Avocado Orchards Research Articles

Forest cover change and land tenure change in Mexico’s avocado region: Is community forestry related to reduced deforestation for high value crops?

Forest cover change in highland pine-oak forests of Michoacan, Mexico is due to a process of conversion of natural forests to avocado orchards. Privately-owned avocado orchards are found on land that was common forest before the 1992 Reform of the Mexican Constitution. We ask how forest cover change was facilitated by policy changes that affected land tenure rules and existing community forestry programs. We use a comparative case study of four communities, an analysis of forest cover change, and interviews and household surveys. Results show that 33.1% of forest cover was lost over a 16-year-period across the region. However, two forestry case study communities lost 7.2% and 15.1% of forest cover, while two adjacent non-forestry communities lost 86.5% and 92.4%, respectively. Interview data show that the Reform of Article 27 combined with the 1992 Forestry Law led to collapse of local governance, illegal division of common forests, and illegal logging in the two non-forestry communities.

First Report of Raffaelea canadensis Causing Laurel Wilt Disease Symptoms on Avocado in California.

Laurel wilt disease is a newly described vascular disease of redbay (Persea borbonia (L.) Spreng.) and other members of the Lauraceae family in the southeastern United States. The disease, caused by the fungus Raffaelea lauricola and vectored by a nonnative redbay ambrosia beetle (Xyleborus glabratus Eichhoff), was first detected in Georgia in 2003 (1). Laurel wilt has caused extensive mortality of native redbay in Georgia, Florida, South Carolina, and recently, Mississippi. The avocado, Persea americana, is in the Lauraceae family and has been shown to be susceptible to the laurel wilt pathogen in Florida (3). The potential spread of this pathogen into California is of concern to the commercial avocado industry. During a survey in 2010 in a Temecula, CA avocado orchard with a history of root rot, an avocado (cv. Hass) tree with a diameter at breast height (DBH) of 45 cm was found to be showing typical laurel wilt disease symptoms. The crown was approximately 80% declined and exhibited dead branches without leaves. Black-to-brown discolored sapwood under the bark and many ambrosia beetle exit holes within 1 to 1.5 m up the bole were also observed. A Raffaelea sp. was consistently isolated from symptomatic branch tissue (from two different branches) plated onto cycloheximide-streptomycin malt agar (2) and incubated at room temperature for 2 weeks. Small subunit (18S) sequences of rDNA (approximately 1,150 bp) of three Raffaelea isolates were amplified using primers NS1 and NS4 (4) and deposited into GenBank under Accession Nos. JF327799, JF327800, and JF327801. A BLASTn search of all three sequences revealed high homology (98, 99, and 98% respectively) to an accession of R. canadensis associated with a species of ambrosia beetle (GenBank Accession No. AY858665). Pathogenicity testing was conducted by pipetting 50 μl of a 105 conidia per ml suspension of each of two isolates (UCR1080 and UCR1081) into five 2-mm-diameter holes on each of two avocado (cv. Hass) trees (10 to 15 cm DBH). Isolate UCR1080 was inoculated into three holes on Tree 1 and two holes on Tree 2. Isolate UCR1081 was inoculated into two holes on Tree 1 and three holes on Tree 2. Sterile water was used as a control in five 2-mm-diameter holes on each tree. Holes were drilled to the cambium within 1 to 2 m up the bole using a 0.157-cm electric drill. Four months later, phloem tissue was peeled back, lesion lengths were measured, and pieces of necrotic tissue were cultured for completion of Koch's postulates. R. canadensis was consistently reisolated from necrotic tissue but not from control treatments. To our knowledge, this is the first report of R. canadensis associated with wilt on avocado in California. R. canadensis is closely related to R. lauricola, however, its impact on the California avocado industry is unknown at this time.

Biocontrol of persea mite, Oligonychus perseae, with an exotic spider mite predator and an indigenous pollen feeder

To improve the biological control of persea mite (Oligonychus perseae) in Israeli avocado orchards we evaluated two approaches: (1) Augmentative inundative releases in commercial orchards of Neoseiulus californicus, an exotic spider mite predator, and (2) Conservation of Euseius scutalis, the prevalent indigenous phytoseiid predator found in avocado orchards, by pollen provisioning. The latter was done at three spatial scales; leaf discs, seedlings and trees. Neoseiulus californicus releases led to a significant reduction in persea mite population densities. Nonetheless, most of the recovered predators consisted of E. scutalis. The leaf disc experiment showed that E. scutalis can significantly reduce persea mite populations even though it cannot penetrate or tear the mite nests. The seedling experiments demonstrated that E. scutalis can suppress persea mite when pollen is available and provisioning maize pollen substantially increased E. scutalis populations. Field trials revealed that conservation of E. scutalis using Rhodes grass (Chloris gayana) as a windborne pollen provisioning cover crop (WPPCC) was highly effective, compared to repeated artificial pollen applications. Densities of phytoseiid populations were significantly higher on trees adjacent to the Rhodes grass patches than on distant trees, whereas persea mite populations on trees adjacent to these patches were consistently lower. In this study, we show that the use of Rhodes grass as a WPPCC for conservation of E. scutalis is both effective and sustainable. While our results indicate that E. scutalis has potential for mite control, future studies are needed to demonstrate the efficacy of this approach in commercial orchards.

Soil surface water repellency induced by treated wastewater irrigation: physico-chemical characterization and quantification

Irrigation with treated wastewater (TWW) is commonly practiced in Israel to relieve freshwater (FW) shortages. We hypothesized that the organic matter (OM) originating from TWW irrigation alters the physico-chemical properties of the soil, induces water repellency in the soil’s top layer, and consequently alters water distribution in the soil profile. In measurements taken in an avocado orchard on a clayey soil, water repellency was found in TWW-irrigated plots. In addition, smaller wetted surface areas were recorded around the drippers in comparison with FW drippers. Drier zone below soil surface was observed in TWW-emitting drippers. OM extraction from the different plots exhibited differences in quantity and quality of organic substances between TWW- and FW-irrigated soils, with a higher quantity of hydrophobic substances in the TWW-irrigated soil extract.

Water savings, nutrient leaching, and fruit yield in a young avocado orchard as affected by irrigation and nutrient management

This project was designed to determine the effect of fertilizer rate and irrigation scheduling on water use, nutrient leaching, and fruit yield of young avocado trees (Persea americana Mill. cv. Simmonds). Seven nutrient and irrigation management practices were evaluated: (1) irrigation based on crop evapotranspiration (ET) with 50% fertilizer at a standard rate (FSR); (2) ET irrigation with FSR (typical for avocado production in the area); (3) ET irrigation with 200% FSR; (4) irrigation based on exceedance of 15-kPa (SW) soil water suction with 50% FSR; (5) SW with FSR; (6) SW with 200% FSR; and (7) irrigation at a set schedule (based on timing and frequency typically used in local avocado production) with FSR. The SW with FSR treatment saved 87% of the water volume applied and reduced total phosphorus leached by 74% compared to the set schedule irrigation with FSR. The SW with FSR treatment had higher avocado fruit production, tree water-use efficiency, and fertilizer-use efficiency than the other six treatments. Thus, the use of soil water monitoring for irrigation management can substantially increase sustainability of young avocado orchards in southern Florida.

ELECTRICAL SIGNAL MEASUREMENTS IN AVOCADO TREES: A POTENTIAL TOOL FOR MONITORING PHYSIOLOGICAL RESPONSES TO SOIL WATER CONTENT?

Monitoring soil water content coupled with phytomonitoring techniques have been shown to be good tools for irrigation management in avocado orchards. There are many well-tested devices for monitoring soil moisture in orchards but options for measuring plant water status are limited. The objective of this study was to determine whether measuring voltage differences between roots and leaves can be used as a technique to measure plant water status related to soil water content. Root and shoot voltage differences were monitored in young ‘Hass’ avocado trees grafted onto clonal rootstocks grown in containers, and in young seedling ‘Mexicola’ avocado trees grown hydroponically, both experiments carried out under laboratory conditions. In container-grown ‘Hass’ avocado trees, root and shoot voltage differences were initially measured for about 2 h to determine steady state conditions. Plants were then exposed to cycles of soil drying and re-watering. In seedling ‘Mexicola’ trees, electrical signals were measured for at least 75 min in control plants and plants exposed to simulated drought stress. The extracellular electrical potential difference between the base of the trunk and the leaf petiole was continuously monitored after exposing plants to treatments. Results indicated that in ‘Hass’ avocado trees, a change in soil water content induced by root drying and re-watering was accompanied by a slow change in the electrical signal at the leaf petiole which was greatest after 52 and 32 min for root drying and re-watering, respectively. This was related to a decrease in stomatal conductance (gs) of plants exposed to drought. Also, in hydroponic conditions, significant voltage differences occurred in plants exposed to drought simulated by the addition of polyethylene glycol (PEG 6000) to the hydroponic medium resulting also in a decrease in gs. These results suggest that it may be possible to use voltage differences measurements as a technique for monitoring physiological responses to soil water content.

Quantification and control of runoff and soil erosion on avocado orchards on ridges along steep-hillslopes

Soil erosion increases after building downward ridges along steep hillslopes, in particular during the first winter. This erosion decreases when trees grow, but runoff increases. This study presents results of erosion under five different treatments: (i) soil cover with native vegetation, (ii) bare downward ridges, (iii) downward ridges with six year-old avocado orchard, (iv) downward ridges with plant cover and (v) downward ridges covered with agroindustrial waste sludge. The results revealed 20 t ha-1 of soil erosion during the first year after ridges were built, while mitigation measures can reduce erosion in 90%. Adult orchard showed the largest runoff, which probably is due to the effect of a high and about constant soil moisture during irrigation period and smaller infiltration capacity of eroded soil. La erosion de suelos en un huerto de paltos cultivados en camellones a favor de pendiente es alta en la condicion de camellon desnudo, especialmente durante el primer invierno. Luego, la perdida de suelo disminuye con el desarrollo de los arboles, ocurriendo lo contrario con la escorrentia. Esta practica, masificada en Chile central durante las ultimas decadas, deja el suelo descubierto y disgregado, favoreciendo la erosion y escorrentia. En el presente trabajo se cuantifica el transporte de sedimentos durante al menos tres anos bajo tres cubiertas diferentes: i) antes de la preparacion de suelo, con vegetacion nativa, ii) camellon desnudo y iii) camellon con paltos adultos. De igual forma, se evaluan medidas de mitigacion como i) camellon con cobertura herbacea y ii) camellon con lodos de agroindustria. Los resultados muestran una perdida de mas de 20 t ha-1 de suelo durante el primer invierno tras el establecimiento de camellones, en tanto que las medidas de mitigacion reducen la erosion un 90%. La mayor escorrentia registrada en el huerto se debe, probablemente, al efecto del riego y la menor infiltracion de un suelo ya erosionado.

Field optimization of the sex pheromone of Stenoma catenifer (Lepidoptera: Elachistidae): evaluation of lure types, trap height, male flight distances, and number of traps needed per avocado orchard for detection

The sex pheromone of Stenoma catenifer was evaluated in commercial avocado orchards in Guatemala to determine operational parameters, such as optimal lure type, trap height, trap density and estimates of the distances that male moths fly. Of four pheromone dispensers tested, gray and white rubber septa were of equal efficacy, whereas 1-ml low-density polyethylene vials and 2×3-cm polyethylene ziplock bags were least efficacious. The height at which wing traps were hung did not significantly affect the number of adult male S. catenifer captured. For monitoring S. catenifer, these data suggest that the pheromone should be dispensed from gray rubber septa in wing traps hung inside the tree canopy at 1.75 m, a height convenient for trap placement and monitoring. Mark-recapture studies of male S. catenifer indicated that, on average, males flew 67 m in one night. However, it is likely that this is an underestimate of the distance that male moths are capable of flying in a single night. Probabilistic modeling of S. catenifer capture data from different numbers of pheromone traps deployed in seven commercial avocado orchards of varying sizes and infestation levels suggested that 10-13 randomly deployed traps per orchard for a 7-day period are needed to detect at least one male S. catenifer with 90% confidence. These data provide sufficient information to develop effective protocols for using the S. catenifer pheromone to detect and monitor this pest in countries with endemic populations that are exporting fresh avocados, and for quarantine detection and incursion monitoring in countries receiving avocado imports from high risk areas.

A SYSTEMS APPROACH TO MITIGATE ORIENTAL FRUIT FLY RISK IN 'SHARWIL' AVOCADOS EXPORTED FROM HAWAII

A multi-component systems approach is proposed to reduce the risk of oriental fruit fly infestation in 'Sharwil' avocados exported from Hawaii into the United States to an acceptable level. This systems approach is based on poor host status, limited distribution and low prevalence. Recent surveys suggest oriental fruit fly populations are naturally low in Hawaii's small avocado orchards. Maintaining low oriental fruit fly numbers in orchards during the shipping period should reduce the rate of infestation to negligible levels. Population levels will be monitored using protein bait traps and if needed, suppression will be achieved using selective reduced-risk insecticide baits. 'Sharwil' avocados will be shipped only to northern tier states and will only be shipped during the winter months of November to March, when temperatures in the distribution area are inhospitable to tropical fruit pests. The cumulative effect of multiple safeguards should provide quarantine security against oriental fruit fly and other quarantine pests in exported avocados.

Molecular Identification of Sphaceloma perseae (Avocado Scab) and its Absence in New Zealand

Avocado scab was recorded as present in New Zealand in international databases on the basis of one isolate (ICMP 10613) identified by morphological features as Sphaceloma perseae. However, sequence analysis of the rDNA internal transcribed spacer (ITS) region showed that this isolate was dissimilar to the ITS region of other Sphaceloma species, and to S. perseae. By phylogenetic analysis, isolate ICMP 10613 was identified as a species of Phaeosphaeria. To identify S. perseae reliably and quickly, specific polymerase chain reaction (PCR) primers were developed and tested. These PCR primers detected the authentic strain and another strain available from international collections, but did not detect isolate ATCC 11190, or the New Zealand isolate ICMP 10613 which were deposited as S. perseae. No other fungi commonly present in New Zealand avocado orchards were amplified by these primers, nor were three other species of Elsinoe (E. ampelina, E. fawcettii and E. pyri). By phylogenetic analysis of ITS sequence, the atypical isolate ATCC 11190 was identified as Elsinoe araliae, whereas isolate ICMP 10613 was identified as Phaeoseptoria sp. (anamorphic Phaeosphaeria). Re-examination of the scar symptoms on New Zealand avocado fruit showed they were dissimilar to herbarium specimens of S. perseae from Florida and from Cuba. Leaf symptoms typical of this disease have not been found in New Zealand, and isolations from over 1000 scars on fruit onto selective media yielded no fungi identifiable as S. perseae. These results show that ICMP 10613 was mis-identified as S. perseae. The record of avocado scab in New Zealand was shown to be incorrect, and there is no evidence that the causal fungus occurs in New Zealand.

Selection and Breeding of Honey Bees for Higher or Lower Collection of Avocado Nectar

Intensive activity of honey bees, Apis mellifera L., is essential for high fruit set in avocado, Persea americana Mill., orchards, but even when hives are located inside the orchard, many bees still search for alternative blooms. We tested for a possible genetic component for a preference of avocado bloom relative to competing bloom. The honey from each hive was extracted at the end of the avocado bloom and the concentration of perseitol, a carbohydrate that is unique to avocado, was analyzed as a measure for avocado foraging. During the first year, five bee strains were compared in three different sites in Israel. Significant differences were found between strains in honey perseitol concentrations, suggesting differences in their efficiency as avocado pollinators, although these differences were site dependent. At two sites, colonies with the highest and lowest perseitol concentrations were selected as parental "high" and "low" lines. Queens were raised from the selected colonies and were instrumentally inseminated by drones from other colonies of this line. During the second and third years, colonies with inseminated queens were introduced to the avocado orchards, together with the selected colonies still surviving from the previous year. Colonies of the high line had greater perseitol concentrations than those of the low line. Selected colonies that survived from the previous year performed consistently vis-à-vis perseitol concentration, in the second year of testing. Heritability value of 0.22 was estimated based on regression of offspring on midparent. The results reveal a heritable component for willingness of honey bees to collect avocado nectar.

Oiketicus kirbyi (Lepidoptera, Psychidae), a key pest in Peruvian orchards of avocado

In recent years, the bagworm Oiketicus kirbyi (Guilding) has become a pest of increasing importance in Peruvian avocado orchards. A study conducted in six commercial orchards evaluated the ecology of, and feeding damage caused by, bagworms on avocado on the southern coast of Peru. In March 2009, the population of live individuals at different locations consisted of second to sixth larval instars. The sex-ratio in the previous generation of bagworms (the parents of larvae) was female-biased, and the mortality rate was higher for females than males. The percentage of mated females varied between 76.7 and 99.1% and declined when the proportion of males was low. The damage caused by bagworm larvae usually results from defoliation, but in the case of O. kirbyi on avocado, the presence of larvae on the fruits was associated with blemishes that limit the marketability of fruits; thus bagworms cause direct economic losses for avocado growers. Future studies are needed to assess the timing of larval emergence with a view to preventing widespread infestation by dispersing neonate bagworms.

ADVANCES IN DIAGNOSIS OF IRON DEFICIENCY IN AVOCADO

Several methods for determination of extractable iron (Fe; or so-called “active Fe”) have been proposed. In this study, three methods of Fe extraction were tested: 1.5% phenanthroline (pH 3) and 1 M hydrochloric acid (HCl) from fresh leaves, and 1 M HCl from oven-dry leaves. A six-year-old avocado orchard (cultivar ‘Hass’), grown on a calcareous soil in the proximity of Cabildo (Valparaíso region, Chile), was selected for the study. Samples of mature (5–7 moths-old) leaves of different degree of chlorosis were collected. Total Fe concentrations in chlorotic leaves were similar or even greater than in green leaves. Regressions between the extractable Fe concentrations and the leaf SPAD-color were statistically significant for phenanthroline method, while non-significant for HCl methods. Thus, phenanthroline method was superior over others for diagnosis of Fe deficiency in avocado. Phenanthroline-extractable Fe concentration of 6 mg kg−1 was considered as a critical value for mature avocado leaves.

Registro de Urosigalphus avocadoae Gibson (Hymenoptera: Braconidae) como parasitoide de Copturus aguacatae Kissinger (Coleoptera: Curculionidae) en México

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Outcrossing between ‘Bacon’ Pollinizers and Adjacent ‘Hass’ Avocado Trees and the Description of Two New Lethal Mutants

Avocado (Persea americana Mill.) has an unusual flowering mechanism, diurnally synchronous protogynous dichogamy, that promotes crosspollination among avocado genotypes. In commercial groves, which usually contain pollinizer rows adjacent to the more desirable commercial cultivars, the rate of outcrossing has been measured with variable results. Using microsatellite markers, we estimated outcrossing in a commercial California ‘Hass’ avocado orchard with adjacent ‘Bacon’ pollinizers. Seedlings grown from mature harvested fruit of both cultivars were genotyped with five fully informative microsatellite markers and their parentage determined. Among the 919 seedlings of ‘Hass’, 688 (75%) were hybrids with ‘Bacon’; the remaining 231 (25%) seedlings were selfs of ‘Hass’. Among the 850 seedlings of ‘Bacon’, 382 (45%) were hybrids with ‘Hass’ and the remaining 468 (55%) seedlings were selfs of ‘Bacon’. The high outcrossing rate observed in the ‘Hass’ seedlings was expected, because adjacent rows of opposite flowering types (A versus B) are expected to outcross. However, the high selfing rate in ‘Bacon’ was unexpected. A previous study in Florida using the cultivars ‘Simmonds’ and ‘Tonnage’ demonstrated differences in outcrossing rates between complementary flowering type cultivars. In both Florida and California, the A type parents (‘Hass’ and ‘Simmonds’) had similar outcrossing rates (≈75%); however, the B type parents (‘Bacon’ and ‘Tonnage”) had highly skewed outcrossing rates of 45% and 96%, respectively. Two new avocado lethal mutants were discovered among the selfed seedlings of ‘Hass’ and ‘Bacon’. These were labeled “spindly” and “gnarly” and are similar in phenotype to mutants described in Arabidopsis and other crop species.

Niveles de microriego y su efecto sobre el crecimiento y productividad de árboles de aguacate

El aguacate (Persea americana Mill. cv. Simmonds) es una fruta de mucha importancia en Puerto Rico y en la comunidad Latina en los Estados Unidos. En los últimos años, el establecimiento de huertos de aguacate en Puerto Rico ha aumentado considerablemente; la producción de esa fruta se colocó tercera, después de la de mango y la de las chinas. Para asegurar el establecimiento de los árboles, la productividad y la reducción de los problemas asociados al manejo inapropiado del riego, se promueve que los productores adopten algún método para calendarizar el microriego. La Universidad de Puerto Rico y la Universidad de Florida recomiendan el uso de tensiómetros para calendarizar el microriego en árboles frutales. En el 2001 se sembró un huerto de aguacate para establecer un experimento para evaluar el efecto de la tensión hídrica, medida con tensiómetros, en el crecimiento y productividad de árboles de aguacate bajo microriego. La serie de suelo predominante en el predio experimental es Coto arcilloso, clasificado como Typic Eutrustox. La distancia de siembra de los árboles fue de 9.1 m x 9.1 m. Los árboles se sometieron a dos tratamientos de microriego calendarizados utilizando tensiómetros instalados a 30 y 45 cm de profundidad. En ambos tratamientos, los árboles se regaban cuando la tensión hídrica del suelo alcanzaba los valores críticos predeterminados, entre 10 y 15 kPa y entre 40 y 45 kPa. Se incluyó un tercer tratamiento sin riego como testigo. Las variables utilizadas para medir la respuesta de los árboles a los tratamientos de microriego fueron rendimiento, volumen de la copa, número y peso de frutas por árbol, y la cantidad de riego aplicada. El volumen de la copa de los árboles a los cuales no se les aplicaba microriego fue significativamente menor que el de los árboles con los dos tratamientos de microriego probados. El volumen de la copa máximo registrado fue de 148 m3/árbol, obtenido cuando la tensión hídrica del suelo alcanzaba de 40 a 45 kPa; éste no fue significativamente diferente al obtenido cuando se regaba a 10 a 15 kPa. El rendimiento más alto fue 84 kg/árbol y se observó en los árboles regados cuando la tensión superaba los 40 a 45 kPa. Solo en el 2005, el número de frutas por árbol en el tratamiento 10 a 15 kPa superó significativamente a los demás tratamientos, con 68 frutas por árbol. En términos generales, los árboles de aguacate sometidos a una tensión hídrica en el suelo de 40 a 45 kPa produjeron significativamente mayor crecimiento y rendimiento.

First Report of Neofusicoccum australe, N. luteum, and N. parvum Associated With Avocado Branch Canker in California

In 1953, branch cankers on California avocado (Persea americana Mill.) trees were attributed to a Botryosphaeria anamorph, Dothiorella gregaria (teleomorph B. ribis) (2), and the disease was known as Dothiorella canker. Since this time, it has been suggested that this fungus should probably be classified as Fusicoccum aesculi Corda (teleomorph B. dothidea) (3). To our knowledge, B. dothidea is the only reported Botryosphaeriaceae species causing Dothiorella canker on avocado in California. Between the summer of 2008 and the winter of 2009, five trees from each of eight avocado orchards in five counties (San Diego, Riverside, Ventura, Santa Barbara, and San Luis Obispo) were surveyed for Dothiorella canker symptoms to verify the associated Botryosphaeriaceae species. Typical Dothiorella canker symptoms observed included darkened and friable bark with a dried, white, powdery exudate. Underneath the bark, cankers were variable in shape and some penetrated into the heartwood. Small sections of tissue (0.5 cm2) were excised from two to four separate cankers per tree and placed onto potato dextrose agar amended with tetracycline (0.01%) (PDA-tet). The most frequently isolated fungi, based on general growth pattern, speed, and colony color, were in the Botryosphaeriaceae with the following percent recovery by county: Riverside-40 and 100% (site 1 and 2, respectively); San Diego-60% (site 3); Ventura-42 and 53% (site 4 and 5, respectively); Santa Barbara-33% (site 6); and San Luis Obispo-32 and 60% (site 7 and 8, respectively). Pycnidia of Botryosphaeriaceae species were also observed on old diseased avocado tree branches. Sequenced rDNA fragments (ITS1, 5.8S rDNA, ITS2, amplified with ITS4 and ITS5 primers) were compared with sequences deposited in GenBank. Four different Botryosphaeriaceae species were identified and included Neofusicoccum australe, B. dothidea, N. luteum, and N. parvum, with species nomenclature based on the work of Crous et al. (1). Pathogenicity tests were conducted in the greenhouse on 1-year-old avocado seedlings, cv. Hass, with one randomly chosen isolate from each of the Botryosphaeriaceae species noted above. Four replicate seedlings were stem-wound inoculated with a mycelial plug and covered with Parafilm. Sterile PDA plugs were applied to four seedlings as a control. Over a period of 3 to 6 months, seedlings were assessed for disease symptoms that included browning of leaf edges and shoot dieback. Mean vascular lesion lengths on stems were 64, 66, 64, and 18 mm for B. dothidea, N. parvum, N. luteum, and N. australe, respectively. Each fungal isolate was consistently reisolated from inoculated seedlings, thus fulfilling Koch's postulates. To our knowledge, this is the first report of N. australe, N. luteum, and N. parvum recovered from branch cankers on avocado in California. These results are significant because Botryosphaeriaceae canker pathogens are known to enter the host plant through fresh wounds (pruning, frost, and mechanical). With high-density planting becoming more common, which requires intensive pruning, the transmission rate of these pathogens could increase in California avocado groves.

Synthesis and Field Evaluation of the Sex Pheromone of <I>Stenoma catenifer</I> (Lepidoptera: Elachistidae)

Field trials of the sex pheromone of an important and potentially invasive pest of avocados, Persea americana Miller (Lauraceae), Stenoma catenifer Walsingham (Lepidoptera: Elachistidae), were carried out in commercial avocado orchards in Guatemala. The results indicated that the pheromone consists of a single component, (9Z)-9,13-tetradecadien-1-ynal; blends of this compound with a range of ratios of the corresponding alcohol and acetate, or with (6Z,9Z)-tricosadiene, which was present in pheromone gland extracts, were equally or less attractive to male moths than the single component. A range of doses from 10 microg to 1 mg were equally attractive, and lures remained attractive for periods of several weeks. Male moth flight activity peaked between 0230 and 0430 hours. Overall, trap catches were relatively low, similar to what was reported for the congeneric Stenoma cecropia Meyrick, suggesting that this species may use other signals in addition to pheromones during mate location. Nevertheless, the pheromone will be useful for detection of S. catenifer, particularly in areas where there is a risk of the moth invading and establishing due to increased commerce in fresh avocados, and for certifying export orchards as being free of S. catenifer.

First record of Heilipus elegans Guérin-Méneville (Coleoptera: Curculionidae) attacking the avocado tree stem in Colombia

The damage on avocado trees was evaluated in a field in Fresno, Tolima, Colombia and the presence of Heilipus elegans Guerin-Meneville, 1844 (Coleoptera: Curculionidae) was registered attacking the avocado tree trunk. The varieties Lorena, Choquette, Santana, Trinidad, Booth 8 and native cultivars were affected by this pest. The damage is characterized by a reddish coloration and exudates from the galleries made by the larvae. A single larva or one pupa was found per gallery. Adults were located in the cracks of the trees bark. The control method of this pest in avocado is performed by removing the larva from the galleries followed by an application of a healing paste onto the wounds. Samples of larvae, pupae and adults were collected and deposited in the entomological collection of the Universidad of Caldas, Manizales, Colombia. In this publication, the damage caused by H. elengans is illustrated as well as the characteristics of the larva, the pupa and the adult. These illustrations can serve as a field guide for the recognition and management of this insect pest in avocado orchards.

Selection of Highly Informative Microsatellite Markers to Identify Pollen Donors in ‘Hass’ Avocado Orchards

‘Hass’ is the most popular avocado (Persea americana Mill.) cultivar in the world. It has been characterized as a crop requiring cross-pollination. However, the potential extent of self-pollination and the most effective pollen donors (best cross-pollinizing cultivars) have not been determined. In this study, 56 markers were screened against ‘Hass’ and nine commonly used pollinizing cultivars grown in southern California: ‘Bacon,’ ‘Ettinger,’ ‘Fuerte,’ ‘Harvest,’ ‘Lamb Hass,’ ‘Marvel,’ ‘Nobel,’ ‘Sir Prize,’ and ‘Zutano.’ Seventeen microsatellite, i.e., simple sequence repeat (SSR) markers, were found to be very promising for paternity analysis. Four highly informative SSR markers were selected to accurately and unequivocally identify pollen parents of ‘Hass’ fruit from an orchard interplanted with these pollinizing cultivars. From 2003 to 2006, 7,984 ‘Hass’ fruit were analyzed for their paternity. Overall, the pollen parents of 99.55% of the analyzed fruit could be unequivocally identified with a single multiplex polymerase chain reaction (PCR). Only 36 fruits (<0.45%) required a second PCR reaction to reach unequivocal identification of the pollen parents.