QUESTION: I have elm trees that have beetles that become quite a pest. They eat the leaves. How can I get rid of them?
ANSWER: A sure way to get rid of elm leaf beetles is to cut down your tree (s) and those of your neighbor's! The larva of the beetles are eating the leaves so you must get rid of them. You can spray Bacillus thuringiensis or B.T., the San Diego strain. This product is sold under several trade names and is an organic insecticide that kills insect larva only and is not harmful to other insects or animals B.T. is a natural occurring soil bacteria that must be sprayed on the leaves and then the treated leaves eaten by the larva. B.T. is washed off by rain and must be reapplied. Another solution is to spray a 2 foot band of Sevin insecticide around the tree trunk 6 to 8 feet above the ground. The elm leaf beetle larva travel down the tree trunk to pupate on the lower trunk or near the soil line. Crossing the Sevin strip will kill the larva and over time reduce the in sect population according to University of California entomologists. This treatment will not destroy adults so if there are a lot of elm trees in your neighborhood other elm leaf beetles will fly to your trees and lay eggs. However, these treatments can significantly reduce larval populations and damage to tree leaves.
QUESTION: I am confused about fertilizers. What do the numbers on the bag mean? What are the differences between organic and chemical fertilizers?
ANSWER: By law 3 numbers are required on a fertilizer bag. These are the percentage by weight of nitrogen (N), phosphorus (P) and potassium (K) or N-P-K in that order. Therefore, a bag of ammonium phosphate is marked 16-20-0 or 16% N, 20% P, and 0% K. The N is actual total N no matter what the form. P is really the percentage of P205 and K is really percentage of K20. (A small side-note-to get the actual amount of P you must multiply the number on the bag by 43% and by 83% to get the actual amount of K. These percentages are derived by taking fee atomic weight of fee element in question and dividing by fee atomic weight of the molecule that the element is in. There have been efforts to revise the current labeling of fertilizers so that only the percentage of P and K appear, but these efforts thus far have ended in failure.) Our soils need N for normal plant growth. This is because it leaches from the root zone. Plants absorb most of their N in the NH4+ ammonium and N03- nitrate. These are both inorganic molecules. Generally plants use nitrate form over the ammonium form. Ammonium is converted to N in the soil by aerobic bacteria and some fungi, therefore cool, wet soils have less active bacteria and will yield less nitrate nitrogen. Nitrate forms of nitrogen are taken up by plants directly and is better used in cool, moist soils. Many nitrogen based fertilizers are made by a process which uses atmospheric nitrogen, the air we breathe is about 78% nitrogen and natural gas or methane under high pressure and heat. Organic forms of nitrogen must be mineralized, that is converted into inorganic nitrogen by soil microorganisms for plant use. Also the carbonaceous material of fee organic matter is broken down into humus by soil organisms and used as an energy source. Organic sources of nitrogen include blood meal which is usually around 15% nitrogen. Our desert soils are also low in native phosphorus and it should be added at planting time. Phosphorus binds with the soil and does not leach or cannot be "melted" into the soil with water like nitrogen. There are several forms of phosphorus, many being produced by treating phosphate rock with an acid like phosphoric acid. This yields triple super phosphate or 0-45-0 on the fertilizer bag and can be neutralized with ammonia to make ammonium phosphate and liquid fertilizers. Organic forms of phosphorus are available with bone meal, 0-12-0 being the most common. Potassium is not needed usually in our desert soils. There are many fertilizers on the market which have other nutrients for plant growth. Higher priced fertilizers have some of these nutrients added and increase the cost. Organic based fertilizers like manures and composts have lower plant nutrient levels but add organic matter to our soils and are more beneficial in this regard than chemically based fertilizers. However, the cost and high amounts needed of organic fertilizers for normal plant growth are very high when compared to bagged chemical fertilizers.