Environmental variables influence the developmental stages of the citrus leafminer, infestation level and mined leaves physiological response of Kinnow mandarin

Abstract

Climate change has not only exacerbated abiotic stress, but has also rendered external conditions more feasible for pests to spread and infest citrus fruit. Citrus leafminer (Phyllocnistis citrella) is a potential pest that directly feeds the newly sprouted leaves and twigs of all three spring, summer and autumn flushes. Increasing temperatures in spring and autumn, leafminer accrued more heat units or developmental degree days to accelerate the biological stages of its life-cycle, thereby increasing the pressure of infestation. Present work was conducted at three different environmental conditions in Sargodha, Toba Tek Singh (TTS) and Vehari districts of the Punjab province, Pakistan; all three experimental sites were located in different agro-ecological zones. More infestation was recorded in all three flushes at TTS and Vehari than in Sargodha. Overall, more damage was observed due to higher temperatures in TTS and Vehari than in Sargodha. After May–June heat stress, spontaneous vegetative growth continued from July to November, produced newly spouted tender leaves for feeding the leafminer larvae, and was seen more in TTS and Vehari. Leafminer larva prefers to enter young and tender leaves with a maximum entrance in leaves up to 1 cm2 in size while observing no entrance above 3 cm2 of leaf size. Physiological response of leaves primarily attributed to chlorophyll and carotenoid contents, both of which were recorded lower in the mined leaves, thereby reducing leaf photosynthetic activity. Similarly, lower levels of polyphenols and antioxidant activity were also recorded in the mined leaves. The on-tree age of mined leaves of three vegetative flushes of Kinnow plant was also less counted than non-mined leaves. Climate change has affected vegetative phenology and become feasible for pests due to extemporaneous leaf growth, particularly leafminer, and eventually causes economic loss by supplying low carbohydrates either to hanging fruits or next-season crops.

Comparative mineral and biochemical characterization of Citrus reticulata fruits and leaves to citrus canker pathogens, Xanthomonas axonopodis

“…The decreased chlorophyll-a concentration was measured in diseased leaves due to leaf miner attack and CC infections. The values in our study were higher, possibly due to genetic diversity, leaf age, foliar micronutrient administration (Zn, Cu, and B), photoperiod, or soil texture [20]. Our findings were slightly higher than those of [21], possibly due to an increased ratio between chlorophyll a and b with higher light intensity.…”

“…Chlorophyll a content was measured in NML and ML. In Sargodha, TTS, and Vehari, NML showed 1.56, 1.75, and 1.33 mg/g FW, while ML exhibited 1.04, 1.07, and 0.8 mg/g FW, respectively [20]. In Tehsil Silanwali, Kotmomin, Bhalwal, and Sargodha, NML recorded 3.05, 4.11, 4.18, and 4.29 mg/g, and ML showed 2.30, 3.07, 3.56, and NS = Non-significant (P > 0.05); * = Significant (P < 0.05); ** = Highly significant (P < 0.01)…”

“…DPPH (1, 1-diphenyle-1-2-picrylhydrazyl) inhibition was used to assess antioxidant activity in relation to seasonal fluctuations (spring, summer, and autumn flushes). This assessment was performed on two distinct groups: NML (with inhibition percentages of 27.66%, 32.27%, and 45.23% for the respective flushes) and ML (with inhibition percentages of 18.12%, 18.07%, and 32.40% for the corresponding flushes), as detailed in the work by [20]. Investigations on diseased and non-diseased fruits revealed a consistent pattern, with healthy fruits showing higher antioxidant activity than their diseased counterparts [20].…”

“…This assessment was performed on two distinct groups: NML (with inhibition percentages of 27.66%, 32.27%, and 45.23% for the respective flushes) and ML (with inhibition percentages of 18.12%, 18.07%, and 32.40% for the corresponding flushes), as detailed in the work by [20]. Investigations on diseased and non-diseased fruits revealed a consistent pattern, with healthy fruits showing higher antioxidant activity than their diseased counterparts [20]. This disparity can be attributed to potential infections and disease manifestations.…”

Abiotic and cultivar effects on the incidence of pest arthropods in 16 citrus scion varieties grafted on two rootstocks

“…Pest densities fluctuate temporally, affecting their levels of potential injury to the crop (Nawaz et al, 2021) and these fluctuations may differ among pests, introducing dynamics in their net potential injurious effects on the crop. Some of this variation is attributable to climatic variables (Rathod et al, 2020;Tandel et al, 2020;Prabhudev et al, 2021).…”