Feeding behavior of Plutella xylostella and Leptinotarsa decemlineata on leaves treated with Bacillus thuringiensis and esfenvalerate

Studies were conducted to examine interactions between esfenvalerate and Bacillus thuringiensis Berl. in their effects on feeding behavior of larvae of Plutella xylostella L. and Leptinotarsa decemlineata Say. Droplets containing esfenvalerate, B. thuringiensis, the two in combination, and water controls were individually applied to leaf disks. Third-instar P. xylostella larvae were allowed to feed for 24 h on cabbage disks and third-instar L. decemlineata larvae were allowed to feed for approximately 18 h on potato leaf disks. For each insect species and each treatment, the proportion of leaf area removed during the feeding period was regressed on the proportion of droplets removed during that period to test for avoidance of droplet residues. No significant differences were found between treatments in these regressions for L. decemlineata. In contrast, B. thuringiensis, either alone or in combination with esfenvalerate, significantly affected the relationship of leaf and droplet consumption for P. xylostella. No evidence of individual droplet avoidance, i.e. a consistently greater proportion of leaf than droplets consumed, was found for any of the treatments. Proportions of leaf consumed and proportions of droplets consumed were compared among treatments to test for effects on feeding rate. B. thuringiensis significantly reduced feeding rate, both alone and in combination with esfenvalerate for P. xylostella and alone for L. decemlineata. We found no statistically significant differences in feeding rate due to esfenvalerate. The species studied can be expected to consume the same amount of B. thuringiensis whether it is mixed with esfenvalerate or not, whereas esfenvalerate dose by ingestion would be reduced if it were mixed with B. thuringiensis.     

Acute and sublethal toxicity of novaluron, a novel chitin synthesis inhibitor, to Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

The acute and sublethal toxicities of novaluron, a novel chitin synthesis inhibitor, to a laboratory-reared insecticide-susceptible strain of Colorado potato beetle, Leptinotarsa decemlineata (Say), were determined. Novaluron exhibited excellent residual (120 h LC(50) = 0.42 mg litre(-1)) and good direct contact (120 h LC(50) = 27 mg litre(-1)) activity against second-instar larvae (L2). Hatch of eggs exposed by direct contact to novaluron solutions > or =100 mg litre(-1) was significantly reduced, as was the ability of emerged first-instar larvae to moult. L2 from eggs exposed to > or =100 mg litre(-1) novaluron weighed significantly less (P < 0.0001) than those from untreated eggs. However, L2 from eggs treated with 1 mg litre(-1) novaluron weighed significantly more (P < or = 0.05) than those from untreated eggs, suggesting novaluron can have a hormetic effect on L decemlineata larval development. Leptinotarsa decemlineata mating pairs fed foliage treated with novaluron at 25 or 75 g AI ha(-1) produced approximately 25% fewer egg masses and eggs per mass. Hatch of eggs on treated foliage was almost completely suppressed, and longevity of male beetles was reduced by approximately 50% when fed foliage treated with novaluron at 75 g AI ha(-1).     

球孢白僵菌可湿性粉剂对马铃薯甲虫的防治效果

从受感染的马铃薯甲虫Leptinotarsa decemlineata（Say）分离出菌株1513,经鉴定为球孢白僵菌Beauveriabassiana（菌种保藏号为ACCC32222）。为了评价其对马铃薯甲虫的防治潜力,本研究测定了不同浓度白僵菌对不同龄期马铃薯甲虫幼虫的毒力作用。结果表明,在室温条件下（22～28℃）,处理9 d时1～2龄幼虫的僵虫率与孢子浓度成正比,其LC50为3.09×107孢子mL 1;处理8 d时,对3～4龄幼虫的LC50为9.92×107孢子mL 1;而孢子浓度为1×107孢子mL 1时,虫卵未受到明显的抑制。田间施菌2250 g hm 2时,在新疆新源县的防治效果较好,18 d时98.87%的虫体落地,地表僵虫率为53.91%;而在新疆尼勒克县,仅在土壤中发现僵虫,僵虫率为19.61%。     

甘蓝田四种鳞翅目幼虫的生物学特性及其田间株内分布

作者研究了不同层次甘蓝叶片对四种鳞翅目幼虫(菜粉蝶、小菜蛾、甜菜夜蛾和斜纹夜蛾)生长发育和取食特性的影响。随着叶片成熟度提高(内层→外层),四种幼虫的存活率和生物量积累均逐渐下降,发育历期和总取食量均逐渐增加,但在低、高龄幼虫之间存在一定差异。在田间,低龄幼虫株内分布通常与其卵的株内分布相一致,而高龄幼虫均集中分布在植株中部以内叶片上;甜菜夜蛾和斜纹夜蛾低龄幼虫表现明显的趋边性,高龄幼虫却表现明显的趋中性。作者讨论了叶片营养状况、害虫自身的生物学特性和其它环境因素对四种幼虫田间株内分布的综合影响。     

Systemic effects of thiamethoxam and chlorantraniliprole seed treatments on adult Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) in rice

BACKGROUND: Feeding assays using adult rice water weevils and foliage of plants treated as seeds with chlorantraniliprole and thiamethoxam at different rates were conducted to evaluate the systemic adulticidal and feeding effects. Dose–mortality relationships were determined for thiamethoxam seed treatments by combining leaf area lost due to feeding and insecticide residues analyzed by LC/MS/MS. Changes in adulticidal activity of thiamethoxam were also investigated by contrasting adult mortalities at the 5–6‐leaf and tillering stages of rice. RESULTS: Adult weevil mortalities and leaf consumption rates on foliage were affected in thiamethoxam but not in chlorantraniliprole treatments when rice was at the 6–7‐leaf stage. The LD₅₀ for weevils feeding on thiamethoxam‐treated rice at the 2–3‐leaf stage was 447 pg insecticide weevil^?1 (95% CL: 25–830 pg weevil^?1) but was lower (142 pg weevil^?1; 95% CL: 102–180 pg weevil^?1) in experiments with 3–4‐leaf‐stage plants. Mortalities on leaves from 5–6‐leaf‐stage plants were consistently higher than on leaves from tillering plants. Thiamethoxam residues measured by ELISA increased with seed treatment rate and differed between plant stages. CONCLUSION: The LD₅₀ values developed in this study are the first values for leaf‐feeding insects on foliage of plants treated as seeds with thiamethoxam. The attrition of adulticidal activity of thiamethoxam in foliage of older plants may help to explain the reduced effectiveness of seed treatments against rice water larvae that is seen at later stages of rice growth in field studies. The differential activity of these two seed treatments on adults suggests that adult mortality contributes to the field efficacy of thiamethoxam but not to that of chlorantraniliprole. Copyright © 2012 Society of Chemical Industry     

Insecticidal properties of essential plant oils against the mosquito Culex pipiens molestus (Diptera: Culicidae)

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth-instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC50 values of 16, 36, 39, 70 and 89 mg litre-1, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8-cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)-(-)-alpha-pinene and (1R)-(+)-alpha-pinene) were tested against the larvae. Thymol, carvacrol, (1R)-(+)-alpha-pinene and (1S)-(-)-alpha-pinene were the most toxic (LC50 = 36-49 mg litre-1), while menthone, 1,8-cineole, linalool and terpineol (LC50 = 156-194 mg litre-1) were less toxic.     

Laboratory and field evaluations of rhodojaponin-III against the imported cabbage worm Pieris rapae (L.) (Lepidoptera: Pieridae)

The activity of rhodojaponin-III (R-III), a grayanoid diterpene compound isolated from Rhododendron molle G. Don flowers, was determined under laboratory and field conditions as an antifeedant, stomach poison, contact toxicant and insect growth inhibitor against Pieris rapae (L.) larvae. The median antifeedant concentration (AFC(50)) values in no-choice leaf disc tests were 1.16 and 15.85 mg L(-1) at 24 h after treatment when tested against third and fifth instars respectively. The median lethal concentration (LC(50)) values in leaf disc tests were 2.84 and 9.53 mg L(-1) at 96 h after treatment against third and fifth instars respectively. R-III showed an almost 30 times higher contact toxicity against third instars than for fifth instars, and the median lethal dose (LD(50)) values for topical application were 1.18 and 34.09 mg kg(-1) at 72 h after treatment respectively. R-III disrupted the development of larvae to pupae or adults with median concentration for inhibiting growth (IC(50)) values of only 1.36 mg L(-1) for third instars and 11.28 mg L(-1) for fifth instars. In field trials, a greater than 80% reduction in the adjusted larval numbers was obtained against P. rapae 14 days after treatment when Rhodo 0.1% EC, a commercial botanical insecticide based on R-III, was applied at both 937.5 and 625 mL ha(-1). These results suggest that further research to develop R-III, and extracts from R. molle, as biorational pesticides or as lead compounds for integrated pest management deserve consideration.     

Effects of a juvenile hormone analog,pyriproxyfen, on Thrips tabaci (Thysanoptera: Thripidae)

Effects of a juvenile hormone analog, pyriproxyfen, on various developmental stadia of the onion thrips, Thrips tabaci Lindeman, were determined on cabbage leaves in the laboratory. Pyriproxyfen was applied at 0.064 or 0.128 g AI liter(-1) on leaves (residual contact-ingestion), thrips (direct contact) and leaf-thrips (residue contact-ingestion-direct contact). Pyriproxyfen did not have any significant lethal effects on thrips pupae in any treatment. Lethal effects on thrips larvae varied depending on application method and dosage. In the leaf and the leaf-thrips treatments, few larvae and pre-pupae molted to the next stage, and none developed to adults. In contrast, in the thrips-only treatment, pyriproxyfen did not show any significant lethal effects. The developmental times of larvae and pre-pupae were prolonged when larvae were treated with pyriproxyfen, and those of pre-pupae and pupae were shortened when pre-pupae and pupae were treated. The longevity and survival rates of thrips adults were generally shorter when they contacted and ingested pyriproxyfen-treated leaves than those in water control. Significantly fewer progeny (0.22-1.15 larvae per female) were produced by females that had fed on and been in contact with the pyriproxyfen-treated leaves than by those in the water control (11.94 larvae per female). However, the number of progeny produced by the thrips females increased significantly (3.32-7.28 larvae per female) when the females were transferred to untreated leaves after feeding on treated leaves for 5 days; the daily larval hatching pattern was similar to those in water control, indicating that female adults were able to produce viable eggs when untreated food was offered.     

玉米田两种阔叶杂草藜及苍耳对草甘膦的敏感性测定

苍耳Xanthium strumarium和藜Chenopodium album是常见的两种阔叶杂草,其在玉米田发生严重,影响了玉米的生长和产量.本文利用整株生物测定法对我国东北及黄淮海玉米产区采集到的苍耳及藜种群对草甘膦的敏感性进行了测定.种子室内培养至5～6叶期,喷施草甘膦后14 d称量鲜重,计算抑制杂草种群50％...     

超高效液相色谱-串联质谱测定氟唑菌苯胺在小麦植株中的内吸传导特性

建立了超高效液相色谱-串联质谱（UPLC-MS/MS）测定氟唑菌苯胺在小麦植株中内吸传导特性的方法;定量分析了在小麦根部和叶部施药2种处理方式下氟唑菌苯胺进入植株后的分布和累积情况。植株样品前处理采用QuEChERS法,在反相色谱柱C18（100 mm × 2.1 mm, 1.8 μm）上,以0.1%甲酸水和乙腈为流动相,利用梯度洗脱,正离子电离（ESI+）,采用多反应离子监测模式（MRM）进行定性和定量。用基质匹配标准溶液外标法定量。结果表明:在0.5~100 μg/L内,氟唑菌苯胺的质量浓度与对应的峰面积间线性关系良好,线性回归方程为y = 12 808.4x + 308.518（r = 0.999 8）。在0.005、0.05和0.1 mg/kg添加水平下,氟唑菌苯胺在小麦植株中的回收率为92%~126%,相对标准偏差为0.50%~9.1%;以3倍信噪比计算,方法检出限为0.037 μg/kg;最低添加浓度为0.005 mg/kg。研究结果表明,氟唑菌苯胺于小麦植株根部施用后,可迅速在根部吸收并向茎部传导,且随处理浓度增大,药剂在不同部位的累积量增加;随处理后时间延长,药剂在不同部位的累积表现为先快速吸收而后缓慢平衡。其中以0.01 mg/L氟唑菌苯胺经根部施药2 h后,药剂在根、茎和叶中含量分别为10.4、0.6和0.3 μg/kg;氟唑菌苯胺经叶部单叶片施药后,亦可快速被叶片吸收,并可跨叶传导至其他叶片,进而在茎部和根部累积。随处理后时间延长,施药叶片药剂快速下降并达到平衡,其他植株部位药剂快速累积并达到平衡。其中以200 mg/L的氟唑菌苯胺经第2片叶施用20 μL,2 h后氟唑菌苯胺在根和茎中的含量分别为109.0和148.0 μg/kg,在第3片叶和旗叶中的含量分别为904.0和112.6 μg/kg。     

缩节胺处理棉株对棉铃虫的影响初报

棉株施用缩节胺后能减少棉铃虫(Heliothis armigera Habner)在棉株上的落卵量48.8%—88%,田间虫量减少39.5%—77.3%,取食嫩叶、花蕾后的2龄幼虫体重下降、发育历期延长,死亡率增加,化蛹率和羽化率都有下降,总的生存率降低了57.62%。测定表明施用缩节胺后,棉株各部组织内棉酚有增加趋势,以蕾内增加较多,为49%—92.1%,铃壳次之,为13.8%—65.5%,叶内较少,为3.6%—39.7%。而单宁量除大铃壳内有增外,大多下降。施用次数与剂量的增加,与棉酚量的提高有共同趋势。花蕾期施用,棉酚量的增加高于花铃期。     

Morphogenetic effects of diflubenzuron,an inhibitor of chitin deposition,on the coconut black-headed caterpillar (Nephantis serinopa myer)

Feeding the last instar larvae of Nephantis serinopa, the coconut black-headed caterpillar, on coconut leaves that had been dipped in diflubenzuron suspensions (0.2-4.0 g litre^?1) and dried, inhibited the moulting process and caused morphogenetic deformities of their pupae. The inhibition of moulting ranged from 27.5 to 75% The maximum effect was produced by suspensions of 4.0 g litre^?1 when only 5% of the larvae survived to become adults against 97.5% of untreated larvae.     

Toxicity,persistence and efficacy of indoxacarb and two other insecticides on Plutella xylostella (Lepidoptera: Plutellidae) immatures in cabbage

Toxicities of indoxacarb on eggs and 5-day-old larvae of diamondback moth, Plutella xylostella L., on cabbage and those of field-aged leaf residues on 5-day-old larvae were determined in the laboratory. The persistence and efficacies of indoxacarb and two other newer insecticides (spinosad and emamectin benzoate) to P. xylostella were tested under field conditions. Results from laboratory bioassays indicate that indoxacarb was highly toxic to P. xylostella larvae through food ingestion, with LC₅₀ and LC₉₀ values of 24.1 and 90.1 mg AI l ^{- 1}, respectively. However, indoxacarb had no significant effects on eggs and larvae through direct contact compared with water control. The toxicity of field-aged leaf residues of indoxacarb (0-, 3-, 5-, 7-, 10-, 14-, 17- and 21-day-old residues) declined slowly and gradually under the field conditions in South Texas. Almost all larvae died on day 5 after feeding on the leaves with 0 - 14-day residue, and the mortalities were as high as 94 and 78% for the 14- and 17-day-old leaf residues. With one application, indoxacarb suppressed P. xylostella larvae below the economic threshold for 14 - 21 days. Two field trials showed that indoxacarb at 0.05 - 0.07 kg AI ha ^{- 1} was effective against P. xylostella, providing marketable cabbage with three applications per season. In addition, indoxacarb was as effective as spinosad, and significantly more effective than emamectin benzoate.     

Molluscicidal effects of neem (Azadirachta indica) extracts on edible tropical land snails

The effects of 350, 500 and 700 mg kg(-1) of crude extracts of neem, Azadirachta indica A Juss, on edible tropical land snails Archachatina marginata and Limicolaria aurora (Jay) were determined and compared with control using pawpaw, Carica papaya L as bait. Responses were measured through normal feeding, cessation of food intake, cessation of crawling, mucus secretion, lack of response to mechanical stimuli (mortality) and decomposition. Results showed no effects on the controls or snails exposed to neem seed oil extract. Crude extracts of bark, root and leaf of neem at 500 and 700 mg kg(-1) produced mortality after exposure for 48 h for L aurora and 72 h for A marginata.     

有机硅助剂对氯虫苯甲酰胺防治稻纵卷叶螟的增效作用研究

为探索有机硅助剂Silwet408对杀虫剂药液理化性能的影响及药液雾滴在稻叶上的行为与对稻纵卷叶螟Cnaphalocrocis medinalis Guenée防效的内在关系,在室内条件下研究了在200 g/L氯虫苯甲酰胺悬浮剂稀释液中添加助剂Silwet408后表面张力、黏度、pH值以及在稻叶上最大持留量的变化,借助OCG法对叶片的表面特性进行表征,围绕叶片倾角分析了单个雾滴在稻叶上的黏附行为,并进行了田间药效试验。结果表明:水稻叶片正、反面表观表面自由能分别为31.48 mJ/m^2和34.19 mJ/m^2;倒二叶和倒三叶的叶角较小,分别为(11.09±2.74)°和(19.98±5.67)°,表明水稻为高倾角叶片形态,不利于雾滴在稻叶上的黏附。200 g/L氯虫苯甲酰胺悬浮剂4000倍和5000倍稀释液的表面张力分别为(44.64±1.04)mN/m和(46.14±0.62)mN/m,均大于稻叶的表观表面自由能,其药液的单个雾滴在79°和70°的倾角稻叶上均呈滚落状态;添加125 mg/L的Silwet408后,药液的表面张力小于稻叶的表观表面自由能,单个雾滴能够黏附在倾角稻叶上并润湿,同时药液在稻叶上的最大持留量也呈极显著增加;200 g/L氯虫苯甲酰胺悬浮剂5000倍稀释液的pH值和黏度在添加Silwet408前后变化不大。田间试验结果表明,添加125 mg/L的Silwet408后,200 g/L氯虫苯甲酰胺悬浮剂5000倍稀释液对稻纵卷叶螟药后14 d的保叶效果和杀虫效果均显著提高。综合研究结果表明,在200 g/L氯虫苯甲酰胺悬浮剂5000倍稀释液中添加125 mg/L的Silwet408可使喷雾药液与水稻植株特性相匹配,进而提高氯虫苯甲酰胺对稻纵卷叶螟的防治效果。     

Phytotoxicity of GF-120 NF Naturalyte fruit fly bait carrier on sweet cherry (Prunus avium L.) foliage

BACKGROUND: Six sweet cherry (Prunus avium L.) cultivars were tested with GF-120 with spinosad (0.2 g L(-1) spinosad bait) or without it (blank bait) to understand leaf phytotoxicity observed in the field. RESULTS: Spinosad bait and blank bait did not differ significantly with respect to damage observed. Leaf damage was found almost exclusively at the abaxial (lower) surfaces with the doses (0, 17, 20, 25 or 40%) and cultivars tested. The effects of the blank bait on abaxial surfaces increased from 24 to 168 h, and with dose, in terms of the proportion of droplets (0.00, 0.42, 0.52, 0.75 or 0.94) and area (0.0, 18.7, 23.5, 40.5 or 91.6 mm) burned. In addition, chlorophyll was reduced with increasing dose on abaxial surfaces (SPAD = 44.6, 36.1, 34.1, 31.0, 21.5), but not on adaxial (upper) surfaces (SPAD = 44.6, 44.2, 44.0, 44.8, 44.4). The chlorophyll level in undamaged leaves (adaxial surfaces) differed by cultivar. Cherry leaves were less damaged by a 20% bait application in June (0.26) than in July (0.46) and August (0.50). Incidental insect leaf feeding at bait locations occurred at a low rate and was highest on abaxial bait surfaces. CONCLUSIONS: Applying GF-120 to the adaxial leaf surface, or at doses of 相似文献   

氟虫腈对家蚕的急性毒性与安全评价研究

氟虫腈是我国稻桑混栽地区水稻上普遍使用的杀虫剂。采用食下毒叶法、口器注入法与药 膜法测定了不同条件下氟虫腈对家蚕的急性毒性。氟虫腈对2龄、3龄、4龄、5龄家蚕的摄入LC50值 (48 h,下同)分别为4.89、6.46、9.47、11.59 mg/L;对5龄家蚕的LD50值为1.38 μg/蚕;在25、30、35 ℃ 3个温度下,氟虫腈对2龄家蚕的LC50值分别为4.81、4.59、2.05 mg/L;桑叶浸药时间为1 s、10 s、1 min、10 min、1 h时,氟虫腈对3龄家蚕的LC50值分别为9.12、6.46、4.39、3.68、2.80 mg/L;家蚕在氟虫腈药膜上爬行1、10、30、60 min后, 对4龄家蚕的接触LC50值分别为2.82、2.35、2.05、1.57 μg/cm2。研究表明,胃毒是氟虫腈对家蚕的主要作用方式,氟虫腈在桑园附近水稻上使用对家蚕有较大风险。     

Insecticidal and fungicidal activity of new synthesized chitosan derivatives

Chitosan, the N-deacetylated derivative of chitin, is a potential biopolysaccharide owing to its specific structure and properties. In this paper, we report on the synthesis of 24 new chitosan derivatives, N-alkyl chitosans (NAC) and N-benzyl chitosans (NBC), that are soluble in dilute aqueous acetic acid. The different derivatives were synthesized by reductive amination and analyzed by 1H NMR spectroscopy. A high degree of substitution (DS) was obtained with N-(butyl)chitosan (DS 0.36) at a 1:1 mole ratio for NAC derivatives and N-(2,4-dichlorobenzyl)chitosan (DS 0.52) for NBC derivatives. Their insecticidal and fungicidal activities were tested against larvae of the cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), the grey mould Botrytis cinerea Pers (Leotiales: Sclerotiniaceae) and the rice leaf blast Pyricularia grisea Cavara (Teleomorph: Magnaporthe grisea (Hebert) Barr). The oral feeding bioassay indicated that all the derivatives had significant insecticidal activity at 5 g kg(-1) in artificial diet. The most active was N-(2-chloro-6-fluorobenzyl)chitosan, which caused 100% mortality at 0.625 g kg(-1), with an estimated LC50 of 0.32 g kg(-1). Treated larvae ceased feeding after 2-3 days; the mechanism of action remains unknown. In a radial hyphal growth bioassay with both plant pathogens, all derivatives showed a higher fungicidal action than chitosan. N-Dodecylchitosan, N-(p-isopropylbenzyl)chitosan and N-(2,6-dichlorobenzyl)chitosan were the most active against B cinerea, with EC50 values of 0.57, 0.57 and 0.52 g litre(-1), respectively. Against P grisea, N-(m-nitrobenzyl)chitosan was the most active, with 77% inhibition at 5 g litre(-1). The effect of different substitutions is discussed in relation to insecticidal and fungicidal activity.     

Salicylic Acid Induces Resistance to Alternaria solani in Hydroponically Grown Tomato

ABSTRACT Alternaria solani is the causal agent of early blight disease in tomato and is responsible for significant economic losses sustained by tomato producers each year. Because salicylic acid (SA) is an important signal molecule that plays a critical role in plant defense against pathogen invasion, we investigated if the exogenous application of SA would activate systemic acquired resistance (SAR) against A. solani in tomato leaves. The addition of 200 muM SA to the root system significantly increased the endogenous SA content of leaves. Free SA levels increased 65-fold over basal levels to 5.85 mug g(-1) fresh weight (FW) after 48 h. This level of SA had no visible phytotoxic effects. Total SA content (free SA + SA-glucose conjugate) increased to 108 mug g(-1) FW after 48 h. Concomitant with elevated SA levels, expression of the tomato pathogenesis-related (PR)-1B gene was strongly induced within 24 h of the addition of 200 muM SA. PR-1B expression was still evident after 48 h; however, PR-1B induction was not observed in plants not receiving SA treatment. Challenge inoculation of SA-treated tomato plants using conidia of A. solani resulted in 83% fewer lesions per leaf and a 77% reduction in blighted leaf area as compared with control plants not receiving SA. Our data indicate that root feeding 200 muM SA to tomato plants can (i) significantly elevate foliar SA levels, (ii) induce PR-1B gene expression, and (iii) activate SAR that is effective against A. solani.     

Enhancement of fungicidal and insecticidal activity by reductive alkylation of chitosan

A series of N-alkyl chitosan (NAC) derivatives were synthesized using a reductive alkylation reaction to examine their fungicidal and insecticidal activity. The chemical structures were characterized by IR and (1)H NMR spectroscopy, and the degree of substitution (DS) ranged from 0.02 to 0.37. Their fungicidal activity was evaluated against the grey mould Botrytis cinerea Pers ex Fr (Leotiales: Sclerotiniaceae) and the rice leaf blast pathogen Pyricularia grisea Sacc [Teleomorph: Magnaporthe grisea (Hebert) Barr] by a radial growth bioassay. It was of interest that most of the NAC derivatives were more active against both fungi than chitosan itself. The most active derivative was N-(2,2-diphenylethyl)chitosan with EC50 values of 0.031 and 0.23 g L(-1) against B. cinerea and P. grisea respectively. In addition, some derivatives, at higher concentrations up to 1.0 g L(-1), inhibited the mycelial growth and spore formation of P. grisea. Bioassays against larvae of the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) with the NAC derivatives at a rate of 5.0 g kg(-1) in artificial diet demonstrated that N-(3-phenylbutyl)chitosan was the most active compound. In addition, N-propylchitosan, N-undecanylchitosan and N-(3-phenylpropyl)chitosan derivatives strongly inhibited larval weight gain in S. littoralis, with respective reductions of 76, 66 and 65% after 4 days of feeding on treated diet.