Optimal profit of the parasitation by Aphelinus mali in an IPM complementary strategy for the control of Eriosoma lanigerum.

During summer the parasitoid Aphelinus mali may certainly reduce the infestation of woolly apple aphid (Eriosoma lanigerum), but studies on the single interaction rarely indicate sufficient biological control in the period May-June. In this period chemical control by spirotetramat or pirimicarb remains indispensable in order to anticipate on dense migration waves and subsequent colonization of extension shoots by E. lanigerum. The limited parasitation by A. mali around flowering is linked with a delayed emergence from diapause and with a slower reproduction rate than its host. In 2010 and 2011 the first adult flights monitored on yellow sticky traps corresponded perfectly with the currently used prediction models for A. mali. Further accurate monitoring all along the season enabled also to determine a well defined endo-parasitic phase of A. mali occurring after the small peak observed around flowering. During this endo-parasitic phase A. mali larvae reside inside their mummified host. Compounds with higher acute toxicity on A. mali adults, like chloronicotinyl insecticides (CNI's), are preferably positioned here. Selectivity in the time can then be claimed. Respecting this principle, the further parasitation potential of A. mali in summer is not hampered. Preservation of the first peak of flights of A. mali in the pre-flowering period is essential for an exponential flight increase. This is essential for the parasitation of E. lanigerum in summer, which constitutes a valuable complement in the integrated control strategy.

Reduction in bacterial ooze formation on immature fruitlets after preventive treatments of Fosethyl-Al against fire blight Erwinia amylovora.

Fire blight, caused by the bacterium Erwinia amylovora (Burill Winslow et al.), is a very important bacterial disease on apple and pear orchards with devastating effects in some production area and in some years. Fire blight control consists in a whole strategy of measures that should start with control measures in and around the fruit tree nurseries. Only the use of Vacciplant (Laminarin), an inducer of the self-defence mechanism, is registered in Belgium since 2009. In other European countries Fosethyl-Al has been registered for fire blight control. Recently, research trials have been done at Pcfruit research station for several years on the activity of ALiette (fosethyl-Al) against fire blight. Fosethyl-Al, also a plant defence enhancing molecule, applied preventively 3 times at a dose of 3.75 kg/ha standard orchard (3 x 3000 g a.i./ha standard orchard), showed a reduction in the host susceptibility and decreased the disease development on artificial inoculated flower clusters and shoots. Also a clear reduction in the ooze droplet formation on artificially inoculated immature fruitlets has been observed with this molecule. This reduction in the bacterial ooze formation is considered as a very important factor in the spread of the disease in the orchard.

The selectivity in the time of thiacloprid (Calypso 480 SC) applied at preblossom on the further Anthocoris nemoralis population build up in pears.

Predatory bugs (Anthocoris sp.) are key predators of the pear sucker (Psyllo pyri) in pear orchards. In order to enhance biological control it is important to verify if crop protection products applied against Psylla pyri display potential short- or long-term detrimental effects on Anthocoris populations. This study focuses on the impact of thiacloprid (Calypso 480 SC), applied at preblossom for the control of the first generation pear sucker Psylla pyri, on subsequent population build up of Anthocoris nemoralis later in the season. Hereto, five large-scale trials on pear Conference were conducted. Two types of orchards were selected: the first type is surrounded by abundant vegetation from which Anthocorids easily can fly in when attracted by the presence of prey (Psylla pyri); the second type has no "reservoir" vegetation around the orchard and here it is considered that mostly the residential population of Anthocorids constitutes the predation. In all five trials positioning of thiacloprid preblossom did not prevent the normal population build up of the predatory Anthocoris sp. population later in the season. As both in orchards with surrounding vegetation and in orchards without adjacent vegetation a regular build up of the Anthocoris sp. population was observed, the outcomes of this study indicate that a preblossom application of Calypso 480 SC can be considered as "selective in time" for further Anthocoridae dynamics.

Methoxyfenozide, a reliable IPM compatible compound against Lepidoptera in pome fruit and vegetables with sterilising, ovicidal and larvicidal efficacy on codling moth.

Methoxyfenozide (Runner 240 SC), a Moulting Accelerating Compound (MAC) currently submitted for registration in Belgium, is an IPM (Integrated Pest Management) compatible compound with strong, broad spectrum activity against lepidopterous pests in pome frunit and vegetables. Field trials have confirmed reliable efficacy against larvae of winter moth O. brumata , both the overwintering and summer generation of the summer fruit tortrix moth, Adoxophyes orana and also the tomato looper, Chrysodeixes chalcites. Methoxyfenozide can be applied in pome fruit from green cluster onwards, and due to its bee safety it can be used also during flowering. The high consistency obtained with methoxyfenozide on the overwintering caterpillars of fruit tortrix moth relates in part to its minimal temperature dependence, to its high rain fastness and to the high intrinsic activity (low EC50) and to the ability to control all larval feeding stages. The effects of a treatment of the hibernating generation of A. orana on the subsequent summer generations is discussed. By special caged trials (semi-field) the pest- stage specificity against codling moth Cydia pomonella was investigated. Applications of methoxyfenozide were made just prior to egg deposition, at peak of egg laying and at the black head capsule stage of the embryo of codling moth. Results revealed evidence of reduced fecundity of female moths and confirmed the outstanding larvicidal and ovicidal properties of the compound (Charmillot, 2001). Application from just before egg deposition to the black head stage in the eggs is recommended and the additional sterilising effect completes the activity profile of methoxyfenozide. Treated females show reduced egg deposition whereas treated males increase the percentage of sterile eggs. Reduced field performance of methoxyfenozide in orchards showing resistance to diflubenzuron (chitin synthesis inhibitor), supports the findings of other authors on the cross-resistance of MACs and diflubenzuron. It is recommended that such orchards are not treated with methoxyfenozide.

Dimerization kinetics of violamycin BI anthracycline--the influence of ionic strength.

Violamycin BI is an anthracycline derivative with two sugars hanging on, each of them carries one positive charge. It dimerizes under conditions, which depend on the concentration of the antibiotic, pH and the ionic strength of the solution. By keeping a constant pH in a phosphate-EDTA buffer, the rate constants of violamycin BI dimerization were determined at various ionic strengths by temperature jump method. The dimerization constant Kd, resulting from the ratio of these rate constants, confirmed the values obtained spectrophotometrically in this study or elsewhere. The influence of ionic strength (0.02-0.2 M) on the rate constant values suggested to us some speculations on the reaction mechanism of the dimerization, in which, the specific mutual orientation of the monomers in the encounter, and perhaps a specific conformation of their side groups is required before a stabilizing action of the binding forces sets in.

The binding of Violamycin BI to poly-C.

The binding constant Kst of Violamycin BI (VBI) to poly-C at small and medium values of the concentration ratio p (0-12) is determined using the procedure of Schwarz under two different conditions: at constant C(VBIo) and variable C(po), and at p = C(po)/C(VBIo) = const. The average value obtained for Kst is 3.3 +/- 0.1 x 10(4) M-1, whereas the cooperativity parameter q of 13 characterizes a moderate cooperative interaction between adjacent bound ligands. In contrast, at large values of p (12-355) the formation of isolated bound dimers on the poly-C chain is observed. At pH 7, VBI dimerizes in solution with a dimerization constant strongly dependent on ionic strength: Kd = 732 +/- 20 M-1 and (9.3 +/- 0.2) x 10(3) M-1 at I = 0.02 M and 0.2 M respectively. The lower and upper boundaries for the binding constant of the dimer to the polynucleotide at large values of p are 1.0 x 10(-5) M-1 and 6.25 x 10(-6) M-1 respectively.