Author: Doc. dr Miloš Petrović, Faculty of Agriculture, University of Novi Sad
Pear is the second most popular when it comes to apple fruit-growing species. Its vegetation cycle is one of the most demanding for fruit growers. The reason for the overall hard management has the foundations laid in pest control. Many species of both phytopathogenic bacteria and fungi, and insects need to be monitored not every day, in some special climatic conditions, every 8 to 12 hours!
Emergence and Persistence of Cacopsylla Lice
Bacteria, Erwinia amylovora, fungi Venturia pyrina and of course ever-present insect species from genus Cacopsylla can make a “wildfire” in pear orchards in no time.
Cacopsylla species belong to the order Homoptera (systematically they are related to Aphids, planthoppers and cicadellidae) and in English it is commonly called jumping plant (pear) lice.
This species has some distinctive biological features that work excellently for the insect but make havoc for a farmer.
First of all – the start of the activity in the orchards. This species is present in pear-growing regions from late January or early February! No other insect species is present in agriculture like this one. During that part of the year, farmers are often concentrated on pruning, fertilizing or vacationing, but unfortunately, that is the time when the working season starts for lice.
After spending a couple of days in orchards they start to mate, and consequently lay their eggs near the leaf or fruit buds. When the plant juices start to flow in the early spring, this is the starting point for the hatching of the first generation.
And by reading this, you could ask yourself:” Okay, this is something similar to aphids, why we just do not spray them, and control them just in the beginning of making a colony?”
The first trap for the farmer is that the first generation is starting to grow during the flowering season when the pollinators are active, and the second is the fact that lice like to play hide and seek and are really good at it. The newly emerged larvae often find themself a pleasant niche in the crevices and holes on branches where pesticide spray often does not cover well.
The final and the biggest problem, when we talk about this species, is “honeydew”. Honeydew is excreta produced during the feeding on the pear plant which is really rich in sugars, has a thick consistency and it almost looks like a sugar syrup you use for cooking. When the honeydew covers the leaves, buds and fruits it becomes a perfect playing ground for a species of fungi, often belonging to the genus Cladosporium which are not considered to be phytopathogenic, but the fact that their mycelia is really dense and dark in color makes if perfect shade for plant, which disables them doing all the physiological and biochemical processes.
The final problem with this species is the number of generations during the year. Some years are suitable for development, and lice can form up to five generations a year. Imagine being a farmer with high hopes of making a perfect fruit in shape and in overall quality and being in a situation to ride a lice control rodeo all over the year!