Two-spotted spider mite of Hemp

Hemp mites are called as two- spotted spider mites, Tetranychus urticae because they have two red spots on their thorax (Photo 1). Although these mites are very tiny (1/20 inch long, oval shaped and  brownish to yellowish in color), they cause serious damage to hemp plants by sucking juice from their leaves and succulent twigs. Heavily infested leaves generally turn yellow, appear mottled and speckled, and eventually they dry and drop off the plants.  These severely damaged plants generally remain stunted and cannot produce new leaves that in turn reduces crop yield. In addition to direct feeding damage, two-spotted spider mites produce webbing on the leaves and small branches with the fine strands that reduces the quality and yield of hemp. Thus the damage caused by two-spotted spider mites can cause in millions of dollars loss to hemp industry.

Two-spotted spider mite, Tetranychus urticae
Photo 1. Two-spotted spider mite (Tetranychus urticae)

Life cycle of two-spotted spider mites

Two- spotted mites generally overwinter as mated females. When temperature is optimum, these females lay hundreds of translucent and spherical eggs on the leaves of their host plants. Then these eggs hatch into small larvae that become adults within 7 days. Under favorable climatic conditions, two-spotted spider mites can complete one generation within 2-3 weeks.

Predatory mites, Amblyseius andersoni.

Currently predatory mites Amblyseius andersoni are used as biocontrol agents for the organic control of two- spotted spider mites in the hemp production. This is because Amblyseius andersoni are very active in finding and feeding on two-spotted spider mites. Amblyseius andersoni can survive, reproduce and develop at a wide range of temperature between 6-40°C (43-104°F) in the greenhouses and growth houses. While feeding on the two-spotted spider mites, predatory Amblyseius andersoni mites continuously reproduce by laying oval shaped and colorless eggs. These eggs hatch into small mites (larvae/ nymphs) and become adults within 2-3 weeks. During development and after becoming adults, these predatory mites continuously feed on the eggs, nymphs and adults two- spotted spider mites.

When and how Amblyseius andersoni mites should be released?

  • Amblyseius andersoni mites are supplied as adults in a container containing a mixture of bran or vermiculite.
  • Hang these containers to plants at every 5-12 feet in the greenhouses or growth houses/chambers.
  • Because Amblyseius andersoni mites are very active, they will walkout themselves out of container and disseminate throughout the greenhouse to seek various stages of two-spotted spider mites as their food.
  • As a preventive control measure, Amblyseius andersoni mites should be released when there is a very low population of two- spotted spider mites.
  • As a curative measure, Amblyseius andersoni mites should be released when there is a very high population of two- spotted spider mites.
  • Release Amblyseius andersoni mites when temperature and relative humidity is between 6- 40°C (43-104°F) and 40-60%, respectively.

How does Amblyseius andersoni kill two-spotted spider mites?

After application in the greenhouses or nurseries, Amblyseius andersoni mites immediately start voraciously feeding on all the different stages of two-spotted spider mites. 

How many Amblyseius andersoni mites should be released?

For the effective control of two- spotted spider mites, it is recommended to follow the schedule given below. 

  • Release 4-5 predatory mites/square feet (0.1 sq. meter) area bi-weekly, 2-3 times.

Whiteflies and two-spotted spider mites

When vegetables or ornamentals are grown in the greenhouse, they are simultaneously attacked by two most economically important pests like greenhouse whiteflies, Trialeurodes vaporariorum (Photo 1) and two-spotted spider mites,Tetranychus urticae (Photo 2). This poses a serious challenge to control both of these pests at the same time using a single chemical pesticide because these two pests are taxonomically and physiologically different from each other and therefore, they can react differently to specific pesticides.

Adult whitefly
Photo 1. An adult of whitefly
Two-spotted spider mite, Tetranychus urticae
Photo 2. Two-spotted spider mite (Tetranychus urticae)

Also, the use of chemical pesticides are currently restricted in the greenhouses because of their detrimental effects on humans and the environment. Therefore, the best option to control both the whiteflies and spider mites simultaneously in the greenhouses is to release beneficial predatory mite, Amblyseius swirskii because they are easy to release, do not cause any harm to either humans or the environment and most importantly, they can feed on both the whiteflies and spider mites simultaneously.

Damage caused by greenhouse whiteflies

Both the mature and immature stages of greenhouse whiteflies cause damage to the leaves of many vegetables, ornamental plants grown in the greenhouses. Whiteflies generally suck juice from the underside of leaves by using their piercing and sucking types of mouthparts (Photo 3). This type of feeding damage generally causes yellowing and drying of leaves.  While feeding, whiteflies also secrete honeydew that stimulates the growth of black sooty mold on the surface of leaves. This black sooty mold affects the process of photosynthesis, reduces the quality of the produce and aesthetic value of many ornamental plants. Whiteflies also transmit different types of plant viruses that can reduce yields of many vegetables and the quality of ornamentals.

The Whiteflies
Photo 3. Whiteflies feeding on the underside of a leaf

Damage caused by two-spotted spider mites

Two-spotted spider mites suck juice from leaves, succulent twigs and stems of many economically important crops like cucumber, eggplant, pepper, strawberries and tomatoes. Heavily infested leaves become yellow, mottled and speckled. Severely speckled leaves also affect the process of photosynthesis that in turn reduces plant’s ability to make its own food. Severely infested leaves dry and drop off the plants prematurally that leads to sever yield loss or the plant death. Furthermore, spider mites also produce webbing on the leaves and small branches with the fine strands (Photo 4) that reduces aesthetic value of many ornamentals such as azalea, camellia, hollies, ligustrum, roses and viburnum. Thus the damage caused by two-spotted spider mites can cause in millions of dollars loss to greenhouse industry.

Spider mite web
Photo 4. Web spinned by two-spotted spider mites that seen as small brown dots in the web

What are predatory Amblyseius swirskii mites?

Amblyseius swirskii are pear-shaped tiny predatory mites with four pairs of legs. Both adults and nymphs of these mites feed on the different stages of both the whiteflies and two-spotted spider mites.

How predatory Amblyseius swirskii mites can control whiteflies and two-spotted spider mites?

Amblyseius swirskii mites are commercially available as mixed stages of adults and larvae. When these mites are released in the greenhouse, they quickly disperse quickly in the greenhouses and seek their hosts including different stages of whiteflies and two-spotted spider mites and start feeding voraciously on them and eliminate their populations quickly and simultaneously in the greenhouses.

How many Amblyseius swirskii mites should be released?

For the effective control of whiteflies and two-spotted spider mites, release over 5000 Amblyseius swirskii mites per acre 2-3 times on a bi-weekly basis. These warm adapted predatory mites perform better when they are released at optimum temperature mentioned above but their activity will reduce if released at temperature lower than 20°C (68°F). These mites will not survive if they are released at really cold and frosty temperatures.

Damage caused by the western flower thrips

The western flower thrips (Frankliniella occidentalis) are one of the most damaging pests of many crops, ornamental plants, field crops and fruits. Both adults and nymphs of mites feed directly on the young succulent leaves, flowers and small fruits using their rasping and sucking types of mouthparts. Feeding damage caused by thrips generally leaves scars (stippling) on the buds, leaves, flowers, fruits and twigs. The symptoms caused by thrips include stunted plant growth, curling/folding (Photo 1) and discoloration of leaves, and flowers. These damaged plant parts can drop prematurely. Also, the scattered thrip feces on the leaves and flowers can reduce aesthetic value of ornamental plants causing a tremendous economic loss to the greenhouse industry. The western flower thrips are also known to transfer plant viruses that can cause severe yield losses to many crops and aesthetic value of many ornamental plants.

Folding of leaves due to thrips damage

Photo 1. Curled leaves due to thrips damage

Identification of the western flower thrips

The western flower thrips are small slender bodied insects with brownish colored body and yellowish hair-fringed wings. The babies of the western flower thrips are called as nymphs (Photo 2) that look like their parents but they are wingless. Both adults and nymphs of thrips have rasping and sucking types of mouthparts that they use for puncturing tissues and sucking the cell sap (juice) from the punctured tissues.

Thrips

Photo 2. A nymph of the Western flower thrips feeding on leaf tissue.

Life cycle of the western flower thrips

The western flower thrips can reproduce sexually or asexually and their females generally insert eggs into leaf or bud tissues. Eggs hatch into tiny first stage larvae that immediately starts feeding on plant tissue. While feeding, young larvae molt into second stages that continue feeding on the leaf tissues until they become mature. The matured larvae then enter into the non-feeding pre-pupal stages that drop off to the soil for pupation. Adult thrips emerge from these pupae, then females met and begin laying eggs and life cycle continues. Depending upon temperature, egg to egg life cycle is completed within 10 to 20 days and under warm weather conditions, thrips can complete more than 10 generations in a year.

Biological control of the western flower thrips, Frankliniella occidentalis

Simultaneous application of both beneficial entomopathogenic nematodes like Heterorhabditis bacteriophora (see below) and predatory mites like Amblyseius (Neoseiulus) cucumeris (see below) is a very effective method of controlling the western flower thrips. This is because the predatory mites when applied to the surface of the leaves, they will feed on all the immature stages of thrips and when Heterorhabditis bacteriophora nematodes simultaneously applied to the surface of the soil, they will find and feed on all the pre-pupal and pupal stages of the thrips. This means both nematodes and predatory mites when applied at the same time, they will disrupt the life cycle of the thrips by killing their both immature and mature stages and pupae and stop the future reproduction of the western flower thrips.  

What are Heterorhabditis bacteriophora nematodes?

Beneficial Heterorhabditis bacteriophora nematodes (Photo 3) are tiny roundworms that use “cruise foraging” strategy in which their infective juveniles actively move to find their hosts like pre-pupal and pupal stages of the western flower thrips throughout the soil profile and feed on them.

Beneficial entomopathogenic Heterorhabditis bacteriophora nematodes

Photo 3. An infective juvenile of Heterorhabditis bacteriophora nematode.

How do Heterorhabditis bacteriophora nematodes kill thrips?

When the infective juveniles of Heterorhabditis bacteriophora are applied to the soil surface, they start searching for their insect hosts. Once they find their host, the nematode infective juveniles will penetrate into the host’s body cavity via natural openings like mouth anus and breathing pores. Then they enter into host body cavity and release their symbiotic bacteria, Photorhabdus luminescens in the insect blood. In the blood, multiplying nematode-bacterium complex causes septicemia and kill their insect host like pupae of thrips usually within 24-48 hours after infection.

How many Heterorhabditis bacteriophora nematodes should be applied to kill thrips?

The optimum rate for the effective control of thrips is 23,000 H. bacteriophora nematodes per square foot area. Use following table to apply correct numbers of nematodes per square foot area for the effective control of the western flower thrips.   

Area  in sq. ft.       = Number of nematodes required

                         1sqft = 23,000 nematodes

                     100 sqft = 2,300,000 nematodes

                      500 sqft = 11,500,000 nematodes

                     1,000 sqft = 23,000,000 nematodes

      43,560 sqft (1 Acre) = 1,000,000,000 nematodes

What are Predatory, Amblyseius (Neoseiulus) cucumeris mites?

Predatory, Amblyseius (Neoseiulus) cucumeris are very small about 0.5 mm in size, pear shaped and tan colored mites that are currently used as beneficial biological control agents for the control of different species of thrips including the western flower thrips. These mites are active feeders of thrips and keep feeding on them  until they die.

How many Predatory, Amblyseius (Neoseiulus) cucumeris mites should be applied to kill thrips?

The predatory mite, Neoseiulus cucumeris can be used both as both preventive and curative control measures for the thrips. As a preventive treatment, mites can be released even before the incidence of thrips in your garden, as these mites can survive by feeding on pollen until they can find their real food, the thrips. As a curative control measure, these predatory mites should be released when there is a high population of thrips present on the plants in your garden.

  1. For low incidence of thrips or as preventive control, release 50-60 mites per square meter area.
  2. For medium incidence of thrips, release about 100 mites per square meter area.
  3. For high incidence of thrips or as curative control strategy, release more than 100 mites per square meter area.

How to release Neoseiulus cucumeris mites?

These mites are sold in bulk quantity in a bran flake substrate that can be evenly spread over the foliage of crop or over the seedlings before transplanting.  When these predatory mites are supplied in small packages, open the boxes and shake them for even distribution of mites on the surface of plants in the garden.

References

  1. Ebssa, L., Borgemeister, C. and Poehling, H-M. 2006. Simultaneous application of entomopathogenic nematodes and predatory mites to control western flower thrips Frankliniella occidentalis. Biological Control 39: 66-74.

Damage caused by strawberry root weevils

Strawberry root weevils (Otiorhynchus ovatus) cause serious damage to strawberries. The adults of strawberry root weevil mostly feed on the edges of strawberry leaves that gives typical notched appearance but their grubs feed by tunnelling the crowns and roots of strawberries. The strawberry root weevils overwinter as grubs in the soil. When temperature warms up early in the spring, these overwintering grubs resume feeding on the strawberry roots and crowns. The most damage is caused from March through June.The main symptoms of damage caused by grubs of strawberry weevils include root pruning, weak and stunted plant growth, and dying of plants. This type of damage reduces the yield of strawberries.

Identification of strawberry root weevils

Adult of the strawberry root weevils are reddish brown to black in color with rows of pits on the forewings. These weevils cannot fly because their forewings are fused together but they can walk very fast and find their host plants.These weevils have long antennae. The strawberry root weevils generally lay small, whitish brown and spherical eggs that hatch into small creamy white colored grubs with tanned brown head capsule. Mature grubs are legless,‘C’ shaped and about 12 mm long. The pupae of the strawberry root weevil are also creamy white in color.

Life cycle of strawberry root weevils

The strawberry root weevils overwinter as grubs in the soil. These overwintering grubs become active when temperature start warming up early in the spring and start feeding on the strawberry roots and crowns again. While feeding, grubs become mature and then pupate in the soil. Adult weevils then emerge from the pupae and start feeding on the strawberry leaves. Females generally lay eggs in cluster at the base of plants in the soil. After hatching from eggs, young grubs continue feeding on the roots until September, then overwinter and life cycle continues. The strawberry root weevils commonly complete one generation in a year.   

Biological control of strawberry weevils with Steinernema carpocapsae

Beneficial entomopathogenic nematodes called Steinernema carpocapsae (Photo 1) can be successfully used as alternatives to chemical pesticides for controlling strawberry weevils. Steinernema carpocapsae nematodes are easy to apply and they are known kill both the grubs and pupae of the strawberry weevils within 48 hours after their application. Thus they can stop the emergence of future generation of adults of strawberry weevils.

When Steinernema carpocapsae nematodes are applied on the strawberry beds, they enter in the soil where they search, infect and kill all the soil-dwelling grubs and pupae of strawberry weevils. Steinernema carpocapsae nematodes generally enter into the body cavity of grubs and pupae of strawberry weevils via natural openings like anus, mouth and spiracles. Once in the body cavity, nematodes release symbiotic bacteria called Xenorhabdus nematophila in the blood where th bacteria multiply quickly and cause septicemia and kill grub or pupa within 48 hours of infection. Thus the killing of both larvae and pupae of strawberry weevils by nematodes completely stops the emergence of future generation of adult weevils.

Steinernema carpocapsae nematodes

Photo 1. Steinernema carpocapsae nematodes

How to apply Steinernema carpocapsae nematodes?

To target both grub and pupal stages of strawberry weevils, use watering can and a knapsack backpack sprayer for spraying nematodes on a small home garden area and on the large areas, respectively. Since nematodes need a film water for their easy movement in the soil, irrigate areas to be treated before and after application of nematodes so that the optimum level of moisture will be maintained in the soil. Also, apply nematodes either early in the morning or late in the evening to avoid their exposure to UV radiation as its short exposure can kill nematodes instantly.

How many Steinernema carpocapsae nematodes should be applied?

The optimum rate for the effective control of fleas is 23,000 Steinernema carpocapsae nematodes per square foot area. Use following table to apply correct numbers of nematodes based on square foot area.   

Area  in sq. ft.       = Number of nematodes required

                         1sqft = 23,000 nematodes

                     100 sqft = 2,300,000 nematodes

                      500 sqft = 11,500,000 nematodes

                     1,000 sqft = 23,000,000 nematodes

      43,560 sqft (1 Acre) = 1,000,000,000 nematodes

 

What are two-spotted spider mites?

Adults of two-spotted mites (Tetranychus urticae) are about 1/20 inch long, oval shaped with four pairs of legs and two red spots on the thorax (Photo 1). These mites can be brownish to yellowish in color that may change with the season (Photo 1). Two-spotted mites lay translucent and spherical eggs. These eggs hatch into small larvae that resemble to their parents but they have only three pairs of legs. These larvae then turn into nymphs that then pass through two different stages; the first stage is called protonymph and second stage is called deutonymph. Like their parents, both nymphal stages have four pairs of legs. Two-spotted mites overwinter as mated females (quiescent stages) under the tree bark and/or plant debris on the ground. Early in the spring, mated females lay hundreds of eggs on the leaves of host plants. Eggs hatch within 2-3 days into small larvae that molt into protonymph and then molt into deutonymph within 5 days. The deutonymphs then molt into adults within 2 day. Thus, under favorable climatic conditions, spider mites can complete their life cycle within 5- 20 days.

Two-spotted spider mite, Tetranychus urticae

Photo 1. Two-spotted spider mite (Tetranychus urticae)

Damage caused by two-spotted spider mites

Two-spotted spider mites are one of the most damaging pests of many crops and ornamental plants. Two-spotted spider mites suck cell sap (juice) from leaves and succulent twigs of their host plants. Heavy feeding injury caused by mites generally give yellow, mottled and speckled (Photo 2) appearances to leaves.  Severe feeding also affects photosynthesis that in turn reduces plant’s ability to make its own food. Infested leaves then dry and drop off the plants prematurally that leads to the death of plant or sever yield loss. The most economically important plant species damaged by two-spotted spider mites included beans, canola, cotton, citrus, cucumber, eggplant, melon, peanut, pepper, strawberries, potato, soybean and tomato. While feeding, spider mites also produce webbing on the leaves and small branches with the fine strands (Photo 3) that reduces aesthetic value of many ornamental plants including azalea, camellia, hollies, ligustrum, roses and viburnum. Thus the damage caused by two-spotted spider mites can cause in millions of dollars loss to agricultural, horticultural and ornamental industries.

Speckled appearance of leaf due to feeding by spider mites

Photo 2. Speckled appearance of leaf caused due to feeding by two-spotted spider mites

Spider mite web

Photo 3. Web spinned by two-spotted spider mites. Note that the small brown dots in the web are mites

Control of two-spotted spider mites with predatory mite, Amblyseius swirskii

Amblyseius swirskii are pear-shaped tiny predatory mites with four pairs of legs. Both adults and nymphs of these mites feed on two-spotted spider mites and develop through three developmental stages and then become adults. These mites are ideal to use for the biological control of two-spotted spider mites because the optimum temperature [between 20°C (68°F) and 29°C (84.2°F)] required for the normal reproduction and development of Amblyseius swirskii is always maintained in the greenhouses for the optimum growth of plants.

How predatory mites can control two-spotted spider mites?

Amblyseius swirskii mites are commercially available as mixed stages of adults and larvae and are currently used as a biological control agent for controlling two-spotted spider mites. Since Amblyseius swirskii mites are very active, they can disperse quickly after their release in the greenhouses find the hot spots of two-spotted spider mites. As both the larvae and adults of Amblyseius swirskii known to feed voraciously on all the stages of spider mites, they can eliminate populations of two-spotted spider mites quickly.  

How many predatory mites should be released?  

For the effective control of two-spotted spider mites, release over 5000 predatory mites per acre 2-3 times on a bi-weekly basis. Predatory mites can be released as a preventive measure before the occurrence of pests or as a curative measure after the incidence of pest mites. These warm adapted predatory mites perform better when they are released at optimum temperature mentioned above. The activity of Amblyseius swirskii mites will be reduced if they are released under cooler conditions. Also, they will not survive under really cold and frosty temperatures.

 

Japanese beetle (Popillia japonica) adults are oval shaped, 1.5-inch long and shiny metallic-green in color (Photo 1). The mature grubs of Japanese beetles are whitish in color with yellowish-brown head capsule and three pairs of thoracic legs. When disturbed, grubs form typical C- shape (Photo 2).  Pupae of Japanese beetles are pale creamy to greenish in color.

Japanese beetle feeding on Foliage

Photo 1. An adult of Japanese beetle

Japanese beetle grubs

Photo 2. C- shaped Japanese beetle grubs

Japanese beetles are serious pests of many plant species including turfgrasses. Japanese beetle grubs mainly cause feeding damage to roots but their adults cause feeding damage to flowers (Photo 3), fruits, leaves and twigs.  Symptoms of feeding damage caused by grubs include formation of localized patches of dead turfgrass in the yards and golf course greens due to severely pruned roots by grubs. As the feeding activity of grub progresses, the small patches of dead turf join together and form the large patches. Due to severely pruned root system, dead turf becomes very it loose and can be easily picked up with hand like a piece of carpet. The most convincing sign of presence of Japanese beetle grubs in the lawn is that the infested areas of lawn is dug by raccoons, skunks or birds that are looking for grubs to feed on them. In contrast, adult Japanese beetles voraciously feed and destroys leaves, flowers and fruits. Heavy infestation of Japanese beetles can completely skeletonize leaves and eventually defoliate the plants.  

A rose flower damaged by Japanese beetle

Photo 3. Japanese beetle adults are feeding on a rose flower

Life cycle of Japanese beetles is usually completed in a year. Briefly, adults of Japanese beetle emerge from pupae in the late June through July and start feeding on leaves, flowers and fruits of different plants. The mated females then lay eggs about 1-2 inches deep in the soil mostly near to the roots of grass. These eggs hatch early in the August into first instar grubs that start feeding on grass roots. While feeding, these grubs complete second and third instars from August through October. In October, as temperature starts cooling down, third instar grubs will move deep into soil for overwintering. During winter season (November through March), these grubs become immobile and stop feeding.  Early in the spring, when temperature begins warming up, overwintering grubs will move back into the turf root-zone and resume feeding on turf roots until they become mature. These matured grubs will then pupate in the soil early in the June. The emergence of adults from pupae begins from the end of June through the end of July, females will then lay eggs and life cycle continues.

The emergence of adults of Japanese beetles have already started at the end of June and it will continue throughout July. Therefore, now is the best time to stop emergence of adults of Japanese beetle by targeting and killing their grubs and pupae in the soil.

The best organic option to kill both grubs and pupae of Japanese beetles is to apply beneficial entomopathogenic nematodes in the home and recreational lawns, and golf courses. Since some mature grubs are trying to pupate and adults are trying to emerge from pupae, both grubs and pupae are easy targets for beneficial entomopathogenic nematodes like Heterorhabditis bacteriophora (Photo 4) and Steinernema carpocapsae (Photo 5).

Beneficial entomopathogenic Heterorhabditis bacteriophora nematodes

Photo 4. An infective juveniles of beneficial entomopathogenic Heterorhabditis bacteriophora nematode used for killing Japanese beetle grubs

Steinernema carpocapsae nematodes

Photo 5. Infective Juveniles of Steinernema carpocapsae nematodes

Both of Heterorhabditis bacteriophora and Steinernema carpocapsae nematodes can kill both grubs and pupae of Japanese beetles within 48 hours after their application. Briefly, when the infective juveniles of these beneficial entomopathogenic nematodes applied individually or together to the soil surface or thatch layer, they will move in the soil and find Japanese beetle grubs or pupae. Once they find a grub and/or pupa, they will enter into their body cavities through their mouth, anus and spiracles. In the insect body cavity, S. carpocapsae will release symbiotic bacteria called Xenorhabdus nematophila or H. bacteriophora will release symbiotic bacteria called Photorhabdus luminescens from their gut in the insect blood. Once in the blood, bacteria will multiply rapidly, cause septicemia and kill Japanese beetle grubs or pupae usually within 48 hours after infection.

For the effective control of Japanese beetle grubs and pupae, apply beneficial entomopathogenic nematodes, H. bacteriophora and/ or S. carpocapsae at the rate of 23000 nematodes per square foot area to the soil surface or thatch layer using either water cans (Photo 6) or traditional knapsack sprayers. The beneficial nematodes are generally susceptible to UV radiation. Therefore, it is recommended to apply nematodes late in the evenings. Since nematodes need a film of water for their easy movement in the soil, apply them when there is enough moisture present in the soil. To maintain optimum moisture level in the targeted areas, applying irrigation before and after application of nematodes so that irrigation water will provide film of water for their movement and wash them from grass blades into soil.

 

Beneficial nematode application with water can

Photo 6. Use watering can for the application of beneficial nematodes

Crop Pollination in greenhouses

Bumblebees, Bombus impatiens (Photo 1) have been used for pollination of many crops including cucumbers, peppers, squash, tomatoes and several fruits like apple, blackberry, blueberry and pear (Photo 2) that require the additional help for setting of fruits. Plants grown in the organic gardens are naturally pollinated by several different kinds insects including honey bees, butterflies, moths and bumblebees. However, in the closed structures like greenhouses, bumblebees are generally released to pollinate vegetables and other crops.  Bumblebees are generally prefered over other pollinators including honeybee because they are bigger in size and faster than other pollinators. Because of their bigger size, they can carry large amounts of pollen and easily come in contact with stamens and pistils. Bumblebees, (Bombus impatiens) hives are commercially available and sold in cardboard boxes with a food source. The best time to introduce bumblebees into the greenhouses is shortly after first appearance of flowers as proper pollination is required for optimum fruit set and production. The activity of bumblebees is generally influenced by temperature as they are very active when temperature is cool but as temperature increases their activity also reduces. The ideal temperature for the optimum activity of bumblebees and proper growth of crops in the greenhouses is between 12°C and 26°C (53.6°F and 78.80°F). When introducing bumblebee hives into the greenhouses, make sure they are placed under shade during hot periods of the day. Bumblebees are easy to release in the greenhouses. After receiving boxes of hives allow them to acclimatize for a couple of hours under shade and then open the door and walk away.  Immediately after opening door, bumblebees will start flying from flower to flower to collect pollen for feeding their babies and simultaneously they will pollinate these flowers. How many bumblebee hives required depends on the numbers of different vegetables need extra help in pollination, numbers of flowers appearing on the plants and size of greenhouse.  Bumblebees (Bombus impatiens) hives are sold in four different types including:

  1. Standard hive with 75 worker bees that are enough for pollinating plants for minimum of 12 weeks.
  2. Medium hive with 55 worker bees that are enough for pollinating flowers for minimum of 6 weeks.
  3. Outdoor hive with 75 worker bees that are enough for pollinating flowers for minimum of 6 weeks.
  4. Four- pack hive containing 4 single colonies each with 75 worker bees that are enough for pollinating flowers for minimum of 6 weeks.

A colony of bumblebees can pollinate about 1000 to 3000 square meter tomato crop for 6-8 weeks and 3000 to 5000 square meter sweet pepper crop during 8 weeks.

Bumblebee polinating dill flowers

Photo 1. Bumblebee on dill plant flowers.

Bumblebees used for pollination of fruit crops

Photo 2. Bumblebee on pear flowers

Damage caused by fleas (Ctenocephalides felis)

Fleas are small wingless insect pests of dogs, cats, humans and rats. Since fleas do not have wings, they can disseminate only by jumping from one host to another host. Fleas use their piercing and sucking type of mouthparts for sucking of blood from their hosts like dogs and cats. In addition, fleas transmit diseases like flea allergy dermatitis to dogs (Photo 1). This disease causes dog hot spots that are basically infected circular patches of skin. Since these hot spots are very itchy, dogs continuously keep them scratching and biting, and turning them into big wounds. Only adult fleas are capable of feeding on the host blood, transmitting diseases and causing direct damage to their hosts whereas their larvae are not harmful as they cannot feed on host’s blood or transmit diseases.

Dogs are the most susceptible hosts of the fleas

Photo 1. Dogs are good hosts of fleas

 

Life cycle of fleas

The life cycle of fleas is very simple. They develop through four different developmental stages including eggs, larva, pupa and adult. Fleas lay eggs on dog’s body but these eggs fall off on the ground where dog usually rests or sleeps. Eggs hatch within 1-2 weeks into small larvae and begin feeding on organic matter. While feeding on the organic matter, larvae develop through three larval stages. The matured larvae then pupate inside the silken cocoons in soil.  Adult fleas generally use cues like carbon dioxide, heat and vibration from their hosts to emerge from cocoons. The emerged adult fleas then hop on the host’s body whenever their hosts are visiting their resting and sleeping place. Once on the host body, fleas feed on the host’s blood, mate and lay eggs. Eggs fall off of host on the ground and life cycle continues. Fleas complete several generations during summer through the fall season and then overwinter as larvae and pupae in the soil mostly at the resting place of their host animals like dogs.  

Organic control of fleas with Steinernema carpocapsae nematodes

Since fleas are serious pests of dogs and cats, timely control of population of fleas is essential to protect dogs and cats from diseases transmitted by fleas.. Application of chemical pesticides on the resting places of dogs to control fleas can not be a safe option because of their detrimental effects on dogs, cats and owners of pets.. Currently, beneficial entomopathogenic Steinernema carpocapsae nematodes are used as alternatives to chemical pesticides for controlling fleas. This is because these nematodes are easy to apply and they can kill both larval and pupal stages of fleas with 48 hours after their application.

Briefly, when Steinernema carpocapsae nematodes (Photo 2) applied on the resting and sleeping area of dogs, they search, infect and kill all the soil-dwelling larval and pupal of fleas. Once applied nematodes come in contact with either larvae or pupae of  fleas, they enter into their body cavity through the natural openings like anus, mouth and spiracles and release symbiotic bacteria (Xenorhabdus nematophila) in the blood. In the blood, bacteria multiply quickly, cause septicemia and kill larva or pupa within 48 hours of infection that in turn completely stops the emergence of next generation of fleas.

Steinernema carpocapsae nematodes

Photo 3. Infective Juveniles of Steinernema carpocapsae nematodes

To target both larval and pupal stages of fleas, apply Steinernema carpocapsae nematodes using watering can (Photo 3) on the areas where dog generally rests or sleeps. The optimum rate for the effective control of fleas is 23,000 nematodes per square foot area. As nematodes need a film water for their easy movement in the soil, make sure that the treatment areas are irrigated before and after application of nematodes to maintain the optimum level of moisture in the soil. Also make sure that nematodes are applied either early in the morning or late in the evening to their exposure to UV radiation as its short exposure can kill nematodes instantly.

Beneficial nematode application with water can

Photo 7. Watering can for the application of beneficial nematodes

 

Use following table to apply correct numbers of nematodes to treat specific size of area for the effective control of fleas.   

         Area  in sq. ft. = Number of nematodes required

                         1sqft = 23,000 nematodes

                     100 sqft = 2,300,000 nematodes

                      500 sqft = 11,500,000 nematodes

                     1,000 sqft = 23,000,000 nematodes

      43,560 sqft (1 Acre) = 1,000,000,000 nematodes

Organic control of two spotted spider mites with predatory mite, Amblyseius andersoni

Two spotted spider mites (Tetranychus urticae) are serious pests of many greenhouse plants and field crops but they can be organically controlled by using predatory mites called Amblyseius andersoni.

What are two spotted spider mites?

Adults of two spotted spider mites, Tetranychus urticae (Photo 1) are tiny, oval shaped mites with four pairs of legs. As name implies, they have two red spots on their body. In their life cycle there are two immature stages including larvae and nymphs exist.  Both larvae and nymphs resemble to their parents but larvae possess three pairs of legs whereas nymphs have four pairs of legs.

Two-spotted spider mite, Tetranychus urticae

Photo 1. Two-spotted spider mite (Tetranychus urticae)

 

Damage caused by two spotted spider mites

Two spotted spider mites suck cell sap (juice) from leaves and succulent twigs many field crops (cotton, peanut, potato and soybean), fruits (citrus and apples), vegetables (beans, cucumber, eggplant, pepper and tomato) and ornamental plants (azalea, camellia, hollies, ligustrum, roses and viburnum). The major symptoms of feeding injuries caused by two spotted spider mites include mottled and speckled appearance of leaves (Photo 2), yellowing and desiccation of leaves, webbing on the leaves (Photo 2) and small branches with the fine strands and premature death of host plants. Heavy infestation of two spotted spider mites also affects the photosynthesis that in turn reduces plant’s ability to make its own food. Severely infested plants can die prematurely.

Pest mites can move from one leaf to other by spinning a web

Photo 2. Webbing by two spotted spider mites

 

Predatory mite, Amblyseius andersoni are currently used for the organic control of two spotted spider mites.

What are Amblyseius andersoni?

Predatory mites, Amblyseius andersoni are currently used as beneficial mites to control two spotted spider mites that are pests of many field crops, fruits, vegetables and ornamentals.

Adults: Adults of Amblyseius andersoni are beige colored tiny and mites that are about 1.0 mm in size.

Eggs: Eggs of Amblyseius andersoni are oval shaped and colorless.

Larvae: Newly hatched mites are called as larvae that resemble to their parents but they have only three pairs of legs.

Nymphs: Next stage of larvae are called nymphs. Nymphs pass through two successive stages called protonymphs and deutonymphs. Both of these stages look like their parents. Like their parents, they also have four pairs of legs.

Life cycle: Overwintering predatory Amblyseius andersoni mites generally become active from January onward and remain active throughout the growing season. During growing season female mites lay eggs onto leaf hairs. These eggs hatch into tiny larvae that develop into two successive nymphal stages known as protonymphs and deutonymphs. Like their parents, both nymphal stages feed on the eggs, nymphs and adults of pest mites like two spotted spider mites. Amblyseius andersoni can survive, reproduce and develop at a wide range of temperature between 6-40°C (43-104°F).

Why Amblyseius andersoni mites are used for the organic control of two spotted spider mites?

Because Amblyseius andersoni voraciously feed on eggs, nymphs and adults of two spotted spider mites. These mites are not harmful to plants, animals and pets.   

How Amblyseius andersoni will kill two spotted spider mites?

  1. After application in the greenhouses or nurseries, Amblyseius andersoni mites immediately start looking for their prey such as two spotted spider mites.
  2. Once Amblyseius andersoni mites come across colony two spotted spider mites, they will start munching on the eggs, nymphs and adults of two spotted spider mites.

When and how Amblyseius andersoni mites should be released?

  • Amblyseius andersoni mites are supplied as adults mixed in a container containing a mixture of bran and vermiculite.
  • Hang containers to plants at every 5-12 feet in the garden or greenhouses.
  • Because Amblyseius andersoni mites are very active, they will walkout themselves out of container and disseminate throughout the garden or greenhouse to seek their food, two spotted spider mites.
  • As a preventive control measure Amblyseius andersoni mites should be released when there is a very low population of two spotted spider mites.
  • As a curative measure Amblyseius andersoni mites should be released when there is a very high population of two spotted spider mites.
  • Release Amblyseius andersoni mites when temperature and relative humidity is between 6- 40°C (43-104°F) and 40-60%, respectively.

How many Amblyseius andersoni mites should be released?

For effective control of two spotted spider mites, it is recommended to follow schedule below.

  • Release 4-5 predatory mites/square feet (0.1 sq. meter) area bi-weekly, 2-3 times.

What is organic insect pest control?

Organic pest control is a method in which beneficial bugs such as parasitic wasps, predatory insects and mites, and plant-based products are used for the control of insect pests of various crops. These biological and plant-based products are not harmful to the humans, pets, wild animals or the environment.

What are Aphids?

Aphids are very small pear-shaped, soft-bodied insects and about 1 to 10 mm long with piercing and sucking types of mouthparts, and long antennae and legs.  Baby aphids are called as nymphs that look like their parents. There are over 4000 species of aphids have been described from all over the world but they differ in color from black, brown, red (Photo 1) green (Photo 2), and pink in color. Both adults and nymphs have two tubular structures called as cornicles that are projected backward out of posterior end of their bodies. These cornicles are used for the excretion of defensive fluids.

Aphids feeding on a host plant

Photo1. Red colored aphid coloney

Green colored aphids

Photo 2. A coloney of green colored aphids feeding on a collard green leaf.

Damage caused by Aphids

Both adults and nymphs of aphids cause direct and indirect damages to many plant species such as ornamentals, field crops, greenhouse vegetables, fruits, weeds and grasses.

Direct damage

Both adults and nymphs of aphids directly feed on the succulent plant parts including buds, flowers, twigs and leaves using their piercing and sucking types of mouthparts. During direct feeding, aphids suck juice from tender plant tissues and cause symptoms like yellowing and curling of infested leaves (Photo 3), stunted plant growth and reduced crop yields.

 

Aphids suck cell sap from leaves and curling of infested leaves

Photo 3. Direct feeding by aphids cause symptoms like yellowing and curling of infested leaves

Indirect damage

While feeding on the leaves, aphids also secrete honeydew (Photo 4) that stimulates the growth of black sooty mold (Photo 5) on the plant surfaces and causes indirect damage to host plants. This black sooty mold (Photo 5) can cover entire leaf surface and affect the photosynthesis, a process used by plants to convert sunlight energy to chemical energy for the synthesis of their own food such as carbohydrates and proteins. The growth of the black sooty mold also reduces the quality of the produce and aesthetic value of many ornamental plants.

 

Aphids cause indirect damage to host leaves by secreting honeydew on the surface of leaves

Photo 4. Honeydew secreted by aphids on the leaves

 

Black sooty mold can cover entire leaf surface and affect the photosynthesis

Photo 5. Honeydew secreted by aphids stimulates the growth of black sooty mold on the plant surfaces and causes indirect damage to host plants

Transmission of virus diseases  

Aphids are vectors of many types of viruses that are transmitted by them from plant to plant. These viruses cause different types of diseases including bean common mosaic virus, carrot virus Y, celery mosaic virus, cucumber mosaic virus, lettuce mosaic virus, papaya ringspot virus, potato virus Y, turnip mosaic virus, watermelon mosaic virus and zucchini yellow mosaic virus. The major symptom by these virus diseases include yellowing and curling of leaves, reduced plant growth and crop yields.

Organic Control of Aphids with parasitic wasp, Aphidius colemani

What are Aphidius colemani wasps?

Aphidius colemani are tiny about 2-3 mm long wasps with slender body, yellowish abdomen and legs, black head and thorax, and whitish wings. Adults of Aphidius colemani (Photo 6) parasitize aphids by laying eggs with their ovipositor inside the body of aphids. Within aphid body, wasp eggs hatch into young larvae that start feeding on the body content of aphids, complete their development and pupate within the dead aphid bodies that then turn into crispy mummies. Within 14- 15 days, adult wasps emerge from mummies and then search for new aphid colonies to parasitize aphids. These wasps are now commercially produced and sold as aphid mummies containing wasp pupae with ready-to-emerge adult wasps.

Aphidius colemani are parasites of aphids

Photo 6. An Adult of parasitic wasp, Aphidius colemani

 

Why Aphidius colemani wasps are used for the organic control of aphids?

Parasitic wasp, Aphidius colemani are used for the organic control of aphids because they can control over 40 species of aphids by killing and feeding on them but they are harmful to the workers, pets, wild animals or the environment.

How does Aphidius colemani wasp kill aphids?

When adult Aphidius colemani wasps are released in the aphid infested organic gardens, greenhouses or fields, they start looking for a suitable size aphids for egg laying using their antennae. After finding an appropriate size aphid is found, female wasps lay eggs inside aphid’s body using their ovipositors. Eggs hatch within the aphid body into small young larvae that start feeding on the body content of aphid, complete their development, kill aphid and pupate within the dead mummified bodies of aphids (Photo 7).

Adults of waps will emerge from these aphid mummies

Photo 7. Mummified bodies of aphids along with an emerged adult wasp

 

How Aphidius colemani wasps should be released in organic gardens?

Aphidius colemani wasps are supplied as aphid mummies (Photo 7) with ready-to-emerge wasp adults (Photo 8). Adult wasps are allowed to emerge from aphid mummies inside the vials from which they can be easily released in the organic gardens or greenhouses by following two simple steps given below for the management of aphids.

An adult wasp emerging from an aphid mummy

Photo 8. An adult of parasitic wasp emerging form an aphid mummy.

  1. First,  take a vial containing wasp adults into the aphid infested garden, then open  the vial, hold it at 45o angle, then begin walking throughout the garden and while walking, keep tapping on the vial so that the adult wasps will escape from vial and spread evenly in the garden. Repeat this procedure until all wasps are escaped from the vials. If some mummies are still intact in the vial, then tie that opened vial to a branch of a plant so that adult wasps will escape from the vial as they emerge from mummies.  
  2. Second way to release wasps in the garden is to tie opened vial directly to a branch of a plant that is heavily infested (hotspots) with aphids for 3- 4 days. During this time, adult wasps will emerge from mummies, escape from the vial and seek aphids to lay eggs in their bodies. Repeat this wasp distribution method by moving and tying vial at different locations within the garden until all wasps are emerged from mummies and escaped in the garden.  

How many Aphidius colemani wasps should be released in organic gardens?

Preventive treatment: As a preventive treatment, release about 5 adult wasps per 100 square foot area weekly.

Curative treatment: As a curative treatment (in hot spot), release about 20- 25 adult wasps per 100 square foot area weekly.