Vegetable Disease Update: August 9, 2018

Downy mildew is becoming more widespread on cucumber across Pennsylvania and has been confirmed on cucumbers in Centre, Clinton, Mifflin, Bucks, Lehigh, and Lancaster Counties.
Vegetable Disease Update: August 9, 2018 - News


Reduced till straw mulch serving as a barrier between developing pumpkin fruit and bare soil protecting against soilborne pathogens that cause fruit rots. Photo: Beth Gugino, Penn State

In the region it has also been confirmed on jack-o-lantern pumpkin, butternut squash and cantaloupe in the Delmarva and NJ. Downy mildew fungicides should be incorporated into fungicide programs on a regular basis. If you have successive plantings it is important to rogue or apply a herbicide to the foliage to reduce inoculum pressure on the farm.

If you suspect cucurbit downy mildew on your farm, please contact your local Penn State Extension Office or let Beth Gugino know via email at or by phone at 814-865-7328. Every confirmed report of downy mildew enables us to improve disease forecasting accuracy for the benefit of cucurbit growers not only in Pennsylvania but all along the east coast. Even reports that are made from previously reported counties. The latest information on reports of cucurbit downy mildew can be found at the CDM ipmPIPE website.

Although there have been suspected reports of late blight, there are no new reports of late blight at this time. For the latest reports visit

Fluffy White Growth On Your Vegetable Fruit? It Might Be Pythium Fruit Rot

Observing dense white fluffy growth on developing fruit is not uncommon under very wet soil conditions. It is caused by a fungus named Pythium, which is commonly found in agricultural soils. It survives overwinter as oospores which are thick-walled long-lived structures (same structure that allows Phytophthora blight to survive in the field for years). When in the presence of free-moisture, they germinate, and eventually produce sporangia and zoospores which are “swimming” spores that move easily in very wet flooded soils and are actually attracted to the fruit.

Pythium fruit rot on immature pumpkin fruit. Photo: John Esslinger, Penn State

This is the same fungus that causes seed decay and damping off in young transplants in spring. It most commonly affects fruit that are in direct contact with the soil and has a very wide host range. It starts off as a small water-soaked spot where the fruit contacts the soil and causes the surface of the fruit to rupture and the fruit will eventually collapse.

Once you see symptoms in the field, not much can be done. In the long-term adopting practices that encourage soil drainage through improving soil health will reduce losses. Also for pumpkin and some other cucurbits, planting into a reduced or no-till system where the straw mulch creates barrier limiting direct contact between the fruit and soil will reduce losses from Pythium as well as other soilborne fruit rotting pathogens.