Alkane diols as chemical pinching agents

#Certain species of plants exhibit at least in the mature stages a tendency to suckering i.e. the formation of subordinate shoots spring from a bud on the stem, so-called axillary buds. This secondary growth has the effect of subverting the maturation of blossoms, fruit, or leaves for ultimate harvesting and is accordingly desirously avoided in cultivation. This tendency is particularly pronounced in the tobacco plant, especially in the maturation stage following topping or decapitation, i.e. the removal of the terminal growth, main leader or stem apex. In other cases, topping or removal of apical meristematic tissue is itself desirably accomplished chemically.

#Large leaf tobaccos as grown in the United States have typically been topped at or shortly after flowering, when dark air cured and fire cured types may have 10 to 16 leaves and burley, flue-cured, Maryland or cigar types may have 16 to 20 leaves. Tops (the blossoms) in tobacco tend to supress sucker growth down the stalk, so when tops are removed rapid and profuse sucker growth occurs at the juncture of the stem and each leaf thus limiting the development of the upper leaves which are by far the most profitable. Also, suckers provide food for young budworms and hornworms in addition to supplying a preferred site for hornworm egg laying. Accordingly, sucker control is essential for commercial cultivation. It is also important for efficient harvesting, as current mechanical harvesters require near-perfect sucker control for proper operation.

#Recently, earlier topping in the button stage has been employed as a means of increasing yields and affording better pest control. The resultant increased tendency to sucker had been controlled in the past by hand removal as often as 3 times in one season. Most recently, control has been achieved by the use of contact chemical control agents, such as methyl caproate in combination with a later application of a systemic agent such as maleic hydrazide which controls subsequent secondary growths. Successful sucker control permits most of the plant resources to be directed into making larger and heavier leaves, with sufficient spread to have desirable quality.

#In the practical application of the invention it is both convenient and economical to take advantage of the most inexpensive and readily available glycol of favorable ecological properties and for these purposes 1,3-butanediol is preferred.

#The active agent is a liquid of low toxicity and volatility and may be stored indefinitely without physical, chemical or biological degration. Concentrates may be readily prepared, at any level of glycol in water or other diluent. It is understood that mixtures in all proportions of the C.sub.2 -C.sub.6 alkane diols is contemplated, and certain of such mixtures may be preferred for selected applications. Commonly, an aqueous solution or emulsion of concentrated agent is prepared for dilution with water in a spray device for such purpose. Where surfactant is employed as desired, the spray may actually form a foam of benefit in localizing the agent. It is, of course, possible to admix the C.sub.2 -C.sub.6 alkane diols with other agents for sucker control or regulation of meristematic tissue, such as tertiary or secondary fatty amine, fatty acid ester or fatty alcohol contact agents; or the systemic agents such as maleic hydrazide. Somewhat less conveniently for mass application, the agent may also be provided as a paste or grease as by compounding with soaps or other thickening agents such as silicas, modified clays, etc.

#Although the growth control agent is commonly applied to tobacco after topping, it is also possible to effect simultaneous topping and agent application as by utilizing the Clip-Oil device described in Information Series Bulletin No. 3, Oct. 1950, Dept. Agr. Eng., N.C. Agr. Exp. Station. The agent may be applied, however, within 1-3 days and may be reapplied 10-21 days later as needed. More commonly, the initial chemical pinching is followed within 7-14 days with an application of maleic hydrazide.