Articles
POST HARVEST CONTROL OF INSECTS AND MITES
Investigations include treatment with gamma radiation and fumigation with methylbromide.
In many species of insects mortality or sterility can be induced by low doses of gamma radiation (10–15 krad).
Reactions of cut-flowers to gamma radiation differ widely; some species tolerate radiation levels of 50 krad, others are damaged already at 5 krad.
There are also indications for a seasonal variation in sensitivity.
Symptoms of damage most frequently found after radiation are: flowers fail to open or open only partially; a lighter colour of the leaves and/or petals; a shorter vaselife.
Fumigation with methylbromide (30 g/m3 for 1 ½ hours at 18–23°C) results in a high mortality of thrips and lepidopterous larvae.
Many cut-flowers, including liatris and iris, tolerate this treatment.
In some species damage was found after fumigation; the occurrence of damage often was positively correlated with the temperature.
A small group of species was very sensitive to the treatment, showing damage after fumigations at lower temperatures.
Also differences in sensitivity occurred between cultivars (e.g., Rosa).
Symptoms of damage most frequently found after fumigation with methylbromide are: a shorter vaselife, leaf scorching, and failure of flowers to open.