April's Ag Advice by April Borders This week I thought that I would just touch on some odds and ends of information that I thought would be useful. Tent caterpillars are out and about now. If you look in the branch crotches of many of the plums and cherries you can see the beginnings of their nests. Now is the time to take action and begin control. You can use Dipel or a similar B.t. formulation to control these insects. This naturally occurring bacteria is highly effective on tent caterpillars, yet does not harm their predators or parasites.
The key to controlling these caterpillars is to get them when they are young. Start control when the caterpillars are less than one-fourth inch long. The bigger they are, more bacteria is needed to kill them. Also, the smaller they are when you kill them, the less they will have eaten on your plant!
We are coming up to the time for shearing your pines. Pines can only be sheared during the candling phase. The succulent new shoots that are forming right now are called candles. If pines are sheared (a portion of the new growth removed) during the candling phase they will become a denser fuller plant. Pines, unlike other evergreens, can only be sheared during the candle phase.
If they are sheared before or after this time they will not be able to set new terminal buds and the improperly sheared shoots will dieback. The ideal time to shear pines is when the new needles forming the candles are about one-half the size of the mature needles and never remove more than two-third's of the candle.
If you are worried about shearing you can also accomplish this task by hand. Just pinch or snap off a portion (not more that two-thirds) of the elongated young growth or "candle". Spruce, fir and Douglas-fir are sheared in the late summer after the candle has completed its development. These trees produce lateral buds, as well as terminal ones so the new growth after shearing will develop from the lateral buds.
Why isn't my tree leafing out very quickly? This has been a common question over the past week. Many people notice that their maples, honeylocust or ash are being very slow to leaf out. Sometimes it is just one tree among many or perhaps even one or two branches on a tree have leafed out. In most instances you can blame the late leafing out on the weather. The warm weather followed by cool has stalled growth on many trees. Once the weather warms up again you should see the leaves complete their expansion.
The next question we are getting asked is about fertilizing your trees at this time of year. Don't do it. Fall, not spring, is the ideal time to fertilize trees and shrubs in South Dakota. Fertilizer applied in the fall is quickly absorbed and utilized for the spring growth. It is fall fertilizing that promotes spring growth, not spring fertilizing.
A lot of people use the fertilizer spikes on their trees. Dr. John Ball, SDSU Extension Forestry Specialist, says these fertilizer spikes are pretty much a waste of time and money. The spikes concentrate the fertilizer in only a couple of locations, rather than spread throughout the rooting zone (typically a radius out equal to the height of the tree). It also doesn't take a lot of fertilizer.
On the agronomy side of things, we need to monitor our corn field. Since we have been receiving fair amounts of rain fall in a short period of time, we need to be watching our field for problems from ponding and crusting. Too much water in low areas of the field may be displacing the oxygen in the soil. There may also be some crusting taking place making it difficult of the seedlings to emerge.
In the early stages of development (germination to V6 stage � when the leaf collar on the sixth leaf sheath becomes visible), corn can survive if underwater for no more than 48 hours.
In cases where the weather is cool, then the plants physiological process slows and in may survive under water longer. If soil and air temperature are warm, 24 hours of flooding may cause plants to die. After the V6 stage, flooded plants can survive four to seven days depending on the temperature.
Producers need to dig up some of the plants and monitor the growing point. If the growing point is yellow to white in color, the plant is OK. If the growing point is brownish to black in color the plant is dying. Areas of the field with prolonged ponding may have dead areas.
Depending on the severity of stand loss, growers may consider replanting. The rule of thumb for corn stands is if 75 percent of the seedling population emerges then it does not pay to replant. In areas of the field that have higher stand losses due to the ponding, replanting may be an option in those areas of the field. If crusting is a problem, a rotary hoe works to break up the crust so that the seedling can emerge more easily.
If you need more information on these subjects or for other questions that you have, feel free to call the Extension Office at 677-7111. Also the Master Gardeners are available to answer your questions on Mondays from 8 to 10 a.m.