Clover Leaf Weevil Research Articles

Assessing chemical control options and their effects on the lesser clover leaf weevil (Hypera nigrirostris) and red clover pollinators in Western Canada

Single-cut red clover (Trifolium pratense L.) is an important forage seed crop in Western Canada due to its winter hardiness and economical value. However, infestation of lesser clover leaf weevil (Hypera nigrirostris F.) can lead to drastic yield losses (over 50%). The aim of this research was to evaluate the effectiveness of insecticides deltamethrin (Decis) and cyantraniliprole (Exirel) in controlling H. nigrirostris in red clover in both field and laboratory conditions and their impacts on the pollinator community. Pest pressure data in red clover fields was tracked during the 2018 and 2019 growing season in six locations. Under the field conditions both deltamethrin and cyantraniliprole were effective at controlling H. nigrirostris numbers. However, only deltamethrin provided rapid pest suppression in 24 h after treatment application. Rearing H. nigrirostris larvae on treated plants in laboratory conditions showed similar results where both insecticides significantly reduced H. nigrirostris numbers in 10–12 days after treatment. The abundances of H. nigrirostris was always negatively related to seed yield regardless of treatment and initial weevil pressure. Seed yield was significantly lower in untreated controls whereas no differences were found between deltamethrin and cyantraniliprole. In contrast, no yield response was found when H. nigrirostris abundance was lower than 4 larvae per 10 shoots. Unexpectedly, densities of bees were not affected by either treatment and were not related to seed yield. Overall, results indicate that both insecticides can provide sufficient H. nigrirostris control, and that pollinator densities are not limiting seed yield, whereas lack of H. nigrirostris management can cause substantial yield losses.

Salinity-mediated cyanogenesis in white clover (Trifolium repens) affects trophic interactions.

Increasing soil salinity poses a major plant stress in agro-ecosystems worldwide. Surprisingly little is known about the quantitative effect of elevated salinity on secondary metabolism in many agricultural crops. Such salt-mediated changes in defence-associated compounds may significantly alter the quality of food and forage plants as well as their resistance against pests. In the present study, the effects of soil salinity on cyanogenesis in white clover (Trifolium repens), a forage crop of international importance, are analysed. Experimental clonal plants were exposed to five levels of soil salinity, and cyanogenic potential (HCNp, total amount of accumulated cyanide in a given plant tissue), β-glucosidase activity, soluble protein concentration and biomass production were quantified. The attractiveness of plant material grown under the different salt treatments was tested using cafeteria-style feeding trials with a generalist (grey garden slug, Deroceras reticulatum) and a specialist (clover leaf weevil, Hypera punctata) herbivore. Salt treatment resulted in an upregulation of HCNp, whereas β-glucosidase activity and soluble protein concentration showed no significant variation among treatments. Leaf area consumption of both herbivore species was negatively correlated with HCNp, indicating bottom-up effects of salinity-mediated changes in HCNp on plant consumers. The results suggest that soil salinity leads to an upregulation of cyanogenesis in white clover, which results in enhanced resistance against two different natural herbivores. The potential implications for such salinity-mediated changes in plant defence for livestock grazing remain to be tested.

EFFECT OF SOWING DATES ON THE INSECT PESTS OF FENUGREEK PLANTS IN RELATION TO ACCUMULATED HEAT UNITS AT QALUBYIA GOVERNORATE, EGYPT

The present work was conducted for two seasons (2010/2011-2011/2012) in the Plant Protection Research Station at Qaha, QalubiyaGovernorate to study the effect of different sowing dates (Oct.30th ;Nov.15thand Nov.30th) on the infestation of fenugreek plants(Trigonella foenum graecum) with insect pests and find models for therelationship between the accumulated heat units and seasonalpopulations of fenugreek pests. The obtained results revealed seveninsect pests infesting fenugreek plants, two species on the leaves(Liriomyza spp. and Bemisia tabaci) and five species on the terminalbuds (Acyrthosiphon pisum ; Aphis gossypii ; Aphis craccivora ;Thrips tabaci and Phytonomus brunneipennis) in different sowingdates and seasons. The seasonal populations of insect pests onfenugreek plants had varied in the three sowing dates and seasons. Inaddition, results showed that sowing fenugreek by mid-Novemberreceived lower infestation with insect pests than early and latelysowing dates (Oct.30th & Nov.30th) and the proper date for sowingfenugreek must be in the second half of November. On the other hand,results showed varied relations for accumulated heat units (DegreeDays Units) and the mean numbers of seasonal populations offenugreek pests. Calculation the accumulated heat units for thefenugreek insect pests confirmed the variability of seasonalpopulations in different sowing dates and seasons. The 1st season hashighly accumulated heat units for most insect pests than the 2nd onesand differences in the accumulated heat units ranged 7.5 -19.9% in thetwo seasons. The larvae of leaf miner, Liriomyza spp. have variedaccumulated heat units mostly increased with 13.8% in 1st season thanthe second ones. The accumulated heat units for B. tabaci were varied(435- 542.7 D°) in the two seasons and the difference reached 19.9%.There for, the insect don’t occur during the season if the accumulatedheat units below than 435 D°. The aphid species have highlyaccumulated heat units in the three sowing dates ranged 1003.3-1188.7D° in the 1st season and 901.0 - 1099.3 D° in the 2nd one withdifferences ranged 7.5 - 10.2%. Cotton thrips, T. tabaci has variedaccumulated heat units (782.7 - 891.7 D°) in the two seasons; the 1stseason has highly Degree-Days Units (DDD) than the 2nd one withdifference 12.2%. The clover leaf weevil P. brunneipennis has variedaccumulated heat units (603 - 715 D°) in the two seasons with difference 15.7%. The obtained results created beneficialmethodological developments for designing ecological zones maps fordistribution the insect pests over the country and designing dynamicprogram for integrated pest management (IPM) under differentecological conditions in Egypt.

Phylogenetic Analysis of the Alfalfa Weevil Complex (Coleoptera: Curculionidae) in North America

The Eastern, Western, and Egyptian strains of alfalfa weevil are pests introduced to North America on three separate occasions, now they share partially overlapping geographic ranges, covering most of the continental United States. Behavior, susceptibility to parasites, and subtle morphological differences separate the strains. The difficulty in differentiating among these strains morphologically has led to the application of molecular phylogeny approaches including restriction fragment-length polymorphism characterization and sequencing of mitochondrial genes. While valuable for strain identification, this approach cannot identify interstrain hybrids because mitochondrial markers are maternally inherited. The work reported here extends previous findings by comparing over 7 Kb of sequence from two mitochondrial and four nuclear loci to increase the resolution of molecular phylogeny for these weevils. The related clover leaf weevil, also an occasional pest of alfalfa, was included in the analysis because the molecular phylogeny of this weevil has not been examined to date. Analysis of nuclear loci indicate that the clover weevil is a distinct species. Furthermore, while the three alfalfa weevil strains are separable based on mitochondrial sequence data they cannot be separated using nuclearloci suggesting that they are all recently diverged members of the same species. These data refine the relationships among these strains and may find application in design of better control strategies.

Thresholds of economic damage by clover seed weevil (Apion fulvipes Geoff.) and lesser clover leaf weevil (Hypera nigrirostris Fab.) on white clover (Trifolium repens L.) seed crops

AbstractSevere reductions in the seed yield of white clover can occur because of feeding by the white clover seed weevil Apion fulvipes and the lesser clover leaf weevil Hypera nigrirostris which together can reduce the seed yield by more than 0·50. From 2002 to 2006 five field experiments were carried out to investigate the relationship between the density of these two weevil species and seed yield of white clover. Damage caused by the weevils was calculated as the difference in the number of weevils and the difference in seed yield between the average of insecticide‐treated and untreated plots. Loss of seed yield was expressed as a proportion of the seed yield in insecticide‐treated plots, which allowed for a comparison between years as yields in insecticide‐treated plots varied. A multiple regression approach was chosen in which proportional loss in seed yield was the response variable and the weevils A. fulvipes and H. nigrirostris were the independent variables. Data obtained from the experiments were used to construct the following threshold model of economic damage: image

Simulated Clover Leaf Weevil Injury and Alfalfa Yield and Quality

The clover leaf weevil (Hypera punctata F.) is a sporadic but potentially serious pest of alfalfa (Medicago sativa L.). Feeding of newly emerged adult fourth instar clover leaf weevil was simulated in a field study at the University of Nebraska Haskell Agricultural Research Lab near Concord, NE, in May 2001 and 2002. Twelve 1‐ by 1‐m plots were arranged in a randomized complete block design with three treatments and four replications. Treatments consisted of two levels of simulated clover leaf weevil defoliation of alfalfa and an undefoliated check. Leaflets were removed over 10 d. Dry matter yield and other plant responses were measured during the first two growth cycles. Yield differences among all three treatments were significant for the first growth cycle. The relationship between percentage defoliation and percentage yield reduction was linear both years. Defoliation did not significantly affect percentages of acid detergent fiber, neutral detergent fiber, and protein. Alfalfa development also was not significantly affected in the second growth cycle. Dry matter yield reduction as a result of leaf removal at the early bud stage was the most important effect of first growth cycle defoliation.

Photoperiodic and Thermal Regulation of Development and Cold Hardiness in Larvae of the Clover Leaf Weevil, Hypera punctata

Effects of photoperiod and temperature on the development and cold hardiness were investigated in larvae of Hypera punctata. At a relatively low temperature (15°C), the larvae fed less and developed more slowly under a 12L:12D (SD) photoperiod than under a 16L:8D photoperiod (LD). SD larvae had lower gut weight against the whole body weight and lower supercooling point (SCP) than the LD counterparts for the same instar and same body weight. This was because the larval SCP is markedly affected by the quantity of the gut content. Laboratory experiments indicated that the low temperature mortality of this larvae occurred mainly due to freezing irrespective of the photoperiod and temperature, suggesting that the lower lethal temperature (LLT) depends on the supercooling ability of larvae. The SD larvae tended to have a lower SCP and hence a lower LLT than the LD counterparts at 15 or 10°C, unlike at 20°C. Thus, the slower larval development under SD conditions at relatively low temperatures may prevent larvae from reaching the later instar, which have a higher SCP and thus less cold tolerance, during the coldest season. The suppressed feeding activity under SD conditions would lower the SCP, thereby reducing the possibility of lethal tissue freezing. Such a photoperiodic and thermal regulation of the larval development and the supercooling ability appear to represent adaptive mechanisms for winter survival in this beetle.

Overwintering Status and Cold Hardiness ofHypera punctata(Coleoptera: Curculionidae)

We investigated overwintering status and various characteristics related to cold hardiness in the clover leaf weevil,Hypera punctata.The larvae continue to feed and grow in winter. The proportion of late instar larvae in a field population increased gradually between December and the following March, and fourth (last) instar larvae were found in mid-February onward. The lower thermal threshold of development was lower in the larval stage than in the other developmental stages. The supercooling point (SCP) varied with developmental stages. There was a close positive correlation between the SCP and larval body weight. Deprivation of food for 3 days increased the correlation and decrease their SCP by 5 to 8°C in larvae at any instar. The SCP of overwintering larvae did not differ from that of fed larvae in the laboratory. The food-deprived early instar larvae in the laboratory died without being frozen, while the lower lethal temperature of fed larvae in the laboratory and overwintering larvae were almost equivalent to the respective SCPs at a temperature normally encountered in the field. These suggested that this weevil may not increase their cold hardiness during winter so far and the SCP may serve as an indicator of cold hardiness.

Use of RAPD analysis to trace the origin of the weevil pathogen Zoophthora phytonomi in North America

In North America, the fungal pathogen Zoophthora phytonomi has been known to cause significant levels of infection in introduced clover leaf weevil populations, Hypera punctata , since 1885. This pathogen was never noted in introduced populations of alfalfa weevil, H. postica , sympatric with clover leaf weevil until 1973 when it was found in alfalfa weevil in Ontario. From 1973 through 1981, Z. phytonomi was progressively found further south from Ontario. Whether these reports of Z. phytonomi infecting H. postica actually demonstrate spread by a novel genotype has previously been proposed and disputed. PCR-RAPD analysis was used to compare isolates of Z. phytonomi from both hosts in North America, and from H. postica in Israel with Z. radicans and Conidiobolus osmodes as outgroups. Both phenetic and cladistic analyses demonstrate that two main genotypes of Z. phytonomi occur in North America; one genotype including only H. punctata isolates with a second more homogeneous and principally including isolates from H. postica . The genotype principally including isolates from H. postica was more closely related to isolates from H. postica in Israel than to the other North American group, but also included one isolate from H. punctata . Based on affinity with Israeli genotypes, this latter strain may have originated in the Eurasian areas where H. postica is endemic. The degree of host specificity of these two North American genotypes of Z. phytonomi will require further investigation.

Alfalfa Consumption by Adult Clover Leaf Weevil (Coleoptera: Curculionidae) and Development of Injury Equivalents for Stubble Defoliators

Experiments were conducted from 1990 through 1992 to determine consumption rates and feeding duration of adult clover leaf weevils, Hypera punctata (F.), to characterize the injury potential of this species during alfalfa regrowth. Adults were fed for 29 d in 1990 and 18 d in both 1991 and 1992. The mean cumulative consumption per adult was 27.2 ± 1.6 cm2 and 92.7 ± 3.5 mg dry weight in 1991 and 24.6 ± 0.9 cm2 and 87.5 ± 2.9 mg dry weight in 1992. The mean cumulative consumption pattern was curvilinear for both dry weight and leaf area consumption. Most consumption was within 11 d of adult eclosion. The peak consumption rate occurred ≈5 d after adult emergence. Because the highest consumption rates and the greatest percentage of defoliation were within the first 11 d of emergence, adult clover leaf weevils potentially can delay regrowth of alfalfa stubble when adult emergence coincides with the 1st harvest. Further, because adult consumption patterns between clover leaf weevils and alfalfa weevils are similar, alfalfa stubble defoliation thresholds developed for alfalfa weevils and cutworms also can be used for clover leaf weevils. Injury equivalents (injury by 1 species in terms of another species) are determined for adult clover leaf weevils, larval variegated cutworm, Peridroma saucia (Hübner), and larval and adult alfalfa weevils, Hypera postica (Gyllenhal).

Distribution and Habitat Preference in Pastures of the Clover Leaf Weevil in Northern Kanto Districts

Distribution and Habitat Preference in Pastures of the Clover Leaf Weevil in Northern Kanto Districts

THE BIOLOGY OF THE LESSER CLOVER LEAF WEEVIL, HYPERA NIGRIROSTRIS (FABR.) (COLEOPTERA: CURCULIONIDAE), ON RED CLOVER, TRIFOLIUM PRATENSE L., IN SASKATCHEWAN

AbstractPopulations of the lesser clover leaf weevil, Hypera nigrirostris (Fabr.), on red clover, Trifolium pratense L., in northeastern Saskatchewan were sampled weekly from May to August 1986 and 1987. Adults overwintered in red clover fields, and began to feed, mate, and oviposit in late April and early May. Eggs were laid subepidermally in stipules, shoots, and leaves from early May to mid-July. Larvae were located on red clover stipules, buds, and fiowerheads and developed through four instars Larvae were collected from early June until mid-August. Spatial distributions of eggs and larvae were aggregated, though the degree of aggregation decreased with succeeding developmental stages. Pupae were collected on shoots and in debris from late June until August. New-season adults first occurred in mid-July; large increases in adult densities corresponded to the appearance of these adults.

Phenology of the Fungal Pathogen Zoophthora phytonomi in Southern Ontario Populations of the Alfalfa Weevil (Coleoptera: Curculionidae)

The seasonal phenology of Zoophthora phytonomi (Arthur) was studied in southern Ontario from 1976 through 1988. The first incidence of disease in the alfalfa weevil, Hypera postica (Gyllenhal), occurred after the accumulation of 204 degree-days (DD) above a base threshold of 9°C from 1 April. In 11 of the 13 yr, epizootics began 57 DD later and lasted for 10 to 14 d, killing up to 99% of the larvae and 50% of the cocooned stages. It is proposed that there are three peaks of conidial production of the fungus in the alfalfa weevil that occur at intervals of 55 to 60 DD. The first occurs when the larvae are small and is coincident with epizootics of the disease in the clover leaf weevil, H. punctata (F.), whose larvae mobilize, increase, and transfer the inocula in early spring. The second occurs at peak incidence of the third alfalfa weevil instar, and the last, just subsequent to peak fourth instar. Larvae infected during the fourth instar die in their cocoons and produce resting spores, which overwinter in the ground litter. The influence of microclimatic factors on epizootics is discussed in relation to threshold densities of the host.

Cytogenetic studies of alfalfa weevil (Hypera postica) strains (Coleoptera: Curculionidae)

Chromosome karyotypes, chiasma frequencies, and Giemsa C-banding patterns were analyzed from eight weevil populations: three of the eastern strain (Beltsville, MD; State College, PA; and Washington Co., IL) and two of the western strain (Logan and St. George, UT) of the alfalfa weevil, two of the Egyptian alfalfa weevil (Yuma, AZ and Westmorland, CA), and one weevil population from Wageningen, Netherlands. All of these weevil populations have the same chromosome number, 2n = 20 + XYp, which is identical to that reported previously for five other Hypera species. The chromosome number for the clover leaf weevil, Hypera punctata (Fabricius), is 2n = 18 + neo-XY which appears to be phylogenetically different from other Hypera species. The lack of cytogenetic variations among the eight weevil populations under investigation leads us to conclude that all weevil strains in the United States are of the alfalfa weevil, H. postica (Gyllenhal), and that the use of H. brunneipennis Boheman for the Egyptian alfalfa weevil of North America should be discontinued.Key words: Hypera postica, cytogenetics, chromosomes, C-banding, alfalfa weevil.

Occurrence of Erynia sp. in Hypera postica in central Georgia

In North America, the fungal pathogen Zoophthora phytonomi has been known to cause significant levels of infection in introduced clover leaf weevil populations, Hypera punctata, since 1885. This pathogen was never noted in introduced populations of alfalfa weevil, H. postica, sympatric with clover leaf weevil until 1973 when it was found in alfalfa weevil in Ontario. From 1973 through 1981, Z. phytonomi was progressively found further south from Ontario. Whether these reports of Z. phytonomi infecting H. postica actually demonstrate spread by a novel genotype has previously been proposed and disputed. PCR-RAPD analysis was used to compare isolates of Z. phytonomi from both hosts in North America, and from H. postica in Israel with Z. radicans and Conidiobolus osmodes as outgroups. Both phenetic and cladistic analyses demonstrate that two main genotypes of Z. phytonomi occur in North America; one genotype including only H. punctata isolates with a second more homogeneous and principally including isolates from H. postica. The genotype principally including isolates from H. postica was more closely related to isolates from H. postica in Israel than to the other North American group, but also included one isolate from H. punctata. Based on affinity with Israeli genotypes, this latter strain may have originated in the Eurasian areas where H. postica is endemic. The degree of host specificity of these two North American genotypes of Z. phytonomi will require further investigation.

Sitona hispidulus . [Distribution map

Abstract A new distribution map is provided for Sitona hispidulus (F.) ( Sitones hispidula (F.)) (Col., Curculionidae) (Clover Leaf Weevil). Host Plants: Broad bean, clover, lucerne, peas, vetch. Information is given on the geographical distribution in EUROPE (excl. USSR), Austria, Belgium, Britain, Bulgaria, Corsica, Czechoslovakia, Denmark, Finland, France, Germany, West Greece, Hungary, Italy, Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland, Yugoslavia, ASIA (Excl. USSR), Cyprus, Iran, Israel, Japan, Syria, Turkey, USSR, NORTH AMERICA, Canada, USA.

Effect of Spatial Distribution on Determining the Number of Samples Required to Estimate Populations of Hypera postica, Sitona hispidulus , and Hypera punctata1 for Specified Probability and Accuracy Levels 2

Sample size (required number of sample units), with specific consideration for spatial distribution and a dispersion parameter, was determined for adult Hypera postica sampled by 1-ft2 (929-cm2) alfalfa quadrats, and Hypera postica, Sitona hispidulus , and Hypera punctata adults sampled oy 1-ft2 emergence traps in wood edge aestivation sites. Taylor's power law ( s 2 = amb ), and the sample size equation N = (100/ c )2 t2 am b−2 provide an efficient means for this determination. Sample size-density estimate curves are presented for four probability (confidence) and three accuracy (precision) levels. Sample size was inversely proportional to adult weevil density in all cases except for S. hispidulus , where the sample size was directly proportional to density. At the 95% probability and 20% accuracy levels 1,173 quadrats are required to estimate an adult H. postica density of 0.1. A 40% accuracy level with this same probability level will estimate densities of H. postica as low as 0.3 per quadrat with only 100 samples.

Occurrence of the Clover Leaf Weevil, Hypera punctata (F.) in Japan

Occurrence of the Clover Leaf Weevil, Hypera punctata (F.) in Japan

Entomophthora phytonomi 1 , a Fungal Pathogen of the Alfalfa Weevil 2 in the Mid-Great Plains

The fungus Entomophthora phytonomi Arthur, which is a common pathogen of the clover leaf weevil, Hypera punctata (F.), was reported infecting larvae of the alfalfa weevil, H. postica (Gyllenhal), in Missouri and Nebraska in 1976 and 1977. In 1977, the infection ranged from 27–81% in 2 study fields in central Missouri. We cannot explain the sudden appearance of the fungus as a potentially significant mortality factor in populations of H. postica .

Resistance of Red Clover to the Clover Leaf Weevill1

Red clover (Trifolium pratense L.) varieties in the third season of growth, that had been exposed to a heavy infestation of larvae of the clover leaf weevil [Hypera punctata (Fabricius)], differed significantly in percentage defoliation, feeding injury score, plant height, and forage production. Based on these four characters, ‘Mammoth,’ ‘Lakeland,’ ‘Dollard,’ and ‘LaSalle’ were highly resistant to larval feeding; ‘Kenland,’ ‘Common,’ and ‘Pennscott’ were highly susceptible. Long term second‐season yield tests including six of these varieties indicated no consistent superiority of any of the varieties in the absence of weevil feeding.