August 30, 2012

News source: Kelly Allsup, 309-663-8306, kallsup@illinois.edu

News writer:

Silphium Weevil

URBANA - The 2012 Master Naturalist class has started, says Kelly Allsup, University of Illinois Extension Educator, Horticulture. A guided tour to study prairie plants highlights the most floriferous season in a prairie: Summer. Purple iron weed, mountain mint, Rattlesnake master, lead plant and four Silphium species were represented.

The compass plant, prairie dock, the cup flower and the whole leaf rosin weed send up a flowering stalk covered in multiple yellow-orange sunflowers held high above the tall grass prairie and are all part of the genus Silphium.

The compass plant (Silphium laciniatum) was in full flower. It gets its name from the north and south orientation for which the leaves are held. Original explorers used the plants to give them directions while walking through the prairie.

The prairie dock (Silphium terebinthinaceum) had sent up flower stalks in preparation of the floral display. The prairie dock boasted very large spade shaped leaves. The cup plant (Silphium perfoliatum) had spent flowers and is beneficial to the prairie because the leaves and stems clasp together like a cup collecting rain water.

The whole leaf rosin weed (Silphium integrifolium) had already flowered earlier in the growing season. Passing by the 5-6' tall flowering stalks, I noticed the flowers had been clipped and left to dangle on the plant or some flower heads had been severed completely from the flowering stalk. Resin was dripping from the cut stems and reflecting the sunlight. This characteristic is indicative to these prairie Silphiums. Of course my venture off the path to explore this phenomenon gave me the answer to the clipped flower heads. I had found a silphium weevil (Haplorhynchites aeneus) probably eating pollen. A weevil is a small beetle with an elongated snout. These are about ¼" long and brown-black. After copulation, the silphium weevil uses her mandible to cut the stem just below the base of the flower so that it hangs on the plant. The adult female then lays her eggs in the ray flowers of the silphium flower head. In about a week the developing larvae hatch and begin to feed on pollen and decaying plant tissue. Around October they fall to the soil to pupate (cocoon) for the winter. The silphiums are not harmed by the silphium weevil's tactics because they are perennial in nature.

August 30, 2012

News source: Kelly Allsup, 309-663-8306, kallsup@illinois.edu

News writer:

Katydid Hunters

URBANA - Katydid Hunters (Sphex pensylvanicus) have been congregating on your flowering plants to feed on pollen and nectar in the garden leaving gardeners to wonder if they should close the gate and go back into the house, states Kelly Allsup, University of Illinois Extension Educator, Horticulture. They are black wasps as big as a thumb and are also called Steel-blue cricket hunters for the iridescence of their black color. The solitary katydid hunter allows the gardener to work right beside them because they are not aggressive. However, their aggressiveness to katydids (Tettigonioidea Family) is what gives these wasps beneficial status.

In mid to late summer, wasps emerge and the female begins to burrow and tunnel in to the ground with the cooperation of her mouth and front legs. She has mated and is ready to lay eggs but first must hunt katydids for her young. Using her stinger, she immobilizes the katydid and drags it back to her nest where she lays her egg on the victim's abdomen. When the eggs hatch, the carnivorous larvae will have nutrition before they pupate in the ground throughout most of fall, winter and spring. This wasp has also demonstrated the ability to use tools by using materials around the nest to pat down the tunnel opening after she has filled it with soil. A female wants her young to be protected from the winter and predators.

University of Illinois Extension suggests avoiding chemical treatments to rid the garden of these beneficial insects unless the populations are large and damaging. Planting ground covers or using mulch may deter them from nesting around your home. If treatment is necessary, a homeowner can use a synthetic pyrethroid with active ingredients called bifenthrin, cyfluthrin, deltamethin or permethrin. These products are applied to the soil as a drench or sprinkled around the nest. Bifenthrin is the most leach resistant and will stay in the area it is applied.

August 30, 2012

News source: Kelly Allsup, 309-663-8306, kallsup@illinois.edu

News writer:

Damsel Bugs

URBANA - Without question when I visit a garden, I will approach the most beautiful flowering plant in the landscape and start inspecting it for garden pests and beneficial insects, states Kelly Allsup, University of Illinois Extension Educator, and Horticulture. My inquiry will cause me to turn over leaves, blow on flowers and look for insect feeding damage or droppings (frass). This manner of exploration has allowed me to spy upon a small slender dainty damsel bug (Nabis spp.) feeding on aphids on a flowering tobacco plant. I also saw them again feeding on squash bug eggs (Anais tristis) that had been laid on snapdragons and cucumbers. Upon close inspection, damsel bugs have a long beak they hold under their bodies and front legs like praying mantid (Tenodera aridifolia sinensi).

Damsel bugs use their front legs to grab their prey and then their beaks to pierce and suck juices from aphids, small caterpillars, leaf hoppers, thrips, beetle larvae, insect eggs and some beneficial insects. Most can be found in sunny locations of the garden from mid-June to mid-August. Damsel bugs overwinter in vegetation and lay their eggs in plant tissue. The nymphs look like the adults but do not have wings. Nymphs and adults prey on garden pests. Birds attracted to the garden will feed on the damsel bugs.

University of Illinois suggests attracting beneficial insects by planting an insectary. An insectary is a collection of plants used to produce pollen and nectar for beneficial insects to feed on or plants that host the garden pests eaten by beneficial insects. For example, herbs like dill, fennel, lavender, coriander or chamomile should be planted to attract damsel bugs for shelter and food. The native purple prairie clover (Petalostemum purpureum) may also provide the damsel bugs with a host of garden pests.

Always inspect plants for beneficial insects before spraying pesticides because they will be killed by the application. Organic pesticides can cause mortality of beneficial insects. However, organic chemicals will not prevent the return of beneficial insects to the garden indefinitely. Common garden pesticides like carbamyl may prevent their return for the rest of the growing season.

Lace Bugs on Sunflowers

By Kelly Allsup

Horticulture Extension Educator

It was the frass (insect excrement) on a sunflower leaf that caused me to stop and take a closer look. Upon further inspection, the frass was lined along the veins of the leaf and looked like black tar. The leaf was covered in stippling (feeding injury) and neucrotic spots (dead tissue). Then the culprits moved when I poked at them. They were chrysanthemum lacebugs (Corythuca marmorata). Chrysanthemum lacebugs are about a 1/4^th of an inch, brown-gray or tan in color have delicate wings held flat with markings giving it the appearance a miniature cut square of lace.

Chrysanthemum lacebugs prefer feeding on asters, sunflowers and goldenrods. The feeding injury is caused from the piercing and sucking mouth parts. The excrement is strategically placed along the vein and secures the eggs to the leaf. They prefer the underside of the leaf but one of the plants I saw had colonies on the upperside because the population was high. Nymphs are small shiny brown and suck sap. They congregate while they are young nymphs on the underside of the leaves. Damage from high populations is more severe in dry weather.

Hover fly larvae, lady beetles and lace wing larvae will prey on these garden pests. Daily water sprays until population is reduced can be highly effective. The University of Illinois suggests treating with horticulture oil, insecticidal soap, neem oil or imidacloprid. If you have chrysanthemum lacebugs this year, look out for stippling when plants are young and population is low. This garden pest is an excellent example of how a gardener's weekly notes can be a valuable management tool when dealing with garden pests in the next season.

Cucumber Beetles: Bug Report

By Kelly Allsup

Striped cucumber beetles (Acalymma vittatum) and spotted cucumber beetles (Diabrotica undecimpunctata) have been attacking our vegetable gardens since the beginning of spring and continue to feast on leaves, blossoms and fruits of many crops. Cucumbers, beans, melons, and squash are the most preferred food source. Another downfall of having a cucumber beetle infestation is they transmit the bacterial wilt and mosaic disease. It takes about 6 weeks for a plant to collapse so if you have had perfectly healthy squash plants die rapidly this could be your culprit. To determine if you have the disease cut a leaf in half and if there is a sticky sap that oozes from the cut, then you have a bacterial disease. The bacterial disease causes blockage in the water conducting tissues causing the wilt.

Adult striped cucumber beetles overwinter in wooded areas and garden debris in Illinois. The adult spotted cucumber beetle migrates from the southern states in the early spring. As adults feed they lay their eggs in the soil at the base of the plants. The larvae hatch in 2-4 weeks and feeds on the roots systems. The larval stage is followed by a pupating stage occuring in the soil.

Cucumber beetles can be devastating pest to several crops. The University of Illinois extension suggests the use of row covers when plants are young. As blossoms form, take row cover off of crops so pollination is allowed. Spinosad and pyrethrum based chemicals can be used to control adults. However, it is important to spray at night so beneficial insects and pollinators are not destroyed in the process. Cleaning up overwintering debris, weeds and crop rotation can be other methods of reducing cucumber beetle infestation. To prevent egg laying, mulch can be a real deterrent. Soldier beetles (Chauliognathus sp.) are considered a very important beneficial predator of cucumber beetles. However, limit or eliminate pesticide applications to encourage beneficial insects into the garden.

Beware Aphids: Aphid lions are hungry

By Kelly Allsup

Beware Aphids; the aphid lions are out ferociously eating about 400 of you in one week. However, the larvae of green lacewings (Crysoperla or Chrysopa spp.) also known as the aphid lion have a plethora of other beneficial insects to compete with. Lady bugs, parasitic wasps, minute pirate bugs, Hover fly larvae, predator stink bugs, praying mantis, assassin bugs and damsel bugs are just some of the beneficial insects you will attract to your garden if you have aphids. Most Master Gardeners agree with the University of Illinois Extension Horticulture Educator, Kelly Allsup, when she says to abstain from treating for aphids with chemical sprays.

Aphids are phloem feeders, plant sap suckers, and congregate on the growing tips of your garden plants or on the underside of the leaves. They are small and round and produce frass (excrement) called honey dew. Honey dew collects on the plant leaves making them sticky. The aphid population in your garden will build at a very high rate due to asexual reproduction by the females, giving birth to already pregnant clones. A female aphid can produce 5-12 offspring in one day. Don't fret lovers of garden plants, the infantry will arrive lead by the ravenous larvae of the delicate green lacewing.

Green lace wing are about as big as the tip of your pinky with green bodies, golden eyes and intricate lace wing they hold upright over their bodies. The green lace wing adult will fly from flower to flower in your garden eating nectar, pollen, honeydew and small insects. When an adult female comes across patch of honeydew and aphids she will stop to lay her eggs. The white oval eggs are connected to the plant by a thin filament. As soon as the green lacewing larvae (aphid lion) hatch they begin eating immediately waving their heads around eating whatever they catch. Thanks to mom's good planning, aphids will be plentiful. Aphid lions look more like miniature alligators than lions. The larvae will eat spider mites, small caterpillars, thrips, mealy bugs, whitefly and other soft bodied invertebrates with the hooked jaws protruding from their heads. They inject digestive juices in prey so they may slurp up there dinner.

Aphid lions will eat for 1-2 weeks before pupating. Forming a white round silken cocoon on the underside, adult green lace wings will emerge and live for 2-3 months. Depending on which, green lace wing genus the insect either overwinters in bark crevices or protected locations as adults or in the pre-pupae stage. They emerge next spring when flowers appear. Contingent on the temperature and weather of the season, there can be 1-4 generations per year.

An infestation of aphids could be just what your garden needs to increase diversity. Not only will the aphid population attract beneficial insects and pollinators but the birds, bats and larger insects looking to dine on them. Many chemicals labeled for garden use can be detrimental on this population of insects and will prevent their return. It is advised to only treat if you see severe plant decline or suspect aphids or phloem feeders are transmitting disease. First step should utilize cultural methods like water sprays or biopesticides like soap or neem oil. An alternative to chemical sprays is releasing beneficial insects bought online. Ultimately, inspect your garden plants and look for signs of garden pests and the beneficial insects that prey on them.