pearsucker

Pear psylla control using
'Anthocoris nemoralis'

In apple cultivation, the use of predatory mites to control fruit tree red spider mite (Metatetranychus ulmi) has been used successfully for many years. Pear cultivation equally presents opportunities to tackle problem insects using their natural enemies. The decline in effective means of control forces the fruit growing sector to look for new control methods.

Integrated control is a good alternative. Taking less recourse to wide-spectrum crop protection agents, and especially less of them, allows us to use natural enemies. Furthermore, this approach will ensure that more naturally occurring beneficial insects remain alive, allowing for the development of an optimal balance between pests and their natural enemies.

In the year 2000, practical tests were set up in collaboration with manufacturer BioPol , the Co-operative Advisory Body for Fruit Farming (Coöperatieve Adviesdienst voor de Fruitteelt, CAF) and Horticoop at a number of farms, using the predatory mite known as ‘Anthocoris nemoralis’ to control pear psylla (‘Psylla pyri’). Prompted by experiences gained abroad, with good results, the decision was taken to distribute predatory mites early in the season when the temperature is high enough to sustain this approach. The objective was to realize a rapid, early population development. The problem one often has to face in practice is the rapid population build-up of pear psylla in combination with a slow development of the predatory mite population. This means that the biological balance between the pest insect and its natural enemy is often established late or to an insufficient extent, which causes damage to the crops, and chemical correction may prove necessary. Between 1,200 and 1,500 predatory mites per hectare were distributed on the test parcels. The agent permitted in the Netherlands for use against pear psylla (‘Amitraz’), has a side effect on predatory mites which causes any ‘balance’ that might otherwise be achieved, to be disrupted.

In addition to lacewing larvae, ladybugs and the predatory mite known as ‘Orius’, the predatory mite known as ‘Anthocoris nemoralis’ is the most effective predatory enemy of pear psylla. The adult female insect lays between 100 and 200 eggs during her life cycle. The eggs are hardly visible to the naked eye and are mainly deposited on young leaf tissue. Depending on the climatological conditions and the food supply, ‘Anthocoris’ can produce 3 generations. Both the larvae of this predatory mite as well as the adults feed on large quantities of pear psylla.

The first results of the use of predatory mites under Dutch conditions can be described as highly successful. At 90% of the farms where predatory mites were distributed in spring of this year, spraying proved unnecessary. The same farms did see serious pear psylla infestation in the previous year. Many fruit farms (approximately 70% of the total area) were confronted with serious pear psylla problems during the summer of 2000. In a number of cases, spraying was necessary in order to curb the strong population build-up of pear psylla. Observations clearly showed that the population of predatory mites kept closer track of the pear psylla population. This means that many eggs, larvae and adults of the predatory mites can be found if there is an increase in the number of pear psylla in the orchard.

The predatory ‘Anthocoris’ mites are sensitive to a number of chemical crop protection agents. The agents known as ‘Sevin’ (carbaryl) and ‘Admire’ (imidacloprid), for example, that are sometimes used to control beetles, mussel scales and capsids, are harmful to various stages of the predatory bugs.

‘Anthocoris nemoralis’ is supplied in bottles filled with buckwheat shells and 200 adult predatory mites. The shelf life of the predatory mites is fairly limited, so it is important to distribute them as soon as possible after delivery. They can be stored for up to 2 to 4 days, provided that the bottles are stored away from light, lying down, refrigerated at a temperature of 10 to 15 degrees Celsius.