Question
Hi John!
We have a Meyer Lemon tree that is doing well apart from teensie black/green bugs congregating on the newly formed leaves and flower buds.  They're leaving some sort of sticky residue as well. What are these things and what's the best way to get rid of them?

Also, how much should we be watering it?  It has some yellow leaves.
Thanks!  

Answer
Hi Sheila,

The sticky residue is called "honeydew" and is common of sucking insects.  There are many of them including scale insects, lace bugs, mealybugs, and aphids.  Aphids particularly collect in masses usually at the soft, tender growing tips or on/in flower buds. So, it sounds as though what you describe is an aphid infestation.  

There are many biological controls, and if you have placed your Meyer's Lemon outdoors, the natural predators will eventually control the aphid population. Some biological controls are ladybird (ladybug) beetles and lacewings as well as a number of parasitic wasps and praying mantis.  If you are so inclined, there are many sources to obtain these online and in specialty, organic, gardening shops.

There are many chemicals that can be used, and I would suggest that you consult your local garden center to see what is effective in your geographical area.  

Aphids are particularly problematic since they are parthenogenic, the females do not need a male to reproduce.  So, these insect populations grow to great numbers very, very quickly.

The chlorosis (yellowing) may be associated with the aphid infestation or , more likely, a nutrient deficiency.  The best treatment is to supplement feedings with micronutrients such as iron, magnesium, etc. in addition to the macronutrients: Nitrogen (N), Potassium (P) and Phosphorous (K).  The lemon should be watered evenly so as to avoid the splitting of fruit.  The plants roots should neither be totally saturated with water nor allowed to completely dry out.  Allowing the plants roots to sit in water continually tends to promote root rot diseases.  Instead, water just enough to keep the root ball moist, but not soggy/saturated.  Allow the surface to dry to a depth of approximately 1/2 to 1 inch (depending on the size of the pot) before watering again.  Any water that collects in the pot saucer should be reabsorbed by the root ball within ~12 hours.  If not, then drain the saucer. In normal indoor humidities in the winter/spring, watering will occur approximately once a week, more in lower humidity.  Also, when the plant is placed in higher light, there will be greater water requirements.