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  • Author or Editor: Harvey T. Chan Jr. x
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The disinfestation protocol for fruit often requires a delicate balance between suppression of the pest and avoidance of fruit damage. In Hawaii both hot-water and hot-air treatments are used for papaya destined for export. A computer simulation of the heat flow can be used to obtain the temperature Tα(x,t) at every point x in the papaya and every time t for any given heating protocol α. The activity of the ethylene forming enzyme (EFE) has been used as a measure of fruit damage and the “kill” of fruit-fly larvae/eggs as a measure of pest control. The degradation of the EFE measured experimentally for a fixed temperature T and at several times t can be analyzed to yield a rate expression R1(T,t). Similarly the survival of fruit-fly larvae/eggs can be used to establish a rate expression R2(T,t).

The temperature space-time expression, Tα(x,t), for a chosen heating protocol α, and the rate laws R1(T,t) and R2(T,t) can be used to calculate the effect on EFE activity, EFEα(x,t), and pest control, PCα(x,t), at every point in the fruit and time of the protocol. For example the effect of different heating schedules, different heating fluids or even the role of “pre-conditioning” can be assessed.

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Phytotoxicity from hydrogen cyanide (HCN) fumigation was measured in several varieties of Hawaiian cut flowers and foliage (Zingiberaceae, Heliconia, Orchidaceae, Marantaceae, Lycopodiaceae, Agavaceae, Proteaceae) as a potential disinfestation treatment. Concentrations tested were 2500, 3700, 4600, and 5500 ppm HCN for 30 min. All foliage and most heliconia were undamaged at fumigation levels of 5500 ppm HCN; most protea and `Midori' anthuriums were uninjured at 4600 pm HCN; red and pink ginger were uninjured at 3700 ppm HCN; and all pincushion protea showed phytotoxicity to HCN. Red ginger was quickly damaged when exposed to sunlight immediately after treatment at 2500 ppm HCN. No injury was observed in simulated shipment tests of red ginger and `Ozaki' anthuriums fumigated at 2500 ppm HCN. Wet, red ginger flowers longer than 6 cm were damaged at 2500 ppm HCN, whereas shorter flowers were uninjured. Wet `Ozaki' anthuriums showed phytotoxicity only at 4600 ppm HCN. Wet, treated lycopodium and bamboo orchid foliage was not injured. The number of marketable days and shelf life of the treated plant material were estimated from the visual ratings.

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