Figure 1. Botrytis fruit rot often starts beneath the calyx where moisture can get trapped, along with petals, where it will persist long enough for the pathogen to germinate and infect the fruit. (photo by G. J. Holmes) A recently published paper in Phytopathology by Naegele et al. adds to the work done by Cosseboom … Continue reading New publication confirms trends in fungicide resistance

A recent publication by Mello et al. reports that strawberry powdery mildew (SPM) was reduced by nighttime application of UV-C to field plots at 200 J m-2 . Disease reduction was equivalent to that provided by weekly fungicide applications in CA and superior to that provided by twice weekly fungicide applications in FL.  No negative … Continue reading New publication reports efficacy of UV-C against powdery mildew in FL and CA

We usually see Zythia leaf blotch (caused by Zythia fragariae) during the early spring when plants are small and the weather is cool and wet. With summer planting in Santa Maria occurring in May, especially in fields close to the coastline where fog and heavy dews are common, the same conditions exist (i.e., small plants … Continue reading Off-cycle Zythia leaf blotch

In the vast majority of seasons, powdery mildew (PM) (caused by Podosphaera aphanis) is the most economically important foliar disease of strawberries in California. Many growers have observed that PM is particularly destructive in glasshouses and under plastic tunnels. This could be due to the difference in temperature and relative humidity or to filtering UV … Continue reading Tunnel plastics, UV and powdery mildew

A new publication by Baggio et al. (2022) out of the University of Florida provides evidence that 1,3-dichloropropene (1,3-D) alone and in mixture with chloropicrin were more effective in reducing inoculum of Macrophomina phaseolina than chloropicrin alone. We generally think of 1,3-D (known under the trade name TELONETM) as an effective nematicide with minor efficacy … Continue reading New research shows 1,3-D is effective against Macrophomina

Figure 1. Rhizopus rot is diagnosed by the conspicuous sporulation on the fruit surface. Under high humidity, sporulation appears "hairy" but is more appressed under drier conditions. Rot progresses very quickly and fruit become liquified within a couple of days. (photo by G. Holmes) June is here and temperatures are rising. Along with rising temperatures … Continue reading Rhizopus rot or “leak”

It's helpful to look at similar systems to learn more about your own. For example, we can learn a lot about Macrophomina in strawberries by looking at the diseases this fungus causes in many other crops where it has been studied more intensively. A recent paper in the journal Plant Disease reviews dry root rot … Continue reading What can we learn from Macrophomina in chickpea?

Strawberry powdery mildew caused by Podosphaera aphanis, is an important disease in California strawberries (Fig. 1). Strawberry Center master's student Michael Palmer recently published his work on fungicide resistance in the journal Plant Disease (https://doi.org/10.1094/PDIS-12-20-2604-RE). Because P. aphanis is an "obligate parasite" all of the experiments were done using live plant tissue (Fig. 2). This … Continue reading RECENTLY PUBLISHED: Fungicide resistance in strawberry powdery mildew in California

Figure 1. Botrytis fruit rot (gray mold) showing typical gray sporulation beginning under the calyx and spreading towards the tip. A lot of people never heard the word "epidemic" (the rapid spread of a disease), "pandemic" (spread of a disease over a wide area) or "epidemiology" (the study of how disease spreads) until the COVID … Continue reading Classic Botrytis data from 1987

Figure 1. Mild bronzing caused by frost on white fruit of cultivar Monterey. This level of bronzing will be harder to detect when the fruit turns red. In my last post, I showed a bunch of photos of frost injury. Later I noticed another effect: Bronzing (Figs. 1, 2 & 3). Just like misshapen fruit … Continue reading Bronzing caused by frost

Recent frosts at the Cal Poly farm has brought frost injury in all its variety. According to the Compendium of Strawberry Diseases "frost injury is probably the most common non-pathogen related and non-insect-related disorder affecting strawberry flowers and fruit." Whenever temperatures dip to below freezing, expect to see a variety of deformed fruit and blackened … Continue reading Frost injury

The author (Michael Palmer) in a strawberry field in Santa Maria, CA. Photo by G. J. Holmes Michael Palmer finished his master's thesis last winter and his second paper just appeared in the journal Plant Health Progress (https://doi.org/10.1094/PHP-12-20-0101-RS). This paper works out the methods for screening strawberry cultivars for their susceptibility to powdery mildew caused … Continue reading JUST PUBLISHED: Strawberry host plant resistance to powdery mildew