Advice On Use Of D.D.T. Prills

Press, Volume CIII, Issue 30366, 15 February 1964, Page 6

Advice On Use Of D.D.T. Prills

SINCE D.D.T. in prill or pellet form, with a high safety factor from a residue point of view, is one of the forms of D.D.T. application permitted under the new regulations governing the use of agricultural chemicals, the following question and answer material about prills supplied, by the Farm Chemicals Company is published for the information of farmers: Q.: What is the idea behind the prill or pellet? A.: D.D.T. prills or pellets consist of an inert core of heavy material such as marble. This core is the vehicle which carries the D.D.T. through the grass foliage to the. soil. Being quite heavy, it resists wind drift apd falls directly on to the target. The D.D.T. itself is a very finely ground micronised material bonded to the core by an adhesive. This adhesive is dissolved by rain and the D.D.T. is released from the core as a very fine wettable powder. When the prills or pellets are spread evenly, the D.D.T. powder released from the cores in this way gives an almost continuous cover of D.D.T. on the ground surface.

Q.: What. are the recommended methods of applying prills? •

A.:. The locally-developed Speed Spreader is a very successful ground machine and consists of a speciallydesigned spinner driven directly off a 12-vblt tractor battery. It is easily handled by one man and can be mounted on any three-point linkage tractor, or utility vehicle, or even a truck. Some of the existing box type topdressers and spinners have been found to be satisfactory for spreading prills. They have also been spread by contractors using bulk handling equipment. The method here is that the Speed Spreader is mounted on the front of the truck and the prills or pellets ' are sown at the same time as the fertiliser.

The swathe width of the Speed Spreader is usually about 30 feet or- double that of the fertiliser, so- this means that the prill sowing rate would have to be halved so that the final application rate would be equivalent to 161 b per acre or 2lb of actual D.D.T. Many thousands of acres have been treated from aircraft using various types of spreaders. Prills or pellets really lend themselves to this method of application as the drift is practically nil and swathe widths of up to 100 feet are easily attained. One aircraft is quite capable of treating 200 to 300 acres an hour.'

Q’.: Can prills or pellets be mixed with superphosphate? A.: We have heard of farmers mixing prills ■ with superphosphate and applying them through usual topdressing equipment with apparently good results, but we would not normally recommend this method. For one thing the mixing of the super with the pellets would be a long job and by the time this is done you could have covered a big area with prills on their own through a Speed Spreader. Twenty acres can be comfortably treated in an hour with the ' Speed Spreader. Q.: How soon after application do prills or pellets begin to affect the grass grub? A.: If rain falls soon after treatment with prills, good results can be expected within three or four weeks. Grass

roots will show signs of reestablishment and increased top growth should begin to show up. In lower rainfall areas this recovery will be slower and results will, be directly related to the extent and frequency of the rainfall.

Q.: Cost is an all important consideration. How about this question? A.: Last year the cost of treating ah acre with prills or pellets was 2s less than the previous year, and this season the cost will be reduced again because of the larger volume now being used, so that the cost of treating one acre with 161 b of prills or pellets will be down to 19s Bd. 161 b is equivalent to 21b of active D.D.T. and at this rate a pasture will be protected from grass grub for up to three years. Q.: Is there much risk of D.D.T. residues bn pastures with D.D.T. prills dr . pellets, and how long does a farmer have to keep his sheep and cattle off pastures after treatment? .

A.: As stated earlier, prills being heavy fall through the pasture to the ground and the actual amount of D.D.T. held on the grass' is very small indeed. Official trials done by the D.S.I.R. have allowed • the withholding periods to be considerably reduced so that sheep and dry cattle must be kept off treated pasture for two weeks and dairy cows for four weeks.

Prills or pellets should be applied early in the year when the grub is in the young susceptible stage qf growth.