Determination of damaged leaf area and physiological responses of melon plants submitted to different infestation levels of Liriomyza sativae

ABSTRACT The leafminer Liriomyza sativae (Diptera: Agromyzidae) is one of the main pests of melon crop (Cucumis melo) in the Brazilian semiarid. The aims of this study were to determine the damaged leaf area and assess the physiological responses of melon plants submitted to different levels of infestation per larvae of L. sativae. The study was carried out in a greenhouse, using plants of melon of the cultivar Iracema (yellow melon). The design utilized was completely randomized, with five treatments {control (no infestation in the leaves) and four infestation levels (1; 10; 20 and 30 larvae per leaf)} and 10 replications (melon plants). Initially we evaluated the physiological aspects: photosynthetic rate (µmol CO2/m2/s), stomatal conductance (mol H2O/m2/s) internal CO2 concentration (µmol CO2/m2) and leaf transpiration (mmol H2O/m2/s). After the measurements of physiological aspects, the evaluated leaves of each plant were cut close to the petiole and scanned individually with a measuring scale on the side, being the determination of the damaged leaf area performed with the aid of software for processing and analysis of images. The averages of damaged leaf area observed were of 1.2; 6.3; 19.6 and 40.8 cm2 for infestations of 1; 10; 20 and 30 larvae/leaf respectively. In relation to the physiological aspects, the rate of photosynthesis, stomatal conductance and transpiration significantly decreased with the increase of leafminer larvae per leaf. The internal CO2 concentration increased with the increase in the number of larvae per leaf.