The agave is a type of succulent plant well-adapted to desert landscapes. These plants can tolerate harsh conditions, including heat, cold, drought and poor soil. Several agave species feature tips with sharp thorns or spines, and some species are well-suited for container growing. Agaves are susceptible to a number of diseases or other problems, but with proper care these plants should remain healthy and long-lived.
Agaves require at least six full hours of sunlight daily to maintain a good appearance and growth rate. These plants need good drainage, ideally in a sandy soil. Container-grown agaves can grow well in a mixture of sand and well-drained potting soil. If the soil is not well-drained, plant the agave above-grade or on a mound. Poor drainage can result in root rot.
Water and Fertilization
Agaves may require occasional water immediately following planting to encourage establishment but typically require no supplemental irrigation after the period of establishment. Small or young plants may benefit from a low fertilizer application, but established agaves do not require any fertilizer, especially if an organic mulch is used.
Anthracnose and Other Fungal Problems
Agaves can be infected by the anthracnose-causing Colletotrichum fungus. This fungus is a problem during moist or humid conditions, if the agave is receiving overhead irrigation or if the plant is in shade. Anthracnose causes lesions on agave leaves and crowns, and a reddish-orange spore mass may be present within the lesion. If the lesion has spores, remove the infected leaf. Certain agave species may also be infected with other fungi, which usually infect plants during cool, wet weather.
Root and Crown Rots
Agave may be affected by several soil-borne pathogens, including Erwinia bacteria and Fusarium fungus. Weevil feeding or other damage likely enables these pathogens to enter. Besides preventing wounds such as those caused by weevils, there is no control for rot once the plants have been infected. Poor drainage conditions will also make agaves more susceptible to rot.
Agave may be damaged by temperatures that fall below its normal temperature range for more than a few hours. Within a few days of the freeze, spots, cracks or water-soaked areas will develop on leaves, and severely damaged parts will become mushy before drying and turning brown. Prevent damage by covering plants before cold weather. You may prune the agave to remove damaged leaves, but this may give the plant an uneven appearance and make it susceptible to pathogens. Luckily, freeze damage often stimulates new growth from the lower plant.
The most serious agave pest is the agave snout weevil, which punctures the base of the plant to lay eggs. This process opens a pathway for microorganisms that attack and decompose the plant tissue, which then acts as a food source for the hatched weevil larvae. Weak plants and plants preparing to flower are the most vulnerable to this pest; the best control method is to maintain plant health and destroy infested agaves. Plant bugs may cause light yellow scars or spots on the plant. Additionally, agaves may be affected by Coccid scales, a type of soft scale.