Plant and Insect Diagnostic Clinic Update - April 14, 2010

The following are highlights and updates about samples and questions recently received in the Clinic:

 
Insects


Clover mites are making their presence known in homes of some unlucky individuals. Clover mites are harmless, but when crushed they can leave permanent purplish stains on walls and tile. Clover mites are very small, about the size of a period. Clover mites feed outside on grass and oher plants. We only notice them in the spring then their migration brings them into our homes. It is a temporary problem, but if there are many coming indoors you can use insecticides on the outside of your house to reduce numbers.


Carpenter ants are on the march again.  If you see large black ants wandering around in your kitchen they could be carpenter ants.  There is no need to be concerned, these are wanderers coming in from the outside.  Carpenter ants have a bad reputation as wood destroyers, but in reality they only make colonies in water damaged wood and they do not eat wood.  They are foragers and come into kitchens for the leftovers.  Unfortunately the ant baits what work well for some other Iowa ant species are less effective at carpenter ant control.  For more information see our IIIN.


 
Diseases


Verticillium wilt on strawberry  is caused by the fungus Verticillium albo-atrum. Initial symptoms appear in the spring, especially if periods of environmental stress, such as a sudden onset of high temperatures, high light intensity or drought, interrupt mild conditions. In the field, if hot weather is sustained, individual plants may recover but they rarely regain economic productivity.   Symptoms of the disease are marginal and interveinal browning of outer leaves, which eventually collapse. Inner leaves are stunted but tend to remain green and turgid.  


Botrytis blight  on geranium caused by the fungus Botrytis cinerea. The symptoms on the leaves vary from distinct spots to large dead areas or V-shaped lesions. Symptoms on stems appear at the base of plants as light-to dark-brown lesions. To manage this disease remove and discard infected plant material, promote good air circulation, avoid overhead irrigation and water early in the day.

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