Pests and Diseases

("here are a number of pests and diseases that attack succulents, but all of them are easily recognized and controlled by simple methods. The best method, of course, is prevention The collector who buys only healthy, vigorous stock, plants and spaces his collection carefully; and provides constant cleanliness, light, and air will rarely encounter more than two or three of these troubles in his career. For, like human ills, these disorders are not natural to succulents but the result of carelessness and poor growing conditions, it is far easier to keep these plants healthy by sound culiural practices io cure them after they have become susceptible to pests and diseases through neglect and mistreatment.

Sucking Pests

The most insidious pests that auack succulents are those that suck the vital juices from stems and leaves and flowers. They are, as a rule, small and difficult to detect, and especially dangerous indoors, where they can multiply unchecked by their natural enemies. Hidden in the soil, in the crevices of roots and stems, in leaf joints and flower buds, they sap the plants of vitality, discolor leaves and flowers, and deform new

growth and buds. Every new plant should be carefully checked for their presence, every old one examined when cleaning or repotting.

Perhaps the prime cause for the growth and spread of several of these pests are ants. They actually carry aphids and mealy bugs irom one plant to another put them to graze and nurse them, and in return eat the honeydew secretion which these pests produce. Controlling ants in the garden and greenhouse can markedly reduce the numbers and spread of these sucking pests, A good ant paste or powder should be used regularly on ant trails and nests, but never applied directly to the plants themselves.

The commonest sucking pest found on succulents are aphids or p:ant lice. These are small, soft-bodied, usually greenish insects which feed by thrusting their sharp beaks into tender young plant cells and sucking out the sap. The results are shown in discolored areas on the foliage, curling of leaves, and blighting of buds and fruit, f ortunately they are easily controlled by spraying with a forty per cent nicotine sulfate-soap solution made of one quart lukewarm water one teaspoon mild soap flakes, and one half teaspoon Black Leaf 40, The plants should be watered thoroughly the day before spraying, shaded lightly after spraying, and the residue washed off in a few hours.

Certainly the most dangerous of all the sucking pests afflicting succulents are mealy bugs. These are fuzzy, gray or white, waxlike bodies about the size of a grain of wheat which are found on the spines, stems, or roots of succulent plants, especially when they are abnormally dry Like aphids, they devitalize the plants by sucking cell juices; but, unlike them, the waxy-coated mealy bugs are far more difficult to kill, A few may be picked off plants with tweezers, killed by touching them with a camclVhair brush dipped in denatured alcohol, or scrubbed off with a toothbrush dipped in the nicotine-soap solution, but extensive infestations can be re-

moved only by more draslic measures. Large plants heavily infested aboveground can be hosed off thoroughly with a strong spray of water, which will not only knock off the bugs but wash away the sticky honeydew. Plants whose roots are

infested may either be set with thesr pois in a pan of the nicotine solution to soak for thirty minutes or, if growing in the ground, a trench can be made around them and the soil thoroughly saturated with the same solution. If there is still any doubt that mealy bugs are in the soil, the plant should be taken out of the soil, its roots scrubbed and soaked quickly in the nicotine solution, and repotted or planted in fresh soil.

The most stubborn sucking pests affecting succulents are scale. They generally appear as brown or whitish raised spots about the size of pinheads on the stems, especially around the areoles of cacti. They are even more difficult to eradicate than mealy bugs because they are closely fitted with a strong shell-like covering that most sprays cannot penetrate. In mild infestations the affected parts may be scrubbed clean with a toothbrush dipped in nicotine-soap solution, but more serious attacks must be sprayed thoroughly at regular intervals with an oil-emulsion spray such as Volck according to the manufacturer's directions.

A very serious pest of some succulents is the root-knot nematode. It is a microscopic wormiike animal which enters the roots of plants such as echeverias and euphorbias and causes irregular swellings, or galls, which prevent the roots functioning properly. Affected plants are usually pale in color and somewhat dwarfed by this injury. Whenever suspicious swellings are found on the"roots of any succulent, they should be root-pruned severely, dried out for a few days, and planted again in fresh soil. Since these pests are soil-borne, the old soil should be destroyed and the new soil used in the planting mixture sterilized if there is any doubt. This is easily done by heating the soil in an oven at 1808F. for an hour.

When succulents are kept too dry and warm, especially m-

doors in winter, Lhrips and red spiders may sometimes attack the plants, draining juices and leaving behind small yellow or white spots on the stems or leaves. These liny mites, which look like bits of animated dust, are easily killed by washing the plants with a strong spray of water or, better still, by a thorough spraying with the usual nicotine-soap solution.

Chewing Pes is

Nothing is so discouraging as to awake one morning to find one's pel echeveria riddled with snail holes or a choice mimicry plant pecked away by a bird. While these chewing pests are neither so insidious nor so deadly as the sucking ones, their kind of damage is just as exasperating. Fortunately. most of them can be dealt with prompily and easil).

Snails and slugs head ihe list as the chief spoilers of succulents i hey arc neither daunted by spiny plants nor beautiful biossoms, for they glide over one to eat the other with the greatest of ease. Every gardener should keep his grounds clear of all weeds and debris that might harbor these pests, ;iiid regularly set out prepared poison-bran baits lhat contain the attractant metaidehyde.

Beetles and sow bugs also occasionally attack succulents, eating at the base of mature plants and destroying seedlings outrighi They should be stopped with the same bait used ¡'or snails and slugs.

Birds cannot really be blamed for finding some of the stone-mimicry mesembryanthemums delectable, for even the natives in South Africa relish their fresh acid taste. But nothing can so quickly reduce a fine collection of these plants to shambles as a thirsty bird, Outdoor plantings should be protected with a removable scrcen of wire mesh.

Sucking Insects Cactus


Red Spid et

Root nematodes



Black rcr*

Sow bugs


V 1 Sunburn





succulents properly located, carefully planted, sensibly watered, and thoroughly rested need little or no fertilizers, hormones, etc 1 he excessive use of these stimulants denotes one of two things: either the plants have been grown improperly to start with, or they are being forced beyond their normal growth and bloom because of the grower's impatience.

A healthy plant making normal growth and bloom needs no further stimulation, even as you and I do not take drugs unless we definitely need them. But there are unfortunately gardening hypochondriacs as well as medical hypochondriacs who insist on dosing and spraying their plants regularly, whether they need it or not. It is a vicious habit, aided and abetted by the patent-cure peddlers, two-bit experts, and the grower's own irresistible impulse to play doctor. Don't feed your plants unless they show they arc hungry. Don t water them unless they are thirsty. Don't medicate them unless ihe> are obviously ill. In short, learn how your succulents were meant to grow in nature and try to give them those conditions as nearly as you can. Then stop playing God! Si: back and enjoy your plants, for you cannot really grow succulents

—they grow by themselves.


One of the best ways to iearn more about succulents is to read some of the many fine books that have been written on them recently. Not so many years ago the collector seeking books on succulents could find relatively few. Most of the serious works in the field were ponderous German tomes of little interest to the beginner But in recent years the problem has reversed itself completely There are so many books on cacti and other succulents in English now that the beginner is at a loss to know which ones to choose Some of these books are cheap, popular treatments hardly worth reading; others are serious scientific monographs so difficult that the beginner cannot hope to understand them. So it is important to set down here a few books that every amateur will find both valuable and interesting, books that have stood out from the welter of titles as being both readable and authoritative.

A really different book for the beginning collector as well as the advanced hobbyist is Cacti and Succulents for the Amateur by Charles Glass and Robert Foster (Abbey Garden Press. Santa Barbara, 1976). Many of the newer and more unusual kinds of cacti and other succulents are pictured and described in family groups.

To better understand the meaning and pronunciation of the

scientific terms and plant names he will find in his reading, every amateur should have the Glossary of Succulent Plant Terms by W. Taylor Marshall and R. S. Woods (Abbey Garden Press. 1945) It is a wonderfully useful book, and though long out-of-print, it is once again available in a special Xerox series from Abbey Garden Press.

Of books on cacti the outstanding work is certainly the monumental four-volume The Cactaceae, by N. L. Britton and J. N. Rose. It is a long and difficult work, however, and now very much out of date Even in the edition reprinted by Dover Publications (New York, 1963) it is fairly expensive. But there is one modern up-to-date book on the Cactus family that is a "must" for every student of cacti, ft is Cactus Lexicon by Curt Backeberg (Blandford Press, Poole, England. 1977), Here in one volume, profusely illustrated with hundreds of photographs, the entire Cactus family is surveyed and the Britton and Rose classification brought up to date in the light of recent discoveries. Another useful handbook is Cacti by J. Borg (Blandford Press. Poole, England.

Fourth edition, 1970).

For the reader interested in a closer study of the other succulents there is one indispensable handbook. Lexicon of Succulent Plants by Hermann Jacobsen (Blandford Press. Poole. England, 1977J. It describes in alphabetical order for easy reference the habitat and forms of over a thousand species.

There are many colorful picture books of cacti and other succulents, but one of the finest is The Illustrated Encyclopedia of Succulents by Gordon Rowley (Crown Publishers, New York, 1978). Over 250 species are shown in brilliant color to illustrate a fine general treatment of succulent plants the world over. Also valuable as a picture reference is The Illustrated Reference on Cacti and Other Succulents in five volumes by Edgar and Brian Lamb (Blandford

Press, Poole, England, 1955-1978).

For the collector who wishes to specialize in particular families of succulents we might recommend the following: The Aloes of South Africa by Gilbert Westacott Reynolds (A. A. Balkema, Rotterdam, Fourth edition, 1982) and his The Aloes of Tropical Africa and Madagascar (The Aloes Book Fund, Mbabane. Swaziland, 1966); Agaves of Continental North America by Howard Scott Gentry (Univ of Arizona Press, "ucson, 1982); Echeveria by Eric Walther (California Academy of Sciences, San Francisco, 1972); Haworthia and Astroloba by John Pilbeam (Timber Press, Portland, Oregon, 1983) and his Mammillaria (B. T. Batsford, London, 1981).

T iere are many more ot these specialized studies of particular succulents ranging from slight pamphlets to weighty monographs. They appear and disappear constantly. The interested reader should avail himself of the excellent annotated catalogs of these books published annually by Abbey Garden Press, P. 0. Box 3010, Santa Barbara, CA

93 130.

And, Finally, to keep up with current developments in the cactus and succulent world every enthusiast should subscribe to the Cactus and Succulent Journal. It is published bimonthly by The Cactus and Succulent Society of America, P. O. Box 3010, Santa Barbara. CA 93130, and is included with membership in the Society.

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