The occupancy and infestation of grain stocks by harmful arthropods

Abstract

The aim and tasks of the study. The aim of research is determination of occupancy and infestation of parties of grain of spiked cultures by arthropod. To achieve this aim following tasks were solved: effectuation of analysis of species composition of arthropod pests of grain of spiked cultures in overt and covert forms; determination of degrees of occupancy of parties by live weevils and mites and total density of infestation and conformity to maximum permissible levels; establishment of internal occupancy of grains by primary pests of grain stocks.

Material and methods. The experiments were carried out during spring-autumn period 2012-2014 years on territory granaries and elevators of Poltava region. For determination of species composition of arthropod-pests of grain stocks of spiked cultures (winter wheat, spring barley and oats) was used method of analysis of average samples and installed food baits and pheromone traps. We defined inner infestation by primary pests using method of cracking of grain and flotation. On basis of obtained results of analyzes were set degrees of occupancy and infestation of grain parties by arthropod. On indicators of total density of infestation of average samples defined compliance their level by maximum permissible norms.

Results and discussion. During conducting researches installed second degree of occupancy of parties of winter wheat by grain weevil, namely quantity of pests was 5.8 and 5.9 ind./kg (2013-2014 years). In samples of oats were totaled 38.6 ind./kg mites, this quantity also equal to second degree. Inner infestation was 1-2 %, reaching maximum of 8 % in winter wheat. Forty parties were infected pests of stocks with of fifty-six of grain parties in 2012 year, in 2013 year – in twenty-six cases with of thirty-six installed presence of mites and insects, in 2014 year – twenty-one parties with of twenty-five infected arthropods. Exceeding of maximum permissible level of infestation of grain was noted for grain weevil (7.65 ind./kg with of allowed 7.5 ind./kg) and caterpillars of Indian meal moth (4.40 ind./kg with of 3.0 ind./kg). The total infestation was 20.49 ind./kg (>5.49 ind./kg), 20.81 ind./kg (>5.81 ind./kg) and 18.63 ind./kg (>3.63 ind./kg), depending on time of accounts. The significant quantity of pests in average samples was noted for Chortoglyphus arcuatus (21.3 ind. /kg), Cheyletus eruditus (8.7-10.8 ind./kg), Dust mite (5.0-17.5 ind./kg). On average quantity of Granary and Rice weevils did not exceed 5.0 ind./kg, flour beetles – 8.0 ind./kg. The maximum quantity of Liposcelis divinatorius was 562 individuals in food trap with sunflower oil. In pheromone trap were encountered up to 109 individuals of Indian meal moth.

Conclusions. By quantity of pests was dominated first degree of occupancy, second degree inherent for weevils in parties of winter wheat and mites in samples of oats, 6.0 ind./kg and 39.0 ind./kg respectively. Latent infestation by primary pests was on average 2 %. In 87 from 117 average samples was noted presence of mites and insects. Insignificant excess of MPL for Granary weevil and Indian meal moth on 0.15 and 1.4 ind./kg was observed. Given overall infestation (≈20.0 ind./kg), exceeding of MPL was about 5.0 ind./kg by TDI.