Chemical Weed Control in Gladiolus

New Zealand Journal of Agriculture, Volume 97, Issue 6, 15 December 1958, Page 535

Chemical Weed Control in Gladiolus

By

J. P. SALINGER,

Horticulturist Department of Agriculture, Wellington

WEED . control in plantings of »» gladiolus is comparatively simple with the use of new types .of weedkillers now becoming available which can be applied to bare soil between growing crops to control germinating weed seeds and yet not harm the crops. These have special value where gladiolus are grown for both corm and cut flower production. These materials are monuron (CMU) or diuron (DCMU), neburon, CIPC, and dinoseb/dinosam with diesel fuel oil.

EFFICIENT and persistent weed control will be obtained only if the following points are observed: 1. The land must be free of perennial weeds and the soil cultivated so that the surface is weed free. 2. The soil must be sufficiently moist to encourage the germination of weed seeds. 3. The materials should be applied when there is a likelihood of some rain or when irrigation can be applied. 4. The correct material must be chosen for controlling the weeds which are likely to occur. 5. After application the soil surface should not be disturbed or cultivated. The application of dinoseb/dinosam should be delayed until weeds have germinated and reached the seed-leaf stage. The efficiency of monuron and CIPC varies with the soil and climate. On light sandy soils or in dry areas they are likely to be less effective than on silts, loams, or clays and in areas of moderate rainfall. Trials carried out at the Department of Agriculture Horticultural Research Station, Levin, for 2 years on a silt loam have shown that two applications of the appropriate weedkiller will replace five cultivations, with no damage to leaves, flower spikes, corms, or cormlets.

Time of Application

Dinoseb/dinosam plus diesel fuel oil should be applied before the growing points of the gladiolus have emerged from the soil (pre-emergence). Monuron and CIPC can be applied both before . and after emergence of the growing points (pre-emergence and post-emergence).

complete control are given below. Treatment 1 is the cheapest, but not the easiest to apply; treatment 6 is the most expensive. The cost of material only in all cases would not exceed £l4 per acre. Dilution with Water The amount of water with which the materials should be mixed depends on the output of the sprayer used for

Recommended Programmes

Several combinations of the weedkilling materials which will provide

applying the materials. All of the materials may be applied by lowvolume sprayers, though there is always a slight danger of spray drift. The important point is to apply the correct total quantity of material per acre. . Even if a - grower does not have adequate equipment for complete spraying of field plantings of gladiolus,

WEEDKILLING TREATMENTS Material Rate per acre Rate per 60 sq. yds. Treatment I: Pre-emergence .. Dinoseb/dinosam .. 4 pints .. .. 1 fl. oz. Diesel fuel oil .. 12 gallons .. .. 1| pints Post-emergence .. CIPC (4 lb. active ingredient) ■ .. 1 gallon .... 2 fl. oz. Treatment 2: Pre-emergence . . Dinoseb/dinosam .. 4 pints .. .. 1 fl. oz. Diesel fuel oil .. 12 gallons . . . . 1J pints Post-emergence .. Monuron .. .. 24 lb. .. .. .. J oz. Treatment 3: Pre-emergence . .. Monuron .. .. 24 lb. .. .. .. 1 oz. Post-emergence .. CIPC .. .. .. 1 gallon .. .. 2 fl. oz. Treatment 4: Pre-emergence .. Monuron .. ... 2J lb. .. ... .. 4 oz. Post-emergence .. Monuron .. .. 24 lb. . . .. .. 4 oz. Treatment 5: Pre-emergence .. CIPC .. . . ... 1 gallon ... .. 2 fl. oz. Post-emergence ... CIPC .. .. .. 1 gallon ... .. 2 fl. oz. Treatment 6: Pre-emergence only Monuron .. .. 5 lb. .. .. .. 1 oz.

he can do band spraying along the rows of plants to save labour in general cultivation. After spraying in this way care should be taken not to throw the cultivated soil between the rows on to the sprayed area. Choice of Materials Both the cost and properties of the various weedkillers should be considered before a final decision is made about which combination to use. Dinoseb/dinosam is poisonous. The operator should wear protective clothing or at least rubber boots, gloves, and goggles when handling the concentrate and, if there is a danger of spray drift, while spraying. The concentrate should be mixed with a small quantity of water and then added to the diesel fuel oil. This mixture should be poured into the spray tank and the remainder of the water added. The chemicals will control seedlings of weeds and some germinating seeds and should be used only at the preemergence stage of the gladiolus.

Monuron is a wettable powder which does not fully dissolve in water and the spray mixture should be well agitated during application. At 5 lb. per acre, treatment 4 (two applications of 2J lb. per acre), there is a danger that the material will persist too long in the soil and affect the germination of the seed of desirable plants sown in treated soil the following season. In this respect the materials diuron and neburon may prove safer and also more effective in high-rainfall areas, but they have not yet been tested on gladiolus. Monuron is particularly effective in controlling Portulaca from seed. CIPC is a liquid which mixes well with water and is the easiest of the materials to apply. At 4 lb. per acre it gives good control of seedling grass weeds and many broad-leaved weeds. At this rate it does not satisfactorily control sow thistle or cruciferous weeds such as shepherd’s purse and twin cress, for which higher rates (up to 6 lb. per acre) may be required. One commercial gladiolus grower has used 6 lb. per acre with no apparent damage to the gladiolus.

Another material, 2,4-DES at 5 lb. per acre, has been tested at various times, but has given very variable results.

Mulching for Weed Control

Small areas of gladiolus corms and cormlets can be kept comparatively free of weeds by mulching the soil after planting with 2 in. of sawdust. Though weeds will penetrate this mulch, they can be easily removed. When sawdust is used, additional nitrogenous fertiliser should be applied either in the base dressing or before the sawdust is applied. The sawdust should be from timber that has not been treated with wood preservatives.