Silvering on red pepper fruits is a visual defect that can at times become a marketing concern (Photo 1). The defect is not caused by a disease or virus. It often occurs in areas on the fruit that rested against a branch (Photo 2) and appears to be the result of compression or rubbing. However, it can also occur on other parts of the fruit not associated with compression (Photo 3) and the reason for this is not entirely clear. At first glance, it seems to be the result of insect feeding. Thrips are most commonly blamed for causing this silvering on pepper fruit. However, examining the fruit closely under a dissecting microscope, there is no sign of the type of damage that would be caused by thrip feeding. Early descriptions of thrip feeding inaccurately claimed that they ‘rasp’ or ‘gash’ the plant tissue and then suck up the juices at the surface, but in fact the feeding process by thrips can be best described as ‘piercing-sucking’. We examined a recent batch of red pepper fruit that came to our office for signs of thrip feeding associated with the silvering, by looking for holes or puncture wounds and did not see evidence of thrip activity. Intact pepper fruit have a uniform cobbled surface (Photo 4). The silvered tissue also has this same texture, but affected cells are bleached of color, but maintain the same uniform cobbled texture (Photos 5 and 6). Other issues on pepper fruit such as cracking (Photo 7) and scarring (Photo 8), are easily distinguished from silvering of pepper fruit.
The exact cause of silvering of pepper fruit is not clear. As mentioned above, one partial explanation may be a reaction to either compression or rubbing. Only the very top epidermal cells are affected (Photo 9). As such, it is a minor defect and it is unfortunate that silvering is occasionally the reason for rejection of pepper fruit from the market.
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