Aloe Vera Diseases: Discover Its 2 Main Enemies
In everything related to aloe vera, we must highlight the existence of José Imery-Buiza, an agronomist engineer and Coordinator of the Research Laboratory in Genetics and Improvement of Aloe vera at the University of Oriente in Venezuela. We found it interesting to share his article on the main causes that cause aloe vera diseases.
We want to thank Dr. Imery for his great research work on the wonderful world of aloe vera.
Aloe vera or sabila is considered a species with few natural enemies and is rather recognized as a source of compounds with biological activity for controlling some organisms.
However, like any other domesticated and extensively cultivated plant, this succulent has not escaped the evolution of its antagonists. Therefore, there is a growing list of scientific studies documenting damage caused by arthropods, mollusks, nematodes, fungi, and bacteria.
In this article, I present a summary of the main diseases we have studied in plantations in America and other observations recorded by fellow researchers from Europe and Asia.
Fungi that infect the aloe vera plant
Regarding diseases caused by fungi, worldwide species such as Alternaria alternata, Alternaria sp., Botryodiplodia sp., Byssochlamys nivea, Cercosporidium sp., Colletotrichum sp., Coniothyrium concentricum, Corynespora sp., Curvularia sp., Drechslera spicifera (=Bipolaris spicifera), Exserohilum rostratum, Leptosphaeria nigrans, Macrophoma sp., Melanospora zamiae, Phyllosticta sp., and Physalospora sp. have been identified as causing leaf spots and necrosis.
In India, the fungus Alternaria alternata has not only caused localized damage to A. vera leaves but also reduces the effectiveness of some of its therapeutic compounds in infected plants, lowering the quality of its derived products.
The fungal species Uromyces aloe had been reported as responsible for rust in other Aloe species; however, in 2004 it was recognized as the cause of foliar damage in A. vera plants cultivated in Catalonia and Valencia (Spain). The following symptoms were described: whitish and yellowish spots on the upper surface of the leaves, often at the base, corresponding to the fungus's spermogonial phase. Later, the spots evolve into eruptive lesions or pustules, ranging from golden-brown to dark brown, coalescing and arranged concentrically in rounded groups of 3-5 cm in diameter, corresponding to the telial phase. If conditions persist (mild temperatures and high humidity), the number of pustules increases, causing the entire leaf blade to dry out.
Other fungi, including Fusarium oxysporum, Fusarium solani, Fusarium sp., Lasiodiplodia theobromae, Pythium ultimum, Phytophthora parasitica, Phytophthora sp., and Sclerotium rolfsii, are responsible for rhizome rot. Fusarium oxysporum; Fusarium solani, Phytophthora parasitica, Phytophthora sp., Rhizoctonia solani, Rhizoctonia sp., and Sclerotium rolfsii also cause root rot, leading to plant toppling and weakening.
Aloe vera diseases
Cases of diseases caused by bacteria: bacteria such as Pantoea agglomerans produce watery spots and subsequent leaf necrosis. In continental America and Caribbean islands, the main pathogen of Aloe vera is the bacterium Erwinia chrysanthemi, which causes watery rots with an incidence of up to 4% of cultivated plants. Focusing on poorly drained soils and excess water from continuous rains or poorly managed irrigation, the incidence can reach up to 35%, exceeding the economic tolerance level. This disease begins with chlorosis in older leaves and progresses with swelling at the leaf base, gas bubble formation, loss of rigidity, leaf toppling, release of leaf content with a foul odor, and plant death 8-11 days after the first symptom.
In the New World, other economically important pathogens include fungi such as Alternaria sp. (3% incidence), Macrophoma sp. (1%), Colletotrichum sp. (0.7%), Bipolaris sp. (0.5%), Rhizoctonia sp. (0.5%), Fusarium sp., and Sclerotium rolfsii (0.4%). It is important that enthusiasts and professionals interested in Aloe vera respect regulations regarding the transfer or exchange of plant material to reduce the introduction of diseases not present in their locality. Additionally, it is recommended to be very attentive to any changes observed in their domestic plants or large plantations and report them to the nearest phytosanitary authorities.
On the other hand, scientists are aware that currently all Aloe vera plants cultivated worldwide represent practically a large clone with very low genetic variability, and we are working hard to develop new cultivars tolerant to existing pathogens and to counter those that inevitably evolve over time.
Dr. José Imery Lover of Biology, Cultivation, and Genetic Improvement of Aloe vera.
