climate. To date, trial results' and limited farmer use indi- . cate that N-Serve has a real place in crops such as cereals, maize and other high nitrogen demanding crops. .

Research work is continu-. ing on evaluating further developments in this group , which undoubtedly will re-i suit in even more effective, products being made avail-’, able to both the forester and agriculturalist. »