In the summer time is when you can encounter trouble with cicadas (Empoasca decipiens). Cicadas are recognizable by their light green colour. In some situations they can cause damage to the leaves or buds of your plants, sucking sap from the plants’ mesophyll (the soft tissue beneath the surface of the plant responsible for photosynthesis).
By doing this they cause rows of speckles on the leaves, flowers and fruits. This reduces the value of the products. In cases of serious infestation large parts of the leaf discolour and even die off. This speeds up the aging of the plant. Some cicadas carry viruses and mycoplasma bacteria, or secrete toxins that can result in plant deformities.
In glasshouse horticulture a single generation will come to maturity in four to five weeks depending on the temperature. Cicadas go through an egg stage, five nymph stages and the adult stage in their life cycle. The adult insects are 2 to 3 mm long and in many species coloured green. A female cicada can lay up to 50 eggs during her life. These are white, kidney shaped and approximately 0.6 mm long. They are laid in the tissue of leaf veins and stems, where they are not visible to the naked eye.
At 15 degrees C. and with an air moisture content between 65-75% it takes about 28 days for the eggs to hatch. At 20 degrees C. that is reduced to 15 days and at 24 degrees C. just 11 days. The nymphs are lighter in colour, and with each succeeding nymph stage the wing construction becomes clearer and clearer to see.
The highly agile nymph has an interesting method of scuttling: diagonally. The nymph stage of Empoasca decipiens lasts 37, 19 or 15 days respectively at 15, 20 and 24 degrees Celsius.
Combating cicadas can only be done by chemical means at the moment.
With financing from the Dutch Horticultural Commodity Board (Productschap Tuinbouw) the agricultural university at Wageningen began research in 2005 into the impact of cicadas on flower growing under glass. They found that Empoasca decipiens was the most common cicada found in this environment.
In enclosed lab conditions the researchers looked at cicada predation by generalist predators. In the field both the nymphs and the adults are very mobile and hard to catch. In a field test it appeared that the parasitic wasp Anagrus atomus was able to reproduce under glasshouse conditions.
However, no significant parasite infestation percentage was achieved, and the possibilities for using these wasps as an effective biological pesticide look slim.
The neo-nicotinoids imidacloprid (Admire), thiacloprid (Calypso), thiamethoxam (Actara) and acetamiprid (Gazelle) are very effective against cicadas, as is the oxidiazine indoxacarb (Steward). This anti-caterpillar agent is a more selective therefore safer option against natural pests than the neo-nicotinoids.