- Author: Jeannette E. Warnert
A tell-tale sign of spring in California is a flush of new leaf growth on citrus trees. Because the feathery light green leaves are particularly attractive to Asian citrus psyllids (ACP), the leaves' emergence marks a critical time to determine whether the pest has infested trees.
“We encourage home citrus growers and farmers to go out with a magnifying glass or hand lens and look closely at the new growth,” said Beth Grafton-Cardwell, UC Agriculture and Natural Resources (UC ANR) citrus entomologist. “Look for the various stages of the psyllid – small yellow eggs, sesame-seed sized yellow ACP young with curly white tubules, or aphid-like adults that perch with their hind quarters angled up.”
Pictures of the Asian citrus psyllids and its life stages are on the UC ANR website at http://ucanr.edu/acp. If you find signs of the insect, call the California Food and Agriculture (CDFA) Exotic Pest Hotline at (800) 491-1899.
Asian citrus psyllids are feared because they can spread huanglongbing (HLB) disease, an incurable condition that first causes yellow mottling on the leaves and later sour, misshapen fruit before killing the tree. ACP, native of Pakistan, Afghanistan and other tropical and subtropics regions of Asian, was first detected in California in 2008. Everywhere Asian citrus psyllids have appeared – including Florida and Texas – the pests have found and spread the disease. A few HLB-infected trees have been located in urban Los Angeles County. They were quickly removed by CDFA officials.
“In California, we are working hard to keep the population of ACP as low as possible until researchers can find a cure for the disease,” Grafton-Cardwell said. “We need the help of citrus farmers and home gardeners.”
Grafton-Cardwell has spearheaded the development of the UC ANR ACP website for citrus growers and citrus homeowners that provides help in finding the pest and what to do next. The site has an interactive map tool to locate residences and farms that are in areas where the psyllid has already become established, and areas where they are posing a risk to the citrus industry and must be aggressively treated by county officials.
The website outlines biological control efforts that are underway, and directions for insecticidal control, if it is needed. An online calculator on the website allows farmers and homeowners to determine their potential costs for using insecticides.
There are additional measures that can be taken to support the fight against ACP and HLB in California.
- When planting new citrus trees, only purchase the trees from reputable nurseries. Do not accept tree cuttings or budwood from friends or relatives.
- After pruning or cutting down a citrus tree, dry out the green waste or double bag it to make sure that live psyllids won't ride into another region on the foliage.
- Control ants in and near citrus trees with bait stations. Scientists have released natural enemies of ACP in Southern California to help keep the pest in check. However, ants will protect ACP from the natural enemies. Ants favor the presence of ACP because the psyllid produces honeydew, a food source for ants.
- Learn more about the Asian citrus psyllid and huanglongbing disease by reading the detailed pest note on UC ANR's Statewide Integrated Pest Management website.
- Assist in the control of ACP by supporting CDFA insecticide treatments of your citrus or treating the citrus yourself when psyllids are present.
- Support the removal of HLB-infected trees.
- Author: Ben Faber
Recently some 'W. Murcott' mandarins were shown to me. Brown spots in the core of the fruit. Another problem caused by drought and lack of leaching rains? Endoxerosis, also called internal decline, dry core, yellow tip, dry and blossom end decline is often confused with Alternaria rot which frequently accompanies or follows it. Internal tissues back of the stylar end break down, dry and become pinkish or brownish in color. Gum commonly forms in the core and either in or nest to the rind. Green fruits lose luster and frequently but not always develop a yellow color in circular areas surround the stylar end. The cut fru9i shows the gummy pinkish to brownish mass of partially dried and collapsed tissue. Gumming may even extend into the twig bearing the affected fruit. When the fruit turns color, the malady is more difficult to detect without cutting.
The cause is believed to be related to water and the physiological conditions within the tree and fruit and temperature conditions in the air and soil influencing transpiration and water stress. It is suggested therefore that water conditions in the soil be kept as favorable for tree heath as possible and pick on time so that they are not over mature.
From: The Citrus Industry, Volume IV, Editor: Walter Reuther, UC Press
In other words, make sure to leach the root zone of accumulated salts from previous irrigations and pray for rain.
Craig Kallsen in Kern County says he often sees this in young mandarins especially on the south and west sides of the canopy, to the point that growers will not even bother to harvest this fruit until the trees are older. The fruit just transpires so much water when it's not shaded that the fruit just dries out.
If my Latin serves me right: endo - inside, xeric - dry. Dry Inside.
- Author: Ben Faber
Arpaia M.L.; Kahn T.L.; El Otmani M.; Coggins C.W.Jr; Demason D.A.; O'connell N.V.; Pehrson J.E.Jr, 1991: Pre harvest rind stain of valencia orange histochemical and developmental characterization. Scientia Horticulturae (amsterdam). 46(3-4): 261-274
Pre-harvest rindstain of California [USA] cultivar 'Valencia' orange Citrus sinensis has economic significance since fresh fruit marketability is reduced. Quantification of the incidence of rindstain as related to tree quadrant has allowed us to designate quadrants where rindstain was most likely to occur (upper outside SW) or least likely (lower inside NE) to occur. Growth and development characteristics of fruit from the two quadrants were measured throughout fruit development. Significant differences in percent weight loss between fruit from the SW and NE quadrants occurred at color break and at commercial maturity. Structural and histochemical changes in flavedo tissue of fruit from SW or NE tree quadrants were monitored over the course of fruit development and maturation. First evidence of periderm formation occurred in October, coincident with observed changes in histochemical staining for lipids. These differences were increasingly evident as the fruit approached horticultural maturity and visual symptoms of rindstain developed. The development of a pronounced periderm in affected fruit suggests that rindstain is due to a physical trauma, although we do not believe it is caused by wind.
This from Mary Lu Arpaia in response from a Central Valley problem that cropped up recently. Fruit looked on the tree, but after getting it into the packing house, it started showing these symptoms
Here is her summation of the abstract above:
1) Fruit were predisposed to this problem as early as colorbreak. We found this out by doing some elaborate fruit manipulations in the field in the fall and looking at symptoms in the spring.
2) Symptoms really started to appear about this time of year and then progressively worse
3) There was a loose correlation to presence of citrus thrips in the previous year
4) Fruit isolations did not find much of anything but weak saprophytic fungi.
5) At this point, it's not clear what a grower can do to prevent it.
Rindstain on Ruby Red Grapefruit in the Hemet area was noted in the 1990's and the observation there was possible moisture from dew or rain focusing sunlight to cause the condition. So it's not really from even a general observation.
/h2>- Author: Oleg Daugovish
When Richard Smith tells you that he is impressed with efficacy of an organic herbicide you better take notice. Richard shared his results on this blog site last year and showed good weed control with 'Suppress' from Westbridge. This OMRI approved herbicide is a mix of caprylic and capric acids and is a contact material that interferes with plant cells membranes causing leakage and desiccation.
It looked like a good fit for organic plasticulture systems such as strawberry that have wet weedy furrows which are difficult to access with mechanical tools because of proximity to plastic. We placed a trial in a very weedy field that also had one of the SoCal classics–yellow nutsedge. 'Suppress' at 6 and 9% by volume was applied to well-established weeds just before strawberry planting.
The effects of application were noticeable in minutes. We learned that:
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Both 6 and 9% rates provided nearly 100% control of common lambsquarter (predominant species) and other occasional broadleaved weeds.
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About 10-15% of common purslane plants survived and yellow nutsedge seemed unaffected by application. However, biomass of both purslane and nutsedge were significantly reduced, suggesting that production of seed and tubers for the two weed species, respectively, may be delayed.
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Good coverage was important and some of the horizontally–inclined leaves of broadleaf weeds likely intercepted the herbicide deposition to vertically inclined nutsedge shoots.
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When we simulated drift by over-spraying strawberry, it responded just like any broadleaf perennial plant—the canopy wilted and dried but in 3 weeks the new leaves developed from the crown. This was also true for the neighboring bindweed that lost above ground canopy but had new growth within a month after 'Suppress' application.
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Since perennial weeds or those in soil seedbank are not controlled, repeated applications are needed with obvious caution of avoiding the spray drift to the crop.
- Author: Ben Faber
Recently some 'W. Murcott' mandarins were shown to me. Brown spots in the core of the fruit. Another problem caused by drought and lack of leaching rains. Endoxerosis, also called internal decline, yellow tip, dry and blossom end decline is often confused with Alternaria rot which frequently accompanies or follows it. Internal tissues back of the stylar end break down, dry and become pinkish or brownish in color. Gum commonly forms in the core and either in or nest to the rind. Green fruits lose luster and frequently but not always develop a yellow color in circular areas surround the stylar end. The cut fru9i shows the gummy pinkish to brownish mass of partially dried and collapsed tissue. Gumming may even extend into the twig bearing the affected fruit. When the fruit turns color, the malady is more difficult to detect without cutting.
The cause is believed to be related to water and the physiological conditions within the tree and fruit and temperature conditions in the air and soil influencing transpiration and water stress. It is suggested therefore that water condones in the soil be kept as favorable for tree heath as possible and pick on time so that they are not over mature.
From: The Citrus Industry, Volume IV, Editor: Walter Reuther, UC Press
In other words, make sure to leach the root zone of accumulated salts from previous irrigations and pray for rain.
Craig Kallsen in Kern County says he often sees this in young mandarins especially on the south and west sides of the canopy, to the point that growers will not even bother to harvest this fruit until the trees are older. The fruit just transpires so much water when it's not shaded that the fruit just dries out.
If my Latin serves me right: endo - inside, xeric - dry. Dry Inside.