At field rates, pymetrozine had the lowest impact on CRW biocontrol but had poor activity against non-parasitised CRW. Laboratory experiments evaluated insect toxicity through direct contact with the agrichemical spray or via exposure to residues on clover foliage. Laboratory experiments were conducted to measure the toxicity of eight agrichemicals used against white clover insect pests or for weed control on CRW (parasitised and non-parasitised) and adults of its parasitoid Microctonus aethiopoides. White clover (Trifolium repens) crops are attacked by various insect pests including Sitona obsoletus (=S. Mixed cultivation systems of forage crops are an economically and ecologically sustainable method of insect pest control. The damage caused by the аlfalfa snout beetle had the most significant negative effect on aboveground and root biomass productivities. The damage caused by Otiorrhynchus ligustici, as expressed by the length of gnawed furrows, in the mixtures with sainfoin, bird's-foot trefoil and alfalfa decreased considerably-by 12.5, 77.8 and 59.5%, respectively-compared to the pure crops.
Damage to nodules by Sitona larvae in mixtures decreased significantly: on average by 33.5% (sainfoin + cocksfoot), by 50.3% (bird's-foot trefoil + cocksfoot) and by 55.6% (alfalfa + cocksfoot) compared to pure grown legumes. A similar tendency was observed with regard to dry root biomass. The weight of dry aboveground biomass in the pure leguminous crops slightly exceeded that of the corresponding leguminous components in the mixtures, whereas the productivity of cereal plants in mixed crops was significantly lower compared to the pure cocksfoot on average by 38.5, 47.0 and 51.7% in mixtures of sainfoin, bird's-foot trefoil and alfalfa respectively. It was found that the productivities of aboveground and root biomasses in binary mixtures were significantly higher compared to the corresponding legume monocultures on average by 30.7 and 39.7% respectively in mixtures with sainfoin, by 15.0 and 73.1% in mixtures with bird's-foot trefoil, and by 18.7 and 49.6% in mixtures with alfalfa.
This work examined the impact on productivity of the cultivation system of perennial legumes such as sainfoin (Onobrychis viciifolia), bird's-foot trefoil (Lotus corniculatus) and alfalfa (Medicago sativa), grown pure and in binary mixtures with cocksfoot and on damage caused by root pests of Sitona spp. lepidus to temperature can be used for developing phonological models to predict the timing of egg hatch which are important for management programs targeting the weevil. The results suggest that of the three models (Lactin, Briere, and Hilbert and Logan), that estimated critical temperatures, (t min, t opt, and t max), Lactin gave the most suitable fit of data. Of the nonlinear models, the Logan-6, Sharpe and DeMichele, and Lactin models were the most accurate at calculating t opt of 27, 27.50, and 28☌, respectively. The suitability of the models was evaluated based on eight indicators (R 2, RSS, R adj 2, AIC, BIC, AICC, W j, and Z i ). The relationship between constant temperature and developmental rate was evaluated using nine models. Using linear regression, the lower threshold temperature was calculated 4.38☌ and the thermal constant was 236.45 degree-days. At 28.5☌, the embryo development period was the shortest (10.35 days) whereas at 9☌, this parameter was the longest (55.08 days). Developmental time decreased with increase in temperature from 9 to 28.5☌ but increased markedly at 30☌. Development occurred over the entire range of temperatures, although hatching percentage at 30☌ was only 24.4% compared to 90.1% at 28.5☌. Development of the egg stage was studied at six different constant temperatures ranging from 9 to 30☌ to improve the basis for phenological forecasts. Larva feeding severely impairs the capacity of white clover to fix atmospheric nitrogen, by attacking the nitrogen-fixing root nodules. is a pest of clovers (Trifolium spp.), particularly white clover (T. The clover root weevil, Sitona lepidus Gyll.
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