GROWING CITRUS Page 1

GROWING CITRUS IN THE Publication Number 31-018C SIERRA NEVADA FOOTHILLS (March 2010) AUTHOR: Cindy Fake, Horticulture and Small Farms Advisor, Nevada & Placer Counties

Mandarins are the signature Mandarins dominate commercial Meyer lemon (22°F) > oranges - fruit of the Sierra Nevada citrus production in the Navel, blood, etc. (24°F) > foothills. Warm days and cool foothills, but many other citrus grapefruit (26°F)> true lemons nights during the growing species can also be grown. (Eureka, Lisbon) (28°F)>lime season provide near-perfect Navel, blood, and Valencia (30°F). Low temperature conditions for production of oranges, lemons, limes, tolerance depends on many high-quality flavorful fruit, the grapefruit and kumquats are all factors, including tree age, produced commercially in the nutritional status, soil water Mountain Mandarin®. Recent research has also revealed that foothills. Microclimates created status, acclimatization, and fruit mandarins contain significant by foothill topography also maturity, among others. These amounts of synephrine. allow production of more exotic temperatures are guidelines, Synephrine is a natural citrus species such as pommelo, given to assist in selecting antihistamine, which can shaddock, limequat, appropriate species. All of the alleviate the symptoms of colds calamondin, and yuzu. Not all citrus species cited can and allergies, so mandarins are varieties can be grown in all successfully be grown in the also health foods. microclimates, however. For right microclimate of the lower more information on citrus foothills. Commercial mandarin varieties, see UCCE Publication production flourishes in the 16C: Citrus Varieties for the foothills at elevations from 400 Foothills. to 1000 feet. Most of the Eco-requirements production is Owari Satsuma for citrus production mandarins: sweet, seedless, zip- skin fruit. A few other varieties Site Selection of Satsumas and some The best sites for citrus are ridgetops or south-southwest Clementine mandarins are also Citrus are subtropical in origin, produced. facing upper slopes, with good thus the cold temperatures cold air drainage. Impediments which occur occasionally in the to cold air drainage such as foothills can pose significant risk vegetated fence lines, brush, of frost and freeze damage. blackberries, or hills may cause Tolerance to cold temperatures cold air to back up and damage varies among the citrus species. the orchard. Mandarin is among Kumquat (18°F) is hardier than the most cold-hardy of citrus, Satsuma mandarin (20°F) >

COOPERATIVE EXTENSION, UNIVERSITY OF CALIFORNIA Placer County WEB SITE: ceplacernevada.ucdavis.edu Nevada County The University of California prohibits discrimination or harassment of any person in 11477 E Avenue, DeWitt Center The University of California, in accordance with applicable Federal and State law and University 255 So Auburn Street. any of its programspolicy, does or not activities.discriminate on the (Complete basis of race, color, nondiscrimination national origin, religion, sex, disability, policy age, statement can Auburn, California 95603 medical condition cancer.related., ancestry, marital status, citizenship, sexual orientation, or status Grass Valley, California 95945 be foundas a Vietnamat http://groups.ucanr.org/ANR_AA/files/54634.pdf)..era veteran or special disabled veteran. Inquiries regarding the University’s nondiscrimination policies may be directed to the Affirmative Action Director, University of California, 530.889.7385 Direct inquiriesAgriculture regarding and Natural Resources, the University’s 1111 Franklin, 6th Floor,nondiscrimination Oakland, California 94607 .5200.policies 510. to the Af- 530.273.4563 FAXUNIVERSITY 530.889.7397 OF C ALIFORNIA COOPERATIVEfirmative Action E Director,XTENSION University 987.0096. of California, ANR, 1111 Franklin St., 6th PLACER & NEVADAFAX 530. COUNTIES273.4769 United States Department of Agriculture, University of California, Placer and Nevada Counties E.Mail: [email protected] Floor, Oakland, CA94607,cooperating. (510) 987-0096. E.Mail: [email protected] GROWING CITRUS Page 2 however, elevation does limit For home plantings of a few foothill soils, as long as they are production. In general, the upper trees, planting next to south- on slopes or soils that drain well. limit for citrus orchards is about facing cement or stone walls or a Clay soils have smaller pore 1,200 feet elevation. patio can mitigate the risk of spaces and absorb more water cold. The stone or cement than granitic soils, so the danger In some areas, absorbs heat during the day, and of waterlogging is greater. Citrus foothill reradiates it back at night, do not tolerate waterlogged roots topography protecting the trees. In marginal and are susceptible to creates zones, containerized trees in wine Phytophthora root disease when locations barrels or tubs can be moved they are overirrigated. Do not where next to south facing walls, or plant citrus in lawns or in areas temperatures indoors for protection in cold which become saturated with are much more weather. winter rains. Plant in raised beds moderate than or mounds if waterlogging is a one would expect for a given If you are interested in planting risk. elevation. These are the so-called mandarins in the foothills, but “banana belts” or warm are unsure of the suitability of Foothill soils typically have low microclimates where citrus your property, it is best to collect native fertility and organic production may be possible temperature data for your matter. Many foothill soils are above 1,200 feet. Citrus particular site for at least a year. clay or decomposed granite and production may also be possible Purchase several maximum/ quite acidic (pH <7). At lower at higher elevations in an area minimum thermometers and elevations, there are more neutral where frost risk is moderated by place them around your and slightly alkaline soils. Citrus a large body of water, pavement, property, especially up and down grow well in slightly acidic soils, or warm upwinds from a canyon slopes, to gauge where cold air but a very acidic soil (below pH or lower elevation. backs up the slope. Record 6) will need to be amended with minimum temperatures lime to correct pH. Citrus require full sun for throughout winter and spring, at flowering and fruit production. A least on a weekly basis. An analysis by a professional soil citrus orchard should be as laboratory is recommended sheltered as possible from strong Soil Conditions before planting. Your winds. Mandarins, in particular, amendment and fertilizer should be protected from winds, Citrus are shallow-rooted trees. program will depend on the without impeding cold air Feeder roots are in the top two results of your soil tests. In order drainage. Their thin rind is feet of soil, with most activity to avoid costly errors, it is best to susceptible to damage from wind occurring in the top 12 inches. use a commercial lab rather than and wind-driven rain from winter Deep soil is not necessary for home soil test kits. See UCCE storms and damage is successful production as the publication 74C: Soil Analysis for exacerbated by cold majority of commercial information on area soil weather. Sites offering mandarins in Placer County are laboratories and analyses. protection from wind will also grown on 18 inches of soil or less. increase the available heat for You will need a number of the trees in frost/freeze events. Citrus do not require deep soils, standard soil tests to provide a but they do need well drained baseline for your soil soils. They will grow well on most management program. Most labs

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION ceplacer.ucdavis.edu GROWING CITRUS Page 3 have a basic package, which future, so it is best to start with for container citrus, but not for provides a good baseline. You high quality planting stock. production orchards. Carrizo should have your soil analyzed rootstock is sometimes used in for: Citrus grown for fruit the foothills, producing high production are almost quality fruit, but later in the  pH: acidity or alkalinity exclusively budded trees. Very season. Carrizo does not impart  soil nutrient status: at N, P, few citrus are grown on their quite as much cold tolerance as K at a minimum; Ca S, Zn, B own roots because they are not Trifoliate, however. Older trees and Fe are recommended. as productive as those grown on are often on Cleopatra rootstock. rootstocks. Budded trees will However, Cleopatra has no  CEC (Cation Exchange consistently produce the same dwarfing characteristics, and Capacity), a measure of true-to-type fruit. Very few trees will become very large, so native fertility citrus fruit produce seed that it has fallen out of use.  organic matter will come true to type. Planting a seed from a citrus fruit rarely The valley citrus industry  ppm (parts per million) of gives you a tree that produces standard is a rootstock called C- Ca, Mg, K, and Na (base the same fruit, and without a 35. It is preferred there because saturation %) rootstock, it will probably be a it begins to bear earlier than  Ca: Mg ratio weak tree. trees on Trifoliate rootstocks. Some foothill orchards are on C- Use a California lab to get Rootstocks 35, however, it has a number of accurate information. If you drawbacks for the foothills. C-35 inform the lab that you will be Each citrus does not provide as much cold planting citrus, they can provide tree has two resistance, and young trees are recommendations on the parts: the often severely damaged by frost. nutrients or amendments rootstock and The C-35 rootstock is very needed. Most labs will give the scion. The vigorous and overgrows the guidance on organic rootstock is a scion, reducing the longevity of amendments, if you specify that species selected for specific the orchard. In addition, the it is organic. For more characteristics, such as disease consensus among foothill information on organic resistance or tolerance of certain growers is that C-35 fruit are not amendments, see UCCE soils. Rootstocks used in the as sweet as those on Trifoliate. publication 72C: Organic foothills are selected for cold Amendments. tolerance and for size control. Rootstocks are usually grown from true-to-type seed Certified Planting Stock Two rootstocks, of the species (available from some nurseries). Poncirus trifoliata, are very well After a year or so, a bud from a Citrus are very long-lived trees, adapted to foothill conditions. often producing for 50 years or certified mother tree of the These Trifoliate rootstocks are specific cultivar (named variety) more. Placer County has Rich 16-6 and Rubidoux, both productive trees that are more of desirable fruit is attached to of which provide cold hardiness the rootstock and the top of the than a century old, and several and are semi-dwarfing. Another major orchards are over 60 years rootstock plant is cut off. The Trifoliate rootstock, Flying two plants are allowed to grow old. Planting a citrus tree is a Dragon, has a greater dwarfing long-term investment in the together and they become the effect (~75%) and is well suited citrus tree.

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION PLACER & NEVADA COUNTIES GROWING CITRUS Page 4

It is important to buy certified tree for your yard, please do not While good land preparation can citrus trees from a reputable bring any citrus from another be somewhat costly, your nursery, even if you only intend state or country. The health of orchard and the quality of your to plant a couple of citrus trees the California citrus industry fruit will suffer in the long run for home use. A reputable depends on abiding by from the lack of soil preparation. nursery will sell trees that are quarantine laws. Poorly prepared ground can certified disease-free and true-to- result in water stress and type. If you are intending to Preparing the Soil and Cover irrigation issues for the life of the plant an orchard, it is best to use Cropping orchard. Giving your plants the a specialty citrus nursery which best possible opportunity to sells to the industry. A If you are planting more than a establish themselves will result in commercial citrus nursery will couple of trees, it is a good idea a long, productive life. not only guarantee certified, true to find out how deep your soil is -to-type plants, but the quality and whether or not there is a Once your soil is prepared, and longevity of the trees will be hard pan. The soil survey, establish a cover crop, especially much better. For many of the available on line (http:// if you are not planting varieties used in commercial websoilsurvey.nrcs.usda.gov/app/ immediately. A cover crop is production in the foothills, trees WebSoilSurvey.aspx or in typically a grass or grass and need to be budded to order. Natural Resources Conservation legume mix, It is used to stabilize Service (NRCS) offices, can give soil, add organic matter, and in you some basic information the case of the legume, fix about your soil. The best way to nitrogen. A cover crop will find out about your soil is to dig protect your soil from erosion in some holes 6 feet deep or more winter rains and can significantly with a backhoe. Many foothill increase soil organic matter and/ soils are layered and you will be or soil nitrogen, depending upon If you buy citrus trees outside of able to see the layers and what is planted. It may also your home county, your County whether a hard pan exists or not. facilitate rainy season work. Seed Ag Commissioner must inspect mixes appropriate for the them before you plant. Citrus can Land should be prepared by foothills are available from local carry many disease and insect ripping before laying out and farm supply stores. All foothill pests, and you could unwittingly planting the orchard. Ripping orchards should have vegetative be bringing in a new pest. There the soil in several directions is cover on the soil. Bare soil and are quarantines between essential in clay soils or if there is intense winter rainfall result in California counties and County a hard pan. It opens up the soil, significant erosion and soil loss in Ag Commissioners have the allowing roots to penetrate and a very short time. Once lost, soil authority to order trees water to drain through. Ripping cannot be replaced. destroyed that do not meet local is particularly critical for citrus quarantine standards. Citrus because of their sensitivity to Plant spacing & planting cannot legally be brought into waterlogging. If possible, add California from other states amendments such as lime or Citrus tree spacing and layout without going through compost before ripping so as to vary greatly in the foothills. If quarantine procedures because of incorporate them. you are planting an orchard, the danger to California’s citrus spacing will depend on several industry. Even if it is only one factors: the species and rootstock,

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION ceplacer.ucdavis.edu GROWING CITRUS Page 5 the degree of slope, the turning The best time to plant citrus is in limit between the trunk and roots radius of your tractor or other springtime, after danger of frost and make sure it is not below the equipment, and your pruning has passed, but well before hot soil line. Trees planted too low or and training plan. Common weather. Planting citrus in in a depression will not thrive. spacings in the foothills range March and April, when the soil is After planting, compost or mulch from 12 to 18 feet. Generally, 10 moist, gives the trees an may be spread on the surface of feet between trees in the row and opportunity to establish roots the soil along the tree line, but 12 feet between rows is adequate before the heat of summer. keep it at least 2-4 inches away for small trees such as mandarin Citrus may be planted in the fall, from the trunk. and Meyer lemon, if they are on a but usually it is better to wait semi-dwarfing rootstock such as until spring as young trees will be Using compost or mulch on the Trifoliate and pruned to easier to protect from frost surface of the root zone creates maintain small size. Oranges and damage in containers. healthy soil conditions for the grapefruit need a minimum of 12 trees. It helps maintain soil feet between trees and wider is Dig each tree hole no deeper than moisture, reduces weed growth, better. the container and twice the and keeps roots cooler in the width. Auguring tree holes in summer, reducing the stress on Orchards are often laid out in clay soils is not recommended, the tree. In addition, it adds north-south lines to facilitate because the augur creates a organic matter, beneficial capturing sunlight. The foothills smooth surface that makes it microbes, and some nutrients to do not have a shortage of difficult for roots to grow out of the soil. Compost or mulch sunlight, but do have slopes. Flat the hole. If you do augur the should be renewed on an annual ground sufficient for an orchard holes, make sure the surfaces of basis for the life of the tree. is not common, so the direction the hole are roughed up before of the slope is much more critical planting the tree. Protect young trees from to row direction than compass sunburn by whitewashing the directions. Generally, it is safer Do not amend the soil in the trunk with a 1:1 solution of white to drive a tractor up and down planting hole with fertilizers or interior latex paint and water. the slope than across the slope, so manures. Plant on a mound or in Paper trunk bands can also it is important to plan your raised beds if soil drains slowly or protect young trunks. orchard layout according to the contains heavy clay. Keep the slope. rootball as intact as possible Frost/Freeze Protection when planting the tree. If the trees have been in containers a Damage to citrus from cold long time, they may have circled temperatures usually occurs in or kinked roots. If that is the early winter (December) before case, make a small mound in the the tree is completely hardened bottom of the hole. Unwind the off. Mature mandarin trees can roots and spread them over the withstand temperatures below mound, ensuring that tips point 20°F; although leaves and green downward. wood will die if temperatures remain at that level for any After planting, trees should not length of time. Fruit are much settle deeper than the level they less cold hardy than the woody grew in their containers or in the parts of the trees and are usually nursery. Look for the crown, the damaged at 26°F, or higher if it

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION PLACER & NEVADA COUNTIES GROWING CITRUS Page 6 remains cold for a long period. For small trees, covering them Learn about your trees’ water use Trees with fruit are less cold- with burlap, rowcover, or plastic by digging shallow holes on the hardy than trees without fruit. may be feasible. The cover edge of the root zone and seeing should entirely cover the tree, how long it takes the soil to dry Young trees (1-3 years old) are but not touch the foliage. Plastic after an irrigation. There are much more susceptible to frost that touches the foliage may many useful tools for monitoring and freeze damage than older actually cause more damage soil moisture, including matrix trees. They may be killed to the because of condensation and blocks and tensiometers, but they bud union in a cold year, if left subsequent freezing that can need to be backed up by unprotected. Leaves and green occur. Remove the cover after firsthand knowledge of the soil wood may be lost in a single temperatures rise each morning. conditions in different sections of incident, but trees usually come Strings of small incandescent the orchard. back after a minor freeze. In lights can be used to protect general, flowers are the most single trees. As subtropicals, citrus trees can sensitive to cold, followed by be stressed by hot, dry foothill fruit, leaves and wood. summers, thus, it is important to keep trees adequately watered. Planting in an area with frost When temperatures above 95ºF hazard requires a plan for frost are predicted for several days, protection. In the past, overhead trees should be irrigated in sprinklers were used for frost and advance of the heat. Keep root freeze protection. However, they systems moist but not saturated. require a lot of water: adequate A saturated soil has all its pore to run 24/7 over the entire Tree Care spaces filled with water, which orchard for the duration of the deprives the roots of oxygen. freeze. More damage can occur if Irrigation the sprinklers are shut off In cold, wet springs, citrus trees prematurely than if the trees are Monitor the soil around newly may turn yellow and look sickly. left unprotected. The weight of planted trees to determine when This occurs because roots are not the ice may also cause damage. to water. When soil begins to dry able to function in cold, wet soils. in the top 6-8 inches, trees need The tree is not able to take up With less water available for to be watered. Young trees have the nutrients it needs, especially agriculture, most orchards have a limited root volume, so it is nitrogen, so it uses up internal moved away from overheads to important to irrigate often with reserves, causing chlorotic microsprinklers (microjet, small amounts of water. (yellow) leaves. Typically, the microspray), which use a much Frequency of irrigation is problem resolves itself as the soil lower volume of water. determined by soil type and by warms and dries. If it does not, Microsprinklers can offer several weather conditions, but generally then consider installing drains in degrees of frost protection. They will be several times a week for the orchard or moving the tree to also must continue to run for the young trees. In time, roots will a location with better drainage. duration of the freeze event. If expand and have a greater area running irrigation for such long from which to extract water and Fertilization periods is not feasible, saturating nutrients, and intervals between the soil before the freeze event irrigations will increase. Citrus are not heavy nutrient will offer the best protection. users, but they need adequate nutrition for quality fruit

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION ceplacer.ucdavis.edu GROWING CITRUS Page 7 production. An effective fertilizer Most orchards need annual growth flushes which are more program is initially based on soil applications of nitrogen and zinc, susceptible to frost and freeze information, and subsequently and many need micronutrients damage. on leaf tissue analysis. For more such as manganese, boron, or information on nutrient iron. In acid foothill soils, Nitrate forms of nitrogen are management programs, see phosphorus may also be needed, recommended for use on acid UCCE publication 11C: and potassium is sometimes soils in the foothills, as Fertilizing Citrus in the Foothills. needed as well. Soil and tissue ammonium fertilizers can further analysis should be used to match acidify the soil. For the first year, the nutrient management about two ounces of actual program to your trees’ specific nitrogen per tree are needed. The needs. second year, ¼ pound actual N per tree; ½ lb. in the third year; Nitrogen is a critical nutrient for and ¾ pound in the fourth year. citrus, but often overapplied. Young trees do not have well Overuse of nitrogen adversely developed root systems, so a slow affects fruit quality and may release form should be used or Leaf tissue analysis is the best contribute to susceptibility to the nitrogen should be split into 4 tool for determining tree nutrient frost and insect damage. It is to 6 applications from March status. An accurate assessment of important to match N through July. plant, rather than soil, nutrient applications from all sources to status will identify deficiencies so actual tree needs, as the trees From the fourth year on, trees they can be corrected. Such an grow. If a legume cover crop is require about 1 pound actual analysis may indicate nutrient used, the nitrogen provided by nitrogen per tree per year. Actual levels above or below optimal the crop should be included in N can be found by multiplying levels, but symptoms may not the fertilizer balance sheet. the percent N in the material by yet be visible. Starting in the the weight of the material. For fourth year, samples should be The majority of nitrogen example: Calcium nitrate (15.5-0- taken every other year in the fall applications should occur in 0) contains 15.5% N. Thus, a 20 and analyzed for nitrogen, spring, as the highest plant needs pound bag (.155 x 20 = 3.1) phosphorus, potassium, zinc, for N occur from bloom through contains about 3 pounds of manganese, and boron. June. Start applications after actual N. So, that 20 lb. bag will heavy rains have tapered off. serve for 3 mature trees or 12 two Nutrient management for foothill Nitrogen is mobile in the soil, year old trees. citrus typically combines the use especially soluble forms, so much of compost or composted manure of it will be lost to runoff and Synthetic forms of nitrogen have with soil or foliar applications of leaching if applied during winter become increasingly expensive in specific nutrients. Increasing rains. Slow release forms are recent years, so growers have organic matter with compost more expensive, but may be more begun to rely on cover crops and helps keep applied nutrients in convenient for small orchards. composts. Some legume cover the root zone to be released as the crops in pure stand can fix up to trees deplete the soil solution. Nitrogen applications should be 250 pounds of N per acre, which Legume cover crops may also completed by late July or early is far more than a citrus orchard contribute nitrogen. August. Later applications may needs. If you plan to use cover affect fruit quality. Late summer crops to provide a portion of your or fall applications promote fall nitrogen, the UC SAREP Cover

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION PLACER & NEVADA COUNTIES GROWING CITRUS Page 8 crops database at http:// uptake, so any fertilizer program Fruit needs sunlight to develop www.sarep.ucdavis.edu/ccrop/ should be based on soil and tissue flavors and sugars. Dense has all the information you need. sampling, not on a standard canopies may not allow enough Compost nutrient content is recommendation. sunlight to reach fruit, so completely dependent on the thinning is needed every few feedstock that went into the Pruning years. A good judge of canopy compost, so each batch needs to density is whether or not you can be tested for nutrient content. Citrus are see dappled sunlight on the evergreen trees, ground underneath the tree at Although foothill soils may thus require less midday. contain adequate phosphorus, it pruning in may not be available to plants, general than There are relatively few citrus and thus phosphorus may need deciduous trees. However, they insect pests in the foothills, but to be applied annually. do need pruning. Young trees most of the problems are caused Phosphorus deficiency may should be topped at planting if by soft bodied insects such as reduce marketable yield as they are tall and spindly to scale. Scale insects, especially deficient trees produce more fruit promote side shoots which will Citricola scale, thrive in dense with thick, coarse rinds and lower develop into a lower, fuller canopies with high humidity and juice content. Potassium canopy. The shorter the tree little air movement. Thinning the deficiencies do occur in the remains, the easier and more cost canopy can significantly reduce foothills as well. Potassium helps effective it is to harvest. scale populations to the point maintain rind integrity and that insecticide sprays are improves sugar acid balance and Any shoots below the bud union unnecessary. flavor in fruit, so some growers should be removed as they apply foliar potassium as fruit appear. Often, water sprouts or Pest Management are maturing. gourmands, which are long, thick, very vigorous branches, Foothill citrus generally have Zinc and manganese are usually will appear in the canopy. These fewer insect and disease pests applied on an annual basis in branches often remain vegetative than other areas with high spring foliar sprays. Iron may for a number of years, density citrus plantings. also be needed, especially in areas contributing little to the However, there are still some key with drainage issues. Do not productive capacity of the tree, pests that affect orchard vigor apply boron unless soil tests and so they should be removed. and productivity. California- tissue analysis show that it is specific information on citrus deficient. The range between Mandarins, in particular, tend to pest management is available at deficiency and excess is very have pendulous branches that http://www.ipm.ucdavis.edu/. narrow, and excess boron can hang to the ground. These are There are separate sections with damage trees. called skirt branches, and they recommendations for backyard can impede weeding, fertilizer and commercial orchards. Pest Some or all of these nutrients and compost application, and management information from may be required in foothill citrus provide pathways for ant other states is not reliable as we orchards. However, soil depth, populations to use the trees. do not have the same pests and nutrient and organic matter Trees should be skirted up every California restricts the use of content vary greatly, even in the couple of years as needed. many pesticides. same orchard. Rootstock and soil moisture also influence nutrient

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION ceplacer.ucdavis.edu GROWING CITRUS Page 9 Gophers can be very such as trees in lawns, these not importing infested citrus destructive in young insects can become problems. fruit or leaves from other orchards. Citrus Mites are very rare in citrus in counties will prevent further roots are not a the foothills, and if they become introductions. Most growers do preferred food, a problem, it is usually a result of not spray for red scale. Natural however, they can cause serious broad spectrum pesticide use or enemy releases are more effective root damage just by tunneling poor irrigation management. and environmentally friendly. through the orchard. Baiting or Commercial mandarin growers trapping can be very effective, if Scale insects are the major insect and a few homeowners cooperate the grower is vigilant and acts pest for most growers. Effective to release Aphytis wasps, a tiny every time a new mound is water and nitrogen management, parasitic wasp specific to red found. Some dogs and cats can be good pruning practices, and scale, each spring and fall. The very effective gopher hunters, controlling ants can prevent most cooperative releases cost about but it is difficult to predict. Most scale problems. There are two $12-15 per acre per release, with other popularly described major scale pests, Citricola and 6-10 releases per year, so they are methods are not effective, California red scale; and several very cost effective. If you wish including propane guns. minor ones, black scale and to participate in Aphytis releases, brown soft scale. Citricola scale is please contact the UCCE Placer Citrus may be affected by a the most common pest issue in County office. variety of insect pests — scale, the foothills. In most years, aphid, mite, thrips, and populations can be managed with Asian citrus psyllid (ACP) has mealybug. However, a well pruning. However, periodically not yet reached foothill orchards, managed orchard with a healthy populations can get out of however, it is the subject of natural enemy population can control and pesticide applications major eradication and quarantine keep most of these insects in may be necessary. Typically efforts in Southern California. balance. Natural enemies are horticultural, neem, or stylet oils ACP can damage citrus trees by insects which prey on or are adequate for population feeding, but its major threat is parasitize insect pests. In the control. Ant populations should that it carries Huanglongbing, a foothills, we have high never be allowed to develop in disease that is deadly to citrus. populations of a variety of trees. Ants not only prey on Many Florida orchards are now natural enemy species. natural enemies but actually affected, and some has been Flowering cover crops and farm and protect honeydew- found in Mexico as well. hedgerows that flower before secreting pests. Skirt prune lower Huanglongbing, if allowed to orchards can provide food and branches to prevent movement of spread, will devastate California’s habitat to encourage natural ants into the canopy, and, if citrus industry. There is no cure enemy populations. Use of broad necessary, use sticky bands and it kills trees in just a few spectrum pesticides will around trunks. years. adversely affect natural enemy populations, and may flare pest California red scale is the other ACP, Huanglongbing, and populations. major scale pest. It has been another disease called Tristeza introduced on nursery stock in are the primary reasons not to Commercial orchards in the recent years, and become bring citrus from other areas into foothills rarely have problems established in a few orchards. the foothills without appropriate with aphid or mealybug. If citrus Inspection of planting stock by documentation and inspection by are overfertilized with nitrogen, the County Ag Department, and the County Ag Department.

UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION PLACER & NEVADA COUNTIES GROWING CITRUS Page 10 Please respect all quarantine office for more information. If citrus/ UC Riverside Citrus regulations. you intend to be a commercial Variety Collection grower, plan to join the http://lib.ucr.edu/agnic/webber/ There are few diseases in foothill Mountain Mandarin Growers orchards. Phytophthora is a Vol1/Vol1TP.html The Citrus Association http:// Industry Vol. 1. pathogen that is ubiquitous in www.mountainmandarins.com/. the foothills. However, it only http://ucanr.org/sites/ becomes a problem when citrus placernevadasmallfarms/Crops/ roots are kept too wet. Citrus/ UCCE Placer/Nevada Maintaining good soil drainage, Mandarin production avoiding overirrigation, and information using recommended rootstocks UCCE Placer/Nevada citrus will prevent disease problems. publications: Weeds can be a major issue in The resources listed were used in Citrus Nurseries in citrus orchards. Young trees preparation of this document and California. UCCE Placer/ have limited root systems, thus it may be helpful in planning and Nevada Publication #10C. is critical to keep weeds away managing your citrus orchard. Fertilizing Citrus in the from the root zone. Mulch can Foothills. UCCE Placer/ References & Resources help diminish weed growth, but Nevada Publication #11C. some weeding around the base of the trees is necessary. Weeds can Citrus. 2003. F.S. Davies and Mandarin and Citrus be controlled mechanically with L.G. Albrigo. CABI Publishing. Information on the weed whackers, mowers, or other UK. Internet. UCCE Placer/ equipment. However, citrus Citrus: Complete Guide to Nevada Publication #12C. bark is thin and easily damaged, Selecting and Growing More Citrus Pest Management so it is important to take care than 100 Varieties. 1996. Lance Summary Sheet. 2008. weeding close to trunks. Walheim. Ironwood Press. UCCE Placer/Nevada Herbicides may be used for strip Tucson, AZ. Publication #13C. spraying on orchards, but be Citrus Growing in the careful to choose sprays labeled Citrus Tissue Sampling. 2008. Sacramento Valley. 1977. UC for citrus and appropriate to the UCCE Placer/Nevada ANR Leaflet 2443. age of the trees and stage of the Publication #14C. weeds. Disking is not The Cultivar. Vol. 14, No. 1. Avoiding Cold Damage to recommended in foothill citrus University of California, Santa Citrus. 2009. UCCE Placer/ orchards because of the damage Cruz. Winter 1996. Nevada Publication #15C. to soil and subsequent erosion. Micronutrient Deficiencies of Citrus Varieties for the Citrus. 1981. UC ANR Foothill citrus production can be Foothills. 2009. UCCE Publication 2115. a profitable enterprise. However, Placer/Nevada Publication being a successful grower requires Protecting Citrus from Cold #16C. Losses more than production skills, it . 1979. UC ANR Organic Amendments. UCCE also involves marketing and Publication 2372. Placer/Nevada Publication business skills. UC Cooperative http:// #72C. Extension offers assistance with www.citrusvariety.ucr.edu/ both. Contact your local UCCE

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