A click beetle was walking around and there is a weevil on top of it.
Any idea why? I would also like to know the exact species of these insects.
Time: 18:50, place: Netherlands / Noord-Hollands / Overveen / the Amsterdamse waterleiding duinen / it's in the dunes near forest and grasslands near the dunes
Nut weevils can be very serious pests of native and non-native nut trees. These damaging insects begin to attack the kernels in the developing nuts while the nuts are still on the tree. However, problems often are not noticed until the nuts are harvested and opened. Occasionally, these weevil grubs are found in homes or other places nuts are stored.
Figure 1. A nut weevil.
Pecan Weevil, Curculio caryae
This is a serious late season pest of hickory and pecan. The greatest damage is caused by the grub that feeds directly on the developing kernel.
Adults are reddish-brown and densely covered with olive-brown hairs and scales. Body length is about 3/8 inch long exclusive of the snout. The female has a snout as long as her body, while the male's is about half that of the female's snout.
Two types of damage are caused by this insect mid-season adult feeding on young nuts causing premature nut drop, and grub damage to the kernels that usually occurs after shell hardening.
Adult weevils emerge from the ground in late August through September, about the time nuts begin to harden. Peak periods of adult emergence usually follow heavy rains. After the nut kernels have hardened, the female uses her long snout to chew a hole in the side of the nut and deposits her egg in little pockets in the nut. Creamy white grubs with reddish brown heads hatch and feed inside the nuts during the fall, reaching 3/5 inch in length.
When mature, the grub chews a perfectly round 1/8 inch hole in the side of the nut and falls to the ground in late fall or early winter, usually between late September and December. They make earthen cells in the ground where they remain as a grub one to two years. Most of the grubs will pupate the following fall. Some, however, do not pupate until the fall of the next year. Adults emerge during the summer following pupation. The entire life cycle requires 2 to 3 years to complete, most of it in the soil.
Weevils usually move only a short distance after emerging and often attack nuts on the same trees year after year, so long as there is a crop of nuts. Weevils apparently prefer trees growing in low areas or those near hickory trees. Early maturing varieties are most susceptible to the weevils. Hickory nuts are attacked by the pecan weevil as well.
Monitoring for Pecan Weevils
Trees can be jarred beginning in mid-August to determine when to apply insecticides. Place a large harvesting sheet under the trees and jar the limbs with a padded pole. The adult weevils will fall onto the sheet and remain motionless for a short period. When three or more weevils are jarred per tree, insecticide applications should begin. Peak emergence cycle usually follow rains. Otherwise spray applications should begin when shell hardening begins and repeated at 10 to 14 day intervals.
Those not prepared to spray can reduce weevil injury by periodically shaking weevils onto a harvesting sheet. Dislodged beetles usually remain motionless on the sheet and can be easily collected and destroyed. Shaking should begin after the first heavy rain in early August and continue through mid-September or until no weevils are collected.
Figure 2. Chestnut weevil grubs.
Lesser Chestnut Weevil and Larger Chestnut Weevil Curculio sayi and Curculio caryatrypes
Of the larger and lesser chestnut weevils, the lesser chestnut weevil is the more common of the two species of weevil infesting chestnuts in Kentucky. These weevils breed exclusively in chinquapin, American and Chinese chestnuts. At one time these weevils were common, but since the passing of the American chestnut they have become much less common.
The 1/4 inch lesser chestnut weevils emerge from the ground beginning in late May until July, about when the chestnuts bloom, but do not lay eggs until the fall. Egg laying begins when the nuts are nearly mature and most eggs are laid after the burr begins to open. Eggs are usually laid in the downy inner lining of the brown shell covering the nut. Eggs hatch in about 10 days and larval development is completed 2 to 3 weeks later.
Soon after the nut falls to the ground, the grubs chew a circular hole in the side of the nut to enter the soil. Most of the lesser chestnut weevil grubs overwinter the first year as grubs, pupate the following fall, and overwinter the following winter as adults.
Some pass two winters in the grub stage and a third winter as adults before emerging from the ground. The life cycle is completed in 2 to 3 years.
Figure 3. Larger chestnut weevil adult.
The biology of the larger chestnut weevil differs from that of the lesser chestnut weevil. Adults begin to emerge in late July and August. The adult is 3/8 inch long exclusive of the snout. The female has a 5/8 inch beak and the male's is 1/4 inch.
Larger chestnut weevils begin egg laying soon after emerging, before egg laying begins with the lesser chestnut weevil. Eggs hatch in 5 to 7 days and the larvae feed for 2 to 3 weeks before leaving the nut. Larger chestnut weevil grubs chew an exit hole in the side of the nut and drop to the ground usually before the nuts fall. Grubs overwinter in earthen cells in the ground. Pupation and adult emergence takes place the following summer. A few grubs will overwinter a second year before pupating. The life cycle is completed in 1 to 2 years.
Weevil infestations can be reduced by picking up chestnuts daily and after curing, heat them to 140˚F for 30 minutes to kill the larvae in the nuts. A cold treatment of holding the nuts at 0˚F for four days may also be effective, but it may also affect the nuts' flavor. Sanitation is important, always collect and destroy fallen nuts before the larvae have a chance to escape and enter the soil. Trees can be jarred similar to monitoring for pecan weevils to determine the presence of adult weevils.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
About Beetles on Camellias
If you see holes in your camellia leaves, the likely suspects are twofold: the black vine weevil, Otiorhynchus sulcatus, or the cranberry rootworm beetle, Rhabdopterus picipes. The adult beetles feed primarily at night while their larvae feed on the root system, making them difficult to identify and control.
The black vine weevil is most detrimental in its larval stage. It feeds on a variety of broad leaf evergreens as well as greenhouse specimens. Adults are equal opportunists and ravage both herbaceous and deciduous plants, and can be found through much of the northern U.S. and into Canada.
This camellia vine weevil overwinters in the grub stage and then awakens in the spring as the soil warms. Adults feed and make holes in camellia leaves and then lay eggs at the base of the host plant in the late summer. Plants that have large numbers of grubs feeding on them can die.
The cranberry rootworm beetle feeds on camellia leaves, leaving tell-tale narrow or crescent shaped holes in the foliage. New growth is most affected.
Generally, the damage done by these pests is purely cosmetic.
Here, there, everywhere
Weevils are technically also beetles. But unlike most of their beetle relatives, several species of weevils can fly. One of the most prolific flyers is the red palm weevil. Scientists have observed adults flying more than one-half mile per day in search of locations for feeding and mating. By contrast, most species of root weevils will drop to the ground if they are disturbed. Instead of flying, the root weevils climb up plants at night to feed, and stay in the dirt during the day.
Armed with this weevil information, you can take stock of your home and garden. If you are seeing large numbers of weevils on your plants or in your home, consider calling a pest management professional to help you identify the type of pest.
Why is there a weevil on top of a beetle? - Biology
Eurhinus magnificus Gyllenhal was first reported in Florida in 2002 when a single specimen was found in an ornamental nursery in Broward County (Feiber 2002). It was collected again in 2003 near Homestead, Miami-Dade County, and was also intercepted in a shipment of bananas from Costa Rica (Fowler 2004). It is likely that this weevil was inadvertently imported into Florida through trade in live plants or plant products. In 2005, all life stages of Eurhinus magnificus were collected repeatedly in both Broward and Miami-Dade Counties from the host plant Cissus verticillata (L.) Nicolson & Jarvis (Vitaceae).
Figure 1. Adult Eurhinus magnificus Gyllenhal, a weevil, (dorsal-lateral view). Photograph by Bryan J. Ulmer, University of Florida.
Cissus verticillata, also known by the common names of possum grape vine, princess vine, and season vine, supports the entire life cycle of Eurhinus magnificus. Eggs are laid within the stem where larvae hatch and begin to feed. The larvae complete five instars, within a gall formed at the location of oviposition, before pupating. Adults emerge from the host plant gall to feed on Cissus verticillata, mate and oviposit.
It is still to be determined if this new weevil will cause damage in the grape cultivars (Vitis spp.) in the grape growing regions of Florida.
Synonymy (Back to Top)
Eurhinus magnificus is a member of the Curculionidae-Baridinae. The original spelling of the genus, Eurhin Illiger 1807, was suppressed by the plenary power of the International Commission on Zoological Nomenclature (Melville 1985), thereby following the arguments of Zimmerman and Thompson (1983) for resolving a nomenclatural conflict between two homonymously used family-group names.
Distribution (Back to Top)
The genus includes 23 species that are widely distributed. Eurhinus magnificus occurs in Belize, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua and Panama (Vaurie 1982, Schall 2002). In 2005, Eurhinus magnificus was abundant and successfully reproducing in various habitats where the host plant Cissus verticillata was present across Miami-Dade and Broward Counties. After first being reported in Florida in 2002, it appears to be established and flourishing in the southeast region of the state.
Description (Back to Top)
Adult: This insect is a robust weevil similar in body form to other Eurhinus weevils (Bondar 1948) and, like many of the other species, Eurhinus magnificus adults are brilliantly colored. The entire body is a vibrant, metallic blue-green with areas of metallic red-copper on the humeri and apex of the elytra and on the pronotum, rostrum, and legs. The mean dimensions of the adult are 5.66 mm long by 3.71 mm wide (Ulmer et al. 2007).
Figure 2. Adult Eurhinus magnificus Gyllenhal, a weevil, (dorsal view). Photograph by Huang Ta-I, University of Florida.
Egg: The egg is milky beige and a mean of 1.24 mm long by 0.72 mm wide (Ulmer et al. 2007).
Figure 3. Cissus stem opened to reveal Eurhinus magnificus Gyllenhal egg. Photograph by Bryan J. Ulmer, University of Florida.
Figure 4. Close up of an egg of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Bryan J. Ulmer, University of Florida.
Larva: Body stout, curved, greatest width near middle, tapered at both ends. The mean head capsule width of a fifth instar larva is 1.6 mm. A full description of the larva and pupa can be found in Ulmer et al. 2007.
Figure 5. Cissus stem opened to show an early instar larva of Eurhinus magnifucus Gyllenhal, a weevil. Photograph by Rita E. Duncan, University of Florida.
Figure 6. Fifth instar larva of Eurhinus magnificus Gyllenhal, a weevil, in a gall. Photograph by Rita E. Duncan, University of Florida.
Figure 7. Head capsule and mandibles of the larva of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Rita E. Duncan, University of Florida.
Pupa: Stout in appearance, with a mean length of 5.66 mm by 3.71mm wide.
Figure 8. Ventral view of a pupa of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Bryan J. Ulmer, University of Florida.
Figure 9. Lateral view of a pupa of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Rita E. Duncan, University of Florida.
Figure 10. Gall with ventral view of newly formed adult Eurhinus magnificus Gyllenhal, a weevil. Photograph by Bryan J. Ulmer, University of Florida.
Figure 11. Sclerotized adult Eurhinus magnificus Gyllenhal, a weevil, emerging from Cissus gall. Photograph by Rita E. Duncan, University of Florida.
Biology (Back to Top)
Adults feed on the outer layers of host plant stems and also within cavities created in the stems and the leaf petioles. Some feeding also occurs on leaf blades at the portion of the leaf directly around the attachment point of the petiole. Females oviposit in young parts of the stem (mean diameter = 2.3 mm) by creating a cavity with their rostrum and depositing a single egg. One or two eggs are laid within a single host plant internode. Gall formation becomes detectable by the first to third instar larva. The largest diameter of the gall is at the pupal stage, at this stage the mean stem size is 4.2 mm and the mean gall size was 9.2 mm.
Figure 12. Adult Eurhinus magnificus Gyllenhal weevils and feeding damage. Photograph by Rita E. Duncan, University of Florida.
Figure 13. Oviposition cavity of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Bryan J. Ulmer, University of Florida.
Figure 14. Gall caused by larval growth of Eurhinus magnificus Gyllenhal, a weevil. Photograph by Rita E. Duncan, University of Florida.
A single specimen of Eurhinus magnificus, reared in a greenhouse in Homestead, Florida, required approximately 83 days to develop from egg to adult during the coldest part of the year. It is likely that the development time of Eurhinus magnificus would be greatly reduced during the summer months. The presence of adults in the field and larval development observed during winter indicate that Eurhinus magnificus is capable of reproducing throughout the year in south Florida. Adults emerging from field collected galls survived nine to 47 days (mean 32 days) from the time of emergence under laboratory conditions (Ulmer et al. 2007).
Host Plants and Damage (Back to Top)
Like other members of the genus, Eurhinus magnificus larvae induce galls on the stems of Cissus spp. (Vitaceae) (Bondar 1948). Vernonia, Andira and Mikania spp. have also been suggested as host plants (Silva et al. 1968, Vaurie 1982). However, the only verified host plant of Eurhinus magnificus in Florida is Cissus verticillata.
Florida contains native species of all four genera which are also represented by species occurring over a wide range in the United States (Fowler 2004, USDA 2006). Cissus verticillata is widely distributed in the Caribbean, Central and South America, and Mexico (Lombardi 2000). It also is considered native to Florida in the United States (USDA 2005). Though Cissus verticillata is sometimes planted as an ornamental, it is a prolific perennial vine that is generally considered a weedy species when occurring with various ornamental and fruit crops in south Florida (Futch and Hall 2003).
In Trinidad and Tobago, Cissus verticillata is used for medicinal purposes against urinary problems (Lans 2006). A single adult was also found on pigmy palm, Phoenix robelenii O'Brien (Arecaceae), and one was collected from avocado, Persea americana Mill. (Lauraceae), foliage. However, no evidence of feeding or oviposition was observed on these two plants and it is likely that the collections were incidental and they are not true host plants.
In general, Cissus verticillata appear healthy and actively growing beyond the point of gall formation. However, the development of Eurhinus magnificus within the stem causes a significant malformation and often has an obvious negative impact on the host plant. Occasionally the gall and resulting damage coupled with environmental conditions results in severing the stem.
Figure 15. Cissus verticillata Nicolson & C.E. Jarvis vine with flowers and fruit. Photograph by Rita E. Duncan, University of Florida.
Figure 16. Damage to Cissus vine caused by gall formed by Eurhinus magnificus Gyllenhal, a weevil. Photograph by Rita E. Duncan, University of Florida.
Eurhinus magnificus is not known to be a pest of commercial grapes and is not considered a threat to attack Vitis spp. (Fowler 2004). However, in a preliminary study Ulmer et al (2007) showed three of four cultivars tested were attacked by adult weevils in a no-choice situation resulting in feeding damage and galls no larval development was apparent on any of the grape species tested. It is conceivable that this weevil could develop on other grape cultivars under different conditions. Additional studies to investigate a wide range of grape cultivars varying in physical and chemical characteristics should be undertaken before eliminating Vitis spp. as suitable host plants.
The impact of the weevil on Cissus verticillata and on other potential hosts, such as Vernonia spp. and Vitis spp., is not discernible at this early stage of colonization but necessitates future research. Further work is also required to better understand the population biology of Eurhinus magnificus and to establish its potential for range expansion in the United States.
Management (Back to Top)
Successful development of Eurhinus magnificus in the field appears to be significantly reduced by predation and fungal agents. However, an examination of approximately 200 specimens of Eurhinus magnificus revealed no evidence of parasitism for any life stage. There are no records of parasitism for Eurhinus magnificus in its native range. Capitonius tricolorvalvus Ent (Hymenoptera: Braconidae) was reared from stem galls of Cissus verticillata in Costa Rica, the host was not identified but presumed to be a beetle (Ent and Shaw 1999). Further sampling is needed to establish the parasitoid fauna, or lack of, associated with this weevil in Florida and its native range.
Selected References (Back to Top)
- Bondar G. 1948. Notas entomologicas da Baía XX. Rev. Entomol., Rio de J. 9 (1-2): 1-54.
- Ent LJ van der, Shaw SR. 1999. A new species of Capitonius (Hymenoptera: Braconidae) from Costa Rica with rearing records. Pan-Pacific Entomologist 75: 112-120.
- Feiber D. (2002). Plant Industry Update. Florida Department of Agriculture and Consumer Services. (no longer available online)
- Fowler L. 2004. Eurhin magnificus Gyllenhal: Weevil Coleoptera/Curculionidae. New Pest Advisory Group (NPAG). Plant Epidemiology Risk Analysis Laboratory, Center for Plant Health Science and Technology. Report 040305: 1-2.
- Futch SH, Hall DW. (2003). Identification of vine weeds in Florida citrus. EDIS. (1 June 2020)
- Lans CA. 2006. Ethnomedicines used in Trinidad and Tobago for urinary problems and diabetes mellitus. Journal of Ethnobiology and Ethnomedicine 2:45.
- Lombardi JA. 2000. Vitaceae: Generos Ampelocissus, Ampelopsis, e Cissus. Flora Neotropica Monograph. 80: 200.
- Schall R. 2002. Eurhin magnificus – A Central American weevil. New Pest Advisory Group (NPAG) Data. p.9. In L. Fowler, 2004.
- Silva A, d'Araújo e G, Rory Gonçalves C, Monteiro Galvão D, Lobo Gonçalves AJ, Gomes J, do Nascimento Silva M, de Simoni L. 1968. Quarto catálogo dos insetos que vivem nas plantas do Brasil. Seus parasitos e predatores, v. I (2).– Ministério da Agricultura, Rio de J., III-XXVI, 622p.
- United States Department of Agriculture. (2005). Cissus verticillata (L.) Nicolson & C.E. Jarvis. Germplasm Resources Information Network. (no longer available online)
- United States Department of Agriculture. (2006). Plants Database. Natural Resources Conservation Service. http://plants.usda.gov/ (1 June 2020)
- Ulmer BJ, Duncan RE, Prena J, Peña JE. 2007. Life History and Larval Morphology of Eurhinus magnificus Gyllenhal (Coleoptera: Curculionidae), a New Weevil to the United States. Neotropical Entomology 36: 383-390
- Vaurie P. 1982. Revision of Neotropical Eurhin (Coleoptera: Curculionidae, Baridinae). Novitates 2753: 1-44.
- Zimmerman EC, Thompson RT. 1983. On family group names based upon Eurhin, Eurhinus and Eurhynchus (Coleoptera). Bulletin of Zoological Nomenclature 40: 45-52.
Authors: Bryan J. Ulmer and Rita E. Duncan, University of Florida Jens Prena and Jorge E. Peña, University of Florida
Photographs: Rita Duncan, Bryan Ulmer and Huang Ta-I, University of Florida
Web Design: Don Wasik, Jane Medley
Publication Number: EENY-417
Publication Date: September 2007. Reviewed: June 2020.
An Equal Opportunity Institution
Featured Creatures Editor and Coordinator: Dr. Elena Rhodes, University of Florida
South American palm weevil
South American palm weevil (SAPW), Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae), is native to parts of Mexico, Central and South America, and the Caribbean. SAPW is an invasive pest in California. It was first collected from infested Canary Islands date palms (Phoenix canariensis) in Tijuana Baja California Mexico in 2010. Weevils were later captured in monitoring traps in San Ysidro in southern San Diego County in 2011 (
5 miles north of Tijuana). Weevil populations likely established in or around San Ysidro in 2014 or earlier. This weevil presents an enormous threat to the ornamental and edible date palm industries in California. The urban landscape in California is defined by palms, especially the ubiquitous Canary Islands date palm (Phoenix canariensis) and edible date palm (Phoenix dactylifera). Some estimates suggest that the ornamental palm industry in California is worth
$70 million (US) per year. Canary Islands date palms have been valued at $500 (US) per 12 inch lengths of trunk and individual “mature” ornamental edible date palms cost around $5,000 (US). The edible date industry in Coachella Valley is worth about $68 million (US), produces approximately 47,000 tons of fruit, employs around 6,000 people, and is grown on about 10,000 acres. In addition to detections in San Ysidro (Bech 2011), R. palmarum was also detected in Alamo Texas in March and May 2012 (El-Lissy 2012), and Yuma Arizona in May 2015 (El-Lissy 2015). There are no reports of established populations of R. palmarum in Arizona and Texas or palm mortality caused by this weevil.
SAPW is a notorious palm pest in its native and invaded ranges. It has been recorded attacking and reproducing on the following palm species: coconut (Cocos nucifera), African oil palm (Elaeis guineensis), açaí palm (Euterpe oleracea), coco de palmito(Euterpe edulis), sago palm(Metroxylon sagu), Canary Islands date palm (Phoenix canariensis), and edible date palm (Phoenix dactylifera). SAPW will also complete development on field planted sugar cane (Saccharum officinarum). Adult weevils have been recorded feeding on ripe fruit of non-palm hosts, including avocados (Persea americana), pineapple (Ananas comosus), custard apple (Annona reticulata), breadfruit (Artocarpus altilis), papaya (Carica papaya), citrus (Citrus spp.), mango (Mangifera indica), banana (Musa spp.), guava (Psidium guajava), and cocoa (Theobroma cacao). SAPW cannot reproduce on these fruit. In the lab, colonies of adult weevils can be maintained for 2-3 months on a mixed diet of cut apples and bananas (with the skin left on), and split sugar cane.
Damage to palm trees results primarily from larval feeding that is concentrated in the apical meristem or the palm heart. This relatively soft and fleshy growing material is typically found in the crown or top part of the palm tree, and it is responsible for generating new fronds. Heavy larval infestations in this region can result in crown collapse and palm mortality. Occasionally, meristematic tissue may occur near the base of the trunk where offshoots grow. Feeding in this region can lead to trunk collapse and palm death.
High levels of feeding damage to the apical meristem can result in palm death as frond and trunk growth originates from this region. Highly damaged areas take on a characteristic appearance as the crown tilts, collapses, and dies. Palms in the advanced stages of attack and mortality have a flattened top, and as the remaining halo of fronds that ring the top of the trunk dry down, the palm looks like a giant brown umbrella or mushroom.
In some instances the top of the palm may drop to the ground because it becomes detached from the top of the trunk because internal feeding by larvae is so severe.
Heavily infested palms will drop fronds the bases of which may be heavily tunneled indicating larval feeding and pupation activity. Basal sheaths, a fibrous material found at the base of the palm fronds, will have holes caused by weevil larvae that have tunneled into the frond bases. Occasionally, pupal cases will drop from heavily infested palms and accumulations on the ground can be observed. Many of these cocoons may be empty as the adult weevils have emerged. Unemerged adult weevils, pre-pupal larvae, and pupae may be found if dropped cocoons collected from the ground are opened.
Fronds damaged by weevil feeding during the early stages of development as they are pushing up from the apical meristematic bulb appear “notched” or to have windows. This damage can be confused with feeding by rats.
Canary Islands date palms showing various levels of feeding damage caused by SAPW
Male weevils release an aggregation pheromone, rhynchophorol, (2E)-6-methyl-2-hepten-4-ol, which attracts male and female weevils to suitable hosts. Female weevils use their rostrum or snout (this is the long “nose” on the head of the weevil) to drill holes into palm material. Eggs are laid in these “holes,” they are relatively large, and female weevils can probably lay a hundred eggs or more over the course of a life time. Females may also lay eggs into cracks or wounds on the trunk or the base of the fronds. Weevil larvae hatch from eggs and consume meristematic tissue. Mature weevil larvae may reach up to five inches in length prior to pupating. Feeding larvae cause significant damage to the apical meristem and when severe, palm death can result. As the infestation progresses, damaged palm material inside the palm will start fermenting and it acquires a characteristic odor. This fermenting “mush” is noticeably warm and very wet, and being inside the palm trunk these conditions may mitigate adverse environmental conditions such as low humidity and temperature. These fermentation odors (especially when coupled with aggregation pheromone) from feeding and other types of damage (e.g., pruning wounds or pathogen infections) attract weevils to palms which intensifies attacks.
(A) SAPW eggs on a US penny. (B) SAPW life stages, from left to right, adult weevil, larva, cocoon, and pupa. (C) Adult SAPW next to a US quarter (top) and a US penny (bottom). (D) SAPW adult exhibiting uncharacteristic orange and black markings. This color morph can be easily confused with the red palm weevil, Rhynchophorus ferrugineus.
(A) The top of a male SAPW rostrum showing the dense comb of setae that characterizes this sex. (B) The top side of the female rostrum lacks setae which makes distinguishing between sexes easy to do
Prepupal larvae spin surprisingly tough cocoons from palm fibers and cocoon construction often occurs in tunnels at the base of fronds. Cocoons tend to be wedged tightly in these tunnels and can be hard to extract. The prepupal larva molts inside the cocoon and develops wing buds. The pupa will molt one more time within the cocoon to reach the adult form which has wings and can fly. The entire life cycle, egg to adult, can take about 3-4 months to complete.
Adult SAPW use their mandibles (i.e., “teeth”) at the end of the rostrum to chew their way out of the cocoon, they are typically black, and live for 1-2 months. A small percentage of the adult population may have orange and black markings that are very similar to another notorious palm pest, the red palm weevil, Rhynchophorus ferrugineus. These orange and black morphs of SAPW have been found in California.
Adult weevils are sexually dimorphic. Males can be separated from females by the presence of a “beard” or “comb” of hairs (i.e., setae) on the dorsal (i.e., top) side of the rostrum. Females lack these setae and the top of the rostrum is smooth. Adult weevils can be found wedged into cracks at the base of palm fronds.
(A) Adult SAPW attached to a flight mill in the lab. (B) Transportation of live palms may inadvertently move SAPW long distances in relatively short time periods
Adult SAPW are strong fliers and have the potential to disperse naturally over long distances. In the lab, flight mill studies indicate that male and female weevils are capable of flying over 15 miles a day or more if they chose to do so. It is unknown if weevils undertake such long distance flights in nature. However, flight mill studies indicate it is possible should weevils elect to do so and this could occur in areas where there are no suitable hosts to attack. In nature, adult weevils tend to fly during daylight hours and some studies suggest that they may only fly 1 mile over the course of a day. Weevils can potentially be moved accidentally by humans over long distances inside infested palms. Movement of live ornamental palms out of infested areas should be avoided to reduce the chances of unintended weevil introductions into new areas.
Trapping and Monitoring
Adult weevils are attracted to traps loaded with commercially-available aggregation pheromone and baited with fermenting fruit. Ethyl acetate (i.e., available as nail polish remover, check ingredients listing) can be used as a synergist to increase the combined attractiveness of the pheromone and bait.
There are two basic types of weevil trap, the bucket trap and the pyramid shaped Picusan trap. Bucket traps can be suspended above the ground or partially buried. Picusan traps are designed to be placed on the ground but they can be suspended.
(A) Bucket trap loaded with pheromone, ethyl acetate, a container of fermenting bait, and antifreeze to kill and preserve adult weevils that enter the trap. (B) Bucket trap suspended from a tree branch. (C) Bucket trap partially buried in the ground. (D) Picusan trap positioned on the ground, and (E) a Picusan trap suspended in a palm tree
Details on making bucket traps and loading them with aggregation pheromone, ethyl acetate synergist, and fermenting bait are available.
Trap placement is important for detecting weevil activity in an area of concern. Studies on red palm weevil in Europe have contributed to the following recommendations for trap placement for SAPW in California. Traps should not be hung from palm trees or placed near (i.e., within 500 yards) palms of interest. Traps are not 100% efficient in capturing weevils. If traps are placed too close to palms adults that are attracted to traps but are not caught may start infestations in the palm that is being monitored. If detecting low levels of palm weevil activity in the general vicinity is the goal of the monitoring program, traps should be deployed outside (perhaps > 0.5 mile away) of the immediate area of concern. If weevils are captured at this distance from the palms of concern it likely indicates that weevil activity is close and steps should be promptly considered and implemented for protecting those palms. Trap efficacy is maximized if traps are placed in areas with partial or full shade. Full sun exposure, especially during the hottest parts of the day, rapidly diminishes trap potency.
(A) Soil injecting a systemic pesticide. (B) Applying a systemic pesticide to a palm trunk. (C) Injecting a systemic pesticide into a palm trunk. (D) Applying a contact insecticide to palm foliage. (E) Canary Islands date palm showing recovery following a crown drench with a systemic insecticide. (F) Close up of the new fronds shown in (E)
Systemic pesticides are at present the most effective tool available for protecting and potentially curing palms of SAPW infestations. Systemic pesticides (mainly neonicotinoids) are translocated within the palm and accumulate in the meristematic tissue where weevil larvae feed. Systemic pesticides can be applied as soil drenches, soil injections, trunk sprays or paints, trunk injections, or as drenches applied to the crown. Contact insecticides (i.e., pesticides that either kill on contact or leave a dry external residue that is lethal upon contact) can be applied to palm fronds or pruning wounds to kill adult weevils attracted to these substrates. Developing a pesticide treatment program should be made in consultation with a professional arborist, and two or more applications per year may be needed in infested areas to protect palms from weevil attack. Systemic pesticides applied as crown drenches can “cure” heavily infested palms allowing meristematic tissue to recover and new frond production results.
(A) Cutting fronds to make a “window” to view the palm crown. (B) The exposed crown after the “window” was cut. Windows can be useful for assessing weevil activity after pesticides treatments have been applied
Efficacy of pesticide treatments on weevil activity in the crown can be checked via a “window.” A window is created by removing palm fronds in the crown which then permits access to the crown so visual inspections for weevil activity can be conducted.
Biological Control of SAPW
Classical biological control is the intentional introduction of a natural enemy (e.g., parasitoid, predator, or pathogen) of an invasive pest with the goal of reducing pest populations to less damaging levels in the invaded area. One potential reason, amongst several, as to why non-native organisms become pests following introduction into a new area is the lack of population regulation provided by upper-trophic level organisms (i.e., natural enemies). The “enemy-release” hypothesis is one explanation for explosive pest population growth and spread when an invasive organism establishes in a new area. Subsequent population control may result when host specific efficacious natural enemies are re-associated with the target pest via a classical biological control program.
Several natural enemies of SAPW are known, but one group of natural enemies, parasitic flies, in the genus Billaea (formerly Paratheresia) (Diptera: Tachinidae), appear to be exceptionally promising candidates for use in a classical biological control program targeting SAPW in California. These flies have a distribution that includes parts of the known range of SAPW (i.e., South America and the Caribbean.) One species, B. rhynchophorae, appears to be particularly aggressive towards SAPW in Bahia State in Brazil. Two different yearlong surveys by Brazilian scientists indicated that parasitism of SAPW larvae/pupae averaged 40% (range 18-50%) in one study and 51% (range 33-73%) in the second survey. Flies attacked immature SAPW year round with seasonal highs (Sept. – Nov) and lows (Jun – Jul) being observed. The average number of fly puparia produced per weevil host inside the SAPW pupal cocoon is around 18.
Biological control targeting SAPW with B. rhynchophorae at the very early stages of the invasion in California could potentially reduce weevil populations. Reduced population densities could slow weevil spread and economic damage.
(A) Fronds being removed a SAPW infested Canary Island date palm prior to being cut down. (B) Infested palm shown in (A) being dropped. (C) Palm fronds and other material infested with SAPW life stages should be chipped before being moved to the landfill. Chipping will kill larvae, pupae, and adults
Removal of Infested Palms
Removal of infested, dying, or dead palms is expensive, potentially dangerous and should be undertaken by professional arborists. It is recommended that infested palm material (i.e., fronds and the bulbous top of the palm) be chipped. All transported material should be covered with a tarp and disposed of at a certified landfill that buries within 24 hours (or sooner) of dumping to reduce risks of spreading adult weevils into new areas either enroute to or around the disposal site. It is not necessary to remove the entire palm trunk. SAPW larvae don’t drill deeply into the palm trunk and infestations are typically limited to the top 25% (or less) of the palm. However, the aesthetics of a dead palm trunk may encourage complete removal and stump grinding.
Red Ring Nematode
Adult SAPW can spread a plant pathogenic nematode, Bursaphelenchus cocophilus, commonly known as red ring nematode (RRN), the causative agent of red ring disease in palms. Nematodes reside within the body of adult weevils and are deposited in palms when weevils feed, defecate, or lay eggs. Weevil larvae become parasitized with nematodes and uninfected adults can acquire nematodes when they come into contact with nematode infested palms. Palms infected with RRN can die in as little as 3-4 months after infection symptoms become noticeable. RRN has not been detected in SAPW captured in California and this nematode is not known from other locations in the USA either. RRN is known from Mexico. As is the case with many invasive vector-pathogen systems in California, the vector is detected first, then normally, several years later, the pathogen is recorded. A similar situation for SAPW-RRN may eventually develop in California. Additional information and photos of RRN and red ring disease are available.
Report an Infested Palm
SAPW is spreading through urban areas in southern California and Canary Islands date palms appear to be a highly preferred host which are very susceptible to attack. To track the spread of SAPW we need the help of community scientists, interested and concerned members of the public, who are willing to take time to report SAPW infestations via the web. To report palms that may be infested with SAPW please visit this site and fill in the online document and submit it.
103 New Beetle Species Named After Star Wars Characters, Mythological Beasts, and More
There are more species of beetle than just about anything else on Earth—approximately 400,000 species described, with perhaps a million or more left to catalog. Now, researchers have identified 103 new species of weevil (a tiny variety of beetle), all from a single Indonesian island.
Trigonopterus weevils are wee, egg-shaped insects, dimpled like a golf ball and blessed with a protuberant schnoz. They’re found in the thickly forested islands flecked in the tepid seas between Asia and Australia, from Sumatra out to Samoa. Plenty of weevils had been found on either end of this range, but smack in the middle was the giant island of Sulawesi, which had only one Trigonopterus, described in the 19th century.
“We had found hundreds of species on the neighboring islands of New Guinea, Borneo and Java—why should Sulawesi with its lush habitats remain an empty space?”, said Alexander Riedel, entomologist at Germany’s Museum of Natural History Karlsruhe and lead author on the study published Thursday in the journal ZooKeys , in a statement.
Riedel—collaborating with the Indonesian Institute of Sciences —decided to take a closer look at rugged island’s rainforests, conducting several field surveys on Sulawesi over a few years. The team collected a couple thousand weevils, and then went through the long process of identifying what they were seeing. This involved looking key physical characteristics on the wee insects, but mostly relied on DNA “barcoding”—analyzing a specific segment of DNA that differs between species.
It turns out Sulawesi has a lot more than one Trigonopterus species.
The researchers described 103 species of weevil that were entirely new to science. All of them appear pretty similar at a glance, but looking closer reveals an array of differences. Some are long and tapered, others chunky and square, and some are shaped like a lightbulb. Many species are smooth and lustrous, but others have curious, scaly filaments on their backs, or ridges and wrinkles. They subtly vary in color, the fuzziness of their feet, and (for males at least) the shape of their penises, apparently.
With so many new species to name, the researchers had to get creative.
Most of the species are named after a quirky physical feature, or the location where they were first found. But the team also drew inspiration from pop culture, naming one particularly small, squat, greenish species Trigonopterus yoda after a revered Jedi Master of a similar mien. They also named a few species after characters in the Asterix comics series. Others were named after figures in Greek mythology, like satyrs (half-beast nature spirits) and Artemis, the goddess of the hunt. Still more were named after influential biologists from history.
Some of the weevils have truly epic names, like Trigonopterus incendium, which was found in Tanjung Api (Cape of Fire), a region that spontaneously burps flaming natural gas. Others, like Trigonopterus squalidulus, whose name refers to how its rough exoskeleton always gets encrusted with dirt and filth, are decidedly more humble.
The diversity of Trigonopterus weevils on Sulawesi is certainly huge, and the discovery of the new species helps fill in a gap in scientists’ understanding of the evolutionary history of the beetles, which are thought to have island-hopped over millennia from Australia, exploding into dozens of species at each stop. This prodigious “speciation” is likely caused by their flightlessness and propensity to specialize on certain plants in small ranges it’s why most of the newly-described weevils seem to be “endemic” to the specific locations they were found.
These same old habits may actually be what puts the weevils at risk of extinction in the face of widespread deforestation on Sulawesi. Unable to fly or live outside of a sole mountain or forest patch, many of the weevils’ fates are grafted directly on the survival of their home habitats.
But for now, the first step to conserving any species is figuring out if it exists at all, so there’s far more of the island to survey. In a statement, Raden Pramesa Narakusumo, coauthor on the paper and curator of beetles at the Museum Zoologicum Bogoriense, Indonesian Research Center for Biology, notes that much of Sulawesi is yet to be explored for such small beetles.
“Our survey is not yet complete and possibly we have just scratched the surface.”
Jake Buehler is a science writer living on Washington’s Olympic Peninsula with an adoration for the Tree of Life’s weird, wild, and unsung. Follow him on Twitter or at his blog .
Jake Buehler is a science writer living on Washington’s Olympic Peninsula with an adoration for the Tree of Life’s weird, wild, and unsung.
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Boll weevil, (Anthonomus grandis), beetle of the insect family Curculionidae (order Coleoptera), a cotton pest in North America. Introduced to the United States from Mexico in the 1890s, the boll weevil was a severe agricultural pest for nearly 90 years, until the launch of an aggressive multiyear eradication campaign in 1978. The campaign almost, progressing slowly but effectively, completely eradicated the boll weevil from cotton-producing states, primarily through aerial release of the insecticide malathion. The boll weevil infestation is estimated to have caused crop losses of 30 to 50 percent in infested areas. The eradication program led to increased crop yields (by 10 percent or more) and a dramatic decrease in the use of insecticides (40–100 percent), leading to a reduction in production costs. In 2013 Texas was the only state to still have areas with boll weevil infestations.
The size of a mature boll weevil varies according to the amount of food it receives during its larval stage, but it averages about 6 mm ( 1 /4 inch), including the long, curved snout, which is about one-half the body length. In the spring, adult boll weevils emerge from a partly dormant state, and their light yellow colour changes to gray or black over several weeks. Females deposit between about 100 and 300 eggs in cotton buds or fruit, though they avoid depositing their eggs in cotton bolls already visited by other females, unless most of the bolls are infested. An average of two to three weeks is required for an egg to develop into an adult, and there may be up to 10 generations each year. The larvae live entirely within the cotton boll, destroying not only the seeds but also the surrounding cotton fibres. Because the larvae and pupae remain inside the cotton bolls for their entire period of development, the application of insecticides at that time is ineffective.
The boll weevil infestation caused many farmers to realize the value of crop rotation and the need for crop diversification rather than total dependence on cotton. In addition to the use of malathion, control programs include early destruction of cotton stalks, cleanup of hibernating areas, seed treatments, early planting, and the development of early-maturing and rapid-fruiting varieties of cotton.
This article was most recently revised and updated by Melissa Petruzzello, Assistant Editor.
Life, death and soil
These blind spots are important because more than a quarter of all Earth's biodiversity lives in soil. These organisms (bacteria, fungi, protists and tiny invertebrates) are responsible for breaking down dead organisms and controlling the cycling of chemical elements through ecosystems. This is essential to life on this planet. With no life in soil, nutrients would move through the soil very slowly. Plants could not grow well and we would have little food.
The recycling of nutrients into the soil from leaf litter and dung has been well studied. Forensic scientists have also carefully studied the stages of decomposition of larger animals by insects and microbes.
But what happens to small mammals and birds has rarely been considered, despite being vastly more numerous. They are often scavenged or eaten by predators and so removed from the system, to be returned as dung. A recent study in the US found that during spring and summer, up to 75% of all small mammal carcasses are secured by carrion beetles.
We have little knowledge of how carrion beetles change the way nutrients are recycled or the effects they have on the animals and microbes living in the soil. This matters. As we soon discovered, carrion beetles have profound effects on soil and soil is central to how an entire ecosystem works, meaning that the beetle is central to that ecosystem. This is actually very surprising, given the long term focus on the relationship between plants and soil. And it may also have long term consequences on how entire ecosystems work, including the climate.
Sheena and I wanted to focus exactly on the impact that the breeding cycle of carrion beetles has on soil organisms. If carrion beetles find a carcass and start breeding in it, they get rid of it in a few days, rather than the many weeks it would take when they are not breeding. Surely, this must affect what happens in the soil?
How can I control vine weevils?
|The grubs of vine weevils live in the roots of plants|
Image: AHDB Horticulture TV
Vine weevils are destructive, but there are several measures you can take to control their numbers and limit their impact on your garden. But whichever solution you choose, you&rsquoll need to stay vigilant to make sure that their numbers don&rsquot have a chance to recover.
- &bull Remove the adult weevils &ndash regularly check the plant (as well as the surrounding area, like under pots) for the beetles and remove them from the plant either by hand or by gently shaking the plant over newspaper. You can also trap them around the pots using special sticky traps.
- &bull Remove the grubs &ndash the grubs are usually found around the plant roots, which aren&rsquot easily accessible, but compost can also be infested. Remove as many as you can.
- &bull Limit their food supply &ndash discourage vine weevils from your garden by growing plants that they are less attracted to. Plants with fragrant leaves &ndash such as Lavender, Lemon Balm, Geranium macrorrhizum, and Mint &ndash appear to be less vulnerable to attack from the adult weevils. They also seem less attracted to furry leaves, such as those of Stachys byzantina.
- &bull Weed regularly &ndash adult larvae love certain types of weeds, such as willow weed, so keeping on top of the weeding may help limit their numbers.
- &bull Encourage natural predators &ndash the natural world can help you keep vine weevil numbers down, with creatures like frogs, hedgehogs, and birds preying on beetles. Create a hospitable environment for these beetle predators by providing food and water.
- &bull Use biological controls &ndash nematodes are effective in killing the larvae in the soil, both in beds and containers, during the warmer months when the soil is at least 5°C.
- &bull Apply a liquid drench to the compost &ndash this kind of pesticide can be applied to compost in containers and will control the larvae. For best results, use it in mid- to late summer so the effects last well into the autumn and spring when the larvae are at their most destructive.
Which plants do vine weevils not like?
Plants with fragrant leaves seem to be less frequently attacked by adult weevils. Plant Lavender, Lemon Balm, Geranium macrorrhizum, and Mint. They also seem less attracted to furry leaves such as those of Stachys byzantina.