NAME OF THE ORGANISM: Podosphaera aphanis (PODOAP)

Yes

Podosphaera aphanis infects leaves, flowers, and fruit.
Early foliage infections are characterised by small white patches of fungus growing on the lower leaf surface. On susceptible plants, dense mycelial growth and numerous chains of conidia (spores) give these patches a powdery appearance. Under favourable conditions, the patches expand and coalesce until the entire lower surface of the leaf is covered. Under such conditions, when infections occur early in the season, massive damage can occur to the leaves, affecting flower set and yield in the crop year.
The fungus also infects flowers, which may produce aborted or malformed fruit.
Via blossom and fruit infections, infestation can also directly affect the crop.
If the disease does not occur until late summer, flower bud set has already occurred and powdery mildew may not affect the crop even if the infestation is more severe. In this case, however, problems must be expected next spring and appropriate measures must be taken (AGES, 2023).
In some strawberry cultivars, relatively little mycelium is produced, making it difficult to see the white patches. Instead, irregular yellow or reddish-brown spots develop on colonized areas on the lower leaf surface and eventually break through to the upper surface. The edges of heavily infected leaves curl upward. At times, dark round structures (cleistothecia) are produced in the mycelia on the undersides of leaves. These cleistothecia are initially white but turn black as they mature.

Minor to Medium

Impact is highly dependent on measures taken by the grower. It can undoubtedly be a severe disease, but many factors play a role, the situation in one region might be different from the situation in another region, which can be linked to e.g. weather conditions, cultural practices and availability of crop protection products.

Climate control: Greenhouse: Appropriate venting will help to reduce crop humidity and help to reduce reliance on fungicides. Venting decisions should be based upon on-farm weather condition forecasts and adjusted in response to observations in the tunnels (Hall et al., 2019). In the field: wind-protected, enclosed sites and multi-row planting systems are favorable to powdery mildew and should be avoided (AGES, 2023).
Fungicides: Fungicide applications should be applied at first sign of symptoms when conditions are conducive to disease (longer periods with temperatures above 15-18 °C, intensive new leaf formation, susceptible cultivars). Rotate between products with different modes of action to reduce the risk of resistance build-up in a field should be avoided in order to reduce the risk on developing fungicide resistance by the pathogen (Hall et al., 2019, AGES, 2023, Anonymous, 2021). Decision Support Systems (DSSs) can help growers identify optimum timing of pesticide applications. Also alternative for fungicides are being researched (for DSS and alternatives overview see Aldrighetti & Pertot, 2023).
New plantings may have low incidence of infection without any visible symptoms. Early application of potassium bicarbonate should be used to control existing infection on new plants, although it provides no protection against further infection. Complementary use of the nutrient silicon helps to modify the cuticle and wax structure of the leaf, which inhibits further infection (Hall et al., 2019).
Scouting: Leaf cupping is associated with early infection and should be treated as a possible first symptom of powdery mildew infection. It should prompt further leaf assessment for the presence of mycelium (Hall et al., 2019).
Cultural control: Manage weeds within the field to help increase air flow and reduce humidity. Renovate June-bearing plantings as soon as harvest is complete to destroy infected tissue, as the disease will overwinter on old plant tissue and persist into the next season. Cleanup last year’s leaves in day-neutral plantings in the spring by pruning out old tissue around the new leaf growth (Anonymous, 2021)
Resistance: avoid using susceptible varieties (AGES, 2023).

Using powdery mildew-free transplants would be a good method to control the disease, but these are difficult to find and even disease-free fields can become infected by conidia blown in from neighboring fields. Cultivars differ in their resistance to powdery mildew. Fields with susceptible cultivars should be surveyed regularly for powdery mildew, especially early in the season. Fungicides should be applied preventively or at the first sign of disease to control powdery mildew on susceptible cultivars. This is especially important when using protectant fungicides, such as elemental sulfur. Systemic fungicides have some limited curative action. In the USA, these include quinoxyfen and cyflufenamid, which have different modes of action and can be applied in alternation. Another group of active substances include myclobutanil; triflumizole; propiconazole; and tetraconazole. These products are treated as a group since they belong to the same fungicide class and have similar properties. For this reason, they should be rotated with other fungicides with different properties to avoid the development of resistance. Other rotational options include pyraclostrobin + fluxapyroxad and penthiopyrad. None of these products should be applied more than four times per season. Usually, controlling foliar infection helps to prevent fruit infection (University of Florida Extension, 2022).

The data are enough to make a decision