Studies on the Potato Sprout Suppressant Chlorpropham

Boyd, Isabella Mackenzie Glen (1988) Studies on the Potato Sprout Suppressant Chlorpropham. PhD thesis, University of Glasgow.

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This thesis is based on studies of problems and consequences which develop from the use of chlorpropham as a potato sprout suppressant. Chapter 1 presents details of the the history of the chemical and its use, both as a herbicide and a sprout suppressant, and how it has become the main chemical in use in the potato processing industry today. A brief overview of the potato industry in the UK is given to enable the reader to understand how chlorpropham fits into sprout suppression in potato storage and also what problems applicable, in particular, to potato storage ensue from its use. Chapter 2 describes available analytical methods for chlorpropham determination and also the modification of an existing method to suit equipment available in our laboratory. Chlorpropham was extracted from potato samples using hexane as the solvent in the presence of anhydrous sodium sulphate. A new clean-up procedure which allows low level ( > 0.035 mg kg fresh weight tuber) determination of the compound is also described. Chapter 3 is a report of a storage and field experiment carried out to ascertain to what extent contamination of potato seed crops with chlorpropham affects subsequent growth. Potatoes of cv. Desiree and Pentland Crown, treated in February, 1977 with chlorpropham adsorbed on alumina to give rates of 0, 0.6, 1.25, 2.5, 5, 10 and 20 mg kg potato tubers, were sampled for analysis immediately before planting at the beginning of May. Chlorpropham residues were determined. Emergence and yield data showed that low levels ( 0.3 mg kg -1 ) that had little effect on total emergence, increased the mean emergence time and reduced yield. High levels of chlorpropham drastically reduced total emergence and yield. The results obtained above prompted an investigation into the influence of storage conditions of chlorpropham treated seed on residues and subsequent growth of the treated tubers (mean emergence time, % emergence and yield) and is reported in Chapter 4. This study involved the airing (for 9, 6, 3 and 0 weeks) of chlorpropham treated seed tubers and corresponding control tubers at two temperatures (8C and 12C). Chlorpropham treatment at a rate of 5 mg kg-1 was chosen for a number of reasons. Firstly, it produced a large enough effect in the field to be significantly different from controls in the previous experiment and secondly, the residues produced were large enough to enable reductions through airing to be quantified and were similar to chlorpropham residues found in contaminated seed received for analysis. When planted out, all chlorpropham treated seed emerged more slowly than controls; the total emergence in many cases was 100%. Even 9 weeks airing at 12C was unable to improve the performance to equal that of control seed. Once seed tubers have been contaminated with chlorpropham, it is unlikely that any changes in storage conditions will be able to completely overcome the effect of the chemical. In addition to problems with its effect on seed tubers, chlorpropham is widely used in the potato processing industry and Chapter 5 describes a study of the distribution of chlorpropham in a large commercial box store. Chlorpropham was determined in tuber samples from the store and considerable variation in residues was found (0.5 - 80 mg kg-1 unwashed whole tuber). It was not clear whether the distribution of chlorpropham was due to uneven application or a redistribution of the chemical after application. As it is difficult to remove tuber samples from box store without disruption, a further study, using filter papers placed at various positions in store during chlorpropham aerosol application, was carried out. Again, considerable variation (3.6 - 457 mg chlorpropham deposited on surface) was found, implying uneven application of the chemical. In Chapter 6, sane conclusions are drawn from the results in other chapters and in particular, the effect of new legislation providing statutory limits of residues currently being implemented is discussed. Suggestions for further work are also presented.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry, Plant sciences
Date of Award: 1988
Depositing User: Enlighten Team
Unique ID: glathesis:1988-77818
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2020 11:53
Last Modified: 14 Jan 2020 11:53

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