October 2010. Samoa would like to use the fungicides ‘Sundomil’ and ‘Kocide 2000 DS’ for an experiment with P. palmivora attacking pawpaw. The two fungicides had been kept in an old fridge used as a cupboard for more than 2 years. Are these chemicals still good for use?
(Editor: Sundomil contains Mancozeb and metalaxyl).
Also, would like to know of any research done on the fungicide Foscheck (or any other fungicide) for the control of P. palmivora on pawpaw.
The Kocide will still be useable ??? it is simply copper hydroxide, which will not deteriorate, but Sunomil, whose active ingredients are metalaxyl and mancozeb, may not be stable in storage. As a general rule, it is best to start with new product for experiments. One of the problems will be that with older (taller) plants there may be a problem getting the spray to the canopy, and you will probably end up with visible fungicide residues on the fruit.
Foschek and other phosphonate products should be suitable against the disease when used as a foliar spray, but canopy coverage on older trees would still be a problem. For that reason, some years ago in Tonga a more direct method using trunk injections was tried. Because the trunk of pawpaw is hollow it is possible to drill a hole into the trunk cavity (sloping upwards so that rainwater does not run in) using a sheep-drenching gun to inject the Foschek solution directly into the cavity. The method was based on the assumption that the solution would be absorbed directly into the trunk tissue surrounding the cavity. Unfortunately, there was no report, but enquiries sometime later suggested that it worked. It is certainly worth trying, as it is a very quick and easy method.