Action and pharmacokinetics of a novel insect growth regulator,halofenozide, in adult beetles of Aubeonymus mariaefranciscae and Leptinotarsa decemlineata

Topical application of halofenozide on adults of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and Aubeonymus mariaefranciscae (AMF) exhibited its effects in a different way in the two coleopterans. In CPB, the fecundity was strongly affected, whereas the main effect in AMF was a drastic decrease of the progeny survival. The rate of penetration of labeled halofenozide through the cuticle followed a similar pattern in CPB and AMF, whereas the rate of excretion was much more rapid in AMF. The extremely slow excretion of the product in CPB suggested that this fact must contribute to the prolonged action of halofenozide on fecundity at its highest dose of 20 μg per adult. Retention of halofenozide in the reproductive system of males of AMF and CPB was low, whereas high levels of radioactivity were recovered in females (ovaries + eggs). Comparing females of both coleopterans, CBP retained a higher amount than AMF. Moreover, treated CPB adults showed a rapid cessation of oviposition due to distorted ovaries, detrimental oocyte growth, and loss of oviposition due to the fact that yolk protein synthesis and/or incorporation into eggs was reduced. In AMF, the development of the progeny was strongly affected, and more than 80% of first‐instar larvae died after egg hatching in the first 25 days after the treatment, due to premature molting and inhibition of ecdysis. Cross sections of intoxicated first larval instars of AMF originating from adults that were topically treated with halofenozide showed the presence of a double cuticle and these larvae could not shed the old cuticle. Arch. Insect Biochem. Physiol. 41:201–213, 1999. © 1999 Wiley‐Liss, Inc.     

Fitness and feeding are affected in the two-spotted stinkbug,Perillus bioculatus,by the cysteine proteinase inhibitor,oryzacystatin I

Plant resistance to insect pests based on recombinant proteinase inhibitors (Pis) could interfere with natural enemies of target pests, as their own proteolytic systems may also be sensitive to large spectrum PIs. Oryzacystatin I (OCI) is a potential insect pest resistance factor currently engineered into a variety of crop plants, including potato Solanum tuberosum. Potential for OCI interfering with female reproduction in Perillus bioculatus, a stinkbug predator of Colorado potato beetle, Leptinotarsa decemlineata, was studied by chronic feeding for 18 days on prey loaded with 1–16 μg OCI/day. Mortality of treated females was negligible, but fertility was reduced by up to 50%. Additional dose-dependent effects in reproducing females included delayed oviposition, reduced fecundity, lower egg mass size, and reduced egg eclosion incidence. Females fed for 18 days on OCI at ≤4 μg/day returned to normal oviposition when switched to prey without OCI after 18 days of treatment, but negative effects persisted for at least 10 days at higher doses. Affected reproduction in P. bioculatus is consistent with the use of OCI-sensitive digestive proteinases by this stinkbug. However, azocaseinase activity in whole body extracts of OCI-fed females increased about twofold indicating compensation, and OCI-sensitive proteinases were still present in extracts. When timed for delay to trigger attack on Colorado potato beetle larvae under controlled conditions, stinkbugs feeding on OCI appeared consistently hungrier than controls fed at similar rate, suggesting that predation by stinkbugs exposed to OCI-recombinant foliage would be higher than normal. Arch. Insect Biochem. Physiol. 38:74–83, 1998. © 1998 Wiley-Liss, Inc.     

Molecular markers locate genes for resistance to the Colorado potato beetle,Leptinotarsa decemlineata,in hybrid Solanum tuberosum x S. berthaultii potato progenies

The wild Bolivian potato, Solanum berthaultii Hawkes, has been used as a source of resistance to the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say, one of the most significant pests of potato. In this study, two reciprocal backcross S. tuberosum x S. berthaultii potato progenies, BCB and BCT, were mapped with RFLP markers and screened for resistance to CPB consumption, oviposition and defoliation. The genotypic and phenotypic data were combined and analysed to locate quantitative trait loci (QTLs) for resistance to CPB. Three QTLs on three chromosomes in BCB, and two QTLs on two chromosomes in BCT influenced resistance. The QTLs were generally additive but one instance of epistasis was noted. Each QTL accounted for 4–12% of the phenotypic variation observed in resistance. In the more resistant BCB population, a three QTL model explained ca. 20% of the variation in CPB oviposition. When alleles at the three QTLs were homozygous S. berthaultii, oviposition was reduced ca. 60% compared to the heterozygotes. The QTLs for resistance to CPB were compared to those previously identified for the type A and B glandular trichomes, which have been implicated in resistance in the same progenies. Generally, the QTLs for resistance to CPB coincided with loci associated with the glandular trichomes confirming the importance of the glandular trichomes in mediating resistance. However, a relatively strong and consistent QTL for insect resistance in both BCB and BCT on chromosome 1 was observed that was not associated with any trichome traits, suggesting the trichomes may not account for all of the resistance observed in these progenies.     

A study on mode of antifeedant effects of epilimonol against Leptinotarsa decemlineata

Colorado potato beetle, Leptinotarsa decemlineata (Say), neonate larvae and adults were bioassayed with the antifeedant epilimonol. Three-day exposure of neonate larvae resulted in increasing delays in development (appearance of 4th instars) corresponding to increasing dosages. At a dosage of 20 g/cm², development was delayed by about 40% without other detrimental effects. Mouthpart coating of adult beetles with epilimonol emulsion resulted in significant feeding reductions, while injection of epilimonol into the haemolymph of female adults did not elicit significant feeding reduction or oviposition suppression. The results indicated that epilimonol did not elicit significant internal toxicity, and feeding reductions were most likely exerted by action on chemoreceptors on mouthparts or in the preoral cavity.     

Feeding behaviour and reproductive biology of Colorado potato beetle adults fed transgenic potatoes expressing the Bacillus thuringiensis Cry3B endotoxin

Colorado potato beetle (Leptinotarsa decemlineata Say) adult longevity and fecundity were studied on transgenic potato clones expressing a Cry3B endotoxin of Bacillus thuringiensis (Bt). Adult longevity and fitness were studied for the first 3 weeks after emergence. Beetle reproductive biology on highly resistant clones, intermediary resistant clones and control potato plants was monitored by dissecting females after 7–15 days of feeding and also by analysing haemolymph protein content after 3 days of feeding. Feeding behaviour on transgenic plants expressing high toxin concentrations and on control plants was monitored individually for 36 newly emerged adult beetles feeding on leaf disks during the first two meals. Lethal Time₅₀ for adult beetles feeding on transgenic clones as the sole source of food was not significantly shorter than for beetles on control clones reared in a growth chamber. Differences tended to be larger when the experiment was conducted in a greenhouse with a less optimal temperature range (LT₅₀ = 9.52 and 10.45 days for two transgenic clones and 13.86 for control). In contrast, female egg production on transgenic plants was almost totally inhibited. Dissection studies indicated that adult males living on high-level Bt-expressing transgenic potatoes were still able to mate and produce mobile sperm, but the females were impaired in their reproductive ability since their ovaries were generally not fully developed. An examination of the haemolymph revealed the protein concentration in females living on transgenic plants to be dramatically reduced ( 50%), and electrophoresis showed a reduced content of vitellogenin in these samples.Feeding behaviour of adult Colorado potato beetles was not affected by the different food plants; this indicates that transgenic potato plants were readily accepted as host plants by beetles. The effects of these findings on the use of transgenic plants as a means of L. decemlineata control are discussed.     

Effects of systemic potato response to wounding and jasmonate on the aphid Macrosiphum euphorbiae (Sternorryncha: Aphididae)

Plant induced responses are activated by multiple biotic and abiotic stresses, and may affect the interactions between a plant and phytophagous insects. The objective of this work was to evaluate the effects of different stresses inflicted to potato plants (Solanum tuberosum) on the potato aphid (Macrosiphum euphorbiae). Abiotic wounding, biotic wounding by Leptinotarsa decemlineata and treatment with volatile methyl jasmonate (MeJA) were evaluated with regard to the orientation behaviour, the feeding behaviour and the development of the potato aphids. Dual‐choice olfactometry showed that plants treated with MeJA lost their attractiveness for the potato aphids, while both abiotic and biotic wounding did not alter the orientation of aphids. Electropenetrography revealed that the feeding behaviour of aphids was only slightly disturbed by a previous L. decemlineata wounding, while it was highly disturbed by mechanical wounding and MeJA treatment. Aphid nymph survival was reduced on mechanically wounded plants, the pre‐reproductive period was lengthened and the fecundity reduced on plants treated with MeJA. Our results bring new information about the effects of various stresses inflicted to S. tuberosum on M. euphorbiae. We showed that wounding and MeJA treatment induced an antixenosis resistance in potato plants against M. euphorbiae, which may influence aphid colonization processes.     

Oviposition preference of Lygocoris pabulinus (Het., Miridae) in relation to plants and conspecifics

Abstract: To predict possible locations of Lygocoris pabulinus (L) in the field during the summer, we determined their oviposition preference under summer conditions. With L. pabulinus reared on potato, oviposition preference was determined for potato, tomato or green bean. As preference may depend on larval or early adult experience, the oviposition preference of bugs reared on green bean for three generations, and of bugs captured from the field 12 h prior to the experiment was also determined. All females showed a strong preference for potato plants, on which fecundity was higher. Hence, although L. pabulinus is a generalist in its feeding habits, the summer generation seems to be an oviposition specialist. Aggregation of ovipositing females does not seem to occur; similar amounts of eggs were oviposited in plants with clip cages containing conspecifics as in plants without conspecifics. More eggs were oviposited in damaged plants than in undamaged plants. Plant volatiles released upon damage may aid L. pabulinus females in finding suitable oviposition sites.     

Fecundity,nymphal development and longevity of field‐collected tropical bedbugs,Cimex hemipterus

This study examined the fecundity, oviposition, nymphal development and longevity of field‐collected samples of the tropical bedbug, Cimex hemipterus (Fabricius) (Hemiptera: Cimicidae). Under environmental conditions of 26±2°C, 70 ± 5% relative humidity and a 12‐h photoperiod, with bloodmeals provided by a human host, six strains of tropical bedbug had a fecundity of up to 50 eggs per lifetime, over 11–14 oviposition cycles. Increased feeding frequency improved fecundity. After feeding and mating, adult females normally took 2–3 days to produce a first batch of eggs. The oviposition period lasted 2–7 days before cessation of the oviposition cycle. The egg incubation period usually lasted 5–7 days before the emergence of first instars. The nymphs underwent five stadia (the first four of which each took 3–4 days, whereas the last took 4–5 days) before becoming adults at a sex ratio of 1 : 1. More than five bloodmeals were required by the nymphs to ensure a successful moult. Unmated adults lived significantly longer than mated adults (P < 0.05). Unmated females lived up to almost 7 months, but the longevity of mated males and females did not differ significantly (P > 0.05).     

Effects of potato plants expressing a barley cystatin on the predatory bug Podisus maculiventris via herbivorous prey feeding on the plant

The aim of this study was to assess the effects of potato plants expressing a barley cystatin on a potentially cystatin-susceptible natural enemy by predation on susceptible and non-susceptible preys feeding on the plant. We have focussed on the impact of the variant HvCPI-1 C⁶⁸ → G, in which the only cysteine residue was changed by a glycine, on the growth and digestive physiology of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and the Egyptian cotton leafworm (ECW), Spodoptera littoralis. Moreover, we have studied the prey-mediated effects of the barley cystatin at the third trophic level, using the predatory spined soldier bug (SSB), Podisus maculiventris, as a model. Feeding trials conducted with CPB larvae reared on transgenic potato plants expressing the C⁶⁸ → G variant resulted in significantly lower weight gains compared to those fed on non-transformed (NT) plants. On the contrary, larger weight gains were obtained when ECW larvae, that lack digestive cysteine proteases, were reared on transgenic potato expressing the cystatin, as compared to larvae fed on NT plants. No negative effects on survival and growth were observed when SSB nymphs were exposed to HvCPI-1 C⁶⁸ → G by predation on either CPB or ECW larvae reared on transgenic potato plants expressing the barley cystatin, despite the fact that the inhibitor suppressed in vitro gut proteolysis of the predatory bug. To investigate the physiological background, biochemical analysis were carried out on guts of insects dissected at the end of the feeding assays. Fernando álvarez-Alfageme and Manuel Martínez are contributed equally to this work.     

Colonization of potato fields in eastern North Carolina by Colorado potato beetle

Rotated and non-rotated commercial potato fields were sampled intensively to follow Colorado potato beetle,Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), colonization and subsequent oviposition patterns in the spring of 1990 and 1991. Maximum densities of colonizing adults ranged from 0 to 14,891/ha and maximum egg mass densities ranged from 0 to 48,451/ha. Crop rotation generally resulted in lower potato beetle populations. Regardless of crop rotation management practices, colonization of fields planted in potatoes began at field edges and progressed inward in all fields for both years. Management of potato beetles is discussed in light of these findings.     

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.     

Effectiveness of entomopathogenic nematodes Steinernema feltiae and Heterorhabditis bacteriophora on the Colorado potato beetle Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) under laboratory and greenhouse conditions

In laboratory and greenhouse studies, the invading ability, virulence, and mortality caused by Stinernema feltiae and Heterorhabditis bacteriophora were compared. After one and two days of exposure to either nematode species, the mortality of Colordo potato beetle (CPB) Leptinotarsa decemlineata larvae at different instars, third and fourth, was recorded and the number of nematodes invading cadavers was more than the number of nematodes inside the larvae at the late last instar (one day before pre-pupa). Two concentrations, 250 and 500 IJs/dish, infective juvenile nematodes/0.5 ml were tested on different CPB larval instar. S. feltiae was more effective, with fourth instar rather than third and late last instar. On the other hand, H. bacteriophora showed a very weak effect with L. decemlineata. Also it was clear that S. feltiae was more effective and faster than H. bacteriophora: more than 70% of larvae were killed within 24 hours compared with H. bacteriophora which killed 40% of larvae within 48–72 hours. A significant difference in invading efficiency was observed with concentration 2500 IJs/pot in the greenhouse test. The number of adult females found in the cadavers of L. decemlineata larvae was always higher than the number of males. Foliage application of S. feltiae and H. bacteriophora resulted in a significant reduction of the number of damaged leaves and a lower index of damage compared with that in the control. We conclude that S. feltiae has significant potential and can help in the management of the Colorado potato beetle.     

Expression of Poplar Chitinase in Tomato Leads to Inhibition of Development in Colorado Potato Beetle

The previously described poplar chitinase, WIN6, is induced during infestation by gypsy moth (Lymantria dispar L.) larvae, thus suggesting a role in defense against insect pests. To test this hypothesis, we produced tomato seedlings infected with a recombinant potato virus X (PVX), which produces WIN6, and tested its insecticidal properties on Colorado potato beetle [CPB; Leptinotarsa decemlineata (Say)], which is a serious pest of tomatoes and other crops. The advantage of PVX is that plant material is ready for insect bioassay within 3–4 weeks of constructing the recombinant virus. Considering that production of transgenic tomato seedlings using Agrobacterium takes at least 6 months, this hastens the rate at which genes can be examined. Upon insect bioassay, only 47% CPB neonates feeding on leaves containing >0.3% w/w WIN6 developed to 2nd instar while 93% of controls reached 2nd instar. To our knowledge this is the first plant chitinase that retards development of an insect pest. Revisions requested 12 December 2005; Revisions received 18 January 2006     

Photosynthetic responses of potato to Colorado potato beetle injury and differences in injury between adult males and females

Establishing rates of injury to plants and the physiological impact of this injury provides essential data in the development of economic injury levels, but variation of sex effects is not often considered. Here, we examined injury by the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), larvae and adult males and females on potato, Solanum tuberosum L. (Solanaceae). Specifically, we looked for adult sex differences between males and females in injury rates (= leaf consumption rates), and examined the impact of all types of injury (larval, adult male, and adult female) on gas exchange parameters of remaining potato leaf tissue. Experiments were conducted in the field and in growth chambers on Frito‐Lay proprietary and Pike chipping‐potato varieties at pre‐blooming and blooming stages. We found no change in photosynthetic rates on remaining (uninjured) leaf tissue infested with male, female, or fourth‐stage larva of Colorado potato beetle. However, when the midrib was cut in trials with male beetles, the remaining tissue above the injury exhibited photosynthetic rate reductions as a result of stomatal limitations. These findings are consistent with the pattern that we and other researchers have observed with gross tissue removal by various insects on other plant species. Adult females consumed more tissue than males, and temperature was positively correlated with feeding rates for both sexes. Sex‐related differences in feeding rate are most important to studies quantifying consumption rates for economically important species because of its potential impact on resulting economic injury level calculations.     

Life history traits of pest and non-pest populations in the phytophagous ladybird beetle,Epilachna niponica (coleoptera, coccinellidae)

Life history traits of the phytophagous ladybird beetle,Epilachna niponica were compared between a non-pest population feeding on wild thistle and a pest population feeding on cultivated solanaceous crops, mainly potato. The pest population had larger females, a higher population growth rate, a more continuous oviposition schedule, and a shorter developmental period in the immature stages, compared with the non-pest population. The two populations showed no clear differences in phenology from spring to autumn, egg mass size, hatchability, and larval survival rate. Significant differences were found in number of eggs laid per female during the first and second periods, and in the developmental period of the immature stages. These life history traits were influenced primarily by food plant. A higher fecundity and shorter immature period appear to be readily altered by the host shift from thistle to potato.     

Transgenic Bt potato and conventional insecticides for Colorado potato beetle management: comparative efficacy and non-target impacts

Field studies were conducted in 1992 and 1993 in Hermiston, Oregon, to evaluate the efficacy of transgenic Bt potato (Newleaf^®, which expresses the insecticidal protein Cry3Aa) and conventional insecticide spray programs against the important potato pest, Leptinotarsa decemlineata (Say), Colorado potato beetle (CPB), and their relative impact on non-target arthropods in potato ecosystems. Results from the two years of field trials demonstrated that Newleaf potato plants were highly effective in suppressing populations of CPB, and provided better CPB control than weekly sprays of a microbial Bt-based formulation containing Cry3Aa, bi-weekly applications of permethrin, or early- and mid-season applications of systemic insecticides (phorate and disulfoton). When compared with conventional potato plants not treated with any insecticides, the effective control of CPB by Newleaf potato plants or weekly sprays of a Bt-based formulation did not significantly impact the abundance of beneficial predators or secondary potato pests. In contrast to Newleaf potato plants or microbial Bt formulations, however, bi-weekly applications of permethrin significantly reduced the abundance of several major generalist predators such as spiders (Araneae), big-eyed bugs (Geocorus sp.), damsel bugs (Nabid sp.), and minute pirate bugs (Orius sp.), and resulted in significant increases in the abundance of green peach aphid (GPA), Myzus persicae (Sulzer) – vector of viral diseases, on the treated potato plots. While systemic insecticides appeared to have reduced the abundance of some plant sap-feeding insects such as GPA, lygus bugs, and leafhoppers, early and mid-season applications of these insecticides had no significant impact on populations of the major beneficial predators. Thus, transgenic Bt potato, Bt-based microbial formulations and systemic insecticides appeared to be compatible with the development of integrated pest management (IPM) against other potato pests such as GPA because these CPB control measures have little impact on major natural enemies. In contrast, the broad-spectrum pyrethroid insecticide (permethrin) is less compatible with IPM programs against GPA and the potato leafroll viral disease.     

Effect of leaf nitrogen content of tomato plants on preference and performance of a leafmining fly

Summary In a study on intraspecific host plant acceptability, Liriomyza trifolii females that had previously been exposed to plants of high nitrogen content, showed a feeding and oviposition preference for plants of high nitrogen (Minkenberg and Fredrix 1989). Females showed a preference to feed and oviposit on the high middle leaves within plants. It was hypothesized that the preference between plants was related to a better performance of females and offspring on high nitrogen plants compared to low nitrogen plants. Different nitrogen dosages were applied to tomato plants, resulting in plants containing 3.4, 3.9, 4.6 or 4.9% leaf nitrogen. L. trifolii females responded to increased leaf nitrogen with significantly increased feeding and fecundity, longer oviposition periods, and higher feeding and oviposition rates. Their offspring on the same plants showed reduced developmental time, lower mortality and increased pupal size. Consequently, intrinsic rate of increase was positively linearly related to leaf nitrogen. Size of L. trifolii females appeared to be independent of fecundity, longevity and developmental time. Pupal length of males increased with increasing developmental time. These results indicate that L. trifolii is well adapted in its intraspecific host plant selection, because the ability to distinguish between plants with differences in leaf nitrogen content will directly lead to an increase in their fecundity, longevity and overall fitness. The implications of leaf nitrogen as a significant factor in the behavior and population dynamics of L. trifolii are discussed.     

Inhibitor of apoptosis is an effective target gene for RNAi-mediated control of Colorado potato beetle,Leptinotarsa decemlineata

The Colorado potato beetle (CPB; Leptinotarsa decemlineata) is one of the most notorious and difficult to control pests of potato and other solanaceous crops in North America. This insect has evolved a remarkable ability to detoxify both plant and synthetic toxins, allowing it to feed on solanaceous plants containing toxic alkaloids and to develop resistance to synthetic chemicals used for its control. RNA interference (RNAi) is a natural mechanism that evolved as an immune response to double-stranded RNA (dsRNA) viruses where dsRNA triggers silencing of target gene expression. RNAi is being developed as a method to control CPB. Here, we evaluated four CPB-specific genes to identify targets for RNAi-mediated control of this insect. Out of the four dsRNAs evaluated in CPB larvae and adults, dsIAP (dsRNA targeting inhibitor of apoptosis, iap gene) performed better than dsActin, dsHSP70, and dsDynamin in inducing larval mortality. However, in adults, the mortality induced by dsActin is significantly higher than the mortality induced by dsIAP, dsHSP70, and dsDynamin. Interestingly, a combination of dsIAP and dsActin performed better than either dsIAP or dsActin alone by inducing feeding inhibition in 24 hr and mortality in 48 hr in larvae. When the dsIAP and dsActin were expressed in the Escherichia coli HT115 strain and applied as a heat-killed bacterial spray on potato plants, it protected the plants from CPB damage. These studies show that the combination of dsIAP and dsActin shows promise as an insecticide to control CPB.     

Cover Caption

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an infamous invasive species worldwide that aggressively attacks potato and Solanaceae crops. It was first found in China in 1993 and has since spread in northwestern areas in Xinjiang. Generally, CPB adults can fly actively to find new hosts within short distance or spread long distance helped by strong wind as well as by transportations. The image shows an adult CPB being ready for flying. Genetic diversity in Xinjiang populations was at low level and retained during its invasion. See pages 643–654. Image by Ying‐chao Li.