1 - Fruitteeltnieuws 12 - 12 juni 2015

Aphids and their parasitoids in fruit orchards

Ammar Alhmedi & Tim Beliën Pcfruit vzw, Department of Zoology, Fruittuinweg 1, 3800 Sint-Truiden, Belgium For more info contact: [email protected] or [email protected]

Fruit tree orchards attract many kinds of pests that damage vegetation and fruit. are among the most serious pests that attacking fruit trees in Belgium, of which they are generating severe economic damage through direct feeding, honeydew producing and virus spreading. These aphids have fortunately insect enemies of their own. Growers can provide safe habitat for beneficial as part of an integrated pest management (IPM) strategy that reduces the need for pesticides.

Problems related to honeydew production by aphids

- Encouraging the growth of black sooty mould. - Attracting ants that play an important role in structuring communities and protecting them against natural enemies (reduce the efficiency of biological control) and addition to helping in spreading disease in fruit tree orchard during their movement from soil to the tree and between trees. - Blocking out the light it needs affecting by the on the photosynthesis process in leaves and the tree health in general.

Why this study?

The lack of information about diversity of parasitoid wasps associated with aphids in fruit orchards in Belgium, in addition to the economic importance of fruit tree crops, lead us to realize this study. Data obtained from this study could be used in developing and subsequently evaluating integrated management strategies for aphid pests. Data availability on tritrophic associations is considered as the key element when we want to develop biological control strategy against aphids, as well as to provide the background information about their host range patterns. Our field observations were weekly carried-out in , and cherry orchards of Sint-Truiden region (pcfruit, Bernissem, Wilderen-Staain, Bevingen, Gingelom) from June and October 2014. The potential importance of alternative habitats of aphid parasitoids lead us also to monitor flora growing naturally in or adjacent of fruit tree crops. 2 - Fruitteeltnieuws 12 - 12 juni 2015

What were aphid species observed attacking fruit trees?

In 2014 season, 11 aphid species belonging to different genera were observed on fruit trees, presented mainly by the rosy apple aphid, Dysaphis plantaginea (Fig. 1A), woolly apple aphid Eriosoma lanigerum (Fig. 1B), green apple aphid Aphis pomi (Fig. 1C), on apple, and black cherry aphid Myzus cerasi (Fig. 1D) on cherry. Pear trees remarkably seemed to be less vulnerable for aphid attacks and their relative damages. Those aphids were subject to attack by a wide range of natural enemies, including parasitoid wasps, predators and pathogens. We focused in the present study on the parasitoid fauna.

A B

C D

Figure 1. Aphids: A: Rosy apple aphid, B: Woolly apple aphid, C: Green apple aphid, D: Black cherry aphid

Aphid parasitoids (parasitic wasps), which are considered as one of the most important natural enemies against aphid pests in agricultural system, include aphelinid (Fig. 2a) and braconid (Fig. 2b) wasps. Parasitoid female lays eggs (Fig. 2a, b) into aphids; the eggs hatch into larvae that consume the internal contents. Eventually, the larva pupates and becomes an adult, which chews out an emergence hole. Parasitized aphids are characteristically swollen, brown, gray to black, and are called mummies (Fig. 2c). During the 2014 season, 15 aphid parasitoids belonging to 8 genera were recorded attacking aphids (but not all aphid species) 3 - Fruitteeltnieuws 12 - 12 juni 2015 in apple, pear, and cherry trees (Table 1). Among the collected parasitoid speci