CHAPTER XI

INSECTS INJURIOUS TO CELERY, PARSNIPS AND RELATED PLANTS

A CONSIDERABLE number of insects attack 'celery, but few are restricted to it as a food, and fewer yet do noticeable damage. A large proportion of the insects which live on it also attack carrot, parsnip, and parsley, preferring one or the other of these three plants. For convenience, however, we may consider the insect enemies of celery separately.

INSECTS INJURIOUS TO CELERY

What is true in this country is equally true in Europe, and there is little danger of the introduction of important pests from abroad. With the increased cultivation of this crop insects which now attack it may increase in injuriousness, but there is no immediate prospect of serious losses accruing from insect attack. It is seldom that beds of celery are entirely free from the celery caterpillar; the same may be said of the zebra caterpillar. The tarnished plant-bug is one of the worst enemies with which the celery grower has to contend, but its having many host plants usually distributes attack except in unusual seasons. Celery generally escapes the ravages of cutworms owing to its late planting and still later replanting, and neither white grubs nor wireworms deter its growth as far as observations go, presumably because of its powerful root and root stalk. The leaves are attacked by leaf-rollers and leaf-tyers and one of these, the celery leaf-tyer, is of considerable importance.

The Carrot Rust Fly (Psila rosa Fab.).—This pest has been injurious to carrots in Canada since 1885 and made its ap

pearance in 1901 in New York in celery fields. In attack on celery the leaves of young plants early in spring turn reddish, and the roots are blotched with rusty patches, particularly toward their tips. Roots of carrot when stored for winter, although not manifesting any degree of injury on the outer surface, are at times perforated in all directions by dirty brown

Fig. 115.-Carrot rust fly. . Male fly; 9, female fly; a. antenna of male; b, fullgrown larva, lateral view; c, spiracles of same; d. anal extremity; e, puparium; f. young larva; g, anal segment from side. Flies, young and mature larva, and puparium, eight times natural size; other portions more enlarged. (Author's illustration, U. S. Dept. Agr.)

ish burrows, from which these whitish yellow maggots may be found projecting. When celery is infested the larvæ seem to begin eating into the thick part of the root when the plant is about half grown, stunting it so as to make it worthless for market.

This species is quite minute, the parent fly measuring only about one-sixth of an inch in length, with a wing expanse of a little more than three-tenths of an inch. The body is dark green and is rather sparsely clothed with yellow hairs. The head and legs are pale yellow, and the eyes black. The two sexes are shown at ♂ and, figure 115. According to Curtis, when the imago issues from the puparium an oval lid on this portion lifts up, permitting the fly to crawl out. The posterior extremity ends in two minute dark tubercles.

The carrot rust fly is a pest in Europe, whence it has been introduced in this country. It is a northern species and is

permanently established in New Brunswick, Ontario and Quebec, Canada, besides occuring in New York and New Hampshire.

The life history of the carrot fly has not been entirely worked out. In the United States it will probably be found to pass the winter usually as a puparium, but as larvæ work also on carrots in store, the flies develop in winter, hence we have great irregularity in development, making generalization impossible until observations are made in the field.

The insect develops rather early in the season and both flies and maggots are found throughout the warmer months, but the latter desert the roots for pupation in the earth, the last generation probably descending much deeper than the earlier ones. Curtis states that the summer generations develop in three or four weeks. There are at least two, and probably more, generations annually. Miss Ormerod has observed that the female fly goes down into the ground where she can find a crack or other opening about the roots of the plant affected. Here she lays her eggs, and the maggots, when hatched, work their way into the root; when this is quite small they often destroy the lower portion.

METHODS OF CONTROL

The carrot rust fly is difficult to reach with insecticides. Our principal dependence is based upon methods of tillage which will avert attack.

Kerosene emulsion in the proportion of one part to ten of water sprayed upon the carrots along the rows, or sand, or ashes, with which kerosene is mixed at the rate of half a pint to three gallons, sprinkled along the rows, have given good results. These substances deter the fly from laying her eggs.

Late sowing and rotation of crops are excellent remedies, as is also the planting of new beds as far as possible from land infested the previous season.

Destruction of stored carrots.—Where carrots are stored for winter use in earth they should be treated to destroy the larvæ or puparia. This may be accomplished by burying the earth deeply; by spreading it in thin layers where it will be exposed to the elements; by throwing it into pools where it will be frozen; or by exposing it to heat or steam in any convenient

manner.

Treatment of celery beds.—As this insect also infests celery, that crop should not follow carrots (nor carrots celery) in rotation. Clean farming should be practiced, which includes the destruction of remnants after the crop has been harvested.

After harvest, it would be a good plan to give celery fields a raking or cultivating of sufficient depth to expose the larvæ or puparia to frost; early the following spring, before the flies issue, if the earth be plowed deeply, it will have the effect of destroying such insects as have not been killed by frost and survive cultivating and raking.

The Celery Caterpillar (Papilio polyxenes Fab.).-Because of its large size and brilliant colors, both as larva and adult, this is one of the best known of the enemies of celery and allied plants. The caterpillar is green, or yellowish, and ringed with black and spotted with yellow. It attains a length of two inches. The parent insect is known as the black swallow-tail. It is velvet black, relieved by yellow bands in the male. The hindwings are ornamented on the interior margin by eye-like markings like those of the peacock and the wings terminate in the tails from which it derives its common name. The female is somewhat faded black and of more sombre appearance than her mate. The wing expanse is about three inches. The chrysalis is dull gray, mottled with dull brown. It measures a little less than one and one-fourth inches. The celery caterpillar is one of the most interesting insects that attack garden plants. It appears to be limited to no special life zone, occurring throughout Canada and every State and Territory in the

Union, southward through Central America and the West Indies to Venezuela. The young larvæ are utterly dissimilar to the mature ones, and five distinct stages have been noted.

This insect affects practically all umbelliferous crops, celery, carrot, parsley, caraway, fennel, parsnip, dill, and related wild plants. It does not appear to attack, except in extreme cases, any plant outside of this botanical family.

REMEDIES. The conspicuous coloration of the celery caterpillars renders them an "easy mark" as they are readily found and can be crushed under foot, and no other remedies are necessary if the work of destruction is begun before the plants are injured. The killing off of the first generation will serve in considerable measure to destroy the insects for the second brood, if this work be done over a considerable area. The butterfly, however, is strong of flight, and cooperation must be had to keep the insect in check when it becomes destructive. The Celery Leaf-tyer (Phlyctania ferrugalis Hbn.)1.—This little insect, known also as the greenhouse leaf-tyer, first came to notice as a pest in 1888. On celery it feeds by preference on terminal leaves, and sometimes burrows into the stems. one occasion in the District of Columbia it was so destructive that one grower had determined to abandon celery culture on this account. Next year, however, the insect was less troublesome; and this was fortunate, for if it were not periodical it might be a very bad pest indeed. In the field this leaf-tyer attacks besides celery cabbage, beets, tobacco, lettuce, cauliflower, parsley, cucumber, sweet pea and strawberry. It causes great injury to many greenhouse plants-violet, rose, chrysanthemum, carnation, ivy, heliotrope, and others.

On

The moth is a pale reddish-brown, expanding about three-fourths of an inch. The fore-wings are pale clay brown, suffused with reddish or ochreous brown, ornamented with black lines (fig. 116, a, b). The hind-wings are gray, with darker margins. 1 For a detailed account see Bul. 27, Bu. Entom., U. S. Dept. Agr.