Greenhouse climate control: an approach for integrated pest management

Modern control strategies for greenhouse climate control can be used in order to reduce disease infection and to influence plant development. Within the concept of integrated plant protection, it is necessary to minimise chemical applications. In addition to existing dehumidification strategies, in particular, the use of climate control for integrated pest control requires registration and simulation of climate conditions in the plant canopy. To avoid intensive and expensive technical measurements, it is necessary to describe the energy and mass transport processes within the canopy, the exchange processes between air and plant elements and other surfaces. The basics of a computer-supported anti-botrytis climate control management have been developed based on a plant canopy model.     

Influence of comb parameters on picking properties for chamomile flowers (Matricaria recutita)

Tools in the form of a comb are generally used to harvest chamomile flowers. The combs can be hand-operated or machine-based. To achieve good picking quality and low losses, the comb parameters have to be optimized. In this paper, the influence of comb thickness (0.5 mm, 1.0 mm and 2 mm) and the shape of the gap between the tines (3 variants) on picking force and remaining stalk length was investigated for German chamomile (Matricaria recutita) under lab conditions. To ensure that the stalks glide along the gap to the ground of the picking blade, the inclination angle was adjusted to be 45° from the blade plane in the direction of movement. For each of the 9 variants, 100 breaking tests were performed. To estimate the breaking force, a specific tensile force measuring instrument was used. The mean breaking strength of the stalks for the investigated 9 variants ranged from 3.62 N mm⁻² to 4.66 N mm⁻². In about 50% of the tests, the comb parameters had no influence because stalks broke outside of the contact point with the comb at the weakest section of the stalk. In conclusion, the picking quality of involved test blades was partially influenced by the thickness of the blade, the shape of the gap between the teeth and substantially by the strength of the individual chamomile stalks.     

Laser rangefinder-based measuring of crop biomass under field conditions

Knowledge of site-specific crop parameters such as plant height, coverage and biomass density is important for optimising crop management and harvesting processes. Sensors for measuring crop parameters are essential pre-requisites to gather this information. In recent years, laser rangefinder sensors have been adopted in many industrial applications. In agricultural engineering, the potential of laser rangefinders for measuring crop parameters has been little exploited. This paper reports the design and the performance of a measuring system based on a triangulation and a time-of-flight laser rangefinder for estimating crop biomass density in representative crops under field conditions. It was shown that the mean height of reflection point is a suitable parameter for non-contact indirect measurement of crop biomass by laser rangefinder sensors. The main parameters for potential assessment were the coefficient of determination (R ² ) and the standard error (RMSE) for the relation between crop biomass density and the mean height of the reflection point in crop stands from oilseed rape, winter rye, winter wheat and grassland during the vegetation period in 2006. For the triangulation sensor, R ² was in the range from 0.87 to 0.98 and for the time-of-flight sensor in the range from 0.75 to 0.99 for both fresh matter and dry matter density. The triangulation sensor had a reduced suitability caused by masking effects of the reflected beam and because of limited measuring range. Based on the results of experiments and technical data, it was concluded that the time-of-flight principle has good potential for site-specific crop management.     

Botrytis cinerea — history of chemical control and novel fungicides for its management

Infections caused by Botrytis cinerea are of considerable economic importance in grapes, vegetables and berries world-wide, especially when grown under protection. Newly introduced botryticides are the anilinopyrimidines pyrimethanil, cyprodinil and mepanipyrim, the phenylpyrrol fludioxonil and the hydroxyanilide fenhexamid. Biochemical studies indicate that the anilinopyrimidines inhibit the biosynthesis of methionin by blocking cystathionine-β-lyase. The target site of fludioxonil seems to lie in the osmoregulatory signal transmission pathway. Although the exact biochemical target of fenhexamid is not yet characterized, there are clear indications that it is different from all other botryticides known. Therefore, fenhexamid is an effective tool for anti-resistance management strategies.