Protection of potato crop against Phthorimaea operculella (Zeller) infestation using frass extract of two noctuid insect pests under laboratory and storage simulation conditions

The oviposition deterrent effect of water extract of Spodoptera littoralis and Agrotis ipsilon larval frass on Phthorimaea operculella adult females was studied using two types of larval food “Natural host and Semi-artificial diet” under laboratory and storage simulation (semi-field) conditions. Extracted frass of fed larvae on semi-artificial diet showed complete oviposition deterrent effect at treatments with 4th, 5th and 6th instars of S. littoralis, also at treatments with 1st–3rd and 6th instars of A. ipsilon, while the same effect was observed when the larvae fed on castor oil leaves as a natural host only at treatment with frass extract of A. ipsilon 6th instar larvae. Presence of low amounts of phenols and flavonoids in water extract of A. ipsilon larval frass resulted in relatively more effect as oviposition deterrent to fertile adult females on treated oviposition sites, while the opposite effect was obtained in S. littoralis larval frass experiments. At semi-field experiments, the percentage reduction of laid eggs reached 100% after two?days at treatments with frass extracts of 4th and 5th S. littoralis larval instars and A. ipsilon 6th instar larvae fed on semi-artificial diet and/or castor oil leaves. Percentage reduction of laid eggs for untreated sacks reached 93.24 and 48.95% after 2 and 30?days, respectively, when placed between treated sacks, in comparison with the mean number of laid eggs for isolated control.     

Oviposition deterrent effect of Spodoptera littoralis (Boisd.) larval frass to adult females of two major noctuid insect pests

Water extract of fresh frass of Spodoptera littoralis larval instars (L_1–3, L₄, L₅ and L₆) fed on Castor oil leaves was prepared by soaking at concentration (20?g frass/50?ml distiled water) followed by steering before filtration. Oviposition deterrent activity of the extract to S. littoralis and A. ipsilon adult females was evaluated as the mean number of laid eggs in treatments in comparison with control under laboratory conditions. Total amount of phenols and flavonoids in larval frass was determined. Extraction of L₆ frass obtained complete oviposition deterrent to S. littoralis adult moths and the minimum number of laid eggs by A. ipsilon adult females (11.8?eggs/female) in comparison with control (1026.0 and 848.2?eggs/female respectively). Maximum number of laid eggs by S. littoralis females was 361.0/f at treatment with L_1–3 frass extract and 748.0/adult female of A. ipsilon at treatment with L₄ frass extract. Low amount of phenols and/or flavonoids in frass extract of L₆ increased the oviposition deterrent effect while high amount of them as obtained in L₄ frass extract (3.504 and 1.610%, respectively) decreased the effect at both of tested insects.     

Feeding damage by larvae of the mustard leaf beetle deters conspecific females from oviposition and feeding

Herbivorous insects may be informed about the presence of competitors on the same host plant by a variety of cues. These cues can derive from either the competitor itself or the damaged plant. In the mustard leaf beetle Phaedon cochleariae (Coleoptera, Chrysomelidae), adults are known to be deterred from feeding and oviposition by the exocrine glandular secretion of conspecific co-occurring larvae. We hypothesised that the exocrine larval secretion released by feeding larvae may adsorb to the surface of Chinese cabbage leaves, and thus, convey the information about their former or actual presence. Further experiments tested the influence of leaves damaged by conspecific larvae, mechanically damaged leaves, larval frass and regurgitant on the oviposition and feeding behaviour of P. cochleariae. Finally, the effect of previous conspecific herbivory on larval development and larval host selection was assessed. Our results show that (epi)chrysomelidial, the major component of the exocrine secretion from P. cochleariae larvae, was detectable by GC-MS in surface extracts from leaves upon which larvae had fed. However, leaves exposed to volatiles of the larval secretion were not avoided by female P. cochleariae for feeding or oviposition. Thus, we conclude that secretion volatiles did not adsorb in sufficient amounts on the leaf surface to display deterrent activity towards adults. By contrast, gravid females avoided to feed and lay their eggs on leaves damaged by second-instar larvae for three days when compared to undamaged leaves. Mechanical damage of leaves and treatment of artificially damaged leaves with larval frass or regurgitant did not affect oviposition and feeding of P. cochleariae. Since no adverse effects of previous herbivory on larval development were detected, we suggest that female P. cochleariae avoid Chinese cabbage leaves damaged by feeding larvae for other reasons than escape from competition or avoidance of direct negative effects that result from consuming induced plant material.     

Larval diet influence on oviposition behaviour inSpodoptera littoralis

Females ofSpodoptera littoralis Boisd. (Lepidoptera: Noctuidae) with different feeding experiences during their larval development were tested for their ovipositional response to methanol extracts of larval frass and semisynthetic diets. The effect of the following frass, diet and diet component extracts was tested: (a) frass fromS. littoralis orAgrotis segetum larvae fed on a potato-based diet; (b) frass fromS. littoralis larvae fed on a wheat germ-based diet; (c) potato and wheat germ-based diets; and (d) potatoes and wheat germ. Ovipositing females without prior experience of the potato diet were deterred by extracts of: (1) larval frass from either species fed on potato diet; (2) the potato-based diet; (3) potato. Also females with experience of the potato diet during only a part of their larval development were deterred from oviposition by frass of larvae reared on the potato diet and by the diet itself. However, for females reared on the potato diet for their entire larval development, oviposition was no longer deterred by either of the three extracts listed above. Extracts of: (1) frass from larvae of either species reared on wheat germ diet: (2) the wheat germ diet; or (3) wheat germ did not significantly affect oviposition. Females with ablated antennae were still deterred by frass extracts from larvae fed on potato diet, when they had been reared on the wheat germ diet. In feeding experiments, larvae of larval stage one and of larval stage three-four reared on either of the two diets preferred to feed on the wheat germ diet. However, the preference was significantly stronger for larvae with no prior contact with the potato diet. The effect of larval experience on the loss of oviposition-deterring activity by extracts of larval frass, diets and diet components is discussed in view of induction and selection.     

Oviposition deterrents in larval frass of the cotton boll worm, Helicoverpa armigera (Lepidoptera: Noctuidae): chemical identification and electroantennography analysis

Oviposition deterrents in the frass of cotton bollworm (CBW), Helicoverpa armigera larvae fed on an artificial diet (FA) and on cotton Gossypium hirsutum leaves (FC) were investigated by behavioral bioassays and electroantennography analyses in the laboratory. It was found that a water suspension or a hexane extract of the frass FA or FC, in contrast to the corresponding foods, significantly deterred oviposition of conspecifics. When hexane extracts of the frass FA and FC were further partitioned into polar and neutral lipid fractions, two polar fractions significantly reduced oviposition. The neutral fraction from frass FC also exhibited significant deterrence, although the activity was much lower than that of the corresponding polar fraction. The polar lipid fractions contained several fatty acids, mainly palmitic and oleic acid at the ratio nearly 1:1. A blend of authentic fatty acids of the same composition found in frass FA or FC mimicked the deterring effect. Moreover, these fatty acids and their blend at the ratio found in frass FA or FC elicited significant electroantennogram responses and typical dose-response curves. Thus, it is suggested that CBW larvae may deploy two types of oviposition deterrents: a non-specific and a specific one. The former is a blend of fatty acids, independent of food and plays an important role in oviposition deterrence, whereas the latter may be produced only when the larvae feed on cotton leaves. The possible explanations of this deployment have also been discussed.     

Influence of larval frass extracts on the oviposition behaviour of Monochamus alternatus (Col., Cerambycidae)

Abstract:  The oviposition behaviour and response of adult females of Monochamus alternatus to short lengths (bolts) of Pinus massoniana trunks treated with hexane extracts of larval frass of M. alternatus was investigated in the laboratory. Females gnawed significantly fewer oviposition scars, and deposited significantly fewer eggs, on extract-treated bolts than on control bolts. These results suggest the presence of a possible oviposition deterrent in larval frass of M. alternatus . Hexane extracts of larval frass were analysed by gas chromatography–mass spectrometry, and α -pinene, β -pinene, 3-carene, limonene, longifolene and butylated hydroxytoluene were identified. Experiments with synthetic mixtures indicated that a mixture of monoterpenes and butylated hydroxytoluene exhibited oviposition-deterring activity.     

Biochemical effects of chlorpyrifos organophosphorous insecticide,camphor plant oil and their mixture on Spodoptera littoralis (Boisd.)

The biochemical effects of the chlorpyrifos organophosphate insecticide and camphor plant oil in addition to their combination were studied and compared against the fourth larval instars of the cotton leaf worm Spodoptera littoralis under laboratory condition. Biochemical analysis showed that the total protein content of the cotton leaf worm larval instars was decreased at 31, 26 and 13.5% by using a camphor extract, chlorpyrifos and combination, respectively. In addition, the activity of acid phosphatase, α-esterase was significantly declined. Biochemical analysis also showed that the alkaline phosphatase activity was increased comparing with control in another side. Acetylcholinesterase enzyme amount and activity were increased with the treatment of camphor extract followed by chlorpyrifos, even though the mixture of them nearly showed the same amount in control trail. In contrast, chitinase enzyme showed a negative effect of both camphor and chlorpyrifos with nearly about the same lowering in the amount and activity of chitinase, while the mixture of them revealed a high positive increasing in the amount and activity of chitinase. On the opposite trend, phenoloxidase enzyme of treated larvae increased by action of chlorpyrifos, followed by camphor, while the mixture of them showed a negative decrease when comparing with the control.     

Nitrogen fertilization rate affects feeding, larval performance, and oviposition preference of the beet armyworm, Spodoptera exigua, on cotton

Nitrogen (N) is one of the most critical chemical elements for plant and animal growth, exerting a variety of bottom‐up effects. Development and oviposition of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were studied in relation to varying N fertilization levels (42, 112, 196, and 280 p.p.m.) in cotton [Gossypium hirsutum L. (Malvaceae)]. Low N fertilization of cotton plants led to reduced plant biomass and a lower percentage of N in leaf blades and in leaf petioles. Development of S. exigua larvae fed with plants with reduced N applications (42 and 112 p.p.m.) was prolonged relative to treatments receiving higher N fertilization. Almost all larvae reared on artificial diets underwent only five instars before pupation. However, most larvae reared on cotton plants, irrespective of N levels, experienced a supernumerary sixth larval instar. Furthermore, significantly more larvae reared on lower N cotton plants underwent supernumerary development compared to larvae reared on higher N cotton plants. Life‐time feeding damage per larva ranged from 55 to 65 cm², depending on the nutritional quality of the food plant, although the differences were not statistically significant. Larvae distinguished between cotton plants with various nutritional qualities and fed preferentially on higher N plants. Female moth oviposition choice was also affected by host plant nutritional quality: cotton plants with higher N levels were preferentially chosen by S. exigua females for oviposition. The mechanisms of these effects are unclear, but they can have important implications for population dynamics and pest status of beet armyworms in the field.     

The parasitoidCotesia glomerata (Hymenoptera: Braconidae) discriminates between first and fifth larval instars of its hostPieris brassicae,on the basis of contact cues from frass,silk, and herbivore-damaged leaf tissue

Adult females of the larval parasitoidCotesia glomerata (L.) respond to chemical cues associated with feeding damage inflicted on cabbage plants by its host,Pieris brassicae (L.). The use of these infochemicals by the parasitoid during selection of the most suitable host instar was investigated. The parasitoid can successfully parasitize first-instar host larvae, while contacts with fifth-instar larvae are very risky since these caterpillars react to parasitization attempts by biting, spitting, and hitting, resulting in a high probability of the parasitoid being seriously injured or killed. Observations of the locomotor behavior of individual wasps on leaves with feeding damage inflicted by the first and the fifth larval instars and on host silk and frass showed that several cues affect the duration of searching by the parasitoids after reaching a leaf: cues on the margin of the feeding damage and cues in the host frass and silk. Whole frass, silk, and hexane extracts of frass obtained from first-instar elicited parasitoid's searching behavior significantly longer than frass, silk, and hexane extract of frass from the fifth instar. The results demonstrate thatC. glomerata can discriminate between first instars, which are more suitable hosts, and fifth instars ofP. brassicae without contacting the caterpillars, by exploiting instar-related cues.     

Orientation Behavior,Development and Survival of <Emphasis Type="Italic">Trichoplusia ni</Emphasis> (Lepidoptera: Noctuidae) Larvae on Cotton Expressing Cry1Ac and Cry2Ab and Conventional Cotton

This study was conducted to determine the effects of Bt cotton leaves (Bollgard II), non-Bt cotton leaves, and a mixture of Bt+non-Bt cotton leaves on larval orientation behavior, survival and development of Trichoplusia ni in the laboratory. Results indicate that in a no-choice test, more first and fifth instars remained on Bt leaves than the third instars. All larvae that remained on the leaves gradually moved to leaf edge. In the choice between a Bt and a non-Bt leaf, more first instars moved to non-Bt leaves, whereas the third and fifth instars did not show significant difference in the first 8 h, but eventually more moved to non-Bt leaves. More first instars fed non-Bt leaves than third instars and fifth instars. When larvae fed Bt leaves, 100% of first instars, 92.7% of third instars and 51.1% of fifth instars died in 108 h. Once larvae pupated, >90% developed to adults. First and third instars that fed Bt leaves developed slower but their pupae developed faster than those on Bt+non-Bt leaves, whereas fifth instars developed similar on the three types of leaves. First and third instars that fed Bt+non-Bt leaves resulted in less heavy pupae than those fed non-Bt leaves; whereas the fifth instars that survived on Bt leaves produced lighter pupae.     

Oviposition deterrence associated with larval frass of the Japanese pine sawyer,Monochamus alternatus (Coleoptera: Cerambycidae)

To determine the effect of larval frass of Monochamus alternatus on oviposition preference of the female adults, three tests were performed in the laboratory. Individual females were provided with a frass-coated, Pinus densiflora bolt and an untreated bolt simultaneously and were allowed to oviposit for 24 h. They deposited a significantly smaller number of eggs on frass-coated bolts. The females supplied with frass-coated bolts deposited no eggs on them, indicating that the larval frass deterred the females from oviposition. When individual females were provided simultaneously with a pine bolt applied with a methanol extract of larval frass and another bolt applied with methanol alone, they deposited a significantly smaller number of eggs on frass extract-applied bolts for 24 h. These results suggest the presence of a putative oviposition deterrent in larval frass of M. alternatus. Each test was replicated 19-20 times using different females.     

Larvicide and oviposition deterrent effects of fruit and leaf extracts from Melia azedarach L. on Aedes aegypti (L.) (Diptera: Culicidae)

Aedes aegypti (L.) (Diptera: Culicidae), the main urban vector of dengue, has developed resistance to various insecticides, making its control increasingly difficult. We explored the effects of Argentine Melia azedarach L. (Meliaceae) fruit and senescent leaf extracts on Ae. aegypti larval development and survival, by rearing cohorts of first instar mosquitoes in water with different extract concentrations. We also analysed oviposition deterrent activity in choice tests with extract-treated ovitraps. The leaf extract showed a strong larvicide activity, with all larvae dying before pupation, and significantly delayed development time. It strongly inhibited oviposition by Ae. aegypti females. The fruit extract showed much weaker effects. This first report of highly effective larvicidal, growth regulating and oviposition deterrent activity of a senescent leaf extract of M. azedarach against Ae. aegypti, suggests that such extract could represent a promising tool in the management of this mosquito pest.     

甜菜夜蛾对不同寄主植物的产卵和取食选择

为了探讨甜菜夜蛾Spodoptera exigua对不同寄主植物的产卵选择及成虫产卵选择与幼虫取食选择间的关联度, 本研究选取玉米、豇豆、甘蓝、黄瓜、棉花、辣椒和番茄7种植物进行了选择性和非选择性实验研究, 并采用Y型嗅觉仪测定了成虫对其中3种寄主植物及其挥发物抽提物的趋性。结果表明：在田间非选择性实验中, 甜菜夜蛾在不同寄主植物上的落卵量依次为：玉米>辣椒>棉花>黄瓜、豇豆、番茄>甘蓝。Y型嗅觉仪的行为测定表明, 雌成虫对玉米及其挥发物抽提物的趋性最强, 黄瓜次之, 对甘蓝的趋性最弱, 这与雌虫的产卵选择性一致。不同龄期甜菜夜蛾幼虫对寄主植物的取食选择性有所不同, 且随观测时间的延长有所改变;低龄幼虫对豇豆、玉米和黄瓜的选择性较强, 对甘蓝、番茄、辣椒和棉花的取食选择性则较弱, 高龄幼虫对辣椒也具有较强的选择性;5龄幼虫对寄主植物的选择性不如低龄幼虫明显。结果显示, 甜菜夜蛾对不同寄主植物的产卵选择性显著不同, 植物抽提物在雌成虫的产卵选择中具有重要作用, 甜菜夜蛾对寄主植物的产卵选择性和幼虫取食选择性并不一致。     

松墨天牛成虫对幼虫虫粪挥发性物质的触角电位反应及林间驱避试验

为了研制松墨天牛Monochamus alternatus Hope驱避剂,本文利用触角电位技术和田间试验的方法研究了松墨天牛雌雄成虫对幼虫虫粪挥发性物质的触角电位反应及幼虫虫粪己烷提取物、合成化合物混合物的林间驱避作用。结果表明：α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯和长叶烯均能引起松墨天牛雌雄成虫一定的触角电生理反应,而4-甲基-2,6-二叔丁基苯酚不能引起松墨天牛雌雄成虫的触角电生理反应。林间驱避试验结果说明,幼虫虫粪的己烷提取物处理过的树干上的刻槽数明显少于对照树干上的刻槽数,二者具有极显著差异;有合成化合物的混合物存在的诱捕器诱捕到的雌虫数（平均值3.80±1.02）与对照诱捕到的雌虫数（平均值16.80±1.16）差异极显著。结果显示α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯、长叶烯和4-甲基-2,6-二叔丁基苯酚的混合物对松墨天牛雌虫具有驱避作用,有望开发出一类新的驱避剂。     

Effect of chlorfluazuron and flufenoxuron on development and reproductive performance of the black cutworm,Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

The black cutworm, Agrotis ipsilon, is an insect pest with great agricultural importance worldwide. In Egypt, it has acquired resistance against most of the conventional pesticides, particularly organophosphate insecticides, applied against it. Therefore, the present study aimed to investigate the effect of two benzoylureas (chitin synthesis inhibitors) namely chlorfluazuron and flufenoxuron on some developmental and reproductive parameters of Agrotis ipsilon that survived treatment of newly molted fourth instars with the LC₅₀ of these compounds (1.00 and 4.68 mg/L, respectively) using leaf–dip method. These two compounds significantly enhanced the mean larval and pupal durations, whereas they significantly declined the mean percentage pupation, adult emergence, pupal weight, adult longevity, fecundity, and fertility compared to untreated insects. The mean pre-oviposition period was not significantly affected, whereas the mean oviposition period was significantly decreased. Both chlorfluazuron and flufenoxuron significantly decreased the mean total protein, carbohydrate, and lipid content in the ovaries compared to untreated insects, except for insignificant decrease in the total protein in flufenoxuron-treated ones. Additionally, the total ovariolar length was significantly atrophied. In conclusion, chlorfluazuron and flufenoxuron interfere with vitellogenesis of A. ipsilon. Moreover, they could suppress the population size of this insect species by affecting its development and reproductive potential.     

Differential utilization of ash phloem by emerald ash borer larvae: ash species and larval stage effects

• 1 Two experiments were performed to determine the extent to which ash species (black, green and white) and larval developmental stage (second, third and fourth instar) affect the efficiency of phloem amino acid utilization by emerald ash borer (EAB) Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) larvae.
• 2 EAB larvae generally utilized green ash amino acids more efficiently than those of the other two species. For example, the concentrations of only six (two essential) and seven (two essential) amino acids were lower in frass from EAB that fed upon black and white ash than in the corresponding phloem, respectively. By contrast, concentrations of 16 (eight essential) amino acids were lower in the frass from EAB that fed upon green ash than in the phloem. In addition, in green ash, the frass : phloem ratios of 13 amino acids were lower than their counterparts in black and white ash.
• 3 The concentrations of non‐essential amino acids glycine and hydroxylproline were greater in frass than in phloem when EAB fed on black ash, although not when EAB fed on green or white ash.
• 4 The concentration of total phenolics (a group of putative defensive compounds to EAB, expressed as antioxidant activity of acetone extraction) was high in EAB frass but even higher in the phloem samples when the data were pooled across ash species and EAB larval stages. This suggests EAB larvae may eliminate phenolics through a combination of direct excretion and enzymatic conversion of phenolics to nonphenolics before excretion. Because the ratio of frass total phenolics to phloem total phenolics in white ash was lower than the ratios in black and green ash, the ability to destroy phenolics or convert them to nonphenolics was greater when EAB larvae fed on white ash.
• 5 Fourth‐instar EAB extracted phloem amino acids, including threonine, more efficiently than third‐instar EAB. The different larval developmental stages of EAB did not differ in their apparent ability to destroy phenolics or convert them to nonphenolics.

     

Leaf biomechanical properties as mechanisms of resistance to black cutworm (Agrotis ipsilon) among Poa species

Biomechanical properties can be important parameters in resistance of plants to herbivorous insects. As plants age, however, there can be dramatic changes in physical defenses that can then influence their susceptibility to insect herbivores. We measured changes in leaf biomechanical properties during ontogeny of Poa species and the relationship of these changes to the development of a generalist herbivore, the black cutworm, Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae), was investigated. Larvae were reared on two representative age classes, i.e., young (<60 days after planting) and old (>1 year after planting), of foliage in laboratory assays. Foliage generally reaches a peak fracture force between 80 and 109 days after planting depending on grass type. Foliage from old plants was significantly tougher than that of young plants, and black cutworm larvae reared on foliage from young plants gained significantly (ca. four times) more weight than those fed on foliage from old Poa plants. In addition, fracture force has a negative relationship with black cutworm development. Plant fiber, particularly neutral detergent fiber accounted for 65 and 46% of the variation in fracture force and larval development, respectively. These results provide additional insight into how plant ontogeny influences physical defenses to an insect herbivore in a grass system. Likewise, this is seemingly the first study to suggest a mechanism for host plant resistance to black cutworm. Plant fiber may be a useful trait to explore in plant improvement programs in which black cutworm is a primary pest (e.g., managed turfgrass).     

Oviposition, development, and reproduction of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) fed on different hosts of economic importance

The host selection for oviposition by Spodoptera frugiperda (J.E. Smith) among corn, millet, cotton and soybean, and its relationship with the biological characteristics were investigated. Free and non-choice tests for oviposition using plots containing five plants each, from each host in plastic greenhouse, resulted in similar oviposition preference among the host plants. In addition, selected biological characteristics of S. frugiperda were determined in the laboratory with larvae feeding on host leaves, and the combination of leaf and cotton boll. Neonate larvae exhibited low success of colonization on cotton boll compared to the leaves of all other hosts. Spodoptera frugiperda fed only on cotton bolls exhibited longer larval and pupal development, and longer adult life span; however with similar egg production. Larvae fed cotton leaves during six days and then transferred to cotton bolls, however, exhibited development and reproduction similar to those reared on corn or only on cotton leaves. Therefore, the variations on immature stages of S. frugiperda were not related with host selection for oviposition which was similar among the studied hosts. Based on our data, the millet as a winter, rotational, and cover crop is a potential host for S. frugiperda, while leaves and cotton bolls were diets of intermediate suitability as compared to corn and soybean leaves.     

An oviposition deterrent for the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae), extracted from larval frass

A methanol-soluble oviposition deterrent has been discovered in the frass of fifth-instar larvae of Ostrinia nubilalis, the European corn borer. Bioassays established a significant linear relationship between reduction in oviposition and concentration of extract applied on the oviposition substratum. Activity of the deterrent under laboratory conditions lasts for at least 72 hr when exposed to air, indicating a low volatility.     

Host utilisation by moth and larval survival of pine processionary caterpillar Thaumetopoea pityocampa in relation to food quality in three Pinus species

Abstract 1. The work reported here analysed host utilisation by the pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae), the relationship between moth oviposition patterns and larval performance, the chemical characteristics of the plant in relation to the performance of different larval instars, and the role of these factors in the outbreak capacity of the species. In order to do this, a combination of field and laboratory techniques was used to study three pine species differing in nutritional characteristics.
2. Moths oviposited in the three pine species analysed, although cluster pine received a lower number of batches. Late-instar larvae were able to feed on all three pine species, however first-instar larvae developed on Scots and black pine but died on cluster pine. Consequently, oviposition in cluster pine can be considered an oviposition mistake, and indicates that moths are rather unselective when ovipositing on different pine species.
3. Chemical analysis of needles suggested that the quantity of nitrogen was the main factor responsible for the difference in survival of larvae.
4. The oviposition pattern of the moth and the larval susceptibility to food quality in Thaumetopoea pityocampa agree with the theory that unselective oviposition of the moth is a precondition for eruptive dynamics in phytophagous insects.
5. The success of the larvae depends mainly on the probability of the moth finding a suitable host. This probability is determined strongly by the changes of structure and coverage in Mediterranean pine woodlands, due to human management.