On return from two weeks leave, it was devastating to find the amount of damage done to our Dahlias by red spider mites in such a short period of time. Despite having not seen a single mite so far this season, and applying a preventative spray before leaving, we were hopeful these little critters would stay away…….but unfortunately that wasn’t the case.
Spider mites spread FAST so it is important to inspect your Dahlias to keep an eye out for these tiny foes every few days. Be mindful they can be quite hard to see, generally webs are only visible once the infestation builds. In the early stages mites are most commonly found as a tiny speck on the underside of the leaf. The ‘specks/mites’ are easily seen in the webs on these photos, but in the early stages a magnifying glass can make the inspection process much easier.
There are a range of commercial and home-made remedies available, but regardless of what you choose to spray, the most important things are to (a) start treatment as soon as possible to avoid rapid infestation and to reduce damage to the plant, (b) ensure the spray is applied to every nook & cranny of the plant as contact is required for eradication. Spray the top and underside of foliage, stems and blooms. In severe infestations it is best to remove blooms and the wort impacted foliage to reduce further infestation and to reduce the stress ont he recovering plant. Finally (c) to ensure the treatment is repeated several times at around 3 day intervals to break the breeding lifecycles of the mites. Eggs hatch in approximately 3-4 days, so several rounds of repeat treatment ensures the eggs do not hatch to create a new infestation of adult mites. It is recommended that treatments are alternated to reduce the likelihood of the plant building resistance to a single brand/type of treatment.
Maintain adequate water to the recovering plants (but don’t overwater), consider applying a soil conditioner and some additional nutrients. The damaged foliage will not recover, but within a few days your plant should be sprouting some new, fresh green foliage. Depending on the time of the season, there may not be enough time for the new shoots to produce blooms, but the new foliage is important to ensure sufficient energy is supplied to maintain healthy tubers until the end of the season. Unless the mite damage is severe enough to kill all foliage and then stem, the tuber should not be impacted.
As far as mites are concerned, prevention and a very watchful eye are definitely better than trying to treat the damage after an infestation.