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• Sunburn assessment: A critical appraisal of methods and techniques for characterizing the damage to apple fruit

  7-14.

  J. Racskó

  Views:

  659

  Many methods and techniques have been introduced for measuring alterations in the fruit and in its surrounding environment related to sunburn incidence. The research objectives, fruit materials and the environment to be evaluated dictate the methods to follow. These procedures are either non-destructive and involve techniques that allow us to track the course of sunburn development and related environmental parameters, or destructive and involve the removal of fruit from the tree for field/laboratory measurements. Techniques employed can be used for pre-symptomatic monitoring (before symptoms become visible) or characterizing the symptoms already present. The principles behind the measurements and their usefulness for sunburn assessments are discussed and critically evaluated in this review paper. Descriptions and evaluations of the methods and techniques were made in the following groups: 1. Thermal measurements; 2. Visual assessments; 3. Fruit quality measurements; 4. Measurements of physiological and biochemical alterations; and 5. Practical evaluation of sunburn damage. Thermal measurements involve methods tracking the ambient temperature and fruit surface temperature, and their relation to sunburn formation. Visual assessments cover all measuring techniques (skin color, chlorophyll fluorescence, radiation reflection, electron microscopy) that are able to detect changes on/in the fruit skin related to sunburn formation. Fruit quality measurements are used to point out differences in qualities (soluble solids, firmness, titratable acidity, and water content) between unaffected and sunburned areas of the fruit. The measurements of physiological and biochemical alterations (gas exchange, pigment analysis, enzyme activity, gene expression) give us a better insight to the mechanism of sunburn formation. Practical evaluations involve many procedures that are used by scientists to characterize the susceptibility of cultivars, evaluate protection technology, etc. For this purpose, the following methods are in use: expressing the percentage of the total fruit surface area affected by sunburn or the percentage of the total number of fruits damaged on the tree, or even a scale based on the severity of the symptoms occurred. All assessing methods and techniques described here have their pros and cons as well as their specific applicability, therefore any of these cannot be favored to use exclusively for assessing sunburn incidence. The combination of these techniques will be the best choice to meet a given research objective perfectly.

• Efficacy of selected botanical extracts against Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) on tomato

  31-36.

  Daniel Kepha Nabutse

  Mwanarusi Saidi

  Joshua Ogweno

  Views:

  364

  Tuta absoluta Meyrick, also known as the tomato leaf miner, is a destructive pest that feeds on tomato plants, causing significant economic losses to tomato farmers globally. Traditional methods of controlling Tuta absoluta involve the use of synthetic pesticides, but these methods have drawbacks such as environmental pollution, development of resistance by the pest, and negative effects on non-target organisms. As a result, there is a growing interest in the use of botanical extracts as alternative and safer pest control options. Three bioassay experiments were conducted to test the insecticidal, antifeedant and repellency effects of botanical extracts on Tuta absoluta. The experiments were conducted as completely randomized design (CRD) with three (3) replicates. There were eleven treatments; pyrethrum, neem, warbugia, each at different concentration levels of (8%, 10%, 12%) and controls positive (Indoxacarb 150g/L) and negative (distilled water). In all the bioassay conducted, the effects of all treatments increased over time, except for distilled water control. Synthetic chemical Indoxacarb exhibited significantly stronger insecticidal properties compared to neem, warburgia and pyrethrum extracts. Application of neem at 8%, 10% and 12% and pyrethrum at 12% had higher antifeeding effect on Tuta absoluta compared to the other treatments while warburgia at 8% concentration and indoxacarb had the lowest repellency effect compared to the other plant extracts.