Spurrey Control in Brassica Crops

New Zealand Journal of Agriculture, Volume 99, Issue 2, 15 August 1959, Page 115

Spurrey Control in Brassica Crops

By

R. C. STEPHEN,

Instructor in Agriculture, Department of Agriculture, Balclutha

IN many districts spurrey or yarr (Spergula arvensis) is a troublesome weed B in turnip, swede, and kale crops. The vigorous growth of spurrey seriously reduces the yields of these crops. Spurrey is worst in districts where frequent showers occur during December and January and where the brassica crop is sown on ground which has been cropped in the preceding season. Where brassicas are sown on ridges spurrey may be controlled by intercultivation of the ridges, but in some areas this is difficult and expensive.

IN the past control of spurrey in brassica crops by weedicides has been unsuccessful due to the extreme damage caused to the crop by the more common weedicides. However, during the past two years trials have been laid down in south Otago to test the efficiency of “pre-emergence” applications of various weedicides as a control of spurrey in brassica forage crops and to examine the reaction of the crop to the application of these weedicides. Treatments 1956-57

In the 1956-57 season the weedicides and rates of application used in preemergence applications on a ridged crop of swedes and white-fleshed turnips were TCA at 10 lb and 20 lb per acre, propham at 1 lb and 2 lb per

acre, and CIPC at 1 lb per acre. These materials were applied in early December to the surface of the seedbed two days after the seed had been sown on ridges but before the seedlings had emerged from the ground. For the rest of the month temperatures were moderate and rain (1| in.) adequate, with the result that a successful establishment of crop but also weed seedlings occurred. Within six weeks the crop in general became heavily infested with spurrey, which formed a dense mat tending to smother the crop.

Germination Counts 1956-57 Germination counts after the crop had established indicated that propham at 1 lb and 2 lb per acre severely damaged the crop, causing a marked

reduction in the density of the estab lished crop (see Table 1).

TABLE I—GERMINATION COUNTS 1956-57

lb per Plants per Treatment acre 10 ft row Difference TCA . . 10 20 TCA .. 20 19.9 —O.l Propham .. 1 14.4 5.6* Propham ..2 9.9 —lo.l* CIPC ..1 19 —l.O

rp^ e TCA and CIPC treatments caused no damage to the crop.

Spurrey Control 1956-57 The pre-emergence applications of propham at 2 lb per acre and CIPC at 1 lb per acre gave complete control of spurrey. Propham at 1 lb gave only partial control of the spurrey, which, however, remained stunted and sparse

and did not interfere with the growth of the crop throughout the trial. The TCA treatments did not control the spurrey, which soon formed a dense mat that restricted the growth of the crop on these plots. Where the weedicides effectively controlled the spurrey the crop grew more vigorously and these treatments outyielded those plots where there was no control of spurrey or where crop damage had been too severe. In this trial propham at 2 lb per acre caused too much damage to the crop. Application of propham at 1 lb per acre caused crop damage, but this was more than offset by extra growth due to control of spurrey; in other words there was a net benefit. CIPC at 1 lb per acre and propham at 1 lb per acre gave good control of spurrey and crop yields were improved (see Table 2).

TABLE 2—CROP YIELDS 1956-57

lb per Dry matter Treatment acre lb per acre Difference TCA . . 10 1,580 TCA . . 20 1,190 —390 Propham .. 1 3,340 1,760* Propham .. 2 2,330 750 CIPC . . 1 3,520 1,940*

Treatments 1957-58 In the following season 1957-58 a similar trial was put down on a crop of ridged kale. The weedicides used as pre-emergence treatments were propham at i lb, 1 lb, and 2 lb per acre, CIPC at I lb, 1 lb, and 2 lb per acre, and TCA at 20 lb per acre. These materials were applied in the middle of December to the surface of the seedbed four days after the kale seed had been sown on ridges and

before emergence of the seedlings. In the month after the application, of the weedicides there were lower-than-average seasonal temperatures and heavier-than-average falls of rain, totalling 4 in. A prolific growth of spurrey together with scattered plants of sheep’s sorrel (Rumex acetosa), docks (Rumex spp.), and fathen (Chenopodium album) established. The spurrey formed a dense mat about 9 in. thick. Germination Counts 1957-58 Germinations counts (Table 3) were made after the kale had become established. The counts indicate that none of the treatments had caused any significant damage to the crop and that there was no reduction in the density of the crop. s ..

TABLE 3—GERMINATION COUNTS 1957-58

lb per’ Plants per Treatment acre 10 ft row Difference Control . . 9.2 ■— Propham . . J 9.2 0.0 Propham 1 9 — 0.2 Propham .. 2 9 — 0.2 CIPC . . i 8 —1.2 CIPC ..1 9.5 0.3 CIPC . . 2 . 8.3 —0.9 TCA .. 20 8.5 —0.7

Differences not significant at 5 per cent level

Spurrey Control 1957-58 In this trial the pre-emergence applications of.propham at J lb and 1 lb per acre and TCA at 20 lb per acre had no effect on the growth of the spurrey. Spurrey was partially controlled with pre-emergence applications of propham at 2 lb per acre and CIPC at J lb per acre. The pre-emergence application of CIPC at 1 lb and 2 lb

per acre gave complete control of spurrey. None of these treatments had any effect on the sheep’s sorrel, fathen, or docks, except that the CIPC treatment suppressed the growth of sheep’s sorrel. Where spurrey was completely controlled the kale grew more vigorously and outyielded those treatments where control of spurrey was poor (see Table 4).

TABLE 4—CROP YIELD 1957-58

lb per Dry matter Treatment acre lb per acre Difference Control . . 790 Propham .. J 880 90 Propham .. 1” 1,200 410 Propham .. 2 1,060 270 CIPC.. .. 1 1,330 540 CIPC .. 1 1,670 880* CIPC . . 2 1,720 930* TCA . . 20 1,290 500

Results of these trials indicate that pre-emergence applications of TCA cannot be relied on to control spurrey even when the weather is favourable; that pre-emergence applications of propham are likely to cause severe damage to the brassica crop; and that pre-emergence applications of CIPC at 1 lb can give adequate ■ control of spurrey without causing, crop damage. In districts with higher summer temperatures CIPC at i lb per acre would probably control spurrey. In contrast to the favourable results obtained in south Otago, in some districts of the North Island where extremely high soil temperatures are common pre-emergence applications of CIPC have given variable results and cannot be recommended.

* Differences significant at 1 per cent level

* Differences significant at 1 per cent level

* Differences significant at 1 per cent level