A calendar narrows the shortlist; it does not diagnose the culprit. Use the month and weather to decide what to inspect, then confirm the damage before acting.
Check today’s pest signalsHow to use this calendar
Start with the damage, inspect at the right time of day and find the organism or another confirming sign. Protect vulnerable crops with physical barriers and growing-space hygiene appropriate to the identified pest.
Year-round watchlist
Protected crops and unusually mild weather can move these windows.
January–February
Outdoor pest activity is generally quieter, but mild, protected places can still hold slugs, snails, aphids or vine-weevil larvae. Check rather than assuming winter removed the problem.
March–April
Young seedlings are easily lost. Slugs become more relevant in damp mild spells, allium leaf-miner activity can begin, flea beetles mark brassica seedlings and aphids may build under cover.
May–June
Carrot fly, cabbage-root fly and brassica caterpillar risks become important. Secure suitable mesh before egg laying rather than trying to repair heavily damaged roots later.
July–August
Warm, dry protected spaces favour red spider mite, while caterpillars, aphids, slugs after rain and leek-moth damage can continue outdoors.
September–October
A second allium leaf-miner period may affect leeks and onions. Cooling, wetter nights can increase slug exposure, while greenhouse pests may persist until conditions cool decisively.
November–December
Growth is slow, so modest feeding can matter. Inspect beneath fleece, pots and boards and ventilate enclosed protection during mild weather.
Preventative timing
Calendar dates are prompts. Move them for your region, crop stage and local observations.
Inspect after dark during mild, damp weather and check beneath pots and covers.
Cover susceptible carrot sowings with suitable insect-proof mesh and seal the edges.
Check leaf undersides and the growing point; make sure netting is not resting on foliage.
Look for fine pale mottling before obvious webbing appears.
Inspect mesh and seal gaps before the autumn activity period.
Weather-led tool
Allium diagnosis
Root protection
Calendar questions
Some are seasonal outdoors, but mild winters and protected spaces can extend activity. Treat the calendar as a prompt to inspect, not proof that a pest is present.
Put suitable mesh in place before the relevant adult lays eggs, then seal the edges and keep the material off the crop. Timing and mesh size depend on the pest.
Moisture, humidity, mild temperatures and sheltered hiding places can raise exposure, especially for seedlings. The live slug-risk panel combines weather signals, but a night inspection is still the best local check.
Sources and scope
This calendar summarises broad UK activity periods for home food growing. Local weather, protection and pest populations vary.