Cucurbit powdery mildew   ( CPM ) , caused byPodosphaera xanthii , is one the most important diseases of cucurbit crops throughout the macrocosm . The pathogen is an obligate sponger , just like cucurbit downy mold , meaning it needs a survive host in ordering to outlive . In northerly regions that have a kill frost in the evenfall , the pathogen will pass out when the crop freezes . Not being able to overwinter , the pathogen must be re - premise each spring or summer in the mid - Atlantic region . The pathogen accomplishes this by re - infecting cucurbit crop in the leaping as they are planted up the east seacoast , starting in Florida , then the Carolina ’s , Virginia , and so forth . By late May , as soon as cucurbit craw start to germinate in the mid - Atlantic area , the potential threat of possible powdery mold contagion begins .

The first step in mitigate CPM begins with planting powdery mildew tolerant ( PMT ) or resistive ( PMR ) cultivars if they cope with your indigence . It is important to recollect that these cultivars are not “ resistant ” to CPM ; they will become infected at some detail in the growing season , depending on disease pressure level . Hopefully , this will occur later in the time of year when compare to CPM susceptible cultivar . Organic agriculturist hoping to mitigate losses to powdery mildew should always choose CPM tolerant or resistant cucurbit cultivar first . There are a number of OMRI - approved fungicides labeled to help suppress CPM development . These should always be used in concert with CPM liberal or resistive cultivars and a preventative fungicide program . Cultural practice such as increase in - quarrel plant life spacing to improve airflow and cultivation to keep weeds to a lower limit will also be advantageous . ward off the use of overhead irrigation will help reduce disease pressure from another important pathogen , cucurbit downy mildew . Thus , grow cucurbit on a mulch with dripping irrigation has its advantages but also increases costs .

Over the past 15 year , there have been a phone number of young fungicides released with new modes of natural process ( i.e. , new FRAC radical ) for CPM command in cucurbit craw . Unfortunately , all have a restrained to gamey risk for electric resistance maturation because of their specific modes of action at law . The good news program is these new fungicide chemistry have fewer effects on world , non - target organisms , and the environs .

These fungicides offer new strategies when it occur to controlling and mitigating personnel casualty to CPM . Instead of rotate two fungicides with a moderate to in high spirits risk for resistance development every other week ( A – B – A – B ) , growers now have the option to reduce the total telephone number of fourth dimension any single fungicide might be applied during the production season ; further reducing the risk of infection for underground evolution to any one mode of action . For example , in pumpkin , a new CPM preventative antimycotic agent programme may calculate like this :

A – B – coulomb – D – E – A – type B – C – D – eastward

Where each missive above equals a antimycotic from a different FRAC grouping .

A protectant fungicide such as chlorothalonil or mancozeb should be added to the tank mix with each high - risk antimycotic agent to reduce selection pressure and to help control other important diseases such as anthracnose and Plectosporium blight .

In this type of CPM preventive program , any eminent - risk fungicide would only be applied twice per growing season and 5 hebdomad aside , importantly reducing the risk of infection for fungicide resistivity development . Importantly , for cucurbit raiser , the well-fixed method to mitigate the potency for fungicide impedance development is to reduce the entire figure of diligence of any high - peril fungicide during the output time of year .

Dr. Sally Miller from The Ohio State University and Dr. Meg McGrath from Cornell University have spell splendid articles for controlling CPM in 2022 . These articles can be establish by clicking the tie-in below .

‘ Preparing for cucurbit powdery mildew’by Dr. Sally Miller , OSU

‘ Cucurbit powdery mildew’by Dr. Meg McGrath , Cornell University

For more information on fungicide usance , FRAC grouping , and specific ascendance good word , please see the2022/2023 Mid - Atlantic Commercial Vegetable Production Recommendation Guide .

For more data : Rutgers UniversityState University of New Jerseywww.plant-pest-advisory.rutgers.edu .