Hi Tui, it looks like my lemon tree has scale insect. Can you tell me what conditions scale find favourable and what time of the year they are likely to hatch.
Yes, that is scale insect on your citrus. They affect plants in the summer months, but are active from spring through to late autumn, when plants are weakened or stressed during dry spells, they are especially active. There is a crawling stage that looks like specks of dust, these are spread by wind, birds or other insects and carried to new plants, if conditions are ideal they feed and multiply forming into adults with the protective shield. They are sap sucking insects and because of their shield, are hard to control. Spray with a plant spraying oil or pyrethrum based spray available from garden centres and DIY stores. You can remove the insects using your fingers, but this may not be practical and doesn't stop them returning. Repeat sprays may be required, make sure the underside of the leaf and around the flower buds are treated as well. Because your tree is flowering, if using a pyrethrum based spray, don't spray while bees are foraging, spray in early morning or late afternoon.
Pick up any fallen leaves or plant material that may have scale on them and dispose of in the rubbish, do not leave them around the plant as they can overwinter in the leaf litter and soil. Give the plant Tui Seaweed Plant Tonic to help stimulate root growth and make the plant more robust, it will also help the plant recover. Make sure the plant is well fed, use a specialty citrus fertiliser such as Tui Citrus Food or Tui Novatec, make sure the tree is well watered and mulched throughout the season to conserve soil moisture. If there are other plants nearby affected by scale they may need treatment too. Tui Team.