Meconopsis aren’t prone to many pests and diseases but it is worth being aware of some of the ones that they can sometimes become susceptible to. Avoidance is always better than cure.
Slugs and snails
Due to the hairiness of their leaves, Meconopsis are not that prone to attack by slugs and snails. However, the young soft growth can end up under attack, so it is worth dealing with them in your usual way, whether that is with chemicals, by use of a barrier, or using nematodes.
Rabbits, deer and other mammals
Again, the hairiness of their leaves saves Meconopsis from attack by mammals that find many other garden plants delicious. If they do develop a taste for Meconopsis, fencing is the only effective option.
Downy mildew
This is mainly caused by irregular watering, especially if the plants are left damp overnight or get wet and damp in too humid an environment. Make sure there is good air flow around the plants. Infected leaves can be removed and destroyed without harming the plant too much.
Damping off
Damping-off can be a problem with seedlings. The chances of this occurring should be minimised by sowing thinly and keeping the pots in a well-ventilated situation. Very dilute fungicide applied on first observing the problem can help, but Meconopsis cannot tolerate many fungicides, so it is sensible to experiment before you have to deal with damping off.
Chryseococcus arecae
Golden root mealybug
This fairly recent newcomer, Chryseococcus arecae , was first found in the UK in 2012, but it is potentially serious, and should be avoided if at all possible, and dealt with if an outbreak occurs. It can affect a range of plants, Meconopsis and Primula in particular. Its presence can be shown by unusually weak growth of plants, and then by inspection of the roots for the pale yellow oval bugs, 2-3 mm long. The risk of infection can be minimised by checking the roots of new plants, particularly those that have been dug from gardens, rather than grown in a nursery. The bugs are active all year, and are clearly visible on the roots.
It is also a good precaution to keep new plants in an area that is separate from planted borders for a growing season. Spread within planted areas is not very rapid, so if an outbreak is discovered, clear an area around it, until the limit of the infection is found. Then treat or destroy all plants within that zone.
Treatment is possible by root washing and application of pesticides, but different controls are permitted in different countries. For root washing, knock all soil from a plant, and break or cut off all its leaves. (They will get broken anyway, and soon regrow.) Then wash repeatedly in water until remaining soil has gone, all visible mealybugs have gone – and then wash again. Washing with permitted pesticides at this stage is helpful; Neem oil has been reported to be effective. Then plant in pots in a compost containing insecticide. Grow plants in an area isolated from other plants, and after six months repeat the process. It is hard work, but it is possible to win the battle. Dispose of all debris, washing water, etc. in a way that does not risk spreading the outbreak.
Frost damage
Frost rarely causes damage. If there are freshly emerged leaves and a hard frost is forecast, covering plants with fleece will protect leaves from damage. Usually the plants will survive anyway, and produce new leaves throughout the season, but they are disfigured, and occasionally can be killed.
Winter wet or Spring drought
Meconopsis need to be kept moist but in the winter some protection is required over the large overwintering rosettes of monocarpic plants to stop Crown Rot. Another issue can be an unexpected dry Spring when plants can very quickly succumb to drought when you least expect it.
Botrytis
Although they like high levels of humidity in the summer to thrive, in their natural environment Meconopsis are under the snow in the winter and are quite dry. If the winter is wet and warm, and particularly when there is little wind, it is very important to keep the plants dry and especially the neck of the plant.
Clear decayed leaves, and mulch with a layer of grit rather than organic matter around the neck, keeping the mulch away from the crown, or even planting them slightly proud of the soil to stop moisture getting in.
If Botrytis does occur, dilute fungicide can be applied to the resting buds of dormant plants, but Meconopsis in general do not like fungicide on green leaves.
Wind damage and sun scorch
Meconopsis can be damaged by wind. They have a high water content in their stems and leaves, and this can cause them to rip and snap if they are in a windy spot.
They also dislike direct sun and especially greenhouses and polytunnels. This can cause the leaves to distort, scorch marks to appear and eventually they may not survive. Make sure they aren’t grown in a place where they get direct sunlight for more than a small part of the day.
Weed killers and other chemicals
Meconopsis are incredibly sensitive to glyphosate and all weed killers so keep a good distance if you are spraying near your plants. Getting too close or even the slightest breeze when applying chemicals can result in the death of plants.
They are also very sensitive to most fungicides. Use very dilute solutions if a spray seems to be essential. Do experiments with various fungicides on plants that you can risk losing. And let us know about successes and failures.
