Recent plantpath_ucd_rw items

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2011

Thu, 16 Jun 2011 00:00:00 +0000

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2011

Evaluation of fungicide programs for management of Botrytis bunch rot of grapes: 2010 field trial

Fri, 14 Jan 2011 00:00:00 +0000

Bunch rot of grapes is caused by Botrytis cinerea, a fast-growing pathogen infecting numerous crops of commercial value. Bunch rot can potentially lead to a reduction in the yield and quality of table, raisin, and wine grapes, with high economic losses in some locations or years (Flaherty et al. 1992). Botrytis overwinters as sclerotia in mummified berries on the ground or on canes. The disease can first appear as shoot blight following frequent spring rains; flowers can become infected during bloom (Bulit and Dubos 1988). In infected fruits, disease symptoms are latent until late in the season. As sugar concentration increases in the berry, the fungus resumes growth and infects the entire fruit, often resulting in berry splitting and sporulation on the fruit surface (Flaherty et al. 1992). Free water is a requirement for the pathogen, and favorable conditions include humidities exceeding 90% and temperatures between 15-27°C (Flaherty et al. 1992, Bulit and Dubos 1988, Gubler...

Fungicide control of apple scab: 2010 field trial

Fri, 14 Jan 2011 00:00:00 +0000

Apple scab, caused by the fungal pathogen Venturia inaequalis, is a significant fruit and foliar disease worldwide (Jones and Sundin 2006). Apples grown in regions of California characterized by spring precipitation or damp microclimates are subject to infection. Initial pathogen colonization of green tissue occurs when water stimulates ascospore release from pseuodothecia located in overwintering leaf litter, followed by dispersal to leaves, flowers or fruit. Asexually-produced conidia from the primary sites of infection on the host can also colonize new tissue if spores are transported in the air or by water splash (Jones and Sundin 2006). In California, periodic applications of synthetic or organic fungicides from approximately March to June are required to control apple scab; the timing of fungicide applications is dependent on season to season patterns in precipitation (Gubler 2006). Based on research in other apple producing regions, additional control measures such as...

Powdery mildew control on pumpkin and zucchini with organic and synthetic fungicides: 2010 field trial

Fri, 10 Dec 2010 00:00:00 +0000

Powdery mildew is an important disease in commerciall members of the cucumber family. The specific pathogen that infects cucurbits in California is Podosphaera fusca (synonyms: P. xanthii, Sphaerotheca fulginea and S. fusca), (Janousek et al. 2009, McGrath and Thomas 1996, Pérez-García et al. 2009). Over-wintering chasmothecia produce ascospores that then develop into whitish colonies on leaves, leaf petioles, and stems (McGrath and Thomas 1996, Glawe 2008). Wind or insect vectors disperse asexually-produced conidia and thus spread the disease (Blancard et al. 1994). Favorable conditions for disease epidemics include temperatures between 20-27°C and lower-intensity light (McGrath and Thomas 1996). Disease outbreaks in the Central Valley of California tend to occur during late summer and autumn months, but coastal areas may be continuously threatened (Davey et al. 2008). Infections have the potential to reduce the yield and quality of fruit and can lead to early plant senescence...

Control of grape powdery mildew with synthetic, biological and organic fungicides: 2010 field trials

Fri, 15 Oct 2010 00:00:00 +0000

Powdery mildew is an economically-important pathogen of grapes worldwide. This report details the findings of our annual powdery mildew fungicide trials on grapevine cultivar Chardonnay (Vitis vinifera). The trials were conducted at Herzog Ranch, near Courtland, California in 2010. Treatments were placed in four adjacent trials in the vineyard. Spraying commenced in mid April, amidst significant rainfall events that likely promoted the release of powdery mildew (Erysiphe necator) ascospores from overwintering chasmothecia. Powdery mildew pressure began slowly with cool temperatures early on, but quickly built to very high disease pressure levels as temperatures warmed. Spraying was completed on July 23 and treatments were evaluated for disease incidence and severity.

Trial I consisted of soft chemistry products, including biologicals, sulfurs, nutrient applications, oils, and other materials. Spray frequencies varied from weekly applications to 21 day intervals. Many...

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010 (updated 5/1/10)

Mon, 10 May 2010 00:00:00 +0000

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010 (updated 5/1/10)

Fri, 7 May 2010 00:00:00 +0000

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010 (updated 5/1/10)

Fungicide control of apple scab: 2007 trial results

Tue, 4 May 2010 00:00:00 +0000

Apple scab, caused by the pathogen Venturia inequalis, is the most important disease affecting apple production throughout the world (MacHardy 1996). In California, the disease impacts orchards in coastal regions, in the Central Valley, and in the foothills of the Sierra Nevada (Ohlendorf 1999). Leaf and fruit infection occurs as V. inequalis ascospores are released from leaf litter (or as conidia are dispersed from tree branches and budscales) in the course of spring rains (MacHardy 1996). A field trial was conducted to evaluate fungicide control of apple scab (Malus x domestica cv Red Delicious) at an orchard near Camino, El Dorado Co., California, in the spring of 2007. The fungicides Procure, Dithane, Sovran, Evito, Endorse, Flint, the organic Champion + Kumulus rotating to JMS Stylet-oil, and the experimental materials A7402 (difenoconazole), Topguard (flutriafol), and LEM17 (penthiopyrad) were compared to an unsprayed control in a completely randomized design. We examined...

EFFICACY AND TIMING OF FUNGICIDES,BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010 (rev. April 1, 2010)

Thu, 1 Apr 2010 00:00:00 +0000

EFFICACY AND TIMING OF FUNGICIDES,BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010 (rev. April 1, 2010)

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010

Fri, 19 Mar 2010 00:00:00 +0000

EFFICACY AND TIMING OF FUNGICIDES, BACTERICIDES, AND BIOLOGICALS for DECIDUOUS TREE FRUIT, NUT, STRAWBERRY, AND VINE CROPS 2010

Control of powdery mildew in grapes: 2007 field trials

Wed, 24 Feb 2010 00:00:00 +0000

Powdery mildew is a pervasive disease of cultivated grape. We conducted six field trials in a mature Chardonnay vineyard in Sacramento County to determine the efficacy of selected chemical and ‘soft chemistry’ fungicides (including new experimental materials) to control powdery mildew. Overall disease pressure at the site was low during much of the 2007 field season, but reached moderate levels by the time of veraison. Treatments exhibited a range of efficacy, with synthetic materials usually providing better control than copper-based products, biological fungicides, or other soft chemistry materials.

Fungicide control of Phomopsis cane and leaf spot on grape: 2009 field trial

Tue, 16 Feb 2010 00:00:00 +0000

Phomopsis cane and leaf spot is a disease that can be economically important in California during wet years along the northern coast and in the northern San Joaquin Valley. A field trial was conducted in Solano County, CA to evaluate the efficacy of several registered and experimental fungicides on control of Phomopsis cane and leaf spot on Thompson seedless grapes. Fungicide treatment significantly affected leaf severity. Kresoxim methyl (at 6.4 oz/acre) and pyraclostrobin + boscalid provided the best protection; kresoxim methyl (at 4.0 oz/acre) and Streptomyces lydicus WYEC108 (12 oz/acre) also reduced leaf severity. Shoot disease severity also differed significantly among treatments; data suggested that the best disease control was achieved by treatment with pyraclostrobin + boscalid or kresoxim methyl (both application rates).

Control of brown rot and shot hole in almond: 2009 field trial

Wed, 6 Jan 2010 00:00:00 +0000

We conducted a field trial to evaluate the efficacy of a synthetic fungicide (Pristine; boscalid and pyraclostrobin) and two organic fungicides (Regalia; extract of Reynoutria sachilinensis and JMS Stylet-oil; paraffinic oil) for management of two foliar diseases in almond. Pristine and Pristine alternated with Regalia effectively reduced symptoms of both brown rot and shot hole following three applications from red bud to post-bloom. JMS Stylet-oil and Regalia alone did not control the diseases.

Evaluation of fungicide programs for management of Botrytis bunch rot of grapes: 2009 field trial

Mon, 7 Dec 2009 00:00:00 +0000

Botrytis bunch rot is an important grapevine disease in California. Twenty eight fungicide programs were evaluated for control of bunch rot in a field experiment in a Chardonnay (clone 4) vineyard in the Carneros region of Napa Valley, California during 2009. Four fungicide applications were made from bloom to harvest with the final application made just prior to heavy rainfall. Disease was rated three weeks following the final application. Disease developed rapidly during the month of October, approaching 60% infected berries in untreated vines. Most fungicide programs failed to give a large (>3 fold) reduction in disease severity, but many partially lowered disease severity. Several products reduced disease to less than 10% severity: fenhexamid (alone and with tetraconazole), fluopyram + tebuconazole and fluopyram + tebuconazole alternated with trifloxystrobin + tebuconazole. Tetraconazole and cyprodinil alone, mineral oil, other soft chemistry products, and boscalid +...

Control Strategies for Trunk Diseases of Grapevine (Vitis vinifera L.)

Wed, 2 Dec 2009 00:00:00 +0000

There are no therapeutic treatments for canker diseases of grapevine. These diseases can be prevented, however, by protecting dormant pruning wounds from airborne inoculum. A single fungicide application after pruning reduced canker incidence in 159/160 cases and canker severity in 16/16 cases. Thiophanate-methyl was most effective against Lasiodiplodia theobromae and myclobutanil was effective against Eutypa lata. Both fungicides were effective against Phaeoacremonium aleophilum and Phaeomoniella chlamydospora. Pruning wounds were found to be most susceptible to canker pathogens in December and least susceptible in March, and late or double pruning was shown to augment fungicide effectiveness in reducing canker disease incidence. Pruning wound susceptibility to canker pathogens was found to decrease significantly three weeks after pruning. The practical implications of these results are discussed.

Powdery mildew control on pumpkin with organic and synthetic fungicides: 2009 field trial

Tue, 10 Nov 2009 00:00:00 +0000

Several species of powdery mildews are obligate biotrophs of crops in the Cucurbitaceae. These pathogens rapidly colonize green tissues via asexual reproduction and can negatively affect host physiology. We conducted a field experiment to evaluate the efficacy of organic and synthetic fungicides (registered and experimental products) for control of powdery mildew in pumpkin cv. Sorcerer. Following six weeks of fungicide applications, disease incidence (percentage of infected leaves within a plot) and disease severity (colony density on the leaf surface) was generally lowest in plants treated with synthetic materials (quinoxyfen, penthiopyrad, triflumizole, and mixed programs of triflumizole/quinoxyfen, myclobutanil/quinoxyfen/ trifloxystrobin, and myclobutanil/penthiopyrad/ trifloxystrobin). ‘Soft-chemistry’ materials such as paraffinic oil, tea tree oil, hydrogen peroxide, and the biocontrol agent, Strepyomyces lydicus WYEC108, were less effective at managing disease when...

Control of grape powdery mildew with synthetic, biological, and organic fungicides: 2009 field trials

Mon, 2 Nov 2009 00:00:00 +0000

Powdery mildew is an economically-important pathogen of grapes worldwide. This report details the findings of our annual powdery mildew fungicide trials on grapevine cultivar Chardonnay (Vitis vinifera). The trials were conducted at Herzog Ranch, near Courtland, California in 2009. Treatments were placed in five adjacent trials in the vineyard. Spraying commenced in mid April, shortly after a heavy rainfall event that likely promoted the release of powdery mildew (Uncinula necator) ascospores from overwintering chasmothecia. Spraying was completed in mid July and treatments were evaluated for disease incidence and severity on 21 July 2009, at about the beginning of veraison.

Trial I consisted of IR-4-funded biofungicide research that focused on two products: caprylic acid (a novel control agent in current development) and Actinovate (a registered product containing the bacterium Streptomyces lydicus WYEC106). Trials II-V included various fungicide products (either currently...

Synthetic and organic fungicide control of apple scab: 2009 field trial

Thu, 15 Oct 2009 00:00:00 +0000

Summary Apple scab, caused by the fungal pathogen Venturia inaequalis, is a significant disease in regions of California characterized by spring precipitation. Disease control is typically attained with periodic application of fungicides. We conducted a field experiment near Camino, California to test the effects of several registered and experimental fungicides on control of scab in mature Red Delicious apple trees. In late spring 2009, following four applications (from green tip into post-bloom), we evaluated disease incidence and severity (lesion density). High disease incidence (>95%) and high lesion density (>12 lesions/fruit) on untreated and water-treated fruits suggested significant disease pressure during the preceding months. Generally, fruits and leaves treated with kresoxim-methyl or mancozeb + flutriafol showed the lowest incidence and severity of disease. Flutriafol (used alone) was moderately effective; tea tree oil, parafinnic oil and monopotassium...

Control of powdery mildew on pumpkin leaves: 2008 field trial

Mon, 5 Jan 2009 00:00:00 +0000

Powdery mildew of cucurbits, caused by the pathogen Podosphaera xanthii or other Erysiphaceae, is an important foliar disease in California. Disease is often managed by application of synthetic fungicides. We tested 11 fungicide treatment regimes to assess control of powdery mildew on pumpkin in a field trial in northern California. Foliage was sprayed weekly or biweekly; two biocontrol treatments were also soil-drenched prior to foliar applications. Disease attained high levels of incidence (nearly 100% of leaves infected) and severity (from 0.97 to 2.2 colonies per cm2) on the upper surface of leaves in unsprayed/undrenched, unsprayed/water drenched and water-sprayed controls. Biological and organic treatments, including Actinovate (Streptomyces lydicus WYEC108) and Phyton 016-B (copper sulfate pentahydrate), did not effectively control the disease. Treatment with Rally alternated with Quintec (myclobutanil/quinoxyfen), LEM17 (penthiopyrad), LEM17 + other synthetics, or Inspire...

Chemical and biological control of grape powdery mildew: 2008 field trials

Mon, 24 Nov 2008 00:00:00 +0000

Powdery mildew is one of the most significant diseases affecting grape (Vitis vinifera) production around the world. The disease is caused by the hyaline ascomycete, Erysiphe necator, a pathogen capable of rapid proliferation under optimal environmental conditions. Disease onset begins in the spring with the release of ascospores from over-wintering chasmothecia (Gubler and Hirschfelt 1992). Once initial colonies are established, the fungus can asexually propagate via large numbers of conidia that disperse and re-infect additional leaves and developing fruits. Powdery mildew effects on the host include reduction in berry mass, potential cracking of berries, and increased susceptibility to berry rots (Gubler and Hirschfelt 1992, Calonnec et al. 2004, Gadoury et al. 2007). Economically, the disease may be damaging to California’s grape industry because of lost yield, a shortened shelf life for table grapes, and alterations in wine flavor (Gubler and Hirschfelt 1992, Gadoury et...

Efficacy and Timing of Fungicides, Bactericides, and Biologicals for Decidous Tree Fruit, Nut, Strawberry, and Vine Crops

Tue, 24 Jun 2008 00:00:00 +0000

This web page will provide certain Plant Pathology and Nematology educational materials to growers, Farm Advisers, Pest Control Advisers and to the public. This information would aid in disease diagnosis, proper sampling procedures for submission to diagnostic labs, and the principles of epidemiology and disease management that underlie the University’s Pest Management Guidelines.

In addition, we will broadcast disease alerts (including outbreaks of new diseases, tracking of new pathogen races, tracking of fungicide-resistant strains, etc.) and disseminating information relating to research advances, poisonous mushrooms, and other issues of importance to Pest Control Advisers, Master Gardeners and other professional and volunteer groups.