1991 British Columbia Cranberry Growers Association
This booklet was made possible because of the consistent interest shown by the B.C. Cranberry Growers Association and their willingness to finance this publication. Collections of insects were made in the 1990 growing season by E.S. Cropconsult Ltd. personnel with partial assistance from Geoffrey Sirois, on a summer position funded by Ocean Spray Cranberries Inc. This project also benefited from the research done earlier by Dr. Deborah Henderson ( E.S. Cropconsult Ltd.), Dr. Dave Raworth ( Agriculture Canada ), and the people involved with the production of their book "Beneficial insects and common pests in strawberry and raspberry crops". Special thanks also go to Dr. Sheila Fitzpatrick ( Agriculture Canada ) for the use of her laboratory facilities and to Wes McDiarmid (Agriculture Canada) for the photographs. Taxonomic assistance given by the Biosystematics Research Institute in Ottawa and Sid Cannings, curator of the Entomology Museum at the University of British Columbia, was greatly appreciated.
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Over the last few years a more cautionary attitude toward the use of pesticides has developed by growers and consumers alike. To accommodate these concerns Integrated Pest Management (IPM) systems are being developed to reduce the amount of pesticides needed and to rely more heavily on natural control agents like beneficial insects. Beneficial insects are in general more adversely affected by insecticides than pests. Through long-time use of these chemicals, population size and variety of beneficial insects have been diminished while pests like aphids have become resistant and have increased in numbers. With the reduction of pesticide use beneficial insects will become more abundant and better biological control can be achieved.
To assess the insects that inhabit a cranberry bog the grower has to be able to differentiate between pests and beneficial insect species. This booklet gives an overview of the beneficial insects that can commonly be found in cranberries in B.C. It is important to note however, that this information has been collected from bogs that have been treated with pesticides over a long period of time and therefore might be lacking in variety of fauna. Insects were collected in pitfall traps, sweep samples and through visual sampling in different locations. The pitfall traps were placed in the soil among the cranberry vines in commercial bogs in Delta and Richmond and were checked weekly from May through August. Additional pitfall traps were located in an abandoned cranberry bog near White Rock and emptied every two weeks. Sweep samples were taken at night on three commercial cranberry farms ( Richmond and Delta ) in late July and usual searches were conducted weekly on eight different farms throughout the season. Many of the insects mentioned in this publication are not only indigenous to cranberries but also occur in other crops and vegetation that provide similar habitats and food supplies.
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The Black Vine Weevil ( Otiorhynchus sulcatus) is a pest in B.C. cranberries and sometimes mistaken for the beneficial ground beetles. Therefore this short key has been included to assist the reader in distinguishing between the two beetles.
1. General shape beetle-like (Fig. 1), with elytra (wing covers, Fig. 1)
present.............................................................2
2(1). Antennae usually with more than five segments, elbowed (Fig. 2) or
straight (Fig. 3)...................................................3
3(2). Body often rounded, head elongated (snout-like), antennae elbowed
arising from front of head (Fig. 5).....................Curculionidae
3'. Body elongated, head not snout-like with well developed mouthparts
(mandibles), antennae straight, arising from side of head (Fig. 4),
elytra (wing covers) usually with vertical grooves and ridges.
............................................................Carabidae
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Although there are over 3000 species in North America the most commonly occurring ground beetle species in B C. cranberry bogs are the Common Black Ground Beetle ( Pterostichus spp. ) and the European Ground Beetle ( Carabus nemoralis ). The beetles range in size from 3 to 36 mm and are often dark and shiny ( Pterostichus ) or brightly coloured and iridescent ( Carabus ) with striated or grooved wing covers ( elytra , Fig. 1). Their bodies are somewhat flattened and the head ends in well developed mouthparts (mandibles, Fig. 4) Ground beetles are mostly nocturnal hunters and predaceous as both adults and larvae (Fig. 6) and the vast majority like the Carabus and Pterostichus species are beneficial. Ground beetles feed mostly on soft bodied insects like caterpillars and other larvae, e.g. those of weevils (Fig. 7) and also on snails. Depending on the species, the female lays her eggs one or more at a time into soil or other dark and moist places. After hatching the larvae move about in search of prey. It takes one to two years before the larvae develop into adults which can live up to two years. Ground beetles, especially the bigger ones like Carabus nemoralis are very susceptible to insecticides and have not developed resistance. Larvae are cannibalistic and control their own numbers as well as those of pests. The higher the density of the pest, the more effective control agents the ground beetles become.
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Ladybird beetles are among the most familiar beetles occurring in B.C. Their often bright colourings, red or orange with black spots, advertise their "bitter" taste to possible predators. The female beetle deposits her yellow-orange eggs in clusters of 10 to 50 on foliage near a food supply. The emerging larvae are elongated and spindle-shaped and often are brightly banded in patterns that identify the species. A full grown larva consumes about 50 aphids in one day. An adult female needs up to 100 aphids before reproducing and will feed on approximately 2000 aphids in her life which can last two months during the warmer seasons. Adult ladybird beetles are very mobile and actively search for food. They are attracted by large numbers of aphids and increase their reproductive rates accordingly - up to 100 eggs per female. It takes 20 to 35 days for an egg to develop into an adult. British Columbia experiences about two to three generations per year depending on the weather. Ladybird beetles are predaceous both as adults and larvae and although they prey mostly on aphids and on young scale insects (nymphs). The larvae have also be observed to feed on small caterpillars like spanworm, as well as on each other. Ladybird beetles are often found overwintering in large swarms of adults under leaves and debris, emerging again in spring.
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Rove beetles are slender, elongated insects ranging in length from less than 10 mm to 25 mm They are wide spread over B.C and often encountered in cranberry bogs. They make up one of the largest families in the insect world. One obvious feature of the rove beetle is the very short wing covers (elytra) under which the well-developed hindwings are folded, leaving the abdomen exposed. The second noticeable characteristic of these beetles is the bending upward of their abdomens similar to scorpions when running or disturbed. The female beetle lays her eggs under stones or leaf litter. The emerging larvae are similar in appearance to the adults and occupy the same habitats. Both the adults and the larvae are predators of mites, worms, and other small insects. In combination with ground beetles, staphylinids can be very effective pest control agents.
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Soldier beetles are elongated, soft bodied insects that bear a resemblance to fire flies (which are actually beetles) but possess no light organ. Almost 3500 species have been discovered world wide. One of the most common species found in B.C. cranberry bogs and their surroundings belong to the genus Cantharis whose solid orange or yellow-orange colouring make them easy to spot. The adult soldier beetles ( 10 to 13 mm ) are commonly found on flowers feeding on nectar, pollen, and small soft bodied insects. The larvae are also predaceous and mostly prey on adult and immature aphids.
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About 3000 species of Damsel bugs exist throughout the world. One of the most common species in B.C. is Nabis ferus which can be found on the leaves of cranberry vines as well as other low growing vegetation. Nabid nymphs resemble the adults but are generally of a lighter brown colour. Damsel bugs (10 to 12 mm) are swift runners and possess long slender legs, the first pair of which is adapted to catch their prey. Both the nymphs and the adults are predaceous and feed on various soft bodied insects like aphids and the young of other hemiptera (true bugs). Some damsel bug species have also been observed to attack the eggs and caterpillars of lepidoptera ( butterflies and moths ).
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The minute pirate bug ( Orius tristicolor ) is a small ( 3 to 5 mm ) insect with a flattened body that is black or brown with lighter markings resembling a pirate flag, hence the name. Minute pirate bugs occur often on the underside of cranberry leaves which makes them less exposed to pesticides. In B.C. Orius tristicolor has three to four generations per year. The eggs, very small ( .25 mm ), clear or white, are deposited into plant tissue and the first generation emerges in early spring. Adults and nymphs, which are similar in appearance, are very active predators feeding on mites, aphids, thrips, and the young and eggs of other insects. Minute pirate bugs are now available commercially.
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Damselflies and dragonflies are often brightly coloured, fairly large insects. Damselflies ( 25 to 51 mm ) appear similar to dragonflies but are more slender and when at rest hold their wings vertically above their bodies. Dragonflies are among the fastest and largest ( 18 to 127 mm ) flying insects and spread their wings horizontally when resting. Both the adults and naiads ( immatures ) of damselflies and dragonflies are predaceous but do not live in the same habitat. Eggs are laid on vegetation below or above the waterline. The resulting naiads are aquatic and, in the case of damselflies, equipped with external gills located on the abdomen. In ponds and slow flowing waters they hunt other aquatic insects, tadpoles, snails and small fish. When ready, the naiads climb onto stems out of the water, where the full grown insects emerge, leaving the empty outer shell of the naiad behind. The adults are fast flying predators, capable of catching their prey in the air. Damselflies and dragonflies feed on small insects like flies, mosquitos, gnats and aphids. Damselflies can be seen from May until November while dragonflies fly from May until October. Both overwinter as immatures.
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These gray - brownish insects are nocturnal and are commonly found in and near wooded areas. The females deposit their eggs on foliage near a food source. The eggs are white, but turn orange or pink and finally brown just before the larvae are ready to hatch. The larval body is elongated and the head ends in big jaws (mandibles) which are used to hold on to the prey, pierce it and suck out the liquid body contents. The development from egg to adult takes 24 to 30 days and there are several generations per year. Canada has 23 species of brown lacewings, with at least one occurring in B.C. cranberry bogs. Brown lacewings are predaceous in their adult and larval stages and feed on spider mites, aphids and other soft bodied insects.
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In B.C., most species belong to the genus Chrysopa, also called Common Lacewing, and can frequently be encountered on cranberries as well as trees, shrubs and other low growing plants in the vicinity of cranberry bogs. There are a total of 25 species in Canada. The species belonging to the genus Chrysopa have green wings, golden or copper coloured eyes and are active predators at night. The large sized and rather conspicuous green lacewing will give off a disagreeable odour when feeling threatened. Both adults and larvae prey on soft bodied insects like aphids and mites. The larvae develop out of white stalked eggs that are laid on leaves. They are called aphid lions because of their ferocious appetite for aphids. The larvae are similar in appearance to those of the brown lacewings but have enormous pincers ( mandibles ) with which they seize their prey and suck it dry. An aphid lion can consume a few hundred aphids in one day. After having reached about 6 mm in length the larvae are ready to pupate in a white silk cocoon attached to the underside of a leaf. It takes 30 to 40 days for the eggs to develop into adults which live 4 to 6 weeks. One female can lay between 100 and 200 eggs in her life time. The adult green lacewings appear at the beginning of the season and are important as early aphid control agents. Later on the larvae take over most of that function. Commercially raised green lacewings are available.
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As the name indicates these flies have disproportionally long legs in comparison to their small bodies ( up to 10 mm ). Longlegged flies are rather colourful insects, often metallic green, copper or blue. The males of this family of flies have a conspicuous genital capsule at the end of the abdomen that is folded forward and underneath the body. There are over 1230 species in North America with at least one, Dolichopus spp., occurring in cranberry bogs in B.C. Adults and larvae are predators and feed on small, soft bodied insects like aphids and spider mites. The larvae of some species are aquatic. Unfortunately not much is known about the life cycles of the Dolichopodidae.
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Marsh flies are rather small ( 4 to 8 mm ), slender, yellowish brown insects with prominent red eyes, fairly long antennae and mottled or spotted wings. These flies commonly occur along the banks of ponds, in marshes, bogs, and ditches around cranberry fields. The adult marsh flies are thought to drink dew and nectar and may play a minor role as pollinators. The larvae either prey on or parasitize snails. Very little is known about their life cycles.
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In B.C. members of the genus Stratiomys are found in several habitats, cranberry bogs included. They can be brightly coloured insects, wasplike or solid dark, with a somewhat flattened, broad abdomen. These medium to larger sized flies are found as adults on flowers where they either feed on nectar or on small prey like aphids and the young of true bugs. The larvae occupy several ecological niches. Some are aquatic, feeding on algae, decaying materials and small invertebrates. Others occur under bark and leaf litter and consume small soft bodied insects like aphids and the nymphs of mites and other organic substances.
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Adult syrphids, also called hover flies, can be either stocky and hairy or have brightly striped bodies and often mimic the movements and colourings of bees and wasps. These colours warn potential predators away from bees and wasps, and are meant to accomplish the same effect for the harmless syrphid flies. Adult syrphids feed on pollen, nectar and the sugary secretion called honey dew produced by aphids but are very efficient predators in their larval stages. This is especially true when their prey, aphids and the nymphs of scale insects, occur in large numbers. The adult female moves up and down a plant, visually searching for aphids while hovering in one spot. After the female has located a colony, she deposits the eggs in small batches among the aphids. Depending on the species, the female lays between 400 and 1000 oblong, white eggs which hatch after a few days. The tiny, blind maggots hunt for aphids by raising the front part of their bodies and swing back and forth until they bump into their victim. On contact with the aphids the syrphid larvae uses it's sharp mouthparts to pierce the aphids, lift it up in the air and suck it dry. One syrphid larva can destroy up to 400 aphids before pupation. After 16 to 28 days, the full grown larvae ( 6 mm ) are ready to pupate and do so either in the soil or rolled up leaves. The metamorphosis (transformation) takes about 7 to 8 days, after which time the adult flies emerge. Depending on the climate 3 to 7 generations a year are possible. In B.C syrphids also play an important role as pollinators and can often be observed in and around cranberry bogs.
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Two commonly occurring species of wasps in B.C. cranberry bogs are the bald faced hornet ( Vespula maculata ) and the yellow jacket ( Vespula spp. ). They are both social wasps and build their nests out of " wasp paper ", a material made from chewed wood and saliva. Yellow jackets ( 12 to 16 mm ), usually with black, yellow and white markings, nest in the ground while the black and white coloured bald faced hornet ( 16 to 20 mm ) constructs nests that are free hanging and often can be found attached to branches or houses. Both species rear their young by "progressive provisioning" which means the larvae are cared for by the adults until they have matured. The larvae are fed pre-chewed insects while the adults live on nectar, honeydew, pollen, ripe fruit and insects. In both species the colony consists of queens, workers and males. The fertilized queens overwinter and start a new colony in spring. The first brood consists of female workers which rear the second generation and take over all duties concerning the nest while the queen does little else but lay eggs. The males develop in late summer from unfertilized eggs and mate with the queens. Only the mated queens overwinter in soil or leaf litter.
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Tachinid flies are a very large family of active flies whose stocky bodies are covered with bristles. They vary in size from 3 to 14 mm and resemble bees or house flies. Adults fly from late spring until early fall and are among the most important parasitic insects. Tachinid flies feed on nectar and secretions of aphids, scale insects and leafhoppers while larvae are internal parasites of a variety of insects. Live young or up to two eggs are deposited on or near a suitable host like the larvae of moths, butterflies, sawflies, beetles, the adults of true bugs and grasshoppers The larvae penetrate the host and feed on its internal organs until ready to pupate in the soil. The host almost always dies from the parasitism. Some tachinid species specialize in a certain host and attack for instance only leaf rolling caterpillars while others prefer cutworms or winter moth. Tachinids play a valuable role in controlling the population levels of certain pests and some of the species occurring in B.C. have been introduced from Europe in an effort to reduce the numbers of some economically important pests.
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The family Braconidae consists of over 1700 species of tiny wasps in North America alone and its members range from 2 to 15 mm in length. The adults are somewhat similar in appearance to ichneumonid wasps but their bodies are stouter, usually black and the ovipositor is seldom carried outside the body. Braconids are important pest control agents and parasitize a number of different insects like aphids, caterpillars, weevil larvae, flies, true bugs, sawflies and other Hymenoptera larvae. One or more eggs are deposited by means of the ovipositor into the host. The developing larvae consume the host from the inside, killing it, and emerge when ready either to pupate or as full grown adults. Parasitized aphids for instance, are recognizable by their golden, black, or silvery colour and by the parchment like texture of the bodies. Only the outer shell of the aphid ("mummy") remains to protect the braconid until it emerges as an adult. The host specific Aphidius species are some of many that parasitize aphids. The presence of mummies in an aphid colony indicates that some or even many of the remaining healthy looking aphids are also parasitized. Lepidoptera hosts ( moth and butterfly caterpillars) are often covered by silk cocoons, webs, and leaf rolls which seems to make them more attractive to some braconids as those coverings can be used as additional protection for the braconid larvae. The larvae which pupate on the outside do so in silken cocoons attached to the host or entirely apart often en mass. Of many species found in bogs at least three are possible parasites of cranberry feeding lepidoptera and gall midges or gall gnats. Some of the species are currently under revision and so names are not available.
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The adult wasps are slender insects with long abdomens and almost always permanently protruding ovipositors that can be several times longer than the body Ichneumonidsds range from 5 to 36 mm in length and vary in colouration. They are rather common insects with over 3100 species in North America. Ichneumonids mostly are parasitic on the eggs and immature stages of a variety of insects and spiders. Most however, are external or internal parasites of Lepidoptera, Hymenoptera or Coleoptera larvae. Like the braconids, the ichneumonids use their ovipositor to deposit one or more eggs on or inside the host. The growing larvae devour the host from within and emerge either when ready to pupate or as adults Ichneumonids are very effective pest control agents and some members of the subfamily Gelinae are commonly found in cranberries.
Note: Small chalcid wasps that parasite fireworm eggs have recently been identified in Wisconsin. Steps are currently being taken to find out if these parasitic wasps, members of the genus Trichogramma are also present in B.C.. Field and laboratory experiments are being conducted by E.S. Cropconsult and Agriculture Canada.
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Bumble bees rank among the most important pollinators of cranberries in B.C.Two species often encountered in cranberries are the Golden Northern Bumble Bee ( Bombus fervidus ) and the Red-tailed Bumble Bee ( Bombus ternaries ). Bumble bees are generally robust in shape and have either black and yellow or black and orange markings. These obvious colourings serve as warning signals for potential predators, indicating distastefulness and possession of a defense mechanism. Unlike honey bees, bumble bees can sting repeatedly without losing their stinger as it has no barbs and does not become embedded in the enemy. Their bodies are covered with a dense coat of hair to which pollen adheres. While visiting different flowers some of the pollen sticks to the reproductive organs of the plants, pollinating them. The pollen is removed from the hair by brushing the hindlegs along the body, collecting it in special indentations called pollen baskets. The pollen can so be safely transported back to the nest. Bumble bees are social insects and build their nests in the ground, often in abandoned mouse burrows, empty bird nests, and even discarded mattresses. Only the mated queen ( 14 to 25 mm ) overwinters, the rest of the colony dies at the on-set of cold weather. The first brood emerges in early spring from eggs laid during the winter and consists of small, sterile females. These workers ( 8 to 18 mm ) enlarge the nest and prepare it for the next generation of workers which, due to the increase in temperature and nest size, are also larger. In late summer males ( drones: 8 to 15 mm ) are produced whose sole function it is to fertilize the queens before dying in the fall.
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Apis mellifera, the only honey bee species, is valued as a major honey producer, but especially as one of our most effective pollinators. Some minor colour variations, golden brown or reddish brown, with black and orange or yellow on the abdomen exist among the bees. Like the bumble bee, honey bees are social insects and build nests in which both workers ( 10 to 15 mm) and queen ( 18 to 20 mm ) overwinter. In contrast to the bumble bee, the honey bee queen cannot start a nest by herself. She needs the help of the sterile female workers which develop out of fertilized eggs. Drones ( 15 to 17 mm ) emerge from unfertilized eggs. If fed " royal jelly ", a honey and nectar mixture, for more than three days the young female larva will grow into a new queen which will either be killed by the old queen or one of the queens will leave the hive with a swarm to start a new colony. A queen lives up to five years during which time she continues laying eggs at intervals and a colony can sometimes consist of more than 80,000 individuals. New queens emerge in late spring or early summer. The drones mate with these new queens and then die. Unmated drones are either starved to death or killed by the workers. Honey bees have a caste system in which the youngest bees perform the most menial tasks while the responsibilities and the importance of the work for instance the rearing of the brood, increases with the bee's age and experience. Due to their complicated communication system, bees are able to inform their fellow workers of food sources and their exact locations.
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Compared for instance with ladybird beetles which as adults feed almost exclusively on aphids, spiders are not very efficient in controlling a specific pest. Spiders are for the most part generalist predators and prey, like most beneficial insects on any kind of insect they are able to catch. In crops like cranberries, both hunting spiders and web spinners ( cribellates ) contribute to the reduction of aphids flies, gnats, caterpillars and other harmful insects. Most orb weavers ( Araneidae ) are unable to catch moths easily because of the moth's ability to shed the scales on their wings. While the webs of most Araneids are designed to catch air-borne and jumping insects, the webs of Segestriidae and Amaurobiidae, commonly found in low vegetation, adhere to the ground and trap crawling insects The web of some Theriidae, eg. Steatoda species will catch both types of prey. The random mass of threads above captures for example flies, while the sticky holding lines haul the crawlers off the ground. The Black Widow ( Latrodectus mactans ) also belongs to this family.
Compared with web-dwelling spiders, individual hunters are not very efficient predators and do not catch nearly as much prey as they consume when fed in captivity. Their significance as predators stems from the fact that hunting spiders occur in vast numbers in small areas and as a group destroy great quantities of insects. Together with ground beetles ( Carabidae ), and rove beetles ( Staphylinidae ), wolfspiders ( Lycosidae ) for instance are effective pest control agents and like beneficial insects are adversely affected by insecticides.
List of species found in 1990.
© 1995 David Buchanan
