储粮环境中米象发生与CO2含量变化的关系研究

为阐明储粮环境中害虫发生与CO_2气体含量变化的关系,研究不同含水量的小麦感染不同虫口密度(0、2、5、10、20、30头/kg)米象后储藏环境中CO_2气体体积分数变化的情况。结果表明:对于含水量相同的储藏小麦,储藏环境中CO_2气体体积分数随虫口密度的增加和储藏时间的延长而显著增加。对于含水量12%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.413%,在第30天达到最大值为14.777%。对于含水量14%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.720%,在第15天达到最大值为17.197%。本研究结果为今后通过检测CO_2体积分数变化来监测粮堆中虫害发生情况提供了可靠信息。     

Insecticidal effect of three diatomaceous earth formulations, applied alone or in combination, against three stored-product beetle species on wheat and maize

Laboratory tests were carried out to examine the insecticidal effect of three commercially available diatomaceous earth (DE) formulations on wheat and maize against three major stored-grain beetle species: Rhyzopertha dominica, Sitophilus oryzae, and Tribolium confusum. The three DEs tested were Insecto^®, PyriSec^®, and Protect-It^®. These DEs were applied alone or in all possible combinations (Insecto^®+PyriSec^®, Insecto^®+Protect-It^®, PyriSec^®+Protect-It^®, and all three DEs together), at three (total) dose rates: 0.25, 0.5, and 0.75 g/kg of each commodity. Adults of the above species were exposed to the treated commodities for 7 d at 26 °C, and 65% r.h., and after this interval the mortality was measured. For each species, adult mortality was significantly affected by the type of DE, the commodity, and the dose rate. All DEs were less effective against T. confusum, where mortality did not exceed 67%, in comparison with the other two species, where 100% mortality was achieved in some combinations. For all species tested, all DEs were more effective on wheat than on maize. Generally, the mix of two or three DEs was more effective than the application of one DE, for all species and commodities. The results of the present work clearly indicate that a blending of several DEs together may produce a new DE formulation that is highly effective at low dose rates.     

Screening of Chinese medicinal herbs for bioactivity against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst)

Extracts of 40 species of Chinese medicinal herb from 32 different botanical families were screened for contact, fumigant and feeding-deterrent activities against the two stored-grain insects Sitophilus zeamais and Tribolium castaneum. Thirty Chinese medicinal herbs exhibited insecticidal or feeding-deterrent activities against the two species of insects. Extracts of Artemisia argyi, Dictamnus dasycarpus, Evodia rutaecarpa, Litsea cubeba, Narcissus tazetta var. chinensis, Polygonum aviculare, Rhododendron molle, Sophora flavescens, Stemona sessilifolia, Tripterygium wilfordii, and Torreya grandis were most active.     

Progress towards a lure to attract three stored product weevils, Sitophilus zeamais Motschulsky, S. oryzae (L.) and S. granarius (L.) (Coleoptera: Curculionidae)

The behavioural responses of Sitophilus granarius, S. oryzae and S. zeamais to synthetic 4S,5R-sitophinone alone and in combination with volatiles from kibbled carob have been investigated with a view to the development of a single lure to attract all three species. Sitophilus zeamais and S. oryzae were shown to respond to 4S,5R-sitophinone at amounts as low as 0.025 ng. Sitophilus granarius gave a significant response to 50 ng 4S,5R-sitophinone. Volatiles from kibbled carob were also shown to attract all three species. This is the first time that attraction of S. zeamais and S. oryzae to carob volatiles has been demonstrated. Fresh lures containing 4S,5R-sitophinone and carob volatiles attracted significantly more insects in pitfall bioassays for all three species than when either component was used alone. However, after 6 weeks a significant increase in response compared to the control was found only for S. oryzae and S. zeamais. The effect of insect age on response to the pheromone and carob volatiles was also studied for all three species. The response to carob volatiles decreased with increasing insect age for all three species. A significant response to 4S,5R-sitophinone was found only for 1-2-day-old adults of S. oryzae and S. zeamais but for all ages tested of S. granarius. The effect of the combination of pheromone and carob volatiles also decreased with increasing insect age.     

4种印楝种子提取物对玉米象的生物活性

测定印楝4种不同提取物（印楝素A、印楝油、印楝乙酸乙酯粗提物和印楝超临界CO，提取物）对玉米象成虫的忌避、熏蒸和毒杀活性。4种提取物对玉米象成虫都具有较好的忌避活性，随着时间的推移，忌避活性呈下降趋势；4种提取物对玉米象成虫熏蒸活件差异较大，活性大小为印楝油〉超临界CO2提取物〉乙酸乙酯粗提物〉印楝素A。毒杀活件测定结果且示，4种提取物毒杀活性均较差，但由于印楝活件成分具有忌避、拒食和其它生物活性，对玉米象种群的数量有较明显的榨制作用。     

Laboratory assessment of insecticidal effectiveness of natural zeolite and diatomaceous earth formulations against three stored-product beetle pests

The insecticidal effectiveness of two natural zeolite formulations (Minazel plus and Minazel), applied to wheat at selected rates of 0.25, 0.50 and 0.75 g/kg, and a diatomaceous earth formulation (DE) (Protect-It™), applied at the recommended rates of 0.15 g/kg for Sitophilus oryzae, 0.20 g/kg for Rhyzopertha dominica and 0.30 g/kg for Tribolium castaneum, were tested under laboratory conditions (24 ± 1 °C temperature and 45 ± 5% relative humidity). The highest adult mortality was observed after the longest exposure period of 21 days and 7 days of recovery, when all three zeolite dosage rates and the recommended DE dosage caused 97-100% mortality of S. oryzae and 94-100% of T. castaneum. On the other hand, 100% mortality was not achieved in any test variant involving R. dominica; the highest (about 92%) was detected for DE, while 52% and 79% mortality was achieved with the zeolites at the highest rate of 0.75 g/kg. Progeny reduction by >90% was achieved after 21 days of contact of all three beetle pests with DE-treated wheat, while the same level of reduction was achieved for S. oryzae and T. castaenum only after contact with the highest rate of the zeolite product, Minazel. Thus the two zeolite formulations are comparable to diatomaceous earth in controlling adult S. oryzae, R. dominica and T. castaneum, but only the Minazel formulation could effectively protect wheat from attack by S. oryzae or T. castaneum, and only with a higher rate of application than for the DE formulation.     

Comparative analysis of upper thermal tolerance and CO2 production rate during heat shock in two different European strains of Sitophilus zeamais (Coleoptera: Curculionidae)

The maize weevil is a major pest of maize crops and post-harvest grain stocks in tropical countries that became established in western and southern European countries a few decades ago. The hypothesis that this species has adapted to the environmental conditions of temperate climates would be supported by significant adaptative changes in the responses to key ecological factors. Response to heat tolerance is one area likely to show such adaptive changes. In order to test the adaptation hypothesis, a comparative analysis of critical points of the kinetics of CO₂ production rate during a heat treatment, using two Sitophilus zeamais strains originating in France (Sze_05) and in Portugal (Sze_19), was carried out by the “thermolimit respiration test” that allowed three critical temperature levels to be determined: 1) the spiracle closing point (SCP), 2) the heat stupor point (HSP) and 3) the death point (DP). The SCP was observed at 45.2 °C and 44.3 °C for Sze_05 and Sze_19 respectively. The HSP was observed at 46.9 °C and 46.3 °C and the DP was observed at 50.0 °C and 48.6 °C respectively for the two strains. The difference between the two strains was significant only for the DP temperature (P = 0.045). Comparison of adult and larval stages revealed a very different physiological response to a “fast” heat increase, with a spiracle closure phase much more marked for larvae than for adults. The understanding of the influence of environmental adaptation on physiological response to heat stress by the thermolimit respirometry test requires further study using fresh strains of S. zeamais originating from temperate countries. However, the methodology used in this trial can be useful for the rapid assessment of the “heat tolerance profile” for insect populations infesting cereal grain or food processing factories so that schedules for heat disinfestation of cereal processing plants can be optimised.     

Assessment for fungal,mycotoxin and insect spoilage in maize stored for human consumption in Zambia

BACKGROUND: Maize constitutes the main staple food and most important crop grown in Zambia. However, maize incurs considerable losses both in field and storage due to pathogens and insects. Some of the pathogens and resultant mycotoxins reduce the nutritional quality of the product. Mycotoxins are toxigenic fungal compounds that can cause cancer and suppress growth. In spite of this health hazard, there has been very little research to document their occurrence. Maize grains stored for human consumption were sampled from different agro‐ecosystems (forest, valley and plateau areas) of three agroecological zones (high, mid and low altitude). RESULTS: Several fungal genera were recovered among which Aspergillus flavus, A. niger, Fusarium verticillioides, F. solani, Rhizopus stolonifer and Penicillium spp. were prevalent. The weevil Sitophilus zeamais and the larger grain borer Prostephanus truncatus were the most damaging. Enzyme‐linked immunosorbent assay (ELISA) tests yielded fumonisins and aflatoxins ranging between 0.02 and 21.44 ppm, and 0.7 and 108.39 ppb in 96.4% and 21.4% of samples, respectively. Fumonisin was more pronounced in villages in forest areas whereas aflatoxin was highest in valley and forest areas in Zone II. CONCLUSION: Strategic interventions to curtail fungal, mycotoxin and insect contamination should be directed towards improved agronomic and post‐harvest practices of maize from fields to consumers. Copyright © 2009 Society of Chemical Industry     

杀铃脲对玉米象的毒力测定

采用饲料混毒法测定了98％杀铃脲原药对储粮害虫玉米象的胃毒毒力。测定结果表明：杀铃脲对玉米象后代具有较强的生物活性,中毒症状为：玉米象爬行缓慢,重心不稳,发生足与触角多次突发性的颤动,最后整个虫体完全静止不动,直至死亡。LC50为0．2438mg／kg,LCgo为0．8298mg／kg。