Every home garden area in the United States harbors, on average, some 10,000 to 20,000 individual insect pests during the summer.
This is more understandable when we consider that one single insect egg hatching on a tree can multiply into millions of insects within a few months or that one pair of insects can produce enough progeny in one season under ideal conditions to cover the face of the earth.
Fortunately, natural factors help prevent insects from crowding us off the earth. Still, when the hordes of surviving insects try to live off and multiply on the plants we grow for beauty, shade, and food, we have but two alternatives: to fight back and put a halt to their efforts, or to do nothing and exist among “Tobacco Road” surroundings.
Pest control is undoubtedly the least-liked chore of gardening. With a bit of knowledge, care and practice, however, it can produce satisfying results as compensation for the work involved.
Aphid Species
In the summertime, almost every plant harbors one or more species of aphid, tiny, compact insects with or without wings and colored in almost every rainbow shade. What they lack in size, they make up in numbers and reproductive capacity.
A few aphids sucking juices from a plant may do no noticeable harm, but when hundreds or even thousands collect on stems, leaves, or growing tips, they consume more sap than the plant can supply.
This results in the curling of leaves, yellowing, and dropping of foliage or the wilting and drying of the plant as a whole or only part of it.
Some species cause conelike galls to form on the twigs of spruces; “others center their sneak attack on the roots of flowers and vegetables. Virus diseases are spread from plant to plant by insects.
The presence of ants on or around a plant usually indicates that aphids are at work. This is because the ants feed on the tiny droplets of honeydew excreted by the aphids.
On heavily infested trees, this honeydew audibly drips on the lower leaves and branches and encourages the growth of a sooty mold fungus.
Four Common Pests
There are four common pests whose injuries to plants may be easily confused by the average gardener:
- Leafhoppers
- Thrips
- Mites
- Lace bugs
Because of their sap-feeding activities, they all produce a grayish speckling or mottling of the top surface of the leaves. In severe infestations, the leaves may turn a rusty color.
Leafhoppers
If leafhoppers are responsible, small, slim insects with wings held rooflike over their backs, or their wingless young, which crawl sideways like crabs, may be found on the undersides of the leaves.
The adults are sometimes so thick that a regular cloud will leave the plants when disturbed. Apples, roses, beans, lettuce, asters, and chrysanthemums are commonly attacked.
Some species of leafhoppers may spread virus diseases, such as aster “yellows,” from plant to plant, and cause more damage by this means than by their feeding activities.
Thrips
When thrips are the culprits, their minute, elongated bodies no larger than a hyphen can be seen crawling about amidst tiny dark droplets of excreta.
Onions, iris, gladiolus, and chrysanthemums must be watched for thrips, but often they may be found on many different trees and shrubs.
Mites
When mites are to blame, these tiny spider-like creatures, red to yellow and no bigger than pinheads, can be seen crawling about on the injured foliage.
They may spin fine spider-like webs on the leaves, among which red or yellow spherical, glistening eggs may be seen.
These eggs are in the overwintering stage of the spruce mite, common on many evergreens; the boxwood mite and the European red mite are common on fruits and roses: English ivy, and many other deciduous ornamentals.
When lace bugs are at fault, these small lacy-winged insects or spiny young may be found on the undersides of the foliage. Rhododendron, pieris, laurel, amelanchier and oaks are favorite hosts.
Various Chewing Insects
Insects that chew up leaves and flowers vary from the numerous types of caterpillars, which are the larvae of moths, butterflies, or sawflies, to the variously colored beetles, with their grublike dull colored larvae.
Their injury makes plants unsightly and consists of making holes in leaves, skeletonizing the foliage, or consuming all the foliage or parts on plants.
In many cases, the damage is noticed once a considerable amount of vegetation has been destroyed. Unfortunately, this tends to prevent the plant’s average growth, weakening it or killing it.
Rhododendron leaves are often found with large holes or extensive areas chewed out with no sign of the culprits, as the pests hide by day and work by night. However, either of the two beetles, the black vine weevil or the Asiatic garden beetle, may be responsible.
Control for most leaf chewers is best directed against the early developmental stages (young larvae) before the damage becomes severe.
Three Lawn Pests
There are three main insect bugaboos to good lawns:
- White grubs, which chew on the roots.
- Chinch bugs, which suck on the stems.
- Ants, which make holes and sand piles throughout the area.
Injury from white grubs (usually the larvae of Japanese beetles) shows up in the fall or spring as dead, irregular patches of sod that can be lifted like a mat because the anchoring grassroots have all been chewed off. The white, fat, curled-up grubs can easily be found in the soil in such areas.
Chinch bug injury may appear in the latter part of June and in the latter part of August and September. Dead, irregular patches of sod also occur, especially in protected, sunny areas, but clovers are untouched.
A careful inspection of the soil surface near the edges of dead patches should disclose such stages as tiny red bugs no larger than a pinhead, larger red bugs with a white band across their backs, still larger bugs grayish-black in color and blackish insects with white wings half or fully covering the back.
Ants may be found anytime during the spring, summer, and fall in lawns, flower beds, and vegetable beds. Their holes, surrounded by small heaps of sand, may be spotted easily.
When ants and ant holes are abundant on the bases of flowers or vegetables, it may indicate that root aphids are at work on the plants.
Loaf Miners
Insects known as leaf miners bore or tunnel as larvae in the internal leaf tissues of many plants, producing defoliation, significantly weakening the plants, or making the foliage unsightly. The tunnel lines may be narrow and winding, or they may be of a blotch type.
Accurate timing is usually necessary to control these pests, as the adults must be killed before they begin egg-laying. This occurs within a few hours after emergence, in the case of the boxwood leaf miner. The miners can be found by peeling the leaf and exposing tunnels.
In the adult stage, the miners may be slight black sawflies (birch leaf miner, elm leaf miner), small gray flies that resemble midget houseflies (holly leaf miners), orange mosquito-like flies (boxwood leafminer), or large flies that resemble houseflies (spinach or beet leaf miner).
Borers
Borers are insects that insidiously attack the internal parts of plants. Some prefer the complex, woody parts of trees and shrubs, some the softer bark, and some soft-stemmed plants.
Their boring or tunneling interferes with the regular movements of water, nutrients, and food in a plant, causing such symptoms as wilting, yellowing of foliage, stunting of growth, wind breakage, or plant death.
The presence of borers at work is often indicated by holes in the trunks or stems that exude frass or adhesive material.
Many tree borers prefer weakened, unhealthy trees to vigorously growing ones. These insects can be heard crunching away on the wood of heavily infested trees when you place your ear against the trunk.
Some borers that attack trees and shrubs are flat-headed, some as round-headed borers, and some as bark beetles. These borers are all beetles in the adult stage. Other common borers may be the larvae of moths.
Such borers include:
- The leopard moth attacks many species of hardwood.
- The peach tree borer attacks peaches and cherries.
- The corn borer attacks sweet corn, dahlias, gladiolus, and a- host of other soft-stemmed plants.
- The squash vine borer attacks the stems of squashes and pumpkins.
Borer control should be directed at preventing the entrance of borers into the plants, as once they are in, they are difficult, if not impossible, to reach.
The usual procedure is the destruction of the adults before they lay their eggs or the newly hatched larvae before they have a chance to bore into the plant.
Application Equipment
Some genius has yet to invent a hand-operated sprayer or duster accessible on the muscles and effective for various plants. The following types of sprayers and dusters are recommended. Pick the one that suits your back, plants, and pocketbook best.
- Knapsack compressed air sprayer. Capacity 2-3 gals. About $10.00. Suitable for small garden areas.
- Wheelbarrow sprayer. Capacity is about 10 gals. About $30.00. Requires two people for effective operation.
- Garden power sprayer. Capacity 12-15 ‘vials. About $150.00. Easy to use and efficient.
- Estate power sprayer, hand- or tractor drawn. Capacity 25-50 gals. About $350.00. Best where many trees and large shrubs must be sprayed.
- Bellows knapsack type of duster. Capacity 5-10 lbs. of dust. About $25.00. Best for spot dusting may be used on shrubs and small trees.
- Rotary fan type of knapsack duster. Capacity 5-10 lbs. of dust. About $15.00- $20.00. Best for row crops.
44659 by Louis Pyenson