A Physiological Age-Grading System forNeochetina eichhorniae(Warner) (Coleoptera: Curculionidae), a Biological Control Agent of Water Hyacinth,Eichhornia crassipes(Mart.) Solms.

Grodowitz, Michael J.; Center, Ted D.; Freedman, Jan E.

doi:10.1006/bcon.1997.0525

Cited by 22 publications

(30 citation statements)

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“…Weevils, which represented progeny of the original stock, were collected as they surfaced, sorted to species and gender, counted, and 10 females of each species from each tank were dissected to ascertain reproductive status (Grodowitz et al 1997). Those remaining were preserved in 70% ethanol in vials labeled to identify the source tank.…”

Section: Methodsmentioning

confidence: 99%

Effects of Host Quality on Flight Muscle Development inNeochetina eichhorniaeandN. bruchi(Coleoptera: Curculionidae)

Dray

2010

Florida Entomologist

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Section: Methodsmentioning

confidence: 99%

Effects of Host Quality on Flight Muscle Development inNeochetina eichhorniaeandN. bruchi(Coleoptera: Curculionidae)

Dray

2010

Florida Entomologist

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“…They were held on ice while awaiting dissection. The reproductive status of each was assessed as per Grodowitz et al (1997). Females with healthy, functioning ovaries were considered 'reproductive'.…”

Section: P L a N T T I S S U E A N A L Y S E Smentioning

confidence: 99%

“…Eggs are inserted in leaf tissue and larvae mine the thick leaf petioles (DeLoach & Cordo 1976;Center 1994). Reproduction is reduced in the southeastern USA during late autumn when the ovaries of most females degenerate (Grodowitz, Center & Freedman 1997). However, N content of the plant tissue increases as plant growth slows, and peaks as the plants recover from winter (Tucker & DeBusk 1983;Center 1994).…”

Section: Introductionmentioning

confidence: 99%

“…It is unclear whether the individuals present at this time have overwintered as adults and have regained reproductive capacity or have emerged from overwintered pupae, but bottom-up regulation during this period may explain the inconsistent levels of biological control produced (Spencer & Ksander 2004). Grodowitz et al (1997) reported that Neochetina spp. females with functioning ovaries comprised <10% of December populations, but this proportion rapidly increased during late winter into spring.…”

Section: Introductionmentioning

confidence: 99%

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Bottom-up control of water hyacinth weevil populations: do the plants regulate the insects?

Dray

2010

Journal of Applied Ecology

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Summary1. Nutrient availability varies widely in aquatic systems and is likely to profoundly affect the outcomes of plant-herbivore interactions in aquatic environments. This has implications in programmes aimed at the biological control of water weeds. We hypothesized that nutrient flux seasonally affects ovarian development of two specialist weevil species, Neochetina eichhorniae and Neochetina bruchi, thereby influencing population growth on the floating plant Eichhornia crassipes. 2. We also hypothesized that the weevils differed in their sensitivities to nutritional quality and interacted differently depending on host quality. 3. To test these hypotheses, we cultured E. crassipes plants under 20 fertilizer regimens then introduced reproductively dormant, over-wintering female weevils as single or mixed species populations. They were later retrieved and dissected to ascertain ovarian status. F 1 progeny was extracted biweekly to compare fecundity with population growth. 4. Ovaries regained functionality and the reproductive proportion of the population increased with fertilizer rate as did the fecundity of reproductive individuals. F 1 progeny increased exponentially from 7 to over 300 weevils tank )1 in the highest fertilizer treatment. 5. Mixed species treatments produced more offspring under high fertilizer rates than single species treatments (236 AE 32 mixed vs. 155 AE 25 N. bruchi or 170 AE 33 N. eichhorniae pure). Neochetina eichhorniae was more productive throughout than N. bruchi, but N. bruchi performed nearly as well in high fertilizer treatments. 6. Ratios of the two species remained consistent whether in single or mixed species populations suggesting a lack of interspecific interference. However, N. eichhorniae seemed more adaptable to a wider range of plant quality and more tolerant of lower nutritional circumstances. 7. Synthesis and applications. The coupling of reproductive status of the parental generation with the population response of the F 1 generation indicates that plant quality drives population growth of both weevil species, demonstrating bottom-up regulation. This largely explains the variable performance of these weevils as biological control agents. These results emphasize the importance of considering bottom-up regulation in evaluating host range trials, predicting efficacy and in postrelease evaluations. In addition, they suggest that partial herbicide treatments to accomplish phased removal of infestations could enhance the quality of the remaining plants, thereby better integrating biological control into current E. crassipes management systems.

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“…However, this method relies on the assumptions that the biological control agents can and do disperse and not sink with the sprayed plants. Grodowitz et al (1997) showed that adult N. eichhorniae and its congener N. bruchi (Hustache) frequently had reduced wing musculature and would thus not be capable of flight, and the sessile stages of all of the agents would sink with the mat. Secondly, the method assumes that the natural enemy populations in the "reserve" are large enough to curb the spread of the weed, and the reserve itself will not become the source of re-infestation.…”

Section: Introductionmentioning

confidence: 99%

Toxic effect of herbicides used for water hyacinth control on two insects released for its biological control in South Africa

Hill

Coetzee

Ueckermann

2012

Biocontrol Science and Technology

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The integrated control of water hyacinth, Eichhornia crassipes (Martius) SolmsLaubach (Pontederiaceae) has become necessary in South Africa, as biological control alone is perceived to be too slow in controlling the weed. In total, seven insect biological control agents have been released on water hyacinth in South Africa. At the same time, herbicides are applied by the water authorities in areas where the weed continues to be troublesome. This study investigated the assumption that the two control methods are compatible by testing the direct toxicity of a range of herbicide formulations and surfactants on two of the biological control agents released against water hyacinth, the weevil, Neochetina eichhorniae Warner (Coleoptera: Curculionidae) and the water hyacinth mirid, Eccritotarsus catarinensis (Carvahlo) (Hemiptera: Miridae). A number of the formulations used resulted in significant mortality of the mirid and the weevil. Products containing 2,4-D amine and diquat as active ingredients caused higher mortality of both agents (up to 80% for the mirid) than formulations containing glyphosate. Furthermore, when surfactants were added to enhance herbicide efficiency, it resulted in increased toxicity to the insects. We recommend that glyphosate formulations should be used in integrated control programmes, and that surfactants be avoided in order to reduce the toxic nature of spray formulations to the insect biological control agents released against water hyacinth.

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A Physiological Age-Grading System forNeochetina eichhorniae(Warner) (Coleoptera: Curculionidae), a Biological Control Agent of Water Hyacinth,Eichhornia crassipes(Mart.) Solms.

Cited by 22 publications

References 10 publications

Effects of Host Quality on Flight Muscle Development inNeochetina eichhorniaeandN. bruchi(Coleoptera: Curculionidae)

Effects of Host Quality on Flight Muscle Development inNeochetina eichhorniaeandN. bruchi(Coleoptera: Curculionidae)

Bottom-up control of water hyacinth weevil populations: do the plants regulate the insects?

Toxic effect of herbicides used for water hyacinth control on two insects released for its biological control in South Africa

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