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Peaches in California


  1. Production Facts

  2. Production Regions

    There are two major growing regions in California. The San Joaquin Valley (Fresno, Kings, Merced, Tulare, Kern, Madera, Stanislaus, San Joaquin Counties) and the Northern Region (Solano, Sutter, Yuba, Placer, Butte and El Dorado Counties). (8)

  3. Cultural Practices

    Deep, fine-sandy loam soils with good internal drainage and freedom from alkali or salinity are best for optimum peach growth and production. Peach trees will not produce commercially acceptable crops under arid California conditions without supplemental irrigation wafer. Most peach orchards are furrow or flood-irrigated. Semi-nocultivation is widely used in California in mature peach orchards. This entails a herbicide-treated berm in the tree row with weeds in the row middles being controlled by cultivation. Fruit thinning is an annual practice and hand labor is preferred over mechanical or chemical options. (8)

  4. Insect Pests

    1. San Jose Scale (SJS):

      A serious pest of peaches and causes economic losses every year. The adults, which feed on limbs, twigs, and fruit, are small, circular, and gray. If the shell-like cover is removed, a bright yellow female body is exposed. Young scale crawlers emerge from beneath the shell and move to the fruit where they cause spotting and pitting. High populations may seriously weaken or kill fruiting branches and main limbs, thus causing permanent injury to mature trees. (6,7)


      Narrow Range Oils, Applied to 97%1 of acres. Application during the dormant season provides partial control; use for light infestations only. Oils are an option for orchards where bloom sprays of Bacillus thuringiensis are planned for control of caterpillars. (4,6,7) Diazinon (50WP), generally a dormant spray but is sometimes applied postbloom. Applied to 48%2 of the acres by ground at an average rate of 2.5 lbs. active ingredient (a.i.) with a 21-day PHI. There have been documented cases of San Jose Scale resistance. (5,6,2,7,9)

      Carbaryl (Sevin) WP, generally a dormant spray but is sometimes applied postbloom. Applied to 8%3 of the acres by ground application at an average rate of 3.5 Ibs. a.i. per acre and has a 1-day PHI. It will cause mite outbreaks. (6,7,4,9)

    2. Oriental Fruit Moth:

      This is a serious pest in California. There are usually five generations per year in California, although a sixth generation has been observed in years with warm weather in early spring. They overwinter as mature, diapausing larvae inside tightly woven cocoons in protected places on the tree or in the trash near the base of the tree. In early spring, pupation takes place inside the cocoon and adults begin emerging in February or early March. Eggs are deposited on newly emerged shoots and the larva feed in terminals where they complete their development. Larvae cause damage by feeding on developing shoots and fruits. The most severe damage occurs where larvae feed on fruit, causing it to be rated off grade. (7,9)

      Biological Control - effective oriental fruit moth control can be achieved with pheromone dispensers. However, this is the least popular control method mainly due to costs. (7,9)

      Mating Disruptants, applied just before first moth emergence in spring. Replaced at the beginning of the second flight or in three months, whichever occurs first. Two current products are Isomate M at a rate of 400 dispensers (1-4/tree) and Checkmate OFM at a rate of 108 dispensers (1/tree). These are applied by hand labor. (6,7,9)


      Azinphosmethyl (Guthion) 5U WP, is applied to 7%4 of the acres by ground at an average rate of 1.75 Ibs. a.i. per acre with a 21-day PHI. Resistance has occurred in some orchards in the Sacramento Valley and in the northern San Joaquin Valley. (7,4,9)

      Phosmet (Imidan) 50WP, is applied to 15%5 of the acres by ground at an average of 2.5 Ibs. a.i. per acre with a 14-day PHI. Timing is critical, may not control heavy populations. (4,7,9)

      Permethrin (Ambush), is applied to 27% of the acres by ground at an average rate of .05 lb. a.i. per acre. There should be caution when using permethrin because of potention secondary pest problems. (4,7,9)

      Diazinon (50WP), is applied to 48% of the acres most of which is a dormant application. It is applied by ground at an average rate of 2.5 Ibs. a.i. per acre with a 21-day PHI. Timing is critical; may not control heavy populations. Resistance is suspected but has not been documented. (6,7,4,9)

      Carbaryl (Sevin) 50WP, applied to 8% of the acres by ground at an average rate of 3.5 lbs. a.i. per acre with a 1-day PHI. Use of this product will cause mite outbreaks. Not recommended for routine use. (4)

    3. Lygus Bugs:

      This pest is not considered a major problem but it can be if neighboring fields contain crops which are host to Iygus bugs. In general adult Iygus bugs are about .20 to .25 inch long L. hesperus adults vary from yellowish to reddish brown and the adults of L. Elisus are pale or yellowish green. Lygus bugs overwinter as adults in plant debris, in the crown of plants on the orchard floor, and in uncultivated areas outside the orchard. As temperature rises, Iygus adults migrate to irrigated areas where mating occurs. It is believed adults are chicfly responsible for damage to fruit orchards. There may be as many as six to ten overlapping generations per year. Damage by Iygus bugs can be either to the growing shoot tips which can cause them to die or the fruit which can cause them to be misshaped. Fruit damage is sporadic and doesn't occur every year; however, in some years severe economic losses can occur. In general, Iygus bug populations are highest in years where there is loss of lush vegetation growing in and around the orchard. (6,7)

      Cultural Practice

      Cover crop manipulation is important in lygus management. Clean cultivation or a weed free orchard floor in lieu of a cover crop will aid in suppressing lygus. (7)

      Formetanate HCL (Carzol) 92SP, applied to 2% of the acres by ground at an average rate of .751b. a.i. per acre with a 21-day PHI. (6,7,4)

      Methomyl (Lannate), Applied to 1% of the acres by ground at an average rate of .80 lb. a.i. per acre with a 4-day PHI. Was used in the past as a clean-up material but the reentry interval has been changed to 4 days so it no longer is used for this purpose. (6,7,4)

    4. Peach Twig Borer (PTB):

      Adult peach twig borer moths are .3 to .4 inch long with steel gray, mottled forewings. The bluntly oval eggs are yellow white to orange and are laid on twigs, leaves, or on the fruit surface. They overwinter on the tree as a first or second instar larva within a tiny cell, called a hibernaculum, usually in crotches of 1 - to 3-year old wood, in prunings wounds, or in deep cracks in bark. Larvae emerge in early spring, usually during the bloom, and migrate up twigs and branches where they attack newly emerged leaves and shoots. First generation larvae usually develop in twigs during May and June and give rise to the next flight of moths in late June or early July. Larvae from this and subsequent generations may attack either twigs or fruit. Shoot damage is most severe on young developing trees because feeding kills the terminal growth. As fruit matures, it becomes highly susceptible to attack; damage is most likely to occur from color break to harvest. (7,4)


      Biological control - PTB has about 30 species of natural enemies. Among those commonly found in California are the chalcid wasps, Paralitomastix varicornis and Hyperteles lividus, and the grain or itch mite, Pyemotes ventricosus. In some years these natural enemies destroy a sign)ficant portion of larvae, but by themselves they generally do not reduce PTB populations below economically damaging levels. (7)

      Bacillus thuringiensis, applied to over 50% ofthe peach acres by ground only during bloom; the first at popcorn or early bloom and the second 7-10 days later, but no later than petal fall. Good coverage is essential. Precede this treatment with an oil spray during the dormant season to control SJS and European red mite eggs. The most effective way to control PTB is to apply a dormant spray of an organophosphate insecticide plus oil to kill overwintering larvae in the hibernacila. All of the organophosphate and oil treatments listed for the SJS are effective for PTB plus the following additions. (6,7)

      Diazinon or Methidathion and Oil, are often applied during the dormant season. (6,7)

      Chlorpyrifos (Lorsban) 4EC, applied to 5% of the acres by ground at an average rate of 1.9 Ibs. a.i. per acre. Chlorpyrifos can only be applied during dormant or delayed dormant period. Meat or dairy animals can not graze in treated orchards. (7)

      Narrow Range Oils, applied to 97% of the acres during the dormant season. Applied at various application rates depending on the product. (6,7,4)

      Azinphosmethyl, (Guthion) 50WP, applied to 7% of the acres by ground at an average rate of 1.75 Ibs. a.i. per acre with a 21-day PHI. This is a postbloom application. (4,7)

      Diazinon, is applied to 48% of the peach acres for various different pest. It is applied after the dormant season by ground at an average rate of 2.5 Ibs. of a.i. per acre with a 21-day PHI. (4,6,7)

      Phosmet (Imidan) 50WP, applied to 15% of the acres by ground at an average rate of 2.5 Ibs. a.i. per acre with a 14-day PHI. This is a postbloom application. (4,7)

    5. Spider mites: This is not a serious pest problem in California. Pacific and two spotted spider mites overwinter as adult females in protected places on the tree or in the litter, trash and weeds on the orchard floor. Mites become active in early spring and begin feeding on weeds or in the lower part of the trees. Both species are favored by hot, dry conditions, and as the weather becomes warmer, they increase in numbers and move up the center of the tree until the entire tree is infested. Peaches can tolerate some mite damage, particularly on water sprouts in the center of trees. Feeding by both species causes a mottling of the leaves, and under severe conditions can cause heavy leaf drop. If defoliation happens early in the season, fruit fails to size properly and limbs and fruit may be exposed to sunburn. (6,7,9)

      Cultural Practice

      Keeping orchards well irrigated and treating orchard roads, if necessary, to keep dust to a minimum helps to manage mite buildups. Proper pruning and adequate amounts of fertilizer to maintain tree vigor will also discourage twospotted and Pacific mites. (7)


      Biological control, predators are very important in regulating pest mite populations in orchards. The three major predators are the western predatory mite? sixspotted thrips and the spider mite destroyer, Stethorus picipes. All of these predators are adversely affected by certain materials applied for control of other pests such as oriental fruit moth and thrips. (6,7) < P>Fenbutatin Oxide (Vendex) 50 WP, applied to 21% of the acres by ground at an average rate of .58 lb. a.i. per acre with a 1 4-day PHI. This material appears to be most effective when applied early in the season. (4,7)

      Narrow Range Oil (Superior, Supreme), applied to 97% of the acres at various application rates depending on the product. (4,6,7)

      Clofentezine (Apollo SC), applied to 8% of the acres by ground at an average rate of .10 lb. a.i. per acre with a 21 -day PHI. This material is more effective in the early part of the year. It kills eggs and young larval stages most effectively. To delay development of resistance, use only once per season. (4,7)

  5. Diseases

    1. Peach Leaf Curl:

      About 90% of the peach acres are treated for this disease. Leaves produced in spring are thickened, curled, and colored red or yellow instead of normal green. Severely affected shoots die. Irregular reddish lesions are sometimes seen on fruits. Badly diseased leaves fall by early summer, and repeated infections debilitate trees and kill branches. Dormant applications are necessary in all peach applied
      growing districts. One application in late winter before bud swell is aufficient except in areas of high rainfall or where leaf curl has become an increasing problem. (4,6,7)


      Chlorothalonil (Bravo), applied to 42% of the acres by ground at an average rate of 2.5 Ibs. active ingredient per acre. Do not use with or closely following oil sprays. (4,7)

      Copper, applied to 89% of the acres by ground at various application rates depending on the product.

      Ziram 76, applied to 49% of the acres mostly by ground at an average rate of 6 Ibs. a.i. per acre.

    2. Bacterial Canker (P. syringae):

      An average of 2-5% of the peach acres are treated for this disease. There are higher incidence of bacterial canker in sandy soils and during cold wet winters. The colder the temperature the high the incidences of this disease. Symptoms are most obvious in spring, and include limb dieback with rough cankers and amber colored gum. There may also be leaf spot and blast of young flowers and shoots. Frequently, trees sucker from near ground level; cankers do not extend below ground. P. syringae survives on plant surfaces, is spread by splashing rain, and is favored by high moisture and low temperatures in spring. Vigorous trees are less susceptible to bacterial canker, while young trees, 2 to 8 years old, are more affected. This disease if left uncontrolled will kill young trees. (6,7)

      Cultural Controls

      Delayed pruning may help. Lovel peach rootstock is usually more tolerant than others. In light, sandy soils and in some heavy soils, control has been achieved with preplant fumigation for nematodes. (7)

      Methyl Bromide, preplant fumigant applied by ground with tarping required. Applied at a rate of 300-600 lb. per acre. Use the higher rates for fine-textured soils. (7)

      Fenamiphos (Nemacur 3), applied to 2% of the acres at a rate of 2.75 Ibs per acre with a 45-day PHI. Apply in mid-October through low volume irrigation (drip line or minisprinkler). This product is often applied several times a year during the first eight years of the trees life for best control. (4,6,7)

    3. Powdery Mildew (S. pannosa):

      Terminal leaves of shoots are covered in powdery, white fungal growth. Leaves become misshapen and puckered and fruits develop powdery white spots. S. pannosa survives as mycellium in bud scales. Growth of the pathogen is favored by cool, moist nights and warm days. (7)

      Benomyl (Benlate) 50WP, applied to 21% of the acres by ground at an average rate of .75 lb. a.i. per acre. Resistance to benomyl may develop if this material is used repeatedly. It is important to alternate benomyl with materials of a different chemistry. (4,7)

      Sulfur, is a preventative treatment and applied at various application rates depending on the product mostly by ground. It is applied to about 40% of the peach acres. Do not apply within 3 weeks of an oil application. (4,6,7,9)

      Myclobutanil (Rally) 40W, applied to 34% of the acres by ground at an average rate of .12 lb. per acre with a 7-day PHI. (4,7,9)

    4. Phylophthora Root and Crown Rot:

      Generally, crown rots advance rapidly and trees collapse and die soon after the first warm weather of spring. Leaves of such trees wilt, dry, and remain attached to the trees. Phytophthora infections typically kill young trees because their root systems and crown areas are small compared to those of mature trees. Periods of 24 hours or more of saturated soil favor Phytophthora infections. Conversely, good soil drainage and more frequent but shorter irrigations reduce the risk of root and crown rot. Also planting trees on a berm reduces the chances of this diseases. (6,7)


      Fosetyl-al (Aliette), applied to less than 1% of the acres by ground at an average rate of 2.0 Ibs. a.i. per acre. It is used as a preplan" treatment for nonbearing trees only. It is a foliar spray, 60-day intervals. (4,6,7)

      Metalaxyl (Ridomil 2E), applied to less than 1% of the acres by air at an average rate of 1.25 Ibs. per acre. The application rate varies with the method of application and size of trees. This is a preplan" application on nonbearing trees. Applications are made in early spring and fall. (4)

  6. Nematodes

    Nematodes are microscopic roundworms that live in diverse habitats. Plant parasitic nematodes live in soil and plant tissues and feed on plants by puncturing and sucking the cell contents with a spear like mouthpart called a styles. Of the several genera of plant parasitic nematodes detected in California orchard soils, root knot, ring, lesion, and dagger nematodes are considered to be the most important.

    Cultural Practice Before fumigating, remove old trunks and large roots brought to the surface by ripping and fallow or plant green manure cover crops for 1-2 years. Use certified nematode- free rootstocks or seedlings to establish new orchards. (6,7)

    Root knot nematode: This nematode is not a problem if Nemgard Rootstock is used. Feeding by root knot nematodes can impair root functions such as uptake of nutrients and water. Root knot nematodes have been implicated in peach disease complexes with fungi and bacteria; for example, M. Javanica has been reported to increase the incidence of crown gall on peach roots. Symptoms of root knot infestation are reduced vigor and yield, patches of unevenly sized trees, and characteristic galls on roots. (6,7,9)

    Ring nematode: Infestation impairs development and function of peach roots which reduces tree vigor and predisposes trees to bacterial canker. (7)

    Lesion nematodes: Penetrate roots and cause damage by feeding and migrating through the root tissues. Lesion nematode infestation reduce overall root presence and may cause reddish brown lesions on roots that later turn dark and ultimately black. (7)

    Dagger nematodes: Feed from outside the roots, but can reach the vascular tissues with their long styles and are capable of reducing vigor and yield of trees. The main damage caused by the dagger nematode is that it vectors a strain of tomato ringspot virus that causes peach yellow bud mosaic which debilitates and can kill trees. Symptoms of dagger infestation include reduced growth and vigor. (6,7)


    Methyl Bromide, preplant application by ground and tarped at a rate of 300-600 lbs. a.i. per acre. Use the higher rates for fine textured soils. (7) Metam Sodium (Vapam), preplant application. Applied to less than 1% of the acres at 300 lbs. per acre. Metam sodium can reduce populations of nematodes if applied properly, but it does not penetrate plant roots very well and it is very difficult to get 4-5 feet down from the surface. Before applying this material, thoroughly cultivate the area to be treated. After cultivation and about one week before treatment, preirrigate the field with 6-8 acre- -inches of water. After treatment, do not plant for 30 days, or 60 days if soil is high in Organic matter or cold (below 50F): (4,7)

    Fenamiphos (Nemacur 3), Applied to 2% of the acres as a post-plant application at an average rate of 2.75 a.i. per acre with a 45- day PHI. Make initial application in fall. All applications should include irrigation to move the material into the root zone. (4,7)

    Sodium Tetrathiocarbonte (Enzone), is a new registration and use patterns are not available at this time.

  7. Weeds

    Generally, there is one preemergent application made in the berm surrounding the trees annually. Weeds in the row middles are generally controlled with one post emergent application followed by cultivation. The spectrum of weeds within an orchard changes so much that loss of the broad spectrum herbicides (glysophate and paraquat) would cause the loss of post emergent weed control in orchards. It would also cause the loss of effective control of perennial weeds. (10)


    Glysophate (Roundup), applied to 71% of the peach acres at an average rate of .5 lb. a.i. per acre by ground application. (4,10)

    Simazine (Princep), applied to 27% of the peach acres at an average rate of 1.0 Ib. a.i. per acre. (4,10)

    Paraquat (Gramaxone), applied to 34% of the peach acres at an average rate of .70 lb. a.i. per acre. (4)

  8. References

    1. USDA/ARS document "Data on U.S. Crop Production", 1994.
    2. 1995 California Agricultural Commissioners' Data.
    3. Personal communication with Rich Hudgins, November 14, 1997.
    4. 1995 CDPR Use Report.
    5. "Kearney Tree Fruit Review", Vol. 2 Based on Dr. Richard Rice field trials.
    6. Personal communication with Harry Andris, November 18, 1997.
    7. University of California Integrated Pest Management "Pest Guidelines".
    8. "Growing Shipping Peaches & Nectarines in California" U.C. Cooperative Extension Leaflet 2851, August, 1983.
    9. Personal communication with Bill Olsen, November 21, 1997.
    10. Personal communication with Kurt Hembree. February 13, 1998.

    The use of trade names does not imply endorsement by the University of California.
  9. Footnotes

    1This refers to the percent of peach acres treated with narrow range oils per year. Narrow range oils are used to control several different pests.

    2This refers to the percent of peach acres treated with diazinon per year. Diazinon is used to control San Jose Scale and Oriental Fruit Moth.

    3This refers to the percent of peach acres treated with carbaryl per year. Carbaryl is used to control San Jose Scale and Oriental Fruit Moth.

    4This refers to the percent of peach acres treated with azinphosmethyl per year. Azinphosmethyl is used to control Oriental Fruit Moth and Peach Twig Borer.

    5This refers to the percent of peach acres treated with phosmet per year. Phosmet is used to control San Jose Scale and Oriental Fruit Moth.