TOXICITY OF SEVERAL FUNGICIDES FOR ORANGE WHEAT BLOSSOM MIDGE, SITODIPLOSIS MOSELLANA (GÉHIN) (DIPTERA: CECIDOMYIIDAE).

The orange wheat blossom midge, Sitadiplosis mosellano (Géhin) (Diptera: Cecidomyiidae), can cause severe losses in wheat grain yield and quality. This pest is known to be susceptible to many insecticides, but various field observations have suggested that some fungicides could also significantly affect S. mosellana. In order to confirm these field observations, the effect on adult midges of several fungicides commonly applied to wheat crops was investigated in the laboratory and in small plots in the field. In each experiment, the fungicides were compared with a positive (insecticide) and a negative control (water). Four fungicides were assessed in the laboratory, each with five doses based on basis of a tenfold dilution starting at the field-recommended dose. The mortality rate was evaluated after 24 hours and the lethal dose 50% (LD50) was determined for each product. In the field, six fungicides were tested at the recommended dose. The effect of each product was compared on the basis of the number of S. mosellana adults caught alive with an insect vacuum sampler (Vortis®) on the morning after the treatments. Both experiments showed a significant effect of several fungicides tested on S. mosellana adults. Chlorothalonil was not toxic for S. mosellana, but tebuconazole, fluxapyroxad and azoxystrobin all induced significant mortality rates.

Unusual occurrence of cocoons in population of Haplodiplosis marginata (Diptera: Cecidomyiidae) in Belgium.

The saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), is a phytophagous species that develops in saddle-shaped galls on stems of wheat Triticum vulgare, barley Hordeum sativum, rye Secale cereale, and some other species of Poaceae. Only one generation develops per year. Full-grown larvae leave galls and drop onto the soil where they remain up to the springtime of the following year. Larvae do not usually spin cocoons. However, formation of cocoons by larvae was observed in populations developing in western Europe: in England in 1954, in the Netherlands in the 1960s, and in Belgium in 2011. On the basis of our analysis, a part of the larval population forms cocoons as protection against unfavorable weather conditions, especially drought.

Study on the sensitivity of three oat varieties to the saddle gall midge, haplodiplosis margina ta (von Roser) (Diptera: cecidomyiidae).

The saddle gall midge, Haplodiplosis marginota (von Roser, 1840) is a univoltine pest of cereals which occurs in Europe. The larvae feed on stems and attractive saddle-shaped depressions, driving to important yield losses when the galls are numerous. After 40 years without any reporting, large populations of H. marginata and important damage have been observed since 2010 in wheat crops in Belgium, especially in the Flemish Polders where clay soils and intensive farming of cereals favour heavy infestations. According to some research conducted in the 1960s during the last outbreak, oat (Avena sativa L.) is known to be one of the less favourable hosts to the saddle gall midge. Our study was performed in order to assess the host sensitivity of three oat varieties currently grown in Belgium: EVITA, EFFEKTIv and FREDDY. Therefore, oat varieties were sown on infested soil in two separate enclosures in a glasshouse. In the first enclosure, only the three oat varieties were grown; in the second one, these three oat varieties were grown together with two varieties of spring wheat: GRANNY and KWS CHAMSIN. TWO parameters were measured: the percentage of leaves with laid eggs, and the number of galls per stem. The percentage of leaves with eggs showed that the infestation was significantly lower on oats when they were in presence of wheat. The egg infestation was also significantly higher on wheat than on oat, which means oat is a much less favourable host plant than spring wheat for egg laying. Oat varieties were significantly different from each other regarding the number of galls per stem, but with very little damage compared to wheat. The FREDDY variety even seemed to be completely resistant to saddle gall midge, as no galls were observed although there was a similar percentage of leaves with eggs for the three oat varieties. Cropping oat could thus contribute to reduce infestations of H. morginato.

Integrated management of wild chamomile (Matricaria chamomilla L.) populations by tillage.

Nowadays, environmental, health and economic concerns encourage reviewing our weed management in agriculture. Integrated pest management is one key element in the development of weed management strategies less dependent from herbicides. To reach this goal, impact of different methods of tillage (Combinations of stubble cultivator and moldboard plow) on biology and dynamic of wild chamomile populations was studied in experimental plots of experimental farm of Gembloux Agro-Bio Tech. In summer 2012, wild chamomile densities were significantly lower in plots tilled with a moldboard plow. The use of a stubble cultivator did not significantly affect M. chamomilla density. In addition, we found higher wheat yields in plowed plots, indicating that the decrease in M. chamomilla densities reduces competition for wheat. These results show well long run impact of plowing and his effect on densities of wild chamomile and the seedbank.

Effect of mechanical weeding on wild chamomile (Matricaria chamomilla L.) populations in winter wheat crop (Triticum aestivum L.).

Currently, economic, agronomic and environmental concerns lead to reduce the use of herbicides. Mechanical weeding can help to reach this objective. Dynamics and biology of wild chamomile (Matricaria chamomilla L.) populations were assessed as well as dynamic of winter wheat (Triticum aestivum L.) for four level of application of a weeder-harrow (0, 1, 2, 3 treatment(s)). After each treatment, an effect of mechanical weeding on wild chamomile density was observed. Density of wild chamomile decreased significantly with intensification of mechanical weeding. A third treatment allowed eliminating late emerged plants.

Chemical control of Haplodiplosis marginata von Roser (Diptera: Cecidomyiidae).

The saddle gall midge, Haplodiplosis marginata (von Roser), has been detected in Belgium since 2010, after several decades without any reporting. It had indeed caused serious damages between 1965 and 1970. This insect is a European cereal pest whose larvae feed on stems and engender saddle-shaped depressions, resulting in yield losses. Face with the resurgence of this pest, it was decided to study its spatial distribution and, because serious damages were observed in some regions, to develop effective curative control. To date, chemical protection seems to be the only immediate solution in case of heavy emergences. Experimentation was conducted in a highly infested field (Meetkerke, Belgian Polders), according to a randomized complete blocks arrangement with four replications. Foremost, a lambdacyhalothrin-based insecticide was used to evaluate efficiency of several protection schemes, ranging between one and four spray(s). The large spread of flights observed during the 2011 spring allowed to highlight the effect of treatment date on the attack intensity and also on the galls distribution along the stem, on the different internodes: the lower internodes were protected by the early sprayings, while last sprayings induced reduction of galls number on the upper internodes. Moreover, several insecticides already registrated in cereals against aphids were compared for their efficacy against saddle gall midge. Studied pyrethroids have shown a very good efficacy, ranging between 75% and 87%, when applied twice with a 2 weeks interval. To be efficient, insecticide applications must thus be synchronized with the flights and egg-laying periods. Monitoring the phenology of flights is thus essential as part of integrated pest management against saddle gall midge.

Dynamic of black-grass populations depending on the sowing time of winter wheat.

Currently, economic, agronomic and environmental concerns, lead to reduce use of herbicides. This reduction can be help by cultural measures like delay of the sowing date. Four sowing dates of winter wheat from 15th of October to 26th of November were tested. Dynamic of black-grass (Alopecurus myosuroides Huds.) populations and their reproduction rate were assessed as well as dynamic of winter wheat for each date. Delay of sowing could significantly reduce reproduction rate of black-grass. It was shown that the emergence rate (pl/m2), but also number of ears per plant and number of seeds per ear of black-grass decreased significantly with the sowing date. This reduction of seeds production already is from sixty per cent for a delay of two weeks sowing.

Diel shifts in carboxylation pathway and metabolite dynamics in the CAM bromeliad Aechmea 'Maya' in response to elevated CO2.

BACKGROUND AND AIMS: The deployment of temporally separated carboxylation pathways for net CO(2) uptake in CAM plants provides plasticity and thus uncertainty on how species with this photosynthetic pathway will respond to life in a higher-CO(2) world. The present study examined how long-term exposure to elevated CO(2) influences the relative contributions that C(3) and C(4) carboxylation make to net carbon gain and to establish how this impacts on the availability of carbohydrates for export and growth and on water use efficiency over the day/night cycle. METHODS: Integrated measurements of leaf gas exchange and diel metabolite dynamics (e.g. malate, soluble sugars, starch) were made in leaves of the CAM bromeliad Aechmea 'Maya' after exposure to 700 micromol mol(-1) CO(2) for 5 months. KEY RESULTS: There was a 60 % increase in 24-h carbon gain under elevated CO(2) due to a stimulation of daytime C(3) and C(4) carboxylation in phases II and IV where water use efficiency was comparable with that measured at night. The extra CO(2) taken up under elevated CO(2) was largely accumulated as hexose sugars during phase IV and net daytime export of carbohydrate was abolished. Under elevated CO(2) there was no stimulation of dark carboxylation and nocturnal export and respiration appeared to be the stronger sinks for carbohydrate. CONCLUSIONS: Despite the increased size of the soluble sugar storage pool under elevated CO(2), there was no change in the net allocation of carbohydrates between provision of substrates for CAM and export/respiration in A. 'Maya'. The data imply the existence of discrete pools of carbohydrate that provide substrate for CAM or sugars for export/respiration. The 2-fold increase in water-use efficiency could be a major physiological advantage to growth under elevated CO(2) in this CAM bromeliad.

Cryopreservation of in vitro sugar beet (Beta vulgaris L.) shoot tips by a vitrification technique.

Sugar beet shoot tips from cold-acclimated plants were successfully cryopreserved using a vitrification technique. Dissected shoot tips were precultured for 1 day at 5  °C on solidified DGJ0 medium with 0.3 M sucrose. After loading for 20 min with a mixture of 2 M glycerol and 0.4 M sucrose (20  °C), shoot tips were dehydrated with PVS2 (0  °C) for 20 min prior to immersion in liquid nitrogen. Both cold acclimation and loading enhanced the dehydration tolerance of shoot tips to PVS2. After thawing, shoot tips were deloaded for 15 min in liquid DGJ0 medium with 1.2 M sucrose (20  °C). The optimal exposure time to both loading solution and PVS2 depended on the in vitro morphology of the clone. With tetraploid clones a higher sucrose concentration during cold acclimation and preculture further enhanced survival after cryopreservation. Survival rates ranged between 60% and 100% depending on the clone. Since only 10-50% of the surviving shoot tips developed into non-hyperhydric shoots, regrowth was optimized.

Cryopreservation of in vitro sugar beet shoot tips using the encapsulation-dehydration technique: influence of abscisic acid and cold acclimation.

It has been previously shown that shoot tips of in vitro plantlets of sugar beet (Beta vulgaris L. clone SES1) can be cryopreserved using the encapsulation-dehydration technique (survival rate of 37% after freezing). This article reports the influence of abscisic acid (ABA) and cold acclimation on survival after cryopreservation. When ABA was added to the multiplication medium of the plants, the survival rate of shoot tips after cryopreservation was not increased (45%). After cold acclimation of the plants, their growth pattern differed (plants became apically dominant) and the survival rate of the shoot tips after cryopreservation clearly increased (70% survival and 50% plant regeneration after freezing). This improved protocol was successfully applied to three other clones.

Does water deficit stress promote ethylene synthesis by intact plants?

The effect of plant water deficit on ethylene production by intact plants was tested in three species, beans (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.) and miniature rose (Rosa hybrida L., cv Bluesette). Compressed air was passed through glass, plant-containing cuvettes, ethylene collected on chilled columns, and subsequently assayed by gas chromatography. The usual result was that low water potential did not promote ethylene production. When plants were subjected to cessation of irrigation, ethylene production decreased on a per plant or dry weight basis of calculation. No significant promotion of ethylene production above control levels was detected when water deficit-treated bean or cotton plants were rewatered. The one exception to this was for cotton subjected to a range of water deficits, plants subjected to deficits of -1.4 to -1.6 MPa exhibited a transient increase of ethylene production of 40 to 50% above control levels at 24 or 48 hours. Ethylene was collected from intact leaves while plants developed a water deficit stress of -2.9 megapascals after rewatering, and no significant promotion of ethylene production was detected. The shoots of fruited, flowering cotton plants produced less ethylene when subjected to cessation of irrigation. In contrast, the ability of bench drying of detached leaves to increase ethylene production several-fold was verified for both beans and cotton. The data indicate that detached leaves react differently to rapid drying than intact plants react to drying of the soil with regard to ethylene production. This result suggests the need for additional attention to ethylene as a complicating factor in experiments employing excised plant parts and the need to verify the relevance of shock stresses in model systems.

Role of ethylene and cytokinins in the initiation of lateral shoot growth in bromeliads.

Aechmea victoriana var discolor L. B. Foster and Aechmea dactylina Bal. are commercially propagated in vitro through lateral shoot growth. A modified Murashige and Skoog medium is used which contains both BA and IAA. These growth substances were shown in the present study to synergistically stimulate the production of ethylene by the cultured plants. The stimulation of ethylene production is correlated with the outgrowth of the lateral buds. The rise in ethylene production was concluded to induce lateral shoot growth, because: (a) outgrowth of the shoots was blocked by preventing an increase in ethylene production, (b) 1-aminocyclopropane-1-carboxylic acid (ACC), the natural precursor of ethylene biosynthesis, substituted for IAA in the promotion of ethylene production and lateral bud outgrowth. Although ACC could substitute for IAA, it could not substitute for BA; therefore, cytokinins are concluded to be essential for lateral bud outgrowth in vitro in Aechmea. These results suggest that cytokinins and ethylene both play roles in natural lateral bud initiation and that the cytokinin function involves two stages of the process.