Lavender plants are starting to recover from frost damage on May 23. Those buds not damaged by frost are starting to turn purple in southern Ontario. Bloom is probably about 10 days away for angustifolia cultivars in these areas. On plants with frost damage confined to the tip of the new shoots, many side shoots are now developing and these will likely have bloom buds. These plants will likely reach full bloom a few weeks later than they normally would.
If all of the new growth of the plants was killed by frost, now is the time to examine plants for new shoots developing from last year’s growth. If there are no new green shoots on these branches, then the branches are likely dead. These should ideally be pruned out to allow more light to reach the green shoots coming from the base of the plant. If there are new green shoots on the branches, then the plants will likely have a delayed and weakened bloom, but nothing has to be done at this time.
Four-lined plant bugs are reaching the adult stage (Figure 1). These insects will likely be present in all established fields. There is not much that can be done at this stage to control the pest. Once they reach the adult stage, they will continue to feed for a few weeks while they are laying eggs for next year. After a few weeks they will die off and there will be no further damage until next year.
Figure 1. Adult four-lined plant bugs.
Garden fleahoppers (Figure 2 and Figure 3) are also active in localized patches in some fields. Most of the time they do not cause any economic damage. However, they can reach very high populations in some cases with hundreds of adults and nymphs on the same plant. This can seriously affect the health of the plant. They have multiple generations per year, allowing populations to build over the entire summer. Insecticidal soaps labelled for suppression of aphids and mites on lavender may also suppress the nymphs of garden fleahopper and reduce the spread of the pest in severe outbreaks.
Figure 2. Adult garden fleahopper.
Figure 3. Garden fleahopper nymph.
