M. E. Matheron

The University of Arizona | UA · School of Plant Sciences

Lettuce drop, caused by the soilborne fungi Sclerotinia minor and S. sclerotiorum, continues to be an important disease on this crop in Arizona. Trials were conducted over a 5-year period to compare different fungicides as well as the number, timing, and method of application. Compared with nontreated plots, disease reduction ranging from 49.6 to 6...

Lettuce drop, caused by the soilborne fungi Sclerotinia minor and S. sclerotiorum, is an important and destructive disease of lettuce. Research trials in Arizona have shown that some fungicides, such as boscalid and iprodione, can reduce disease incidence up to 50 to 60%. Prior research also demonstrated that viability of S. minor and S. sclerotior...

A unique foliar disease of spinach, determined to be caused by Pythium aphanidermatum, was observed on spinach in Yuma County, AZ and Imperial County, CA desert spinach production areas in both 2015 and 2016. The foliar symptoms of the disease included water-soaked foliage, rapid collapse of young plants, and white, aerial, cottony mycelia. The dis...

Bell and chile pepper plants are affected by the economically important disease Phytophthora blight, which is caused by the oomycete pathogen Phytophthora capsici. Greenhouse and field trials were conducted to evaluate and compare the ability of nine different fungicides to reduce development of the crown and root rot phase of Phytophthora blight a...

Phytophthora blight, caused by the oomycete pathogen Phytophthora capsici, is an economically important disease in bell and chile pepper. Fourteen different fungicides were evaluated with respect to inhibition of stem lesion growth on chile pepper seedlings inoculated with mycelium or with zoospores of P. capsici 1 or 3 weeks after treatment of pla...

Matheron, M. E., and Porchas, M. 2013. Efficacy of fungicides and rotational programs for management of powdery mildew on cantaloupe. Plant Dis. 97:196-200. Powdery mildew of cucurbits, caused by Podosphaera xanthii (syn. Sphaerotheca fuliginia auct. p.p. (Schltdl.) Pollacci), is a common and often severe disease in most areas of the world. Field t...

Fusarium wilt of lettuce, caused by the soilborne fungus Fusarium oxysporum f. sp. lactucae, affects all major lettuce production areas in California and Arizona. In trials at UC Davis, we found that lettuce cultivars differ significantly in susceptibility to the disease, with some leaf and romaine types highly resistant under all test conditions....

Fusarium wilt of lettuce caused by Fusarium oxysporum f. sp. lactucae continues to spread and cause economic losses in Arizona lettuce fields since the initial discovery of the disease in the state in 2001. Studies were initiated to assess the potential of summer soil solarization and flooding as management tools for Fusarium wilt of lettuce in sou...

Field experiments were conducted over 2 years in Yuma, AZ, and Holtville, CA, to establish the relationship between soil sclerotium density of Sclerotinia sclerotiorum and the incidence of lettuce drop on different lettuce (Lactuca sativa) types under different in-igation systems, and to deterrnine the efficacy of the biocontrol agent Coniothyrium...

Tecoma capensis (Thunb.) Lindl. (Bignoniaceae, common name: Cape honeysuckle), native to southern Africa, is grown as an ornamental plant in warm regions of the USA. The powdery mildew reported previously from T. capensis in North America was an undetermined Oidium species in Florida. The present report documents the occurrence of the powdery milde...

During the life of a citrus planting, the population of Phytophthora pathogens call build to significant levels in orchard soil. A Study was initiated to examine the impact of some nonchemical Cultural practices on survival of P. nicotianae, the most prevalent Phytophthora sp. in Arizona citrus groves, in soil formerly planted to citrus. In three t...

Field experiments were conducted over 2 years in Yuma County, AZ, and Imperial County, CA, to determine the efficacy of several biocontrol agents for the management of lettuce drop caused by Sclerotinia spp. Commercial formulations of Trichoderma harzianum (Plantshield, Super sivit), Gliocladium virens (Soilgard), Coniothyrium minitans (Contans), a...

Bright yellow, interveinal chlorosis was observed for the first time on leaves of the older and mid-growth of cucurbit plants in southern Arizona and Sonora (Mexico) during September and October of 2006. Some cultivars exhibited substantial yield losses of 30 to 80%. In Arizona, symptoms were in Cucumis melo (muskmelon and honeydew melon) fields in...

Brown heartwood rot, which often is found in branches within lemon groves in southwestern Arizona, is caused by two basidiomycete fungi, Antrodia sinuosa and Coniophora eremophila. Another fungus, a species of Nodulisporium, has been recovered from small, dying lemon tree branches with ail internal white wood rot. Studies were conducted from 1999 t...

During the winter (December through February) of 2003-2004, and again during 2004-2005, spinach (Spinacia oleracea) crops in the Yuma region of Arizona developed a foliar disease that previously had not been diagnosed in this geographic area. The problem was found on only a few acres and severity was low. The first symptoms consisted of round to ov...

Races 1 and 2 of Podosphaera xanthii (syn. Sphaerotheca fuliginea ) were defined in Imperial Valley, Calif. 1938 when P. xanthii overcame genetic resistance in `PMR 45'. Race 3 was first observed in the U.S. in 1976 in Texas; 15 additional races of P. xanthii have been reported in the literature since 1996. Races 1 and 2 have been common in Arizona...

Fusarium wilt of lettuce, first recognized in Japan in 1955, has since been discovered in the United States (California in 1990, Arizona in 2001), Iran (1995), Taiwan (1998), and Italy (2001). In Arizona, the causal agent, Fusarium oxysporum f. sp. lactucae, has been recovered from lettuce plants in 27 different lettuce fields during the 2001 to 20...

Three races of Fusarium oxysporum f.sp. lactucae, cause of fusarium wilt of lettuce, are known in Japan, where the pathogen was first observed in 1955. Fusarium wilt first affected commercial U.S. lettuce production in 1990 in Huron, Calif., but did not become a serious problem in the U.S. until 2001 when it reappeared in Huron and appeared in the...

The effect of soil temperature and moisture on eruptive germination and viability of sclerotia of Sclerotinia minor and S. sclerotiorum in field soil was examined. In two trials at constant temperatures, the proportion of sclerotia of both pathogens that germinated in wet soil ( greater than or equal to-0.02 MPa) tended to decrease as soil temperat...

Sclerotinia drop is a major disease of lettuce caused by two soilborne fungi, Sclerotinia minor and S. sclerotiorum. Fungicides such as dicloran (Botran), iprodione (Rovral), and vinclozolin (Ronilan) are currently available in the United States to manage this disease. Studies were conducted to investigate the relative effect of some new fungicides...

A new wilt and root rot disease was observed in 6 and 11 commercial fields of lettuce (Lactuca sativa) in western Arizona during the fall of 2001 and 2002, respectively. Distance between infested sites ranged from approximately 0.5 to 39 km. Five head lettuce cultivars as well as a red leaf lettuce cultivar were affected. Disease symptoms included...

The activity of the registered fungicides fosetyl-A1 and metalaxyl (subsequently replaced with mefenoxam by the manufacturer) was compared with other potentially useful compounds, azoxystrobin, dimethomorph, fluazinam, and zoxamide, for suppression of canker development on citrus bark after inoculation with Phytophthora citrophthora or P nicotianae...

The fungicide mefenoxam is registered for the control of Phytophthora blight of peppers caused by Phytophthora capsici. Isolates of the pathogen that are insensitive to mefenoxam, however, have been detected in some locations. Consequently, alternative methods are needed to control Phytophthora blight of peppers. Acibenzolar-S-methyl (ABM, Actigard...

Brown heartwood rot is commonly found in mature lemon groves in southwestern Arizona. Two basidiomycete fungi, Antrodia sinuosa and Coniophora eremophila, have been isolated from symptomatic trees. Similarities between the two pathogens include the following: each fungus grows optimally at 30 to 35°C, neither organism produces a fleshy fruiting bod...

In March 2000, plants began to die within two garbanzo (Cicer arietinum L.) fields about 48 km apart in southwestern Arizona. Initial symptoms included wilting of leaves and stem necrosis on individual branches, followed by entire plant necrosis and death. White mycelium was present on plant stems near the soil surface. In one field, small black ir...

The activity of five fungicides, azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and metalaxyl (subsequently replaced with mefenoxam by the manufacturer), was compared for effects on the development of root, crown, and fruit rot of chile pepper and on recovery of Phytophthora capsici from naturally infested soil. When inoculated with zoospores,...

In vitro activity of azoxystrobin, dimethomorph, and fluazinam on growth, sporulation, and zoospore cyst germination of Phytophthora capsici, P. citrophthora, and P. parasitica was compared to that of fosetyl-Al and metalaxyl. The 50% effective concentration (EC50) values for inhibition of mycelial growth of the three pathogens usually were lowest...

Septoria leaf spot was detected in the United States for the first time in 1964 within an experimental pistachio planting at Brownwood, Texas. The first observation of the same disease in Arizona pistachio trees did not occur until 1986. In 1988, a survey of the 2,000 acres of pistachio orchards in southeastern Arizona revealed a widespread inciden...

Erysiphe cichoracearum is the fungus that causes powdery mildew of lettuce, a disease favored by warm and dry weather conditions. Several potential new fungicides were evaluated for control of this disease in 1999. Untreated lettuce plants were heavily infected with powdery mildew, whereas the disease was very light to virtually nonexistent in plot...

Downy mildew of broccoli, cauliflower and cabbage is caused by the fungus Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several potential new fungicides were evaluated for control of this disease on broccoli in 1999. The final severity of downy mildew in this trial was moderately h...

Studies were conducted to compare existing and potential citrus rootstocks with respect to resistance to root rot and gummosis caused by Phytophthora citrophthora and P. parasitica in greenhouse and growth chamber experiments and horticultural performance under simulated nursery conditions. Depending upon rootstock and experiment; mean root weights...

In 1964, Septoria leaf spot was detected for the first time in the United States in experimental pistachio (Pistacia vera) plantings at Brownwood, Texas. A moderate level of the same disease, caused by the fungus Septoria pistaciarum, was first observed in 1986 on leaves of pistachio trees in Arizona. In 1988 a survey of the 800 ha of pistachio orc...

Coniophora eremophila and Antrodia sinuosa cause brown heartrot in living lemon trees in southern Arizona and California. They can be distinguished in the field by differences in rot characteristics. Both have a high optimum growth temperature of approximately 35 °C. Coniophora eremophila has a cultural morphology typical of other Coniophora specie...

The distribution and seasonal population dynamics of Phytophthora citrophthora and P. parasitica within citrus orchards in southwestern and central Arizona were determined over a multiple-year period. In central Arizona, P. citrophthora alone, P. parasitica alone, or both pathogens together were recovered from 7, 37, and 41% of sampled orchards, re...

Studies were conducted to evaluate potential chemical disease management tools for Alternaria fruit rot on navel oranges and Coniophora brown wood rot on lemon trees, to investigate the possible effect of branch diameter on development of Coniophora wood rot on lemon trees and to summarize our evaluations of citrus rootstocks with respect to relati...

Studies compared colonization of citrus rootlets by Phytophthora citrophthora or P. parasitica under constant favorable or inhibitory temperatures to root colonization under various daily combinations of favorable and inhibitory temperatures. Colonization of rough lemon rootlets after incubation for 96 h in the presence of soil naturally infested w...

A survey of mature lemon trees showed an average of 30% of trees with symptoms of brown heartrot caused by Coniophora eremophila. Growth of C. eremophila inoculated into branches of Valencia orange, Marsh grapefruit, Orlando tangelo, or Lisbon lemon on rough lemon rootstock was significantly higher in lemon than in other types of citrus. C. eremoph...

The activities of sodium tetrathiocarbonate (STTC) and metalaxyl on the viability of Phylophthora capsici within colonized pepper tissue, the recovery of P. capsici from soil and the development of root and crown rot on chile pepper were evaluated and compared. P. capsici was not recovered from colonized chile pepper stem tissue buried in soil that...

Studies were established in 1992 and 1993 in a mature commercial pistachio orchard to determine the effectiveness of several fungicides for control of septoria leaf spot (Septoria pistaciurum). Fungicide treatments used in 1992 were Bravo 720F at 3.0 lbs./A (ai.) and 4.5 lbs./A a.i.; Kocide 101 50W at 8.0 lbs./A a.i. plus Benlate 50W at 1.0 lb./A a...

Root and shoot segments from Lisbon lemon trees established on sour orange, rough lemon, and volkamer lemon rootstocks were evaluated for seasonal changes in susceptibility to Phytophthora citrophthora and P. parasitica. Plant material was wounded, inoculated with P. citrophthora or P. parasitica, then incubated in moist chambers. Root segments of...

Studies were initiated to determine the effect of sodium tetrathiocarbonate (STTC) on mycelial growth and viability of sclerotia of Sclerotinia minor and S. sclerotiorum and to evaluate the efficacy of this material for control of Sclerotinia leaf drop of lettuce. No growth of mycelia from agar disks containing either S. minor or S. sclerotiorum wa...

Abundant production of sporangia by Phytophthora citrophthora and P. parasitica occurred between 20 and 30 C. P. citrophthora was recovered from at least 50% of tested rootlets of Citrus jambhiri (rough lemon) plants incubated at temperatures of 10, 15, 20, and 25 C in the presence of preformed sporangia, whereas P. parasitica was recovered from at...

The activity of sodium tetrathiocarbonate (STTC) on sporulation and growth of several species of Phytophthora in vitro has recently been demonstrated. This study was initiated to evaluate and compare the effect of root and soil treatments with STTC, metalaxyl, and fosetyl-Al on the subsequent development of Phytophthora root rot on citrus. Growth o...

(...)Isolates of P.p. from citrus were highly virulent to rough lemon seedlings, causing crown rot and significant reduction of root weight. Isolates of the pathogen from noncitrus hosts demonstrated low virulence to rough lemon, with no crown rot and only minor reduction of root weight. All tested isolates of P.p. were highly virulent to tomato se...

Four rootstocks and two commercial cultivars of citrus were evaluated for temporal variation in susceptibility to colonization by Phytophthora citrophthora and P. parasitica. For 24 consecutive months, terminal shoots were collected from field-grown trees of Citrus macrophylla, C. jambhiri, C. aurantium, and C. volkameriana. They were then wounded,...

At a concentration of 0.5 μg/ml radial growth of the pathogen was significantly reduced by bitertanol, chlozolinate, diniconazole, iprodione, terbutrazole, vinclozolin, and CGA-449. At the ED 50 concentration of tested compounds, sclerotia production was reduced in the presence of diniconazole or SC-0858 and was increased in the presence of chlozol...

A transaminase (aminotransferase, EC 2.6.1) fraction was partially purified from shoot tips of pea (Pisum sativum L. cv. Alaska) seedlings. With alpha-ketoglutarate as co-substrate, the enzyme transaminated the following aromatic amino acids: d,l-tryptophan, d,l-tyrosine, and d,l-phenylalanine, as well as the following aliphatic amino acids: d,l-al...

Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2000. Powdery mildew appeared in our plots by Feb 9 and reached high levels by plant maturity on Ma...

Septoria leaf spot was detected in the United States for the first time in 1964 within an experimental pistachio planting at Brownwood, Texas. The first observation of the same disease in Arizona pistachio trees did not occur until 1986. In 1988, a survey of the 2,000 acres of pistachio orchards in southeastern Arizona revealed a widespread inciden...

Downy mildew of broccoli is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of weather conditions favorable for disease development. Potential new fungic...

Powdery mildew occurs annually on melons in Arizona. Podosphaera xanthii (Sphaerotheca fuliginea) is the plant pathogenic fungus that causes powdery mildew on cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant levels...

Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this first discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from approximately 30 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Cultural disease control meas...

Six mulches were compared to no mulch on cantaloupes at Yuma in the Spring of 1996. The IRT film and black mulches caused "Mission" cantaloupes to produce significantly higher early yields than white mulch or no mulch. Silver mulch gave good early and total yields. All mulches seemed to favor total production but in this test differences for total...

In the 2001-2002 production season, Fusarium wilt was observed for the first time in six different lettuce fields in the Gila and Dome Valley production areas of Yuma County, Arizona. The disease was found in 11 additional sites during 2002-2003. Fusarium wilt presents a serious threat to the health of the lettuce industry in Arizona. The only effe...

Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation or rainfall event. Disease severity can increas...

Nine different cultivars of lettuce were planted at the Yuma Valley Agricultural Center. Plants were treated four times with two different rates of Actigard. Control plants were not treated. Near plant maturity (Mar. 23, 2000) the severity of powdery mildew was recorded. Among nontreated plants, Cibola, Conquistador, and Coolguard had the lowest le...

Introduction Alternaria rot of citrus is a serious problem in citrus production world wide. In Arizona, the disease is most commonly found in Minneola tangelos and navel oranges grown in Maricopa County. Alternaria rot occurs primarily as a stem-end rot on fruit held in cold storage. However, under optimum conditions the disease occurs as a stylar-...

Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation or rainfall event. Disease severity can increas...

Bremia lactucae and Erysiphe cichoracearum, respectively, cause downy and powdery mildew of lettuce. Cool moist environmental conditions favor the development of downy mildew, whereas warm and dry weather is conducive for powdery mildew. Several potential new fungicides were evaluated for control of these diseases of lettuce in 1998. The final seve...

Powdery mildew can occur on melons annually in Arizona. Podosphaera xanthii (Sphaerotheca fuliginea) is the plant pathogenic fungus that causes powdery mildew of cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant lev...

Sclerotinia drop on lettuce is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperatures favor this disease. Some registered products as well as new chemistries in development were compared for their ability to suppress Sclerotinia drop on lettuce during the winter vegetable growing season in 2005-2...

Leaf drop of lettuce is caused by the plant pathogenic fungi Sclerotinia minor and S. sclerotiorum. Cool and moist environmental conditions favor disease development. Potential new fungicides were evaluated in field trials for control of this disease in 1994 and 1995. In the 1994 trial, Fluazinam and Topsin M provided significant decrease of diseas...

Sclerotinia leaf drop in Arizona is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperature favor this disease. Some new products in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 2000-2001. Sclerotia of each pathogen were applied to plo...

Gummosis caused by Phytophthora parasitica and P. citrophthora is a serious problem in Arizona citrus groves. In a 15-year -old Orlando tangelo planting at the Yuma Mesa Agricultural Center, a 20 cm section of trunk on each tree was painted with phosphorous acid , metalaxyl or fosetyl -Al. After treatment, pieces of bark were periodically removed f...

Powdery mildew occurs annually on melons in Arizona. Podosphaera xanthii (Sphaerotheca fuliginea) is the plant pathogenic fungus that causes powdery mildew on cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. Development of powdery mildew on melons is favored by moderate temperatures and relative humidity, succulent plant gr...

This study was conducted in the greenhouse at the Yuma Agricultural Center. Thirty-nine experimental lines of pepper from the Texas A&M pepper breeding collection were seeded and grown in the greenhouse in 8 fl. oz. plastic pots. When plants were 2 months old (Aug 8), the potting mix in each pot was infested with Phytophthora capsici. Plants were p...

Sclerotinia drop of lettuce, caused by the pathogenic fungi Sclerotinia minor and S. sclerotiorum, is a serious disease in most regions where this crop is grown. Conventional fungicides, such as Rovral (iprodione) and Endura (boscalid), are usually applied after lettuce is thinned and once more 2 to 3 weeks later. Two biological products, Contans (...

Septoria leaf spot was detected in the United States for the first time in 1964 within an experimental pistachio planting at Brownwood, Texas. The first observation of the same disease in Arizona pistachio trees did not occur until 1986. In 1988, a survey of the 2,000 acres of pistachio orchards in southeastern Arizona revealed a widespread inciden...

Downy mildew of broccoli, cauliflower and cabbage is caused by the oomycete pathogen Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several fungicides were evaluated individually or combined with another material (applied as a mixture or in a rotational program) for control of this...

Sclerotinia leaf drop of lettuce is caused by two different species of this fungal pathogen, Sclerotinia minor and S. sclerotiorum. Cool and moist envrionmental conditions favor this disease. Some new fungicides in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing seasons of 1996 -97 and 1997 -98. Sc...

Phytophthora parasitica and P. citrophthora are routinely recovered from diseased citrus groves in Arizona. Stem sections were collected monthly from Citrus macrophylla, rough lemon, .sour orange, Cleopatra mandarin, Troyer citrange and Citrus volkameriana. Stem pieces were wounded, inoculated with mycelium of P. parasitica or P. citrophthora, then...

Powdery mildew on melons is an annual disease problem in Arizona. Sphaerotheca fuliginea is the plant pathogenic fungus that causes powdery mildew of cucurbits, which include cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant levels. F...

Before replanting a citrus grove in Arizona, different preplant cultural activities may be performed, such as immediate replanting of the new citrus grove, allowing soil to lay fallow for various lengths of time, or planting the site to alfalfa for one or more years before the new citrus grove is established. A study was conducted to compare the ef...

Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this first discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from approximately 30 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Cultural disease control meas...

Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation. Disease severity can increase dramatically due...

Powdery mildew of cucurbits, which include cantaloupe, honeydew, watermelon, cucumber and squash, occurs every year in Arizona. Moderate temperatures and relative humidity, succulent plant growth and reduced light intensity brought about by a dense plant canopy are factors that promote development of powdery mildew, which is caused by the pathogeni...

Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this initial discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from over 40 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Soil solarization has shown promise...

Phytophthora blight of peppers (Capsicum annuum), caused by the oomycete pathogen Phytophthora capsici, occurs in most regions where this crop is grown. The root and crown rot phase of the disease develops on plants in areas of the field where soil remains saturated with water after an irrigation or rainfall. Subsequent periods of soil saturation e...

Experiments were initiated to evaluate potential new citrus rootstocks for their relative tolerance or resistance to root rot and gummosis caused by Phytophthora citrophthora and P. parasitica and to determine the efficacy of potential new fungicides for disease control. In greenhouse trials conducted in 1994 and 1995, the range of root loss due to...

Fusarium wilt of lettuce was first recognized in Arizona in 2001. The pathogen, Fusarium oxysporum f. sp. lactucae, has been recovered from infected lettuce plants in 27 different fields during the last three years. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Historically, control of Fusarium wilt on crops ot...

In 1992, a species of wood-decaying fungus, Coniophora eremophila, was first reported to be associated with a brown heartwood rot occurring on lemon trees in Yuma (Matheron, Gilbertson & Matejka, 1992), although wood decay had been documented in lemon trees for at least 30 years earlier. In 1997 a second fungus was isolated from decayed heartwood o...