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tion. The first application is to accomplish the destruction of the beetles before they deposit their eggs, and the second and third are to kill beetles that may come from other plants. Rotation of crops and the avoidance of planting in the vicinity of neglected ground that has grown up with bindweed and wild morning-glory are also advisable.

The Common Sweet-potato Sawfly (Schizocerus ebenus Nort.). -The larvæ of two species of sawflies have been observed doing injury to sweet potato.

They

are comparatively

new as pests and of similar

habits and distribution from New York to the Gulf and northward to Nebraska.

The present is like other sawflies, four-winged, and somewhat smaller than a house fly, the body is black,

and the wings infuscated

or dusky. The male has Fig. 157.-Eubadizon schizoceri.

Parasite of

sweet-potato sawfly. (After Insect Life)

forked antennæ while the female has shorter simple ones. Eggs are deposited in the leaf of sweet potato. Attack has been observed in August and September in Mississippi, and a parasite (fig. 157) has been reared from the larva. This parasite, and a tachina fly, which also preys on it, no doubt hold the insect in check and prevent serious injury.

The Larger Sweet-potato Sawfly (Schizocerus privatus Nort.). The first record that we have of injury by the larvæ of this sawfly was in July, 1890, when it damaged sweet potato in Virginia. At that time plants that were attacked produced no yield whatever. This sawfly is larger than the preceding, the wing expanse being nearly 3/5 of an inch, and both sexes have yellow abdomens. Other differences can be made out by

comparison of the illustration of each. According to Marlatt, deposition of the eggs is on the under surface of the leaf, and by reference to figure 158, a, it will be seen that eggs are placed usually in parallel rows bordering the larger veins of

[graphic][subsumed][subsumed][subsumed]

Fig. 158.-Larger sweet-potato sawfly. a, Female sawfly . antenna of male; b. young larva; c, section of infested sweet-potato leaf. showing egg deposit d same showing larva hatching and feeding. a, b, d, 6, Enlarged; c, natural size. (Adapted from Marlatt.)

the leaf. Larvæ are seen hatching from the pouch-like egg receptacles or blisters at b.

REMEDIES. Both these sawfly larvæ when abundant may be easily controlled by the prompt application of hellebore or arsenicals when they make their first appearance.

Cutworms. Since sweet potato is cultivated in seed-beds, it is subject to the ravages of cutworms when set out in newlyplowed fields. One of these, the dark-sided cutworm (Carneades messoria Harr.), appears to be particularly identified with attack of this nature. It is a common species, and in addition to various garden crops seems to revel in onions. A

more complete account, with illustrations, has been furnished on page 246. The variegated cutworm, in years when it indulges in uprisings, also injures sweet potato and some other cutworms and other caterpillars of less importance occasionally cause losses to this plant.

REMEDIES for these insects are duly treated on page 54.

Mealy-bugs (Dactylopius spp.).—A species of unidentified mealy-bug has been mentioned by Dr. J. B. Smith as destructive in Salem County, N. J., in 1901, to sweet-potato in forcing beds.' They were found clustered at the bases of the sprouts and of the small leaves. It is not probable that these insects would survive normal outdoor conditions when plants are set out in spring in New Jersey, but in the Gulf region they doubtless would develop out-of-doors quite as well as under glass. For protection against mealy-bugs cellars and storerooms should be thoroughly whitewashed and cleaned before the seed tubers are stored and the temperature should be kept low while in the beds where the roots are forced in spring. Cleanliness should be observed and the roots should be inspected before putting them in, and such as show the mealy-bugs should be rejected and destroyed.

1 Rept. Dept. Ent. N. J. Agr. Coll. Exper. Sta. for 1901 (1902), p. 489.

CHAPTER XVI

INSECTS INJURIOUS TO MISCELLANEOUS VEGETABLE CROPS

THE ONION AND OTHER BULB CROPS

feed on the others.

BULB crops are so similar that what will attack one is apt to Six crop plants (genus Allium) are included in this group: the common onion, Welsh onion, shallot, cive, leek and garlic. Of these only the first is grown to any extent in North America. "The onion," some one has remarked, "is one of those strenuous vegetables about which one cannot be indifferent. One either yearns for it with a passionate longing or else utterly repudiates it." The same is true as regards insects, since few species are overfond of it. The leading species are the onion maggot and onion thrips. A few insects of omnivorous tendencies, however, not infrequently do much injury to this plant. Of such are some forms of cutworms, and especially the dark-sided cutworm, wireworm, and the imbricated snout-beetle. The pungent odor of the onion and its kind renders it unpalatable to many insects, but some resort to these plants in the absence of other vegetation.

Insect injury to onion and related plants is peculiarly local or intermittent, and in spite of the injurious species which will be treated, and the immense amount of damage that they have done, it is no uncommon sight, but in fact the rule, to see fields grown to these crops year after year for long periods without their sustaining any material harm. Such is the case about the District of Columbia, where no insects what

ever have been noticed in recent years injuriously affecting the onion crop.

The Imported Onion Maggot (Pegomya cepetorum Meade).This maggot injures the onion by eating into the bulbs, the subsequent decay of the affected portions frequently destroying them. It is a most important drawback to the culture of onions here and in Europe, from which continent it was introduced years ago. It is nearly related to the seed-corn, and cabbage, maggots treated in former pages. In the adult state it resembles, as do the others, the common house fly. The average size is a little larger than the flies of the two root-maggots that have been mentioned, the body being about 3/16-inch long and the wing expanse nearly 3/8-inch. The maggot itself and the puparium can be distinguished from those of other root-maggots only by careful comparison.

The life history is very like that of the cabbage maggot, the differences being due to the different character of the vegetables attacked. It follows that the natural enemies which prey on one are liable to attack the others, and the remedial measures to be adopted are also much the same.

REMEDIES. For a discussion of remedies the reader is referred to the account of the seed-corn maggot.

The Black Onion Fly (Tritoxa flexa Wied.). This is an old enemy of onion and a native species, recorded from the Atlantic coast to Illinois. The fly is about one-third of an inch long, black, with three oblique white stripes on each wing. The maggot itself is white and larger than the root

feeding species previously treated. Fig. 159.-Black onion fly. Three

It feeds on onions and cives both in

[graphic]

times natural size. (After Walsh)

the field and in store. General remedies are the same as for the

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