This is the the last instalment of the Root Awakening column for the month of June 2011. Answers to two questions were provided.
The first question was about why the leaves of a frangipani showed signs of drying up. This could be a sign of a mealy bug infestation. One may want to check the undersides of the leaves for an infestation of mealy bugs which suck sap from leaf tissues. They appear as white cottony masses that congregate along the mid-rib and veins of leaves. Leaves that have been attacked often become warped and deformed and they finally dry up and fall off. Control the population of such sucking pests by spraying the underside of leaves with white summer oil (organic) or any other pesticide that is indicated for treatment of mealy bug infestations. You may want to remove and discard badly infested leaves before spraying to reduce the amount of pests to be dealt with.
Another point to add is to check for infection by the rust fungus. Severely infected leaves will eventually dry up and fall off. One should make an effort to remove all infected leaves as the spores from infected leaves will go into the soil and infect other frangipani plants.
The second question was about curling and yellowing of the leaves, as well as, deformation of flowers seen in the hibiscus plant. The symptoms described may be indicating that the plant is lacking in certain mineral nutrients. To correct the problem, one may want to feed plants with a water-soluble fertiliser that contains chelated elements. Look at the ingredient list on the fertiliser’s label. The correction of a severe deficiency may take many months. The symptoms of any minor element deficiency show up on the new growth with the new and younger leaves being affected. When the deficiency is corrected, the new growth will be normal in appearance.
Note that even with a good feeding programme, nutrient deficiencies can still occur due to changes in soil acidity, organic content and drainage. As Singapore’s soil is often clayey and compacted, it is beneficial to improve the quality of soil by the addition of organic material such as good quality compost. Compost is valued for its soil conditioning value. Incorporate compost into the top few inches of soil to improve its properties.
One more point to add is to check also for mealy bug infestations in the leaves. Infestations by sucking insects will also cause leaves to become deformed.