Today I would like to discuss the use of oil sprays for early season control of some insect pests of fruit crops.

Horticultural oils have many different names and come in many different types. Most are quite effective at helping to control rosy apple aphid, European red mites, and San Jose Scale. Oils fit IPM programs quite well because they are applied when beneficial or predatory mites are not present. A properly timed early season application at the dormant or delayed dormant (around ½ green) stage of development will often lead to fewer applications of insecticides and/or miticides later in the season.

Not all oils can be applied to all types of growth. You should look for the words superior, supreme, or 70-second on the label. These are acceptable spray oils for use on fruit crops.

There are two main ways that oil sprays work. The first is suffocation. Eggs covered in oil and adults with oil plugging their breathing structures suffocate. The second is that oil acts as a repellant. Application of oil before the start of pear psylla egg deposition was found to delay egg laying for up to 5 weeks. It is also thought to prevent scale crawlers from settling.

It is best to use lots of water as a carrier for oils. If you have had annual problem with mites, you might even want to consider a handgun application. Getting oil into the cracks and crevices where the eggs are is essential. Do not concentrate more than 2x with oils.

There are some other precautions with oil. Do no use within 10 to 14 days of a spray that contains sulfur (such as Captan). Temperatures within 24 hours before and after an oil application should be above 40 degrees. Check the 2005 Fruit Management Guide for more details.

That is all for today, this has been Al Gaus for Michigan State University Extension in Berrien County.