Project Overview

Reports

Commodities

Target Pests

Practices

Over the past two decades, vegetable production in California has shifted from direct seeding to planting vegetable seedlings (transplants), creating a new type of agricultural production in the state that generates significant economic returns. The demand for year-round, high-quality vegetables drove this transition. However, several diseases pose recurrent management challenges to transplant production, causing economic losses to stakeholders. Currently, Botrytis blight is a major disease concerning the vegetable transplant growers in California’s Central Valley and Central Coast, impacting numerous crops like processing tomatoes, broccoli, cabbage, and others. To manage this disease, growers mainly rely on fungicide applications and use multiple products during the short production period before shipping vegetable seedlings to the field. Several challenges arise from the frequent application of products with a single site of action and fungicides with medium to high risk of resistance development, leading to shifts in the sensitivity of Botrytis population to the applied fungicides. In addition, the genetic diversity and short life cycle make Botrytis cinerea more prone to developing fungicide resistance, posing environmental and management concerns. This project aims to evaluate and confirm the presence of resistance in the B. cinerea population to commonly used fungicides in California's vegetable transplant industry. Preliminary findings indicate the presence of potential resistance, particularly to azoxystrobin, and wider screening is needed to monitor the sensitivity and confirm the presence of resistance to several applied fungicides. The outcomes of this project will help define management decisions and grower recommendations. The proposed research aligns with regional IPM priorities on "Pest-Resistance Management" and seeks to provide crucial insights into the current status of B. cinerea resistance, recommend effective management decisions, and the adoption of alternative control measures in vegetable transplants.

Our research endeavors to explore the potential development of fungicide resistance of Botrytis populations in vegetable greenhouse and nursery crops against commonly sprayed fungicides. The comprehensive approach involves three primary objectives:

1) Survey and Sampling: Conduct extensive surveys and sampling activities across various vegetable transplant nurseries in California. This will facilitate the collection of diverse isolates, allowing us to assess the current landscape of Botrytis populations (March-May 2024).

2) Fungicide Efficacy and Disease Control: Investigate the impact of fungicide sensitivity on disease control in vegetable transplants through greenhouse fungicide efficacy trials. By analyzing the efficacy of commonly used fungicides against Botrytis isolates with varying levels of sensitivity (based on our in-vitro assays), we aim to identify the fungicides exhibiting optimal control and no-control over Botrytis blight (August-October 2024).

3) Characterization of Fungicide Resistance Mechanisms: Delve into the molecular aspects of fungicide resistance by characterizing resistant isolates of B. cinerea. This will involve a thorough examination of resistance mechanisms against various fungicide groups, specifically targeting quinone outside inhibitors (QoIs), succinate dehydrogenase inhibitors (SDHIs), and Sterol biosynthesis inhibitors (SBIs) (December 2023-February 2024).

By determining the effectiveness of different fungicides in managing Botrytis blight and characterizing resistance mechanisms, we aim to equip stakeholders with information essential for making informed disease management decisions. Additionally, in the event of confirmed resistance, our research will contribute recommendations for fungicide resistance management strategies, ensuring a more sustainable and effective approach to disease control.