Physical, chemical and biological behaviour of fumigants on cottonseed.

Fumigation is required to protect cottonseed in storage and pre-shipment from insect pests and/or microorganisms. Fumigation of cottonseed with carbon disulphide (CS), carbonyl sulphide (COS), ethanedinitrile (CN), ethyl formate (EF), methyl bromide (MB) and phosphine (PH) showed that >85% of the fumigants disappeared within 5 h of exposure. COS maintained >20 mg L for 24 h. After 1 day of aeration, 75%-85% of the absorbed COS and MB and 20%-40% of the absorbed CS, EF and PH were released from treated cottonseed. The fumigant residues were reduced by 80% for COS, 50% for EF or MB and 25% for CS after 1 day of aeration. After 13 days of aeration, fumigant residues were reduced by 95% for MB, 65% for EF, 55% for CS and to natural levels in the COS residue. Carbon disulphide, COS, PH, EF and CN had no effect on the germination of cottonseed, but germination was reduced to 50% by MB. COS has potential as a fumigant for control of insect pests in cottonseed because it dissipates quickly and does not negatively impact germination. On the other hand, MB appears to strongly absorb and requires an extended period for residues to dissipate, and it negatively impacts germination.