Home -> Pacific Rural Press -> 1000 Questions Answered in California Agriculture -> Part IX - Pests and Diseases of Plants
Part IX. Pests and Diseases of Plants Control of Grasshoppers. This county is having trouble with the grasshoppers as are other counties. Would you kindly inform me what I could do to exterminate them on my young orchard? The best thing for grasshoppers is to fix up a lot of poison. This is made in the proportion of 40 pounds of bran, 2 pounds of molasses and 5 of arsenic, mixed together as a mash. They will take this wherever they find it, even when nice green leaves are close by, but it has to be kept moist. Grasshoppers can also be reduced by driving a "hopper doser" over ground where they are. This is made somewhat like a Fresno scraper, but is much longer and the bottom is covered with crude oil. When disturbed the hoppers jump up and fall into the oil. Besides the poison, you should also protect the trunk of the tree to prevent the hoppers from climbing up it. This can be done by applying tree tanglefoot, or putting on one of the tree guards that prevent climbing insects from passing up to the leaves. The combination of poison and tree guards will give you about all the protection you need. Sunburn and Borers. Please state the best remedy for keeping the borer out of young fruit trees. Sunburn can be prevented in many ways. The manufactured tree-protectors are good if they are light colored and are kept in place so that the sun does not scald above or below them. Wrapping spirally with narrow strips of burlap, torn from old grain sacks, from the base to the forking of the branches, is also good. A very effective and widely used method is to apply a good durable whitewash which may be made of 30 pounds of lime, 4 pounds of tallow and 5 pounds of salt, adding the salt to the water used in slaking the lime, stirring in the tallow while the slaking is in progress and hot, and then adding water to thin the wash so that it will work well with pump or brush. Gumming of Prune Trees. I write to ask for information concerning my prune trees. They are from two to six years old and the gum is exuding from them. As I notice the branches dying I cut them out, but this doesn't seem to save the tree. I would appreciate any information you can give me. This is a pretty hard matter to diagnose from a distance. There is a good probability that the trouble is caused by sunburn, a point you could determine on inspection. Whitewash would be a protection against this and more or less of a cure also. Furthermore, borers may be the cause, which can be determined by examining the points where the gum exudes, seeing if any wood grains are present. These borers should be dug out and whitewash applied, which latter also protects against this trouble. Lastly, your ground may be drying out, which also you can determine and remedy. Borers in Olive Twigs. There are quite a number of olive trees in this locality that have something wrong with them. They make a growth of five or six inches and the center twig dies back, then it sprouts out at the sides and makes another growth in the same way. This makes a thick bush instead of the tree coming up as it should. The dying back is caused by a beetle which bores into the twigs. The twigs above the point where the beetle enters dies and then, of course, buds come out from healthy wood below. No treatment has been devised against it, though its breeding ground is limited if all dead wood and brush and litter is cleaned up and twigs are cut off below the point of injury whenever the work of the insect is seen. Raspberry Cane Borer. Can you tell me what to do for my Loganberries and raspberries? A small worm got into them in the new growth of wood lost summer, right in the tips of the new growth of wood, and then worked down through the pith of the wood, and as fast as they worked down the can wilted. This is the raspberry horn-tail, or the cane-borer. The adults are wasp-like insects about a half-inch long and very active. They come out of the canes in spring and the females soon lay eggs in the tender tips of the young shoots. These eggs soon hatch and the larvae eat their way up toward the tip, which causes it to wither and die. It is this injury that causes much notice. As the tip dies, the larvae turn and go down into the canes, as in the sample sent, also injuring them greatly, though possibly not killing them for some time. The only way to attack them is to pinch the spots where the eggs were laid; then those that escape and cause the tips to wilt should be destroyed by cutting off the tips below the point of injury or cutting off the canes when they show damage. Likewise, the insects work on the wild rose, and cutting all those out around a place will prevent enough adults from developing to permit little damage to be done, always provided the berries are well looked after. Control of Red Spider. Can you give directions for the prevention of injury by the red spider to almond and other trees in the Sacramento valley? The red spider on almond and prune trees is usually controlled by the thorough application of dry sulphur to the foliage. On almonds the first sulphuring should be done as soon as the leaves appear in March. A second application is advised from the 1st to the 10th of May. A third application should be made from the 1st to the 10th of June. Prune trees should be treated as soon as the spider appears. In the Sacramento valley this usually occurs about the first week of July. Full-grown trees require about a pound of sulphur which should be thoroughly distributed throughout the foliage. The old method of throwing a handful of sulphur in the branches of the tree or on the ground under the tree is valueless. The use of a blower is economical in large orchards, but a can with perforated bottom is frequently used on young trees or small orchards with good results. In normal seasons the spider is easily, controlled by dry sulphuring. When the pest does not yield to this treatment, a spray is recommended. Liquid Spray for Red Spider. Is there any liquid spray I can use in my spraying that will kill the red spider without injuring the foliage of the almond? A liquid spray for red spider is made by taking sulphur 30 pounds; lime (reduced to milk form by water), 15 pounds; water, 200 gallons; or use commercial lime-sulphur, 4 or 5 gallons to 200 gallons of water. These sprays can be applied without injuring the foliage. They are more expensive in labor cost than dry sulphuring, but are more effective. Apple-Leaf Aphis. I am sending herewith a small piece from one of my young apple trees. If you can, will you kindly tell me what the insects are an it, and what I had better do for them? The apple twig which you send is infested with the eggs of the leaf aphis or leaf louse. These eggs are very difficult to kill. A good thorough spraying with lime-sulphur might, however, get rid of many of them and would be good for the trees otherwise - diluting according to condition of tree growth. The chief campaign against the leaf aphis, however, must be made early in the growing season, just as these pests are beginning to hatch out and to accumulate under the leaves of the new growth. They should then be attacked with properly made kerosene emulsion or tobacco extract with a nozzle suited to land the spray on the under side of the leaves. Unless these pests are attacked early in the season and repeated if necessary, your apples on bearing trees will be ruined so far as they attack them, being small, misshaped and worthless. On young trees the destruction of the foliage is fatal to good growth. Woolly Aphis. Will you kindly inform me what you consider the best treatment for apple trees affected by woolly aphis? The best way to kill the woolly aphis on the roots is to remove the earth from around the tree to a distance of one or two feet, according to the size of the tree, digging away a few inches of the surface soil, Then soak the soil around the tree with kerosene emulsion, properly made, of 15 per cent strength, and replace the earth. Be sure you get a good emulsion, for free oil is dangerous. For the insects above ground on the twigs, a good spraying while the tree is out of leaf will kill many, but some will survive for summer spraying, and for this a tobacco spray may be most convenient. Blister Mite on Walnuts. I am sending you some walnut leaves with some swellings an them. They are very plentiful on some trees here. Is the trouble serious and will it spread? This is merely Erinose, or Blister Mite, which is a very common trouble on walnuts, but does not do enough damage to call for methods of control. These swellings are caused by numerous, very small insects which live within the blisters on the under side of the leaf amongst a felt-like, heavy growth which develops there. While this effect is very common, it produces no appreciable injury and needs no treatment for its control. Scale on Apricots. I would like to know how to check the scale on apricot trees. The most common scale on apricots, the brown apricot scale, is usually held in check by the comys fusca, which is as widely distributed as the scale itself. If it gets beyond the parasite, you should spray in winter with crude oil emulsion. If some scales are punctured or have a black spot on top, the comys fusca is busy and you probably will be safe enough without doing anything. Fumigating for Black Scale. I would like to know the best method of eradicating the black scale from my orange trees, whether by spraying or fumigation? Spraying has been given up as a suitable method for controlling the black scale on citrus trees, and the only recognized method of merit where the scale is bad is by fumigation with hydrocyanic acid gas. You should communicate with your county horticultural commissioner, who, through inspectors, will see that you have a good job done, at the right time and at as moderate price as is compatible with good work. It is impossible to 'eradicate' the black scale, but there is a great difference in the amount that can be killed, and it pays to have a job done as near perfectly as possible. Similar methods of attacking other scale insects on citrus trees are used. Finding Thrips. How can the presence of pear thrips be detected in a prune orchard? Will the distillate emulsion-nicotine spray control brown scale as well as thrips? You can find thrips by shaking a cluster of blossoms, as soon as they open, over a sheet of paper or in the palm of your hand. The thrips are very minute, transparent, somewhat louse-like insects. The spray you mention would probably have little effect on the brown scale which would still be in the egg state and under cover, at the time the early spring spraying for the thrips. Control of Pear Slug. I am sending, under separate cover, some samples of cherry tree leaves that have been attacked by a small snail or slug. Kindly let me know what they are, and how to rid the trees of them. The creatures you speak of are the pear slugs, or the cherry slugs, as they are sometimes known. Although slimy, like the big yellow slug that is a pest in vegetable gardens, it is no relation thereto, but is the larva of an insect. Its olive green color, slimy appearance and the way it eats the surface of the leaves make it about the easiest of all insects to identify. Parasites and predacious insects usually keep it in fair control. Whenever artificial methods of control are needed the slugs can best be destroyed by sprinkling dust of any kind upon them. If you can get a machine for sulphuring a vineyard and use some air slaked lime or other fine dust, it will fix them quickly and inexpensively, though any way of applying dust may be used. Cutworms and Young Trees. What method should be used to protect young fruit trees from cutworms? Hoe around the trees or vines and kill the fat, greasy grubs which you will find near the foliage. Put out a poisoned bait which the worms like better than the foliage, viz. Bran, 10 pounds; white arsenic, 1/2 pound; molasses, 1/2 gallon; water, 2 gallons. Mix the arsenic with the bran dry. Add the molasses to the water and mix into the bran, making a moist paste. Put a tablespoonful near the base of the tree or vine and lock up the chickens. Control of Squash Bugs. We are troubled with pumpkin bugs. Please tell us what to do for them. When the bugs first make their appearance in the field they can be easily disposed of by hand picking and dropping into a bucket containing about two inches of water with about one-fourth inch of kerosene on top to kill the bugs. The picking should be done in the morning, as the bugs are apt to fly in the warm part of the day and scatter where already picked. Two persons can pick over an acre in one and a half hours, and two pickings are usually sufficient for a season, as after the vines begin to run over the ground pretty well the bugs will not be able to hurt them much. A pair of thin old gloves will help to keep off one's hands some of the perfume from the bugs. The sooner the work starts the fewer bugs to pick. Cleaning up of all old vines in the fall and removing litter in which the mature bugs hide for the winter will permit less eggs to be laid in the spring and there will be fewer bugs to pick as a result. The Corn Worm. Last year all my ears of corn were infested with maggot, growing fat thereon. Can you help me scare them away? You have to do with the so-called corn worm which is very abundant in this State and one of the greatest pests to corn growing. It is the same insect which is known as the boll worm of the cotton in the Southern States. No satisfactory method of controlling this has been found, although a great deal of experimentation has been done. Nearly everything that could be thought of has been tried without very satisfactory results. A late planted corn has sometimes been free, for the insect is not in the laying stage then. If it were not for this insect the canning of corn would be an important industry in this State. Melon Lice. I have in about four acres of watermelons, and there seem to be lice and a small gnat or fly, and also some small green bugs and white worms on the under part of the leaves, which seem to be stopping the growth of the vines, making them wilt and die. They seem to be more in patches, although a few on all the vines. Can you please tell me what to do for them? Melon lice are very hard to catch up with after you have let them get a start. Spraying with oil emulsions, tobacco extracts, soap solutions, etc., will all kill the lice if you get it onto them with a good spray pump and suitable nozzles for reaching the under sides of the leaves. The gnats you speak of are the winged forms of the lice; the white worms may be eating the lice; the "small green bugs" may be diabroticas. If you had started in lively as soon as you saw the first lice you could have destroyed them in the places where they started. Now your chance lies largely in the natural multiplication of ladybirds and the occurrence of hot winds which will burn up the lice. It is too late probably, to undertake spraying the whole field. Wire Worms. Is there any way to destroy or overcome the destructive work of the wireworm, which I find in some spots takes the lion's share of crops, such as beans, potatoes, onions, etc.? We do not know any easy way with wire worms. Nitrate of soda is believed to kill or repel them, but you have to be careful with it, for too much will either over-stimulate or kill the kill; about 200 pounds per acre, well distributed, is the usual prescription for the good of the plants. Wire worms can probably be killed with carbon bisulphide, using a tablespoonful poured into holes about a foot deep, three or four feet apart. The vapor would permeate the soil and kill all ground insects, but the acre-cost of such treatment must be measured in its relation to the value of the crop. The most promising policy with wire worms is rotation of crops, starving them out with a grain or grass crop and not growing such crops as you mention continually on the same land. Bean Weevil. How can I keep certain insects from getting into my dry beans? I have finished picking the crop. Every year a little, short, stubby beetle gets in them before spring and makes them unfit for use. You have to do with the bean weevil. The eggs are inserted by the insect while the beans are still green in the pods; subsequently the eggs hatch and the worm excavates the interior of the ripened beans. The beans can be protected after ripening by heating carefully to 130° Fahrenheit, which will destroy the egg, or the larva if already hatched. Of course, this heating must be done cautiously and with the aid of a good thermometer for fear of destroying the germinating power. The work of the insect can also be stopped by putting the beans in a barrel or other close receptacle, with a saucer containing about an ounce of carbon bi-sulfid to vaporize. Be careful not to approach the vapor with a light. After treatment for one-half hour, the cover can be removed and the vapor will entirely dissipate. This is a safer treatment than the heating. Similar methods of control can be used on other pea and bean weevils. Slugs in Garden. Can you advise me how I can get rid of slugs in my garden? When barriers of lime, ashes, etc., are ineffective, traps consisting of pieces of board sacking and similar materials placed about the field prove inviting to the slugs. They collect under these and by going over the field in the early morning they may be put into a salt-water solution or otherwise destroyed. Arsenical sprays applied with an underspray nozzle to the lower surface of the leaves will help control the slugs. Poison bran mash consisting of 16 pounds of coarse bran, 2 quarts of cheap syrup, and enough warm water to make a coarse mash, is very good for cutworms and should be equally effective for slugs. It should be placed in small heaps about the plants to be protected. Cabbage leaves dipped in grease drippings and placed about the fields also prove attractive bait for the slugs, which may then be collected there. If a person has a taste for poultry, the keeping of a few ducks may solve the slug problem without further bother. Cultivation or irrigation methods that give a dry surface most of the time also discourage these pests. Cause of Mottle Leaf. What is the cause and cure of mottle leaf of citrus trees? There are apparently a number of causes of this trouble, all more or less obscure and hard to overcome. It is generally thought that it is due to poor nutrition, whatever the reason for poor nutrition might be. The presence of a nematode or eel worm on the roots has found to be a cause of mottle leaf in many cases. Poor drainage, too sandy soil and a number of other things frequently cause it. Whatever the cause, no one good method of cure has been found. Potato Scab. I think most of my potatoes will have some scab. Will you please tell me if my next crop would be apt to have scab, provided I got good clean seed and planted in the same ground? It seems demonstrated that a treatment of the seed will practically insure against potato scab. One method is dipping the potatoes in a solution of corrosive sublimate. Dissolve one ounce in eight gallons of water and soak the seed potatoes in this solution for one and one-half hours before cutting. Gopher Poison. I have some alfalfa, some hogs and some gophers, also some strychnine and carrots. If I put the strychnine on the carrots, and endeavor to poison the gophers, and the hogs get hold of the poison will it kill them? You will find that hogs are liable to poison like any other animal, and the safest way to poison the gophers, while the hogs are running in the field is to bury the poisoned carrots very deeply in the gopher hole and then put a row of sticks or branches over the mouth of the hole so that the hogs cannot root around and get at the poisoned carrots. How to Make Bordeaux. Use copper sulphate (bluestone) 5 pounds; quick-lime (good stone lime), 6 pounds; water, 50 gallons. Put the bluestone in a sack and hang it so it will be suspended just under the surface of a barrel of water over night, or dissolve in hot water. Use one gallon of water to one pound of bluestone. Slake the lime in a separate barrel, using just enough water to make a smooth, clean, thin whitewash. Stir this vigorously. Use wooden vessels only. Fill the spray tank half full of water, add one gallon of bluestone solution for each pound required, then strain in the lime and the remainder of the water and stir thoroughly. The formula may be varied according to conditions, using from 3 to 8 pounds of bluestone to 50 gallons of water and an equal or slight excess of lime. Use the stronger mixture in rainy weather. Keep the mixture constantly agitated while applying. Formula for Lime-Sulphur. To make lime-sulphur take quick-lime, 20 pounds; ground sulphur, 15 pounds and water 30 gallons. Slake the lime with hot water in a large kettle, add the sulphur and stir well together. After the violent slaking subsides add more water and boil the mixture over a fire for at least one hour. After boiling sufficiently strain into the spray tank and dilute with water to the proper strength. If a steam boiler is available, this mixture may be prepared more easily on a large scale by cooking in barrels into which steam pipes are introduced. This mixture cannot be applied safely except during the winter when the trees are dormant. A large proportion of the lime-sulphur used in the State is purchased already prepared in more concentrated form.