Garden Word of the Day
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Citrus sadness is not a case of lemon tree depression. But citrus growers around the world are pretty sad about this plant pandemic.
Citrus sadness, more scientifically known as citrus tristeza virus (CTV), is the costliest citrus virus. It has killed more than 80 million citrus trees and made an added 40 million more citrus trees useless for growing edible fruit. And it spreads quickly.
First seen in South America in the 1930s, this disease was called “tristeza” which means sadness in Spanish and Portuguese. Citrus sadness attacks several citrus species and passion flowers (Passiflora gracilis).
Symptoms of citrus sadness
Symptoms of citrus sadness vary depending on the infected plant species. They are generally grouped into one of three categories: decline, seedling yellows, and stem-pitting. In each case, viruses populate the phloem, causing chlorosis, vein clearing, leaf speckling, fruit dwarfing, and stem dieback.
Decline can be fast or slow. It presents as chlorotic leaves and stem dieback. Citrus sadness decline may take only days to kill a mature tree (fast), or it may take years (slow). In the case of slow decline, infected trees often exhibit a bulge just above the graft. Decline is most commonly seen in grapefruit, mandarin, and sweet orange trees.
Seedling yellows most commonly affects lemon, pomelo, and sour orange. This type of citrus sadness causes overall yellowing and dieback.
Stem-pitting is the most virulent form of citrus sadness. It most often infects sour orange, a variety commonly used as rootstock for several other citrus species. [Which rootstock is your orange tree grafted onto?] Symptoms of stem-pitting match its name: pits form along the trunk and branches. This damage reduces crop yield and weakens the tree, making it susceptible to other diseases and pest damage.
Citrus sadness prevention
Citrus sadness is spread by aphids, especially brown citrus aphids and oriental citrus aphids. As you probably already know, controlling aphids is an ongoing battle. Aphids can have wings, and they reproduce at mind-boggling rates. As much as possible, monitor and treat for aphids. And be sure to buy certified disease-free and disease-resistant rootstock. And if you wrap tree trunks with sticky barriers, ants will be unable to protect aphids from their natural predators.
If you suspect citrus sadness has found its way to your tree, contact your local County Extension Office right away.
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