Controlling perennial weeds with chlorates

The commercial use of chlorates for weed control purposes in Idaho has met with gratifying success. There are certain features which limit the effectiveness of the treatments. These may be summarized in a general way from extensive observations made during the entire growing season. It has become very apparent that the full effectiveness of the treatments is not evident until the following season. It is not uncommon for the plants to continue to grow after the applications, only to disappear entirely after the winter season. In order that best results be obtained, the areas should not be cultivated just prior to the application of chlorates. The under-ground root system should be represented by an appropriate amount of top growth. The effectiveness of the treatments increases as the plant approaches maturity. This possibly may be attributed to the fibrous nature of the plant nearing maturity and the ease of dissemination of the chemical through the root system. The borders of the treated areas should be watched closely the following season, since it is apparent that the underground root system extends beyond the outer limit of the top growth. Areas should not be irrigated following treatment. This apparently results in dissemination of the chemical through the soil moisture and subsequent leaching from the soil. In instances where the water table approaches the surface of the ground at certain seasons of the year, it has been noted that treatments are more effective if the water table remains stationary at the time of application or is slowly lowering. In case the water table is continually approaching the surface of the ground, there is a zone of roots near that water table which will not be effectively killed. The temperature of the air and the time of the day during which the application is made appear to have very little influence upon the effectiveness. Complete eradication does not follow with sufficient frequency to warrant the statement that a single application is sufficient. Experience has shown that it is much better to inform the farmer that he should not expect complete control with a single application and have him pleased if no further work is necessary, than it is to inform him that complete control may be expected and have him disappointed if further work is required. Under irrigation, it would seem that the following general recommendations might be made: Dissolve the chemical in water at the rate of 1 pound per gallon. Apply to plants in undisturbed areas after full bloom stage and in sufficient quantity to moisten all vegetation. Leave the area undisturbed through the remainder of the season, except in the case of white top where a second application may be required to prevent seeding. Repeat the application the following season, if necessary. In non-irrigated areas, the general recommendation for all perennial weeds is to apply a 10% solution in sufficient amount to wet the weeds thoroughly.