• Korean journal of applied entomology
• /
• v.34 no.3
• /
• pp.256-265
• /
• 1995

The effect ground-cover weeds on the occurrence of apple pests and their natural enemies was studied in an apple orchard in Ahnsung, Kyung-gi do during seasons of 1993 and 1994. The major apple pests and their parasitoids and predators were surveyed on the apple tree canopy in tow experimental plots; a weed-free lot where all weeds were removed by herbicide treatment, and a mowed plot where weeds were allowed restrictly by cutting with an asickle. Also, a sweep net sampling was taken from ground-cover weeds in the mowed plot. There were no significant differences in the abundance of mite and aphids between two plots, although mite densities tend to be lower in the mowed plot. The apple leaf miner, Phyllonorycter ringoniella, was significantly fewer in the mowed plot,. The densities of natural enemies of mites and aphids were slightly higher in the mowed plot. The parasitism of apple leaf miner in the mowed plot was 6~10% and 20~25% higher than that in the weed-free plot in 1993 and 994, respectively. Several natural enemies such as Apanteles kuwayamai (Braconidae), Orius sauteri (Anthocoridae), Chrysopa sp. (Chrysopidae), coccinellidae, and Eulophidae were collected both from weeds and the apple trees, However, potential apple pests were not observed on weeds. The development of insect community on the apple tree canopy was restricted by the pesticide spray on apple trees, while the insect community on weeds was maintained without significant destruction by pesticides spray on apple trees. Consequentely, the ground-cover weeds under apple trees affected occurrences of apple pests and their natural enemies in apple trees. te specialist natural enemies such as apple leaf miner's parasitoids dispersed from weeds to the apple canopy and affected apple leaf miner density significantly. However, generalist predators that have preys available on weeds stayed on weeds, hence their control effects for mites and aphids on the apple canopy were low.

• Korean journal of applied entomology
• /
• v.27 no.1
• /
• pp.47-54
• /
• 1988

Phytophagous insects were surveyed for biological control of weeds in the southern part of korea from April 20 to July 31, 1987. Phytophagous coleopteran insects representing 12 families, 52 genera and 61 species, hemipteran insects 7 families, 18 genera and 20 species, homopteran insects 4 families, 16 genera and 21 species, hymenopteran insects 2 families, 2 genera and 3 species, and orthopteran 2 familes, 6 genera and 6 species were recorded from 58 weeds. Some chrysomelids and orthopteran insects were potential agents for biological control of weeds.

• Korean journal of applied entomology
• /
• v.61 no.1
• /
• pp.255-266
• /
• 2022

This study was conducted to examine the effects of grass vegetation (W: manual weeding, NW: herbicide sprays) and pyrethroid spray (P: pyrethroid spray, NP: no pyrethroid spray) on the population dynamics of Panonychus citri and natural enemies in citrus orchards. Two essential hypothesis were made to test the population dynamics: 1) weed planting promotes natural enemies by offering habitat and alternative food sources, resulting in the reduction of P. citri populations, and 2) pyrethroid spray removes natural enemies by its non-selective toxicity, resulting in the increasement of P. citri populations. The observed natural enemy populations (mainly Phytoseiids and Agistemus sp.) were not different largely from the expected values in the hypothesis, which assumes more abundant natural enemies in weeds and no pyrethroid plots. Although some discrepancy was occurred in NW+NP and W+NP plots in 2011, the observed values were almost same with expected values in 2012. In overall, pesticide effect was strongly significant and pyrthroids removed largely natural enemies. Although habitat (weeds) effect showed a conflict result, natural enemy population increased in plots allowing weed growth, when considering the increased autumn population relatively compared to that of spring-summer population. The decreased abnormal P. citri populations in pyrethroid plots could be explained under the assumption of a strong repellent behavior of P. citri to the pyrethroids.

• Korean journal of applied entomology
• /
• v.44 no.2
• /
• pp.115-123
• /
• 2005

Historical changes of population abundances of European red mite (ERM), Panonychus ulmi (Koch), and two-spotted spider mite (TSSM), Tetranychus urticae (Koch) (Acari: Tetranychidae), were described in selected apple orchards in the National Horticultural Research Institute (NHRI, Suwon, Korea), based on research reports of the NHRI from 1958 to 1998. ERM was an abundant species up to 1970, and TSSM became a dominant species after 1980. The change occurred around mid 1970. Three hypotheses were made to explain the change: TSSM competitively replaces ERM, ground cover weeds are a major influencing factor on movement of TSSM (TSSM movement into trees is accelerated by destroying weeds), and ERM and TSSM populations are regulated by natural enemy complexes when the orchard system is not disrupted. And long-term results of the interaction between two species were projected according to the combination of different orchard management strategies: pesticide sprays (non-selective toxic pesticide spray : heavy pesticide pressure (HPP), and selective soft pesticide spray = low pesticide pressure (LPP)) and weed control methods (grass planting, and clean culture system with herbicides). In the HPP and grass planting system, ERMs are abundant because ERM can avoid competition with TSSM as movement of TSSM to trees are restricted, and natural enemy complexes are destroyed by toxic pesticides. In the HPP and clean culture system, TSSMs are abundant because TSSM moves to trees from early season and competitively replaces ERM. In the LPP and grass planting system, ERMs are abundant because movement of TSSM to trees is reduced, but they do not build up a high population density since their densities are regulated by natural enemy complexes. In the LPP and clean culture system, TSSM moves to trees and competes with ERM, but the competition pressure is reduced because population densities of mites are regulated in a lower level by natural enemy complexes. So, ERM can occurs in late season. Thus, two species can coexist temporarily with more ERM in early season and more TSSM in late season. TSSM abundant phenomenon presented in this study can be partially explained as a result of long-term interaction between ERM and TSSM under the HPP and clean culture system.

• The Korean Journal of Pesticide Science
• /
• v.11 no.3
• /
• pp.210-215
• /
• 2007

This study aims to investigate if the properly use of pesticide in Ginseng farmland at Gangwon-do, Korea. Questionnaire included 36 questions such as control method for plant diseases, pests and weeds and pattern of pesticide use was answered by 271 Ginseng farmers lived in 4 cities and 8 counties at Gangwon-do. Ginseng farmers have noxious plant diseases, insects and weeds such as leaf spot, anthracnose, snail, stem-mining fly, horseweed and hairy crabgrass. To control of these, 35% of farmers relied on various type of pesticides and 31.5% of farmers used pesticides mingling with natural enemy, microorganism and organic materials. Farmers selected the pesticide based on the their own experiences or by recommendation of market dealers and neighbors, resulting in the use of inappropriate pesticides in the Ginseng farmland(78.8 % ). They followed standard dosage of the pesticide from Handbook of Pesticide Application(96.3%). They, however, used the same pesticides from 2 to 5 years(44.1 %). This consecutive use of pesticide could be induced resistance. This survey resulted that study for pesticide resistance and systematic educational program for proper use and selection of pesticide to Gingseng farmers should be conducted in farmland at Gangwon-do, Korea.

• Korean journal of applied entomology
• /
• v.35 no.1
• /
• pp.38-44
• /
• 1996

These experiments were conducted to investigate the ecological characteristics of Amblyseius womersleyi Schica,which was biological agent in the integrated management of tea red spider mite, Tetranychus kanzawai Kishida.At four constant temperatures of 15, 20, 25, and 30$^{\circ}$C, the periods of A. womersleyi from egg to adult emergencewere 22.8, 9.6, 4.8, and 3.6 days, respectively. Developmental threshold and effectively cumulative degree-day from egg to adult emergence were 12.7"C and 61.4DD, respectively. Preoviposition periods of A.womersleyi were shorter than oviposition and postoviposition periods. The number of eggs laid per female was21.7, 28.1, 34.2, and 48.0 at the respective temperatures. The intrinsic rates of increase were estimated to be 0.064, 0.139, 0.349, and 0.402; the mean generation times were 36.0, 19.3, 8.6, and 7.7 days; the populationdoubling times were 10.8, 5.0, 2.0, and 1.7 days, respectively. A. womersleyi overwintered on green weeds, fallenleaves and in the soil surface as adult females. A. womersleyi gravid female consumed 3.0, 4.9, 15.7, and19.4 eggs of T. kanzawai per day at 15, 20, 25, and 30$^{\circ}$C, respectively. A. womersleyi protonymph consumed4.6 eggs, deutonymph 6.3 eggs, and female during oviposition consumed 19.4 eggs, and 6.8 eggs of T. kanzawaiduring postoviposition per day at 30$^{\circ}$C. at 30$^{\circ}$C.

• Korean journal of applied entomology
• /
• v.15 no.1 s.26
• /
• pp.7-16
• /
• 1976

In order to increase utility efficiency of red wood ants, Formica rufa truncicola var. yessonesis Forel as a resource of natural enemy of pine caterpillar, Dendrolimus spectabilis Butler, by finding out ecological and environmental factors in the habitat of red wood ants, the nest distribution and its density in habitat, plant distribution and density, stand-density of red pine, nest building and fixing plants, relative humidity of surface soil, physical and chemical natures of soil, and breeding rate were examined. The obtained results are summarized as follows: 1. The nest of red wood ants was densely distributed, in the lower-and middle top of mountain but no nest was found in the top. 2. The economical distribution of nest of habitat was estimated as $2.85/m^2$ and the lowest density as $1.93/m^2$ and these estimation lead us to confirm that pine caterpillar could be controlled. 3. The ecological characteristics of habitat seemed to be represented as higher stand-density of red pine of 10-20 years of age with large areas of eroded land under trees. The major grasses prevailing in this area were Andropogon brevifolius. Arundinella hirta, Miscanthus purpurasens, Eulia speciosa, Themeda japonica, Cymbopogon goeringii, and Eccoilpus cotulifer 4. Red wood ants seemed to build the nest by using red pine, Arundinella hirta, Miscanthus purpurascens, Themeda japonica or Cymbopogon goeringii as a fixing plant. 5. The limited point of humidity percent in habitat of red wood ants was estimated as $76\%$ during the acting period of May to September and as $72\%$ during pre-period of hibernation of October to November. 6. Soil analysis in habitating region showed higher concentration of organic matters and lower concentration of calcium and magnesium, and habitat was largely composed of silt and fine sand rather than coarse sand. 7. When the separated colony was transplanted to non-habitating red pine forest that seemed to have the similiar conditions as those of habitat, propagation and establishment of nest was possible.