Environment
Aphids are the main vector by which CTV is transmitted. Initially the United States only had the melon (cotton aphid) Aphis gossypii, spirea aphid Aphis spiraecola, and black citrus aphid Toxoptera aurantii. These aphids transmit the virus much less efficiently than the brown citrus aphid Toxoptera citricida. Toxoptera citricida had been found in East Asia and South America, and had slowly made its way up through Central America and the Caribbean Islands. By 1993 it had reached Cuba, and in 1995 it was found in Florida. The aphids require at least 30 to 60 minutes of feeding to acquire the virus, and remain viruliferous for at least 24 hours after. T. citricida is much more efficient than the other aphids, and it can transmit CTV strains causing severe stem pitting or decline that the other aphids cannot vector. Even though A. spiraecola is less efficient, it tends to have higher populations and thus can still transfer the virus fairly well. T. aurantii has been shown to only transmit certain strains of CTV. Of the three lesser efficient aphids, A. gossypii has a 78% transmission efficiency, while A. spiraecola and T. aurantii are between 0-6%. The main cultural practice that increases the severity of the CTV is when the citrus trees are grafted onto the sour orange rootstock. Using CTV infected budwood for grafting can transfer the CTV from the original tree to the new one.
Read more about this topic: Citrus Tristeza Virus
Famous quotes containing the word environment:
“For those parents from lower-class and minority communities ... [who] have had minimal experience in negotiating dominant, external institutions or have had negative and hostile contact with social service agencies, their initial approaches to the school are often overwhelming and difficult. Not only does the school feel like an alien environment with incomprehensible norms and structures, but the families often do not feel entitled to make demands or force disagreements.”
—Sara Lawrence Lightfoot (20th century)
“Today the young actors regard their environment with rage and disgust. They regard their Master not as disciples regard their Master, but as slaves regard their Master.”
—Judith Malina (b. 1926)
“White males are the most responsible for the destruction of human life and environment on the planet today.”
—Robin Morgan (b. 1941)