In This Issue

Postharvest Is the Time to Prevent Important Olive Diseases

Copper, applied prior to winter rain, prevents infection from the Peacock Spot (a.k.a. Olive Leaf Spot) fungus and the Olive Knot bacterium. It is important that applications be made before fall/winter rains as copper only provides protection and does not cure established infections. Fall is the most important infection period for the Peacock Spot fungus.

Once the fall application of copper is applied, additional applications are not necessary for Peacock Spot control. However, if temperatures low enough to cause olive shoot injury occur (i.e., <26° F), an immediate additional application will be needed to protect against Olive Knot infection. Most proprietary coppers and Bordeaux mixes that use 4 lbs of metallic copper per acre are equally effective in controlling these diseases. Note, some coppers can be combined with insecticides applied for black scale control. Be sure to consult with the sales representative for the insecticide you will be using to ensure its compatibility.

Caution: Oil olives are often harvested in late fall after the optimal treatment timing with copper. Many buyers will not accept fruit that has been treated with copper. So, if you intend to sell olives for oil, consult with your buyer as to acceptability of copper treated fruit before any treatment is made.

July Is the Time for Leaf Tissue Analyses

Leaf tissue analyses provide excellent information to guide a grove's fertilization program. July and August are good months to take olive leaf samples for analyses of the grove's nutrient status.

The elements of most concern and that require annual monitoring are: nitrogen (N), potassium (K) and boron (B).

NOTE: Always observe your trees carefully to detect visual symptoms of nutrient deficiency or excess. Visual observations provide an excellent complement to any lab analyses and indicate when special analyses are needed.

Remember to Apply Preemergence Herbicides Prior to Winter Weed Growth

Immediately postharvest is the best time to apply preemergence herbicides to control winter annuals. Remember, most of these herbicides kill annual weeds as they germinate and not when they are up and growing. Once weeds have emerged, "postemergence" herbicides will be required. Attached is a list of herbicides of use in olives.

R = registered; NB = registered in nonbearing orchards and vineyards only.

Note: This is intended as a general guide only! Before use of any herbicide consult the label carefully, labels change frequently and often contain special restrictions regarding specific use of a company's product.