Mulch plants before summer heat hits

Typical weeds popping up now are the mustards. These are filling some people's yards with fast-growing plants with tiny yellow blossoms. They were the first weeds to show up after the rains and flower with small yellow flowers. This is because they are winter annuals -- they germinated from seed last fall waiting for spring as tiny plants in a rosette and then flourished in the rains of this spring.

There are numerous species of weedy mustards. Their distribution is almost universal, and they have flourished for centuries throughout areas of Europe and Asia. Two ordinary types that are common here are yellow rocket and shepherds purse, which are small tough weeds usually 6 inches to a foot or so tall. Yellow rocket is so prevalent in the East that whole fields turn yellow in the spring.

Some of the larger wild mustard species are used for pot herbs as their name suggests. Unless picked when young, they will be too pungent for consumption.

The mustard family is famous for good eating. Vegetables that are in this family include cabbage, turnip, radish, cauliflower, rutabaga, broccoli, brussel sprouts, kohlrabi, watercress, kale and mustard. Seeds of the wild mustard furnish spice mustard and prepared table mustard. If you can still find some leaves that are young and tender, you can use it for salad greens. Pick the small ones.

Now is the time to mulch plants in preparation for summer heat. Mulching soil in the spring helps to delay heating of soils as summer approaches. Mulching in the fall helps to delay the cooling of soils as winter approaches. Cover bare soil with mulch to reduce weed problems and conserve water. Mulch fruit trees, as well as trees and shrubs in bed areas.

Aerate lawns now to prepare for deeper rooting of lawn grasses and improve drought and heat tolerance. Lawn fertilizers containing potassium are known to improve drought tolerance. If you apply a lawn fertilizer soon, a mixture containing slow-release nitrogen, moderate phosphorus and high potassium would benefit lawn grasses particularly after aeration.

Weed control of existing weeds in lawns, such as dandelions with herbicides, is best done now while it is still cool. These weeds are much more resistant to weed killers when it gets hot. Make sure you keep pets and children off of treated areas for several irrigations afterward.

Removal of major branches from trees and shrubs should be done by now. Thin-barked trees like Palo Verde are easily sunburned if they are limbed up too high. These trees have limbs that should be left on so the lower trunk is still shaded. Sunburned plants frequently develop pest problems such as borers.

Right now we are still applying dormant oil on those fruit trees that are not flowering. This should be done every two to three weeks. It can be done after bloom, as well. We are applying Bt sprays at the pink stage of bloom (when we first see color in the bud but not yet in bloom) to petal fall (bloom is over) to control peach twig borer.

Bt is one of the few pesticides that can be applied during bloom and will not affect bees. It is typically available in nursery or garden centers as Dipel or Thuricide. Bt products contain bacteria called bacillus thuringiensis. These bacteria will kill the immature stage of many garden pests that will develop into moths. This includes cabbage loopers, tent caterpillars, tomato hornworms, tomato fruitworms, peach twig borers and fall webworms.

Bt is highly selective and will not harm humans, other mammals, plants, or most beneficial insects. It is a living organism and does not pose a pollution problem like many chemical insecticides do.

Bt is a stomach poison that is generally most effective on young, hungry larvae, the juvenile stage of many insects. When the insect eats plant material treated with Bt, its gut is destroyed. The pest stops feeding immediately, though it may be several days before it actually dies of starvation. More than one application may be necessary for pest control. Carefully read and follow label directions.

Be sure to paint the trunk and lower scaffold limbs of fruit trees with tree paint. You can use white latex paint diluted with an equal amount of water. This helps to prevent sunburn after pruning heavily and some borer protection.

Question: I have what appear to be borers in my plum tree. There is sap coming from the trunk and the bark is peeling off. How do I control these things?

Answer: Borers are the immature forms of certain types of boring insects that need the interior of plants to finish their life cycle. The female mature form of the insect lays her eggs on the outside of a plant after mating with the male. The eggs hatch in a few days to a week and the small immature form, a larva, burrows into the inside of the plant.

The inside of the plant provides food and shelter while the immature gains size enough to pupate to an adult. Once the insect pupates into an adult, it emerges by tunneling out of the inside of the plant, leaving an exit hole, and seeks a mate for reproduction. The life cycle repeats itself.

There are many different types of boring insects. Boring insects are usually either a beetle of some sort, moth or fly. Their life cycle varies with each different insect and the climate where they live.

Making generalizations about borers is sometimes difficult since there are so many different kinds and each has its own specific life cycle. The sap usually appears when the insect is feeding inside or exiting the plant when it matures.

Once inside the plant, control is difficult since it is well protected. Even the insecticides that are injected into the plant are usually relatively ineffective at this time. The best time for control is when the insect is outside of the plant and the best time to apply some sort of chemical control on the plant is just before, or immediately after, the eggs are laid.

Determining when this is might be is difficult. The timing has been worked out for some boring insects that are considered economically important. Insects like the peach tree borer and elm bark beetle are well known by researchers and the timing for sprays has been worked out with the use of traps. Many others are not well known so we are left with our best guesses as to when to spray.

Generally speaking, many of the boring insects mate and lay eggs in the spring, very close to the time when plants begin growing. For this reason, if a chemical is to be applied for the control of borers, it would be best to apply after blooming is finished or when new growth begins.

Do not apply any chemical during bloom. The chemical is applied to the trunk and limbs more than 2 inches in diameter but not over the entire plant.

Apply a second spray when the label directs, or if the label does not specify, about six to eight weeks after the first spray. Use chemicals labeled for the plant being sprayed and the insect being controlled.