Posts Tagged: lemon
'Bitters', 'Carpenter' and 'Furr' trifoliate hybrids are three new citrus rootstocks released in August 2009 by the University of California Riverside. These three rootstocks are hybrids of Sunki mandarin x Swingle trifoliate orange. As rootstocks for citrus, they produce good quality fruit on small ('Bitters') or medium-large ('Carpenter' and 'Furr') trees. They all show good tolerance to Citrus tristeza virus (CTV), but vary in their tolerance of Phytophthora and nematodes. They all produce uniform seedlings due to high levels of nucellar embryony, and are graft compatible with sweet orange, Lisbon lemon and grapefruit. They also appear compatible with mandarins based on observation of 11 year-old satsuma and ‘Pixie’ trees. We are comparing their performance compared to ‘C-35’ as a standard and with ‘sour orange’. These are being grown with ‘Pixie’ and ‘Lisbon’ lemon scions. Sour orange grows well on calcareous, heavy soils and are less prone to nematodes. It turns out that mandarin and lemon are not prone to tristeza virus when grown on sour orange rootstock. Trees will be planted this coming spring. Stay tuned.
In coastal lemons, there has been a major increase of broad mite and the damage it causes on fruit and leaves this year.
Broad mites are often found in depressions on fruit where the females lay their eggs, which are dimpled, translucent, and covered in white speckles. These mites are so small you need a hand lens to see them. Broad mites are yellowish in color and adult females have a white stripe on the back.
Broad mites feed on fruit and leaves, preferring young fruit up to about 1 inch (2.5 cm) in diameter that are located on the inside of the canopy or on the inward facing side of outer fruit. Feeding results in scarred tissue that cracks as fruit grows, leaving a characteristic pattern of scars and new tissue. Although most feeding occurs on fruit, broad mites may also feed on young expanding leaves causing them to curl. This cupping and curling of leaves can appear similar to mild damage caused by glyphosate-Roundup applications.
Broad mites are occasional pests of coastal lemons from late July through early October; infestations are enhanced by the presence of Argentine ants. This mite often occurs in conjunction with Citrus Rust Mite, with the rust mite usually predominating in number. Populations of broad mite tend to be most severe in warm, humid conditions such as found in greenhouses. No treatment thresholds have been developed for broad mite in citrus. If high and increasing populations warrant treatment, use miticides with the least toxicity to predaceous mites. The predatory mite Neoseiulus californicus appears to be a good biocontrol agent.
Check out the IPM website for a greater discussion of pesticides available for use on broad mite.
Broad mite on fruit and the damage it causes to leaves.