- Author: Ben Faber
There have been a lot of new avocado orchards planted during the last few years. These often have been in old ‘Valencia’ orchards or lemons that had poor production. In order to save money, growers have just cut the trees at ground level and replanted the avocados near the stumps. Avocados have recognition of being resistant to Armillaria, but in this environment of high disease pressure, they can fail.
Armillaria root rot is common, yet is an infrequently identified and poorly understood disease. It is capable of attacking most species of trees and other woody plants growing in California. It is sometimes called “shoestring root rot” and the causal fungus is often referred to as the “honey mushroom.” Because oak is one of the preferred hosts, it is also called “oak root fungus.”
If a tree undergoes a slow to rapid decline without any obvious reason, suspect Armillaria as the cause. Certain areas, such as drainage areas from chaparral or woodlands are likely areas for this disease. Old roots left underground provide a food base for continued fungal growth and survival.
General symptoms of Armillaria resemble those of other root disorders. These symptoms are disrupted growth, yellow foliage, branch dieback, and resin or gum exudates at the root collar. Trees may die rather abruptly without showing any decline symptoms. Avocados typically have a rather protracted death, but in citrus it can be rapid.
Only rarely can the disease be diagnosed without examining the larger buttress roots and root collar of the tree. After carefully removing the soil, examine for the presence of:
1) Rhizomorphs, or fungal ‘shoestrings’ attached to the wood under the bark. These may occur beneath the bark for some distance above the soil line in advanced cases, rarely they may radiate from the wood into the soil. Rhizomorphs may also grow out from the larger roots, resembling feeder roots in appearance. They are about the diameter of pencil lead and vary in color from black to reddish brown. The interior consists of white mycelial tissue.
2) Decayed areas of wood at the root collar or on the crown roots. Armillaria causes a white rot and the wood develops a stringy texture. Roots in advanced stages of decay may be soft, yellowish and wet.
3) Veined, white mycelial fans between the bark and wood where the cambium has been killed. Sometimes this fan (or fans) extends quite far above the soil line beneath the bark.
4) Soil remaining attached to the roots.
5) Characteristic mushrooms on the lower trunk or on the ground near the infected roots. These short-lived annual fruiting structures of the disease-causing fungus may develop during the fall or winter rainy season and may occur in small clusters or in large numbers. The stalk is typically yellow and 3 inches or more long. Usually a ring is connected to the stalk just below the cap. The cap is 2-5 inches across and often honey-yellow. It may be dotted with dark brown scales. The underside is covered with loosely spaced white or yellow gills radiating from the stem.
After the disease has been identified, the grower should study the situation to determine the role Armillaria root rot has played in causing the decline or death of the tree. Frequently the fungus is only involved in a secondary manner by invading and destroying roots after the tree has been exposed to stress of some form, such as severe drought, water logging, or soil fill over the roots. The fungus can also act as a saprophyte feeding on dead wood. It is frequently involved in the decay of old tree stumps and roots.
Many oaks are lightly infected with the disease for years with no resultant damage except for isolated pockets of buttress root rot which are walled off by the tree and have no ill effects. Other infected trees show no damage until subjected to stress. Accumulating evidence suggests the type of root exudate that is produced influences the susceptibility of the tree. Certain forms of stress cause a shift in exudates that promote rapid development of the fungus and may hasten tree invasion and decay.
Spores are produced by the mushroom fruiting structures (mushrooms) and disseminated by air currents and introduced into new area. Once the fungus enters the cambium and bark tissues, mycelial fans develop during the parasitic phase of the attack. Subsequently, mycelium invades and decays the woody tissue of the roots and sometimes also the base of the trunk. Under proper conditions the fruiting structures form at or near the base of the infected tree, completing the life cycle.
Direct control of the fungus in a diseased tree is not possible with present technology. However, in many instances the fungus is incapable of causing severe damage unless the tree is first subjected to substantial stress. Thus, keeping the tree healthy and avoiding severe stress is one important approach in preventing loss of trees to Armillaria.
Drought and leaf defoliation are two major forms of stress that favor Armillaria. In dry years it is advisable, as in all years, to make sure irrigation scheduling is appropriate. Stresses such as defoliation from persea mite, soil compaction and physical injury can exacerbate the disease. Nutrient management may minimize Armillaria effects, although little research information exists on this subject.
The second most important means of minimizing Armillaria damage is to avoid or eliminate the fungus inoculum before planting. Trees planted in former orchards will quite possibly be exposed. Since these sites cannot be avoided, here is a suggestion that will be helpful: remove stumps and old roots from the old orchard to the greatest extent possible.
Below:
Armillaria mushrooms and hyphal plaques under the bark
- Author: Craig Kallsen
Many citrus trees in the southern end of the San Joaquin Valley are grown on moderately calcareous soils and frequently have high levels of boron in the leaf tissue. Citrus is sensitive to boron. Boron, when excessive, may cause defoliation and significant yield loss. At high, but nontoxic concentrations, leaf symptoms are similar to those caused by excessive salt, deficient potassium, heat stress, or biuret toxicity from urea foliar sprays. Therefore a leaf tissue analysis is important for delineating causes.
Excessive levels of boron produce a yellowing of the tip of leaves and yellow spotting of the leaf surface. Death of the leaf tissue may occur along the margins. Higher levels of boron may cause brownish, resinous gum spots on undersides of leaves but this symptom is not always present. Leaf symptoms are most severe on the “hot” south side of the tree. Boron accumulates in the leaves as they age so symptoms usually appear on older leaves first. Older leaves with high concentrations of boron are relatively short lived compared to trees that have boron at optimum concentrations. Often excessive boron and sodium appear together in leaf tissue analyses. Boron is associated with a decreased distance between leaf nodes. Trees with high leaf tissue boron concentrations appear to be less vigorous with shorter branches, probably as a result of the association of boron with decreased distance between leaf nodes.
Discussion of levels of boron which would be considered excessive in September-sampled spring-flush leaf tissue may be misleading because the particular leaves that are selected for the sample can greatly influence results. If only leaves with the most severe symptoms are sampled, such as leaves that are mostly yellow with dead margins, concentrations of boron can reach into the thousands of parts per million (ppm). A truer picture of the boron status of the grove can be gained by pulling leaves with ‘average’ symptoms. Using this sampling technique, the highest level of boron in orange leaves seen in this office over the past eight years has been 600 ppm from an isolated and particular calcareous part of an orchard located near the town of Edison in Kern County.
Standards from citrus in Florida for the concentration of boron in leaf tissue (4-6 month old leaves on nonfruiting terminals) correlate well with observations made in the San Joaquin Valley as follows:
Deficient <20
Low 21-35
Optimum 36 - 100
High 100 - 200
Excess > 250
Leaf boron concentrations greater than 250 ppm are excessive, but in older orange, lemon and grapefruit trees visible leaf symptoms are not usually manifested until leaf-tissue boron concentrations exceed 300 ppm. A range of 300 to 400 ppm show little outward sign of boron toxicity except for some slight tip yellowing and some reduction in vigor. Excessive defoliation does not usually begin in most citrus until concentrations of approximately 450 ppm are reached. Trees at 450 ppm and greater will, generally, exhibit a thin-canopied, unthrifty, somewhat stunted appearance. The yield of the tree does not appear to be affected nearly as rapidly as the appearance of the canopy. At least one large lemon grove in Kern County, that characteristically produces excellent yields of early-maturing, good quality fruit, has elevated leaf-boron levels. Moderate levels of leaf boron, in the 300 to 400 ppm range in this orchard appear to reduce tree growth, reducing the need to prune, while yield remains relatively unaffected.
Leaf boron concentrations greater than 300 ppm probably warrant further investigation as to the source of the boron. Orange leaf tissue samples taken from trees planted in the 1960’s or early 1970’s in Kern County routinely show levels of 300 to 400 ppm. Young trees appear to increase in boron concentration rapidly but at about 300 to 400 ppm the concentration tends to plateau. Why boron levels tend to plateau is not known. Chandler pummelos appear to be the most sensitive to excess boron, followed by lemons, grapefruits and oranges. Leaf boron concentrations of 400 ppm in Chandler pummelos appear to have caused severe stunting of the trees in several orchards in Kern County, while similar levels in Melogold (a pummelo x grapefruit hybrid) resulted in only some tip burn.
There are actions the grower can take to reduce the amount of boron in the tree. First the source of the boron should be determined if possible. If boron levels are increasing in the leaf tissue, analyze both surface water and well water. Avoid using water with greater than 0.5 ppm of boron for irrigation of citrus. Levels of boron that are beneficial to cotton or pistachio can cause severe problems with citrus. Surface water comes from diverse sources in Kern County. Surface delivered water may have started out as well water, or in some instances as diluted oil-field waste water which may contain relatively high concentrations of boron. Water districts will know if oil-field waste water is being diluted in irrigation water. Use of oil-field waste water can be seasonal and irrigation derived in part from oilfields may fluctuate in boron concentration. If boron is in the water even at slightly elevated levels, avoid spraying it directly on the trees when treating for insect pests or when applying foliar fertilizers. Fertilizers are foliarly applied because of the quick uptake of dissolved minerals through the leaves. If boron is in the spray solution, it will be absorbed quickly by the tree along with the potassium, zinc, manganese, nitrogen and other foliar nutrients. Organic matter, manure, composted materials, and mulches on the ground have been shown to reduce boron uptake by the plant from irrigation water with high concentrations of this element.
In the southern San Joaquin Valley, soils should be tested before citrus is planted. Areas of soil with high boron are found in the most unexpected places. Boron may have accumulated on some properties when high-boron well water was used before the advent of easier access to water from Sierra snow melt.
If leaf-tissue boron is high and the water or soil is not, check the foliar fertilizer blends being used. Often, boron is included in many micronutrient mixes because boron can be deficient in acid soils. Determine how much boron soil amendments may contain. Pit gypsum can have varying quantities of boron in it. A ton of this gypsum may contain as much as 20 pounds of boron.
Discovering the cause of high boron in citrus leaves may require an extra soil test in addition to the typical saturated pest extract. Soil tests for ‘available’ boron using a saturated pest extract can be deceiving. In many instances where the concentration of boron in a ‘typical’ leaf averaged greater than 300 ppm, plant-available boron in the soil and water frequently averaged less than 0.25 ppm. However, total soil boron in these same orchards was at very high levels. Total soil boron estimates both available and unavailable boron. To help determine where the boron in the trees originates, both readily available and total soil boron should be sampled. This disparity between plant-available and total boron suggests that boron moves between the relatively small plant-available pool in the soil and the much larger ‘unavailable’ pool tied up in these calcareous soils. Soil acidifying agents and acid-forming fertilizers probably increase the availability of boron to citrus trees by making boron that is relatively unavailable to the trees at high pH, more available at lower pH. At any given time, plant-available boron may be relatively low but its constant replacement from the unavailable pool keeps the boron concentration in trees relatively high. In orchards where total soil boron is elevated; soil pH should probably be kept as high as tree health permits. Where the total amount of soil boron is moderate and soils are relatively well-drained and topography is flat, acidifying and leaching is probably the preferred option for reducing boron levels. Acidifying the soil and not supplying sufficient water to leach the boron from the root zone can compound the problem by making more boron readily available to the tree.
If boron is not found in the upper soil profile, but is found or suspected to exist deeper, irrigations could be scheduled that are more frequent but of shorter duration so that most of the citrus roots remain in the upper, lower-boron portion of the soil profile.
Actively growing, vigorous trees may dilute the concentration of boron in the leaf tissue through the production of a thick canopy. Old leaves tend to accumulate boron and drop. Adequate nitrogen ensures that enough nitrogen is present for production of new leaves. Increasing the nitrogen fertilization rate can encourage vegetative production and enhance this effect, but too much nitrogen may be associated with adverse fruit quality characteristics like regreening of Valencias, later maturity of early navels or higher yields of smaller fruit. Keeping other nutrients in the leaf in balance is important if boron is present at excessive concentrations. Maintaining high concentrations of phosphorous and calcium in the leaves through an appropriate fertilization program should be beneficial as these nutrients have been shown to reduce absorption of boron.
- Author: Kurt Hembree
While both horseweed and hairy fleabane have been here since farming began in the region, it’s only since about 2003 that they have become such an obvious problem, particularly in tree and vine systems and non-crop areas.
In the past, the traditional use of combinations of pre- and postemergence herbicides and/or cultivation was adequate to manage them. However, recent changes in environmental regulations, economics, herbicide use patterns (toward more postemergence-only programs), treatment timing, and glyphosate-resistant biotypes have all contributed to the problem. Other factors contributing to their spread include, high seed production, wind dissemination, lack of seed dormancy requirement, preference for undisturbed areas (i.e. tree and vine rows), and adaptability to both moist and dry soils.
To get these weeds back under control, it is important that growers, managers of non-crop areas, and other land owners all do their part to help resolve the issue. Regardless of control tactics used, preventing new seed production is a must to be successful. It is also critical to understand what we’re dealing with when it comes to timing management efforts.
Although considered summer annuals, they have also been seen emerging in early October in the southern San Joaquin Valley (see Figure). During this time, they appear to go through an over-wintering or “survival” stage, where root growth seems more important than leaf production. So, by the time spring emergence occurs in mid-February, plants that actually emerged several months earlier may only appear to look the same as those that just emerged. This may help explain why some late-winter or early-spring applications of postemergence herbicides are not as effective.
Relying only on postemergence products can make horseweed and hairy fleabane very problematic. Consider including effective soil-residual herbicides (Table 1) where possible. Once under control, apply treatments every 2nd or 3rd year to maintain their control. Also consider making split-applications in Oct/Nov and again in Jan/Feb if you have seen them emerge during these periods in your specific area. If you farm in a groundwater protection area (GWPA), you will have to get a permit to use some of these products (refer to your county agricultural commissioner for local GWPA regulations). It is important to know, that while most of the effective materials on these weeds fall under GWPA regulations, they can still be used in many cases and should be considered.
Table 1. Preemergence herbicides for horseweed and hairy fleabane control in tree and vine crops in California |
|
Herbicide |
Notes |
Bromacil (Hyvar X) |
Citrus >4 years, GWPA permit needed, 3-4 lb/A in fall and winter, HW=C, HF=C |
Bromacil + Diuron (Krovar) |
Citrus >3 years, GWPA permit needed, 3 lb/A in fall and winter, HW=C, HF=C |
Diuron (Karmex, Direx, etc.) |
Established fields, GWPA permit needed, 2 lb in fall and winter, HW=P, HF=P |
Isoxaben (Gallery T&V) |
NB fields only, 10.6 oz/A, HW=C, HF=C does not control grasses |
Flumioxazin (Chateau) |
Bearing almond/pistachio/grape, NB others, 6 oz/A fall and winter, HW=C, HF=P |
Norflurazon (Solicam) |
Established fields, GWPA permit needed, 2.5-5 lb, adjust to soil type, HW=P, HF=P |
Oxyfluorfen (Goal, etc.) |
NB citrus, bearing/NB others, 6-8pt/A, HW=P, HF=P |
Simazine (Princep, etc.) |
Established fields, GWPA permit, 2 qt or 2 lb fall + winter, mix w/diuron, HW=C, HF=P |
Thiazopyr (Visor) |
Bearing/NB citrus, NB others, 4 pt/A winter or 2 pt in fall and winter, HW=P, HF=P |
NB = non-bearing only HW = horseweed HF = hairy fleabane C = effective control P = partial control This is not a complete list of registered products available. Check with your pesticide dealer for other products available. It is not a written recommendation for herbicide use. Always read and follow all label recommendations. |
Sensitivity to postemergence herbicides decreases the older horseweed and hairy fleabane get. Use higher label rates of effective materials (Table 2), proper coverage, and treat when they have
Table 2. Effect of glyphosate rate and timing on control |
|
Hairy fleabane growth stage and lb ai/A for good control |
Horseweed growth stage and lb ai/A for good control |
3-6 leaf = 0.5 |
5-8 leaf = 1.0 |
7-12 leaf = 1.0 |
11 leaf to 4” bolted = 2.0 |
13-19 leaf = 1.5 |
4” to 12” bolted = 4.0 |
20-21 leaf = 2.0 |
|
>25 leaf = erratic |
|
Prather, UC KAC 1999 and Shrestha et. al., UC KAC 2005 |
Table 3. Herbicides and rates for control at
Herbicide |
Rate/A |
Rely + AMS |
1 to 1.5 gal |
Gramoxone Inteon, etc. + NIS or COC |
2.0 |
Roundup Weathermax, etc. |
47 fl oz |
Shark EW + COC |
2 fl oz |
2,4-D (Dri Clean, etc.) |
1.55 lb |
Glyphomax, etc. + Chateau |
64 fl oz + 4 oz |
Read and follow label for rates and recommendations. |
Also consider using spray additives (citric acid, ammonium sulfate, spreaders, etc.), if allowed on the label, to improve activity. Tank-mixing various postemergence products can also work well (i.e. glyphosate at 2 lb ai/A plus 2,4-D at 1.5 lb ai/A or Chateau at 2-4 oz/A) are effective treatments. There are numerous products sold in California that contain glyphosate, but they do not all contain the same amount of active ingredient. Read the label carefully to make sure you are using the correct amount of product that will give you a rate of at least 2.0 lb ai/acre (Table 4). If you are using recommended label doses and herbicide timing and are using properly calibrated and operating spray equipment and you still have some of these weeds escaping control, contact your local farm advisor and chemical representative to make sure you do not have an herbicide-resistant biotype. If it is determined that you do, you will need to make changes to your weed management program as soon as possible to eradicate the problem.
In addition to appropriate herbicide selection and use, cultivation can also play an important role in horseweed and hairy fleabane management. Use shallow cultivation to dislodge small plants (
Table 4. Comparative rates of some glyphosate products |
|
Herbicide |
Fl oz for 2.0 lb ai/A |
Touchdown Hitech |
42 |
Roundup Weathermax |
47 |
Touchdown Total |
50 |
Roundup Original |
64 |
Glyphomax |
64 |
Touchdown |
70 |
Managing horseweed and hairy fleabane can seem like a daunting task. However, with the proper selection and use of chemical and mechanical tools, management can be possible. One thing to keep in mind when attacking these two weeds, other weed species may also be waiting for their opportunity once you have got these out of the way. So, it’s a good idea to routinely monitor your fields following each herbicide application and check for any kind of weed escape or shift in the types of weeds present.
Below: Horseweed on top and Hairy Fleabane on bottom.
- Author: Jim Doyle
- Author: Louise Ferguson
The California fig industry is currently producing on about 16,000 acres. A “2002 Statistical Review” published by the California Fig Advisory Board and California Fig Institute at Fresno lists seven cultivars used primarily (although in some cases not exclusively) for dried whole figs and fig paste. These seven cultivars are Calimyrna (6,559 acres}, a four cultivar grouping identified as “Adriatics” but including Conadria, Adriatic, Di Redo and Tena (3,364 acres in combination), Kadota (1105 acres) and Mission (3702 acres). Two additional cultivars are used in California primarily for the fresh market. These are the California Brown Turkey (about 2000 acres) and a new 2005 UC release, the Sierra fig (about 200 acres). The above nine cultivars differ substantially from one another in aspects of usage, horticultural type and fruit characteristics. The Sequoia fig is being released for use in the fresh market. Although of good quality when dried, it develops both a dark skin and a dark pulp color that limits its acceptability as a dried product. Of the above nine cultivars, only five are sold fresh. These are the CA Brown Turkey, Sierra, Calimyrna, Mission and Kadota. Only these five will be compared, as follows, to the Sequoia. The four “Adriatic” class figs are used only as whole dried figs or fig paste. All are of too small a size for the fresh market.
Horticultural Types
Two horticulture types of figs are found in the California Industry. The first of these, the “Smyrna” type fig, needs to be pollinated (caprified) in order to set fruit that will persist on the tree until maturity. The Calimyrna is the only cultivar of this type grown commercially for fresh consumption in California. All of the other four fresh market figs listed above, as well as the Sequoia, are of the “common” type. These common types do not need to be pollinated in order to set and mature fruit. The advantages of the common type figs over the Smyrna type are substantial. A common type fig grower does not need to maintain caprifig trees or to buy caprifigs from other growers, does not need to treat the caprifigs to disinfect the wasps (the pollen vectors) living in the caprifigs, does not need to distribute the caprifigs throughout the Calimyrna orchard and does not have to deal with the variables or the costs of the caprification process. Climatic factors such as heat, cold, rain, wind and disease can have a substantial impact on the success of the insect vector of the pollen and the eventual level of productivity of the Calimyrna crop. A good Calimyrna orchard often produces only in the 0.5 to 1.0 ton of dried fruit range in comparison to at least twice (sometimes three times) that tonnage from common types. Were it not for the excellent quality of the Calimyrna product, when well grown, it would probably not be planted in California at all.
Usage
The CA Brown Turkey is grown almost exclusively for the fresh market. It does not dry well. The Calimyrna, Mission and Sierra are dual-purpose figs, all three dry well, with some growers often directing part of the crop to the fresh market. The Kadota is a multiple use cultivar that can be dried, canned and picked for the fresh market successfully.
Fruit Characteristics of the Five Fresh Market Figs Grown in California
The Calimyrna fig is a green-yellow to yellow skinned fig with amber pulp. As noted above, the cultivar requires caprification to set a crop. The first (Breba) crop drops without coming to maturity because caprifigs containing pollen and the vector wasp are not available at the time the Calimyrna Brebas require pollination. The second crop is abundant but of limited duration (from late August to late September in Fresno County). Fruit set coincides with the mid-summer (or profichi) flight of the fig wasp. When the flight is complete, no more fruit is set for that season. Early in maturity of the second crop, fruit size is large, although size can drop off in late September. The size of the Calimyrna fruit eye (or ostiole) is the largest of all the commercial cultivars and can range from 2.2 to 3.5 mm, allowing substantial amounts of internal insect infestation and spoilage. The cultivar is also prone to large numbers of eye splits during periods of high humidity, cool weather or rain. Fruit quality, when the fruit is grown well, sets the standard for excellence.
The California Brown Turkey is a purple-violet colored fruit with areas of yellow to yellow-green visible, especially over the fruit neck and near the fruit stem. Pulp color is a strawberry red. This cultivar is of the common type, not needing caprification. The CA Brown Turkey can set a small crop of large sized first crop (Breba) fruit. As grown in California, however, the tree is severely pruned in the winter to keep it short in height and to facilitate hand harvesting of the large second crop from the ground. This pruning essentially eliminates the first crop. The second crop is abundant and the fruit is large and retains its large size well into the harvest season. Since the CA Brown Turkey is a common type fig, once fruit production begins in late August, fruit will continue to develop and mature until fall. Production ceases only when the orchard dries out and the tree stops producing extension growth, or when a weather event (rain, frost, etc…) damages the fruit or sends the tree into dormancy. The fruit ostiole is relatively large and in some locations the fruit can be subject to insect infestation and souring. Fruit quality is good when harvested with sufficient maturity.
The Mission fig is a violet-black colored fig with the coloration usually covering the entire fruit surface. Pulp color is a strawberry red. This cultivar is a common type fig not needing caprification. The cultivar usually sets a good crop of Breba fruit that are large in size and of very good quality. These Mission Brebas are often harvested from orchards that have been established to produce fruit for drying. Such trees are often very large and picking can be difficult and expensive. The Mission second crop is abundant and also of very good quality. Fruit size of the second crop is large enough to pack fresh for a week or two, but then size diminishes rapidly, eliminating its use for the fresh market. The fruit ostiole of both the Breba and second crop is quite small and fruit spoilage is usually not a problem. Fruit quality of both crops is very good.
The Kadota fig is a medium sized greenish-yellow skinned fruit that is grown only in limited quantity for the California fresh market. Pulp color is amber. The Kadota is a common type fig. Production of a Breba crop can be variable, from light to good in volume. The second crop is abundant but most fruit is too small to be valuable for picking fresh. Towards the end of the season many small, dry, commercially worthless fruit, known as “puffballs”, can be present. The fruit ostiole is medium in size, partially restricting insect access. Fruit quality of the Brebas and second crop is sweet and good.
The Sierra fig is a new cultivar, released for planting to California growers by UC in 2005. Although developed as a high quality fig for drying, initial plantings are being made for the fresh market so that the new cultivar appears to be suitable for both purposes. Skin color of the Sierra is a yellow-green and pulp color is amber. The Sierra is a common type fig. The Breba crop of Sierra to date does not appear to have commercial value. The Breba crop has been light and the figs produced have not been particularly large or highly flavored. The second crop, however, is abundant. The fruit is medium to large in size and holds fruit size well into the fall. The fruit ostiole is very tight, effectively restricting insect access to the fruit interior. Fruit flavor is very good.
Sequoia Comparisons
The new Sequoia cultivar that is proposed for plant protection and release to the California fig industry has been developed for the fresh market. The fruit is yellow-green in skin color with reddish-amber pulp. This skin color is competitive with the yellow-green Calimyrna, Kadota and Sierra but complimentary to the violet-black colored CA Brown Turkey and Mission. The Sequoia is a common type fig. This gives it an advantage over the Smyrna type Calimyrna in productivity and production efficiency. The Breba crop of Sequoia ranges from light to medium in volume. The Brebas are large in size with very good quality. The production of saleable Brebas gives the Sequoia an advantage over the Calimyrna, CA Brown Turkey and Sierra cultivars that either develop very few or no Brebas at all. The second crop of Sequoia is abundant with large to medium size. The Sequoia appears to maintain fruit size well into the fall in contrast to the small late-season fruit size of the Mission and Kadota and the absence of fruit on the Calimyrna. The ostiole or eye of the Sequoia is very tight, similar to the Sierra and Mission but substantially tighter than the Calimyrna, CA Brown Turkey and Kadota. The fruit flavor and quality of the Sequoia is as good as or better than all of the five established cultivars listed here with the exception of the Calimyrna. The Sequoia, which has Calimyrna in its pedigree, approaches the flavor of Calimyrna, but the Calimyrna, with all of its many production problems, still retains its position as the premier quality fig.
- Author: Craig Kallsen
Not too many years ago, most growers and pest control advisors were unaware that earwigs were a potential pest problem in citrus. Earwigs simply were not often found in large numbers in citrus orchards. Earwigs’ increasing pest status is probably related to advances in integrated pest management techniques and attendant reductions in use of broad-spectrum organophosphate and carbamate insecticides for control of common citrus pests. On the plus side, fewer toxic, broad-spectrum pesticides treatments reduced the safety hazard for pesticide applicators, field workers and the environment and biologically integrated pest management has been effective for controlling most pests. However, once general broad-spectrum pest suppression was removed by significant reductions in these insecticides, some secondary pests, or insects that were not known to be pests, began to do serious economic damage to citrus under some conditions.
In April 2000, samples of earwigs collected in the act of chewing on citrus fruit by Robert Walther, private pest control advisor in Kern and Tulare Counties, were sent from the University of California Cooperative Extension Office in Bakersfield to the California Department of Food and Agriculture for identification. These earwigs were identified as the European earwig (Forficula auricularia). The adult European earwig is about ¾ inch long, with a reddish brown head and darker body. A distinctive feature of the adult earwig is a pair of prominent appendages that resemble forceps at the tail end of its body. These forceps are straighter in the female and more curved in the male. The European earwig has wings hidden under short, hard wing covers. Earwigs are capable of flight, but when disturbed during daylight hours, usually scurry and hide under any available cover. Immature insects look like adults except are smaller and lack wings. Females lay eggs in the soil and produce a single, if somewhat extended, generation per year.
Earwigs are active and feed mostly at night, especially during hot days in spring, summer and fall. They prefer to inhabit cool, moist and dark places. Generally, earwigs will return to the ground before daylight after feeding in citrus at night. During the day they are often found in tree wraps commonly placed on the trunks of young citrus for frost protection and under heavy leaf litter adjacent to irrigation emitters in mature orchards. High populations of earwigs do not normally develop in citrus unless protective, shaded habitat is present. Earwigs damage citrus leaves and small-diameter developing fruit. Often growers and pest control advisors do not correctly identify earwig damage as such, and snails, citrus cutworms, leaf rollers, katydids, other chewing insects or wind damage are often incorrectly blamed. Examples of earwig, citrus cutworm, katydid and similar scarring can be viewed in the University of California Agriculture and Natural Resource publication #8090 “ Photographic Guide to Citrus Fruit Scarring” that is available at UC Cooperative Extension Offices and downloaded at
http://anrcatalog.ucdavis.edu/pdf/8090.pdf.
For earwigs to be an economic problem in citrus, they usually have to be present in large numbers. Fifty earwigs in a tree wrap is not an unusual find in infested young orchards. In young trees, earwigs are capable of causing severe defoliation. Buds, newly expanded leaves and soft, fully expanded leaves are all susceptible. Earwigs gouge leaves, and chew irregular holes in leaves and around the edges of leaves. Recently expanded spring flush leaves can be chewed down to the midrib Heavy infestations of earwigs in newly planted trees may require treatment, in that severe defoliation may result from their feeding activities.
In mature orchards the principal damage results from the earwigs chewing newly developing fruit in April and May. This damage is typified by holes gouged at the base of the fruit near the attachment to the stem or shallow crescent or star shaped slashing marks across the fruit. Badly damaged fruitlets will fall from the tree, but the scars on fruit that remain on the tree continue to expand as the fruit grows, and the fruit will not be marketable. Earwigs usually stop feeding on fruit larger than about an inch in diameter.
Pruning citrus so that branches do not contact the ground and blowing or raking leaf litter from under the tree into the row middles away from the wetted irrigation pattern can reduce earwig populations in mature orchards. In young orchards, simply removing trunk wraps can remove the earwig problem. Finding pesticides specifically labeled for control of earwigs in citrus may be difficult. Some growers have observed that after treating an ant infestation with an appropriately labeled chlorpyrifos formulation, that earwigs are effectively controlled as well.