Pea Powdery Mildew
Pea powdery mildew caused by the obligate biotrophic fungus Erysiphe pisi DC is an air-borne disease of worldwide distribution, being particularly important in climates with warm dry days and cool nights. The disease can cause 25-50% yield losses, reducing total yield biomass, number of pods per plant, number of seeds per pod, plant height and number of nodes. The disease can also hasten crop maturity, rapidly raising tenderometer values beyond optimal green pea harvesting levels. Severe pod infectation leads to seed discolouration and downgrading of seed quality. It can also damage quality of processing pea giving tainted and bitter characteristics. Conidas and fungal debris from heavily infected crops can cause breathing and allergy problems for machinery operators.
“Crop rotation is of limited usefulness in managing powdery mildew. Powdery mildew epidemics sweep large areas with ease, and the separation of crops in time and space can delay epidemics but not prevent them.
Fungicide must be applied when the number of plants infected is still low and infection level on each plant is minimal (<5% infection).
Generally, only one application is required, unless infection comes in very early and/or conditions conducive to infection persist. In this case, follow-up applications may be required.
Extensive research throughout the agrochemical industry expanded options for powdery mildew control in the 1980s through introduction of several triazoles (sterol demethylation inhibitors) and two additional members of the morpholine group, fenpropimorph and fenpropidin. These have proven very effective in controlling pea powdery mildew.
More control options are recently available with the broad-spectrum fungicides strobirulins and anilinopyrimidines and the powdery mildew specifics spiroxamine and quinoxyfen. New mixtures are continuously being tested and approved for powdery mildew control in pea, such as the formulation mixture of the strobirulin pyraclostrobin plus the carboxamide boscalid.”
Authors: Fondevilla, S., and D. Rubiales.
Affiliation: University of Cordoba, Spain.
Title: Powdery mildew control in pea. A review.
Source: Agron. Sustain. Dev. 2012. 32:401-409.
Brown Rot on Peaches
The University of California’s IPM Guidelines list 37 fungicide products available for controlling diseases in peach orchards. Major flower, foliar and fruit diseases of peach include peach leaf curl, shot hole, brown rot, powdery mildew and rust. The key is to select the best fungicide product with the broadest spectrum of activity against these pathogens and time the application at a critical stage.
“Fungicides are the most effective and safe way for managing diseases of cling peach. Fortunately, there are numerous choices because multiple fungicides with different modes of action (MOA) are registered for each disease. This may appear to make a decision more difficult, but having multiple active ingredients available allows for competitive pricing, development of highly effective management programs that target problematic diseases at individual orchard sites, and resistance management. …In recent years, many active ingredients have become available as generic products under different trade names. This has further increased the complexity but also allows for reducing fungicide costs to the grower.”
Author: Adaskaveg, J. E.
Affiliation: UC Riverside
Title: Effective and Economical Management of Flower, Foliar, and Fruit Diseases of Cling Peach
Source: Orchard Notes. January 2014. Pgs. 2-4.
Powdery Mildew On Grapes
Powdery mildew exists wherever grapes are grown for wine. The fungus that causes grape powdery mildew is an obligate parasite, which means it must grow on grape tissue and will not parasitize any other species of plants. The fungus penetrates only the epidermal cells sending tubular suckers into them to absorb nutrients. The mass of fungal growth on grape skin give the impression that the grapes are sprinkled with flour. This impression is enhanced by the smell of moldy flour released by the diseased grapes. Fungicide sprays effectively control the incidence of powdery mildew of grapes from 99% to < 1% which is very important for the quality of wine.
“Analysis of wines made from powdery mildew-affected grapes has revealed that even slight infection leads to compositional changes, an oily mouthfeel and undesirable fungal/earthy flavours when compared with wines made from disease-free grapes.
The strongest link to the effect of powdery mildew was elevated ratings of ‘oily’ and ‘viscosity’ attributes in wines made from grapes with as little as 1-5% powdery mildew compared to wines made from disease free grapes.
…wines made from diseased grapes were rated as having more pronounced fungal, earthy and cooked tomato aroma attributes than wines made from uninfected grapes.
Juice from the most severely diseased grapes had a dusty and mushroom aroma and acid taste compared to the others.
When subjected to the heat test, wines made from grapes with severe powdery mildew showed greatest haziness, so there is the potential for spoilage of wine during storage due to haze.”
Authors: CRCV Update
Title: Powdery mildew impacting on wine quality
Source: Wine Industry Journal. 2004. 19:71-75.