Friday, June 29, 2012

A Sharp Dressed Pest - Cucumber Beetles

(By U of I Plant Clinic Student Worker, Sean Mullahy)

These infamous garden pests come in two patterns, spotted and striped, and are fantastic at destroying all things cucurbit. So beware their interesting fashion sensibilities, and protect your garden against these nasty little pests. 

The first step to keeping them under control is proper identification. The spotted beetle is about ¼ inch in length and has yellowish green forewings with twelve distinct black spots. The striped cucumber beetles are nearly the same in size, also averaging about ¼ inch in length. These have much simpler fashion sensibilities, with two distinct black stripes running down each of their wing covers. The innermost stripe on each matches up with the one on its partner wing, making it appear as though they only have three black stripes. It can also be easy to confuse the striped cucumber beetle with the western corn rootworm. They have similar color and patterns, but the western corn rootworm has a yellow abdomen, and the striped cucumber beetle has a black abdomen. The larvae for both are striped, but spotted cucumber beetle larvae are whitish – yellow in color. Cucumber beetle larvae are much bigger than their adult stage, ranging from ½ to ¾ inches in length, and they have dark brown heads and three pairs of very short legs. 
Adult southern corn rootworm (a.k.a. spotted cucumber beetle), Diabrotica undecimpunctata howardi (R.L. Croissant,

Striped cucumber beetle (Whitney Cranshaw, Colorado State University,
Striped cucumber beetle (David Cappaert, Michigan State University,
Western corn rootworm beetle (Whitney Cranshaw, Colorado State University,

As for life cycle, both spotted and striped cucumber beetles overwinter as adults. The striped beetle is the only one that will be a big issue in early spring however, the spotted beetle has a much lower success rate in surviving the Illinois winter. It, however, can be a bigger problem in southern Illinois. Once active, they begin feeding, and can survive off the pollen and petals of many different plant species before cucurbits are planted or growing. Once the cucurbits are actively growing, they move onto these, with the ability to feed on foliage and fruits and truly devastating anything they can munch. These adults eventually lay eggs at the base of their hosts, and once hatched, the larvae will feed on the roots. Depending on location, this cycle can be repeated up to two times per season, with this only happening in warmer locales. 

If the direct damage to your tasty melons, butternuts, cucumbers, and all your other favorite hard shelled veggies wasn’t enough, the cucumber beetle also spreads a number of nasty pathogens. Throughout localized plantings, they will spread squash mosaic virus, which can be quite nasty to the fruits. They can also spread bacterial wilt of cucurbits, which affects most of your favorite fruit bearing cucurbits. 

Management of the Cucumber Beetle can be done preemptively with the application of a systemic insecticide to the soil at the time of planting. This however might be a bit much for the homegrowers out there. The only other option available is to spray a foliar insecticide when adult beetles show up.  Applications are recommended based on total adult beetle count, and if it exceeds one per ten plants at the seedling stage, or one per plant at flowering.  If you’d like to practice non-chemical control of this pest, the easiest thing to do is dress your plants in a mesh cloth to keep the pests out. The earlier the better for this method, and make sure the mesh is open enough to let in ample sunlight, while also being tight enough to keep the pests out.

Further Reading:

Friday, June 15, 2012

Sick African Violet Plant Sample

The African violet foliage showed a number of symptoms, with the majority of the sample showing mild leaf curling, bleaching, or yellowing of tissue, brittle leaves, and these symptoms seemed to affect the younger leaves more than the mature ones. It was noted that the plants were still flowering, although not as much as they had before the symptoms began appearing. What could be the problem?

Cyclamen mites can be a problem on African violet.  They can cause young leaves to be thick, hairy, deformed, brownish-green, and the cup downward.  They can be difficult to control because they can be down in the crown of the plant.  They can only be seen with a dissecting scope.  The mites must be alive and present when treated.  They can be treated with insecticidal soap or a miticide.  Read and follow label instructions.  Heavily infected plants should be destroyed to protect uninfested plants.

African Violets cannot handle temperatures below 65F at night and 70-72F during the daytime. When exposed to cold temperatures leaves can become discolored, brittle, and curl under. All of which were observed symptoms.

Too much light could also be an issue. Excessive light can lead to stunted plants with crinkled and discolored leaves.
African violets prefer a soil in the range of 6.0-6.5, and soil should be adjusted for accordingly.  A soil pH imbalance could lead to nutrient deficiency in the plant. For future adjustments, it is recommended to use something more stable such as lime or calcium, and to test the soil with a soil pH test kit.

Excess watering can also cause leaves to curl.

In addition we used the resources: How to Grow African Violets by Harrison, Heimann and Pellitteri, African Violet Care by Lerner and Dana, Growing African Violets by Cindy Haynes, and Growing African Violets by Charles Fischer (all found on the web).

Friday, June 1, 2012

Bagworms AHOY!

Bagworm (Thyridopteryx ephemeraeformis)
(By Sean Mullahy, U of I Plant Clinic Student Worker)

The U of I Plant Clinic received a very fun sample in today. What we thought was a bag full of fir samples to be diagnosed, also contained a freshly hatched bunch of bagworms! Bagworms are an extremely common pest of a large number of ornamental woodies, including spruce, fir, locust, pine, sycamore, and so on. Bagworms are one of the easiest pests to identify and remove, but are also one of the least controlled.
A mature, egg filled, bagworm cocoon

Baby bagworms emerge from eggs in their mother’s bag in late spring, after spending the entire winter inside. After the babies emerge they will almost immediately begin to create their own casings from whatever debris they can find. After making their casings they begin their upward climb to begin the ballooning process. Baby bagworms will feed as they climb, and upon reaching the top of their host will spin webbing of two to three feet in length, and swing off the branches of their hosts. This process is called ballooning, and eventually the wind will grab the bagworm to carry it to a new host. The bagworm hopes that this new host will be suitable, but if not they can always balloon again. After landing on a suitable host the caterpillars will begin to feed. They will start on the upper side of leaves, but quickly make their way to the underside. They prefer to feed from the tops of trees down, destroying it in their wake. As they feed throughout the season they will continually add debris to their casings to keep up with growth. Sometime in late August – early September they will reach full maturity, and find a branch to pupate on. 

Tiny, recently hatched larvae fulfilling their destiny to climb ever upwards

Pupation is around the time the bagworm lifecycle gets very interesting. Bagworms construct a large cone shaped cocoons, making identification easy. The bagworm males will emerge as moths after they finish pupating, the females however will finish the rest of their days in the homes they spent the season constructing. The males emerge as black moths with clear wings, and are about 1” in length. These will fly around hunting for female bags to mate with. Once mating has occurred, usually in late September, the female will lay her eggs in the bag. These eggs will remain dormant until the spring when the caterpillars will emerge, eat their mother’s corpse, and then begin the cycle anew. 

Recently hatched baby bagworms taking their first bites off of foliage, and beginning to build their lifelong husk companions

Bagworms are generally easy to control, if proper care is taken. The easiest time for this would be in the fall when bags have formed. Once bags have formed on host trees, they can be plucked off and collected, with burning being highly recommended. This can be before or after males have emerged from their bags, although after will ensure the destruction of eggs. The only problem with this method, however, is that getting to the uppermost branches of hosts can be difficult. It can also be quite easy to miss a large number of them hidden among the branches. So this technique can thin numbers considerably, but is not a method of complete control. Another check can also be done in spring to remove bags before hatching. If spraying is necessary, late spring or early summer, after the larvae have recently hatched is the best time to do so. If insecticide applications are delayed too far, the worms will have become too big for easy control and will most likely survive the application. It is best to get them before they balloon onto other hosts.  
A mature bagworm, in bag.