Strawberry grey mould: protect flowers and remove infection sources
Botrytis fruit rot produces grey, dusty spores on affected berries. Infection starts during flowering and can remain inactive until the fruit develops. Rotten berries at harvest can therefore reflect an infection acquired much earlier.
Dead leaves and leaf stalks support survival and spore production. Remove runners and crop debris lying on the polythene. Diseased berries become secondary infection sources.
Botrytis protection centres on the flowering period: the flowers and the relevant plant parts have to be thoroughly wetted.
A strawberry fungicide needs a crop authorisation for the production setting and the disease; the HSE register guide leads to it.
Powdery mildew, red core and crown rot
Powdery mildew can cause dark red blotches and inward-curled leaf margins. A white coating may develop on the exposed lower surface, flowers or fruit. Hot, dry conditions favour the problem, and affected plants can appear drought-stressed.
Red core attacks roots. Plants can become dwarfed, with dull bluish-green foliage and red-tinged older leaves. Feeding tips rot away; a lengthwise cut through an affected root reveals red central tissue. Infected runners, soil on implements and drainage water can spread infection. Poor drainage and high winter rainfall favour it.
Crown rot causes young leaves to wilt and can rapidly collapse the plant. Cutting the crown lengthways reveals browning. A lifted plant may break at the crown.
Tomato leaf mould: control humidity before an outbreak
Tomato leaf mould is caused by Passalora fulva. Humid glasshouse conditions favour severe infection, and the pathogen can persist between successive crops on a nursery. Yellow spots on the upper leaf surface are among the visible signs.
Prevention combines humidity management, crop husbandry and varietal resistance with any authorised chemical control.
The best fungicide for tomato leaf spot depends on which disease produced the spots. A mancozeb fungicide for tomatoes needs a current crop authorisation for tomato.
Botrytis stem infection and pruning wounds
Botrytis attacks weakened plants and wound sites in humid glasshouses. Old fruit trusses are an important route for tomato stem infection. Remove them cleanly: leaving a stub increases the opportunity for infection at the removal site.
Botrytis forms survival structures called sclerotia in plant material. Infected debris therefore stays an infection source between crops.
Root diseases and vascular wilts
Pythium and Phytophthora are fungus-like water moulds. Resistant oospores support survival, while zoospores provide a water-associated dispersal stage. Poorly drained media and crop stress are relevant when investigating Pythium root damage.
Fusarium enters through roots and disrupts water conduction. It can persist in soil and dead tissue as thick-walled spores. Verticillium can produce vascular staining.
Pathogens can be present in hydroponic tomato roots without obvious yellowing, wilting or stunting.
Bacterial disease needs a separate response
Infected seed or young plants commonly introduce bacterial canker. Root mat, historically called Agrobacterium disease, is another bacterial problem.
Disinfection evidence depends on the setting tested: a suspension test, a concrete-surface trial and treatment of a living crop expose the organism and plant differently.
Strawberry pests: monitor, release predators, then check insecticides
There is no single best pesticide for strawberry plants: the pest decides, and for the two worst pests the answer starts with monitoring and predators. Western flower thrips is resistant to insecticides, so its control has to rely on non-pesticide methods.
Thrips. Count adults in the flowers, not on traps alone. Tap at least 20 medium-age flowers from the top of the plant onto paper and count the thrips that run. Without predatory mites, about four adult thrips per flower caused fruit-downgrading damage on the everbearer Camarillo; with the predatory mite Neoseiulus cucumeris present, damage was avoided up to eight per flower.
The most successful programmes release predators regularly from before flowering or from the first flowers: Neoseiulus cucumeris, combined with one or more of Stratiolaelaps scimitus, Orius species or blue sticky roller traps. They avoid crop protection programmes that are harmful to predators.
Spider mite and aphids. Phytoseiulus persimilis is the main control for two-spotted spider mite. Five aphid species are common on strawberry in the UK: strawberry aphid, potato aphid, melon and cotton aphid, glasshouse-potato aphid and shallot aphid. Monitor the crop regularly for them, because few conventional aphicides are now available.
Before any insecticide. Check the product against the predators you have released using a product compatibility table, and confirm its approval for strawberry in the HSE register guide.
Product choice, resistance and organic production: strawberry leaf scorch fungicide and tomato fungicides
A strawberry leaf scorch fungicide, like any fungicide for strawberry, must be authorised for strawberry in the register for the target disease; identify the leaf disease before choosing a product. For the best fungicides for tomatoes, or any pesticides used in tomato farming, the disease decides first (leaf mould, Botrytis, root disease), and the product must then be authorised for tomato in the HSE register guide.
Powdery mildews mainly require living host tissue and can have narrow host ranges. Fungicide resistance risk is high.
A natural or organic fungicide on an organic strawberry or tomato holding needs acceptance from the approved control body as well as a crop authorisation.
Distinguish disease carry-over from growing stress
Disease develops through an interaction between a susceptible host, a pathogen and favourable surroundings. Ventilation, irrigation, nutrition, light and heating all affect susceptibility in a glasshouse crop.
Root mat causes abnormal proliferation of new root tissue. The bacterium can transfer a root-initiation plasmid into the plant. Once the root-initiation plasmid infects a plant, no known treatment prevents subsequent symptom development.
Red spider mites feed beneath strawberry leaves and cause mottled yellowing; heavy infestations can leave bronzed, webbed foliage. Vine-weevil grubs feed on roots and excavate the crown, while adults leave characteristic notches at leaf margins. These feeding injuries can accompany collapse or poor growth.
Next step
See the IPM assessment, the HSE register and the organic-input guide.
