Overwintering biology of the carob moth Apomyelois ceratoniae (Lepidoptera: Pyralidae)

The pomegranate fruit moth, Apomyelois ceratoniae (Zeller), is the most important pest of pomegranate orchards in Iran, where infestations lead to 20%–80% fruit loss. A. ceratoniae overwinters as larvae in several instars. The success in overwintering determines the fruit loss in the following season, thus overwintering physiology of A. ceratoniae could provide insights into population prediction. To this end, overwintering strategy and some seasonal physiological and biochemical changes were investigated in the field-collected larvae of A. ceratoniae. The lowest supercooling point was recorded in November (−14.6 ± 0.9 °C) and the highest in both October and March (−10.2 ± 0.9 °C). The median lethal temperature (LT50) of larvae was higher than supercooling point, suggesting that A. ceratoniae is chill-susceptible. Overwintering larvae had slightly higher concentrations of glycerol and sorbitol compared to summer larvae. There were no significant seasonal changes in body water content or hemolymph osmolality. Current winter temperatures in Iranian orchards are higher than the cold tolerance thresholds of A. ceratoniae, suggesting that overwintering mortality is not a key factor in determining A. ceratoniae populations

Functional response and mutual interference of Diaeretiella rapae (Hymenoptera: Aphidiidae) on Brevicoryne brassicae (Homoptera: Aphididae)

Functional response and mutual interference are the most important behavioural characteristics that reveal different aspects of host–parasitoid interactions. In this study, functional response and mutual interference of the parasitoid wasp, Diaeretiella rapae (M’Intosh) attacking the cabbage aphid, Brevicoryne brassicae (Linnaeus) were investigated. Logistic regression was used to distinguish the shape of the functional response (type II or III). Nonlinear least-square regression was used to estimate the attack rate (a) and handling time (Th). Nicholson’s model and linear regression were used to determine per capita searching efficiency and interference coefficient, respectively. Logistic regression suggested a type II response on B. brassicae nymphs. The per capita parasitism decreased significantly from 80.80 (67.33%) to 11.85 (9.88%) as parasitoid densities increased from 1 to 8 females. Consequently, the per capita searching efficiency decreased significantly from 1.173 to 0.205 as parasitoid densities increased from 1 to 8. The rate of parasitism increased as the host density increased from 2 to 50, and subsequently the parasitoid density decreased from 8 to 1. Therefore, different host–parasitoid ratios could affect the efficacy of D. rapae

Cold hardiness strategy in field collected larvae of Scrobipalpa ocellatella (Lepidoptera: Gelechiidae)

The beet moth, Scrobipalpa ocellatella is recognized as a widespread agricultural pest. Cold hardiness strategy of the beet moth larvae was investigated through monitoring seasonal changes at supercooling points and lower lethal temperatures. Furthermore, the role of microhabitat in winter survival was studied. The mean SCPs of the last instar larvae was not significantly different from November 2010 to April 2011. Mean inoculative freezing point (-8.0 ± 1.44 °C) of the last instar larvae was significantly higher than mean SCP (-14.9 ± 0.93 °C). The cold hardiness of the pest shows seasonal fluctuation in response to reduction of air temperature. A 50% mortality (LT50) occurred at -11 ºC in November and -14 ºC in January and reduced to -18 ºC in February and finally increased to -14.5 ºC in April. Glycerol, sorbitol, trehalose, and myo-inositol were identified components in whole body extracts of S. ocellatella larvae. However, total cryoprotectants could not have significant effects on the cold tolerance. Larvae of S. ocellatella could tolerate subzero temperatures near their SCPs. Our findings show that beet moth larvae utilize moderately chill tolerance strategy during winter

幼苗期と成熟期のオオムギ系統間における禾穀類アブラムシの密度とグラミン含量の関係

The relationship between the indole alkaloid gramine concentration and aphid population was examined seedling and maturation stages in 14 barley lines of Hordeum spontaneum and H. unlgare. The density of Schizaphis graminum did not differ significantly with the gramine concentration in the seedling in the greenhouse. However, the population of Rhopalosiphum padi sometimes differed with the seedling. The plant resistance to the natural infestation of cereal aphids was obvious at the heading stage. There was a negative correlation between the high population density of aphids and gramine concentration. The gramine concentration was high in matured resistant resistant lines, especially wild lines, as compared with susceptible lines due to higher biodegradation activity.オオムギ（Hordeum spontaneum及びH.vulgare）14系統の幼苗期と成熟期における、アブラムシの密度とインドールアルカロイド化合物であるグラミン含量の関係を調べた。温室内の幼苗では、グラミン含量に関わらずムギミドリアブラムシ（Schizaphis graminum）の寄生密度に有意差は認められなかった。一方、ムギクビレアブラムシ（Rhopalosiphum padi）の密度は、幼苗間で異なる場合もあった。圃場におけるアブラムシの寄生に対して、抵抗性は出穂期に顕著に現れた。アブラムシの寄生密度とグラミン含量の間には負の相関が認められた。成熟期のオオムギでは、グラミンの分解活性の高い感受性系統と比較して、抵抗性系統のグラミン含量は多く、特に野生系統では著しかった

Sorghum Resistance to the Sugarcane Aphid, Melanaphis sacchari (Zehntenr) Amounts of Surface Wax and Nutritional Components

The differences in the amounts of leaf surface wax and nutritional components such as sugar and free amino acids were compared among resistant (PE 954177), moderately resistant (IS 84) and susceptible (Redlan B) sorghum varieties to the sugarcane aphid. Melanaphis sacchari (Zehntner). (1) The kind of aphid appearing on the leaves of the sorghum varieties was only the sugarcane aphid, Melanaphis sacchari in the field. The number of aphids infesting a leaf was ca 0,30 and 3,500 in the resistant, moderately resistant and susceptible varieties at the middle of August, respectively. (2) The amount of leaf surface wax was approximately constant among these three varieties. (3) The total sugar content was slightly higher in the two resistant varieties than in the susceptible variety. (4) The total free amino acid concentration was higher in the two resistant varieties than in the susceptible variety. (5) These findings suggest that neither leaf surface wax nor nutritional components seem to affect the aphid populations on the leaves of the three sorghum varieties, showing that biogenic substances such as dhurrin, benzylalcohol, p-hydroxybenzaldehyde, aconitic acide, etc. may affect the aphid populations.ヒエノアブラムシの寄生密度にソルガム葉の葉面ワックス、栄養成分である糖と遊離アミノ酸がどのように影響するかを明らかにするために、抵抗性、中間、感受性の3系統のソルガムを用いて、これらの物量の含量を比較した。（1）ソルガムに寄生するアブラムシとしては、ヒエノアブラムシのみであった。8月中旬のアブラムシ寄生数は抵抗性系統で0、感受性系統で約3,500頭、その中間系統で約30頭であった。（2）葉面ワックス量は3系統ともほぼ同じであった。（3）全糖含量は抵抗性、中間系統の方が感受性系統に比べわずかに高い傾向であった。（4）全遊離アミノ酸含量は抵抗性、中間系統の方が、感受性系統よりも高かった。（5）これらの結果、葉面ワックス、糖、遊離アミノ酸はソルガムのアブラムシの寄生に影響を及ぼさないようにみえた。二次代謝産物であるデューリン、ベンジルアルコール、パラヒドロキシベンズアルデヒド、アコニット酸等が、ソルガムでのアブラムシの寄生密度を制御していると思われる

Effects of Pyriproxyfen on Life Table Indices of Plutella xylostella

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a major pest of Brassicaceae family in Iran. This study investigated the sublethal effects of pyriproxyfen, a juvenile hormone analogue, on DBM, for two subsequent generations. The leaf dip bioassay method was adopted in conducting this experiment. Sublethal concentrations resulted in a significant decrease in fecundity, oviposition period, and pupal weight of parents and offspring generations. Also, the development time of DBM was prolonged after exposure to pyriproxyfen. The biological parameters such as net reproductive rate (R0) and intrinsic (rm) and finite (λ) rate of increase were lower than control in treatment groups, significantly. From our investigations, pyriproxyfen is a good choice for control of the diamondback moth population through continuous generations

Changes of supercooling point and cold tolerance in diapausing pupae of sugar beet moth, Scrobipalpa ocellatella (Lepidoptera; Gelechiidae)

Sugar beet moth (SBM) Scrobipalpa ocellatella (Boyd) is one of the important pests of sugar beet that causes quantitative and qualitative yield loss late in the season. Pest damage is occurred in the central buds and the root of the sugar beet plant. The last instar larvae enter the soil and pupate for overwintering at harvest time of sugar beet in Karaj, Iran in November. The younger larvae having suitable habitat and enough food for development may have chance to pupate in soil gradually whenever weather permit. In order to study the overwintering potential of the pest, pupae were collected monthly from November 2015 to April 2016. Seasonal changes in cold hardiness indices such as supercooling point and lower lethal temperature of the beet moth were studied. The mean supercooling points of field collected pupae varied from –13.2 ± 0.33 to –18.2 ± 0.23 °C. The highest cold hardiness of diapausing pupae was found in November, December and January, and the lowest in April. The cold hardiness of diapausing pupae was higher than that of nondiapausing pupae at -10, -15 and -20 °C. Lethal temperature for 50% of population (LT50) changed from -13.99 ºC in November to -5.5 ºC in April. In spite of the fact that the supercooling point of the diapause pupae did not exceed -15 °C in the late-winter and April, the pupae could not withstand temperatures below zero under a supercooling point. However, the findings show that the ability of pupae to tolerate in the diapause stage is more than the capacity of cold and frost environment, and therefore, temperatures below zero in winter cannot be considered as a significant risk for the survival of sugar beet moth

Effect of Silybum marianum methanolic extract on nutritional indices, crustacean cardioactive peptide, α-amylase and protease activities of Helicoverpa armigera (Lep.: Noctuidae)

The efficacy of milk thistle, Silybum  marianum methanolic extract was investigated on the third instar larvae of cotton bollworm, Helicoverpa armigera (Hübner). The experiments were done at 25±1 °C, 65±5 RH and photoperiod of 16:8 (L: D) h. The LC50 and LC20 values were estimated 10449 and 5654 ppm, respectively. One hundred microliters of the plant extract at 5654 ppm was added to 0.9 grs of artificial diet. Nutritional indices, crustacean cardioactive peptide (CCAP) content and digestive enzymatic (α-amylase and protease) activities were measured after 72 h. Plant extract decreased nutritional indices including approximate digestibility (AD), relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI) and efficiency of digested food (ECD). Methanolic extract of S. marianum decreased α-amylase and protease activities in the midgut of H. armigera. The activity of α-amylase from 194 mU in control decreased to 86.8 mU in treatment. It also decreased protease activity from 108.2 mU in control to 60.6 mU in treatment. Incubation of dissected midgut with CCAP increased α-amylase and protease activities in H. armigera whereas the buffer alone had no effect. Feeding on artificial diet containing methanolic extract of S. marianum caused CCAP level in the midgut of the insect to decrease. Feeding on artificial diet containing methanolic extract of  S. marianum inhibits release of CCAP in the midgut and leads to reduction of α-amylase and protease activities

Evaluation of Iranian Onion Germplasms for Resistance to Thrips

ABSTRACT The onion thrips (Thrips tabaci Lindeman) is the major foliage pest in field cultures of Iran and onion is one amongst those. Since, there is a little information about resistance of onion to thrips; this experiment was carried out on 15 Iranian onion genotypes to: a) find the resistant genotypes to thrips, b) evaluate the traits related to thrips resistance and c) identify promising materials for preservation and breeding programs. Results showed that genotypes "Meshkan", "Sefid-e-Kurdistan", "Sefid-eQom" and "Eghlid" had the lowest thrips infestation, percentage of leaf infestation, leaf wax in comparison to susceptible genotypes. Genotypes with glossy foliage were resistant and genotypes with nonglossy foliage were susceptible to thrips. Results suggested that resistant thrips could be used for crossing with susceptible genotypes and producing resistant cultivars