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Cucurbit Disease Scouting & Management Guide

butternut squash in bins

Cucurbit crops comprise almost 30% of all vegetable crop acreage in New England, and are grown on over 4,000 acres in Massachusetts.  The number, severity and complexity of diseases attacking these vital crops have increased in the past decade.  In particular, Phytophthora capsici has increased dramatically in the past five years and is causing severe crop losses and infecting more and more vegetable acreage.  Plectosporium, a fungal disease that affects summer squash, zucchini and pumpkin leaves, stems and fruit, is relatively new to the region and is spreading rapidly.  Bacterial wilt affects increasing numbers of cucurbit crops, including pumpkin.  Downy mildew has reached the area early in the growing season on several occasions, causing loss of foliage in August.  The fungal, bacterial, and viral diseases and the abiotic disorders covered in this guide are the ones that are most commonly seen in the Northeastern U.S.  Correctly identifying these diseases and understanding the biology of the pathogens is necessary in order to produce healthy cucurbit crops.

An effective management strategy for these diseases requires employing a variety of tactics. Selection of resistant cultivars, crop rotation, proper field preparation, and other cultural practices detailed in this manual can have a significant impact in slowing or preventing the development of these diseases. Proper soil health & crop nutrition can help to suppress disease development.  Monitoring for diseases in the field and identifying them correctly are crucial to creating an effective and timely spray program.

When deciding when and what to spray to protect the crop from diseases, it is critical to consider the entire disease complex which exists on their farm and the efficacy of different materials against the full range of diseases.  Because certain fungicide groups are more likely to lose efficacy against some diseases due to the development of fungicide resistance in pathogen populations, resistance management also needs to be considered.

The goal of this handbook is to help growers identify the diseases they see in their cucurbit crops, use preventative practices as effectively as possible, and develop a more complete understanding of how to design a spray program to address all these different diseases.

A bound copy of this handbook is made available at most Extension Vegetable Twilight Meetings, and is available as an attachment below.

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