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Articles

27 Jul 2026
Valencia Orange Trees
By Firstfruits Consulting Website Articles , , ,

Effects of Foliar Applications of Urea or Nutriphite on Flowering and Yields of Valencia Orange Trees

Valencia orange yields have been related to the number of flowers in the spring bloom, and the number of induced flower buds is determined by climatic stress factors such as cold and drought. Winter foliar sprays of urea have been reported to enhance the number of flower buds, flowers per inflorescence and yields under California conditions. Sprays of urea (28-31 kg N/ha) or Nutriphite (6.1 l/ha of 0-28-26 product) were applied to mature Valencia trees in two locations in South Florida in 1994-95. Urea or Nutriphite applied between the dates of 25 Dec. and 11 Jan. increased flowers.

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27 Jul 2026
Citrus with Ice
By Firstfruits Consulting Website Articles , , ,

Screening Citrus Cultivars for Freezing Tolerance by Reliable Methods

Citrus species are comprised of susceptible plants that can barely tolerate freezing temperatures. To determine the relationship between cold stress tolerance (LT50) and some important physiological traits, four commercial citrus cultivars of citrus species were studied. These were Citrus unshiu, Citrus sinensis var. ‘Thomson navel’, Citrus paradisi var. ‘Star Ru by’ and Citrus limon var. ‘Lisbon’. Assessments of cold-stress tolerance were carried out at 4, -4 and -8 °C. Ultimately, the results showed that the Japanese mandarin and ‘Thomson navel’ had the highest stress tolerance (LT50). Citrus unshiu tolerated cold stress up to -8.4 LT50.

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26 Jun 2026
Cold Accumulation
By Firstfruits Consulting Website Articles , , ,

Cold Stress in Citrus: A Molecular, Physiological and Biochemical Perspective

Due to climate change, we are forced to face new abiotic stress challenges like cold and heat waves that currently result from global warming. Losses due to frost and low temperatures force us to better understand the physiological, hormonal, and molecular mechanisms of response to such stress to face losses, especially in tropical and subtropical crops like citrus fruit, which are well adapted to certain weather conditions.

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26 May 2026
Symptoms caused by Phytophthora- spp. on-citrus
By Firstfruits Consulting Website Articles , , , ,

Phytophthora-citrus interactions and management strategies: A review

Citrus production is declining worldwide due to several biotic and abiotic factors. The diseases caused by Phytophthora spp. present major economic risks since they are soil-borne and spread quickly if environmental conditions are favorable, or irrigation is poorly managed. Phytophthora species are present in all citrus-producing areas around the world causing significant losses in crop yield and affecting tree health. Bark infection, damping-off, root rot, gummosis, brown rot, and cortical root rot are among the typical symptoms caused by Phytophthora spp.

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28 Apr 2026
Frost on Citrus
By Firstfruits Consulting Website Articles , , , , ,

Physiological and biochemical adaptive strategies in citrus plants facing cold stress

Climate change has increased extreme weather events frequency and intensity. Although the incidence of high temperatures has been studied on several plant species, the study of low temperatures has been relegated to the background, whereas crops as citrus could be particularly sensitive to chilling due to their origins in tropical and subtropical areas. In this work, plants of two citrus genotypes, Carrizo citrange (CC) and Cleopatra mandarin (CM), were subjected to cold stress at 10/4ºC (day/night) temperature, maintaining control plants at 25/18 ºC, with a 16 h photoperiod. Leaf tissue was sampled after 3 and 7 days for further analyses. The results exhibited a similar photosynthetic response in both genotypes, decreasing of gas exchange parameters. The study of different osmoprotectants revealed a major role of proline and soluble sugars in the osmotic response of citrus to chilling.

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23 Mar 2026
Hand holding soil
By Firstfruits Consulting Website Articles , ,

Determining soil health parameters controlling crop productivity in a Citrus Greening disease affected orange grove.

Soil health is an important aspect for maintaining adequate crop production, but the specifics of what entails a healthy soil can vary from region to region and crop to crop. In highly managed agricultural systems, unhealthy soil can be masked by intensive management practices, yet there must be detrimental cutoff points in various characteristics, such as soil organic matter (SOM) concentrations, where even highly managed systems start to lose productivity. This negative impact was observed in a Florida citrus grove containing Valencia orange trees with observable differences in tree size yet were otherwise managed identically. A soil health index demonstrated that the areas with smaller trees had a significantly lower index score and those soils contained significantly less SOM (average SOM ​= ​0.57%) compared to areas with larger trees (average SOM ​= ​0.94%).

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23 Feb 2026
Valencia Orange Orchard
By Firstfruits Consulting Website Articles , , , , ,

Soil and Leaf Nutrient Status of Selected Valencia Orange Orchards in the Gharb Plain of Morocco

Monitoring the nutrient status of citrus orchards is fundamental to ensure optimum fruit yield and quality. In the present study, soil and leaf samples of 20 Valencia Late orange orchards were collected in the Gharb plain of Morocco, the second-largest citrus area in the country. The objective was to assess the status of essential macronutrients (N, P, K, Ca, and Mg) and micronutrients (Fe, Zn, Cu, and Mn) in Valencia orange orchards and investigate the relationships between soil properties and nutrient contents in soils and leaves. Soils of the studied orchards had a medium to heavy texture, with low to moderate levels of organic matter content (6–31 g kg−1). They were also non-saline and mostly alkaline and calcareous. These soils exhibited a wide range of macro- and micronutrients. Suboptimum levels of total N, available Fe, and Cu were observed in most soils. Most of soils had also sufficient levels of available P, Mn, and Zn. All soils were sufficiently supplied with available Ca, Mg, and K. Similarly to soil analysis, leaf analysis indicated the prevalence of adequate to very high levels of P, Ca, Mn, and K. Leaf N and Fe status were below optimum levels in most orchards, which is in line with the observed low levels in soils.

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