Welcome to Pest Alert. Categories for topics are as follows, H - Herbaceous plants and flowers, W - Woody Plants, V - Vegetables, F - Fruit and L - Lawns.
DISEASES
F,W FIRE BLIGHT infections are now quite evident on trees and should be treated by pruning out any signs of the infection. The most susceptible plants include apple, pear, crab apple, mountain ash and cotoneaster. Dip the pruning saw or shears in a 10% bleach solution between cuts and thoroughly rinse and dry tools when you are finished. Blossom or spur infections can be numerous making pruning difficult. In severe cases, especially where other susceptible plants are in the same yard, consider completely removing the most severely infected plants.
INSECTS
F APPLE MAGGOTS should be emerging and begin laying their eggs on apple fruit. The "railroad worm," as it is called, is the larva of a small insect that resembles a house-fly but has dark markings on the wings. The adult emerges from the soil and goes off in search of apples. The adult lays an egg just under the skin of the apple. The egg soon hatches into the maggot that feeds inside the apple. Infested apples will typically have a small black speck on the skin of the apple. The apple may also be "dimpled" where the egg has been laid. Small brown streaks will be seen in the flesh of the apple where the maggot has fed. Infested fruit, while unattractive, is still edible but has a much shorter storage life. Sticky red ball traps may be used to monitor for the emergence of the adults. Some people have reported good results by simply using 6 to 8 sticky traps in a few trees in a yard to reduce damage to tolerable levels without using insecticides. Or, apply protective sprays of malathion, diazinon, Imidan or use a combination orchard spray to reduce infestations.
W CEDAR BARK BEETLES are generating many calls, particularly within the area south of I-90 and west of the James River. The bark beetles are killing the branches of eastern redcedars and Rocky Mountain junipers and occasionally killing entire trees. You can tell if the tree has been attacked by the bark beetle by looking for 2-inch long galleries beneath the bark. The galleries are usually cut against the grain. The adults are reddish brown, shiny and about 4 mm long. There are one to two generations per year but details regarding the development of this insect are not clear. Control is limited to killing the adults with a long-lasting insecticide, such as bendicarbo, placed on the bark.
W COTTONY MAPLE SCALE crawlers are moving about the twigs of maples, elms and other deciduous trees. The old, and now dead, females can be easily spotted on twigs. Their flat shell is raised from the twig by a white mass of eggs that appear almost foam-like. The crawlers will move from the branches to the leaves where they develop into adult females. The crawlers can remove tremendous quantities of sap from the tree, through usually not in sufficient amounts to cause injury. The primary problem is the sticky honeydew that falls on everything beneath the tree. The crawlers can be treated with a number of insecticides, however, many will also harm the scale's natural enemies as much as the scale itself. The two best controls that leave the predators and parasites intact are insecticidal soap and superior oil. Either should be used with caution as misapplications can result in plant injury. Always read and follow the label directions carefully.
V IMPORTED CABBAGE WORMS AND LOOPERS are actively feeding in many home gardens. They will attack most cole crops but seem to prefer cabbage and broccoli. They damage plants by chewing irregular holes in the leaves and leave lots of frass behind where they have been feeding. The imported cabbage worm is velvety pale green with a yellow stripe. The looper is green with pale stripes down the back and moves in an "inch-worm" fashion. Both are often difficult to spot since they blend in well with the foliage. Probably the best method of control is prevention. Horticultural fleeces or row cover fabric can be used to exclude the adults from the plants, thus preventing the laying of eggs. The caterpillars can be picked from the plant or the plants may be treated with B.t. (Bacillus thuringiensis) during early stages. Sevin, Rotonone and Diazinon are also effective.
W SPRUCE NEEDLE MINER is out flying in South Dakota. The moths are flying during the day and they are brown and have about a ½ inch wingspan. The adults are laying eggs on the new needles. The eggs will hatch in about 14 days. The larvae will begin mining the needles and as they become larger hollow out the needles and web them together. Treatments should begin now with carbaryl with a second treatment made again in 14 days.
WEEDS
V KEEP UP ON WEED CONTROL efforts, especially if some weeds are beginning to flower. Remember that some weeds can produce many thousands of seeds which translate to a lot of future weed control work. Some extra time spent now can save lots of work later. Many weeds, especially purslane, will tend to re-root if it is pulled but left on the soil surface. Try to remove the weeds from the garden and put in a compost pile or other area where they will not cause future problems. If an area of the garden gets completely overgrown consider mowing the area to remove flowers and developing seed heads.
OTHER NOTES
V BLOSSOM-END ROT will soon arrive in many home gardens. This physiological disease is caused by a calcium deficiency in the fruit. The plant takes up less calcium than it should during times of rapid growth. This often happens during wet weather following a dry period. Since there is not enough calcium in the plant, the end of the fruit doesn't get enough to develop properly. Typically, determinant tomato varieties are more severely affected since much of the fruit develops at one time. The best way to treat the problem is to discourage growth spurts from fluctuating soil moisture levels. Use a mulch to keep the soil moister, water during dry periods and try using semi-determinant and indeterminant tomato varieties. Applications of calcium are generally not effective since our soils generally have adequate levels of calcium.
W EVERGREENS DO NOT RECEIVE 85% OF THEIR WATER THROUGH THE NEEDLES. This is a common statement that is not based in fact. Evergreens, as with the vast majority of plants, receive their water through the root systems. While there are "fog forests" along the Pacific coast, even there the large evergreen trees depend upon the roots for their moisture. Watering the foliage doesn't hurt and even helps to cool the tree, but watering should be limited to the surrounding soil.
V ROTTING SQUASH fruit generally means that the female flower was not adequately pollinated to allow for the development of the fruit. Without pollination, the fruit may survive for a couple days but then begin to rot from the blossom end. This is NOT like blossom-end-rot which is found in tomatoes and peppers. Extremely heavy, dense vine growth, wet conditions, odd weather patterns, excessive use of insecticides or just a lack of pollinating insects can increase the likelihood of this problem occurring. Generally the problem will disappear on its own. Also, warmer temperatures will promote the production of more female flowers to allow for more potential fruit than during cooler weather. Incidentally, bumble bees are much more effective pollinating insects for cucurbits than honey bees.
H,V,W,F,L WATER ON THE LEAVES IS NOT A PROBLEM. Each summer we received calls about the danger of watering leaves during the daytime. Apparently the water droplets will magnify the sun's rays and burn a hole in the leaf. There is no truth to this. Water on the leaves will evaporate and actually cool the leaf, not heat it up. The real problem with watering during the day is the water that evaporates before it can reach the soil, which wastes water. Syringing the foliage or lite watering during the day is sometimes recommended to help keep newly transplanted plants from being stressed on hot sunny days. It will not burn the leaves.
V,H,L,W WATER PROPERLY when the plants need it. Generally most lawns, gardens and flowers need about 1" of water per week. If your area has not been receiving this amount, supplemental watering may be needed. The important point to remember is to water thoroughly when you do water. Try to saturate the root zone of what you are watering. This means applying at least 1/2" at one time, preferably more like 1" should be applied at one watering. Then allow the soil to dry before watering again. You can tell when it is time to water by sticking your finger into the soil to see if it feels moist in the top 2" of soil. If it is dry, it is probably time to water. Watering from below is generally better than overhead. This can be done using soaker hoses or a drip system. Overhead watering tends to waste water and can promote disease problems if the foliage is allowed to go into the night wet.
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Most recent revision Thursday, June 16, 1998 by David F. Graper.