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| Figure 36. Mine in bramble leaf caused by blackberry leafminer. |
Blackberry Leafminer, Metallus rubi Forbes
The blackberry leafminer is a very small sawfly with adults not exceeding 5 mm (1/5 inch) in length and the white larvae being nearly 12 mm (1/2-inch) long when fully grown. The larva mines the leaves of blackberries (Figure 36) and at times may cause serious injury. Larvae hibernate in the soil, transform to pupae in the spring, and begin emerging as adults in early June. Two generations are produced annually, the second occurring in mid-August.
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| Figure 36. Mine in bramble leaf caused by blackberry leafminer. |
Raspberry Leafroller, Olethreutes permundana (Clemens)
Terminal leaves of raspberries are sometimes webbed together in May and early June into a twisted mass (Figure 37) by a small dark green larva with a black head and thoracic shield. When fully grown, the larva usually folds over a part of a leaf, forming a cavity in which it pupates. Moths appear about two weeks later. Wing expanse is about 12 mm (1/2 inch), and the moth's forewings are dull yellowish or greenish-brown with irregular lighter markings crossing the wing obliquely. Hind wings are ash brown.
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| Figure 37. Group of leaves tied together by raspberry leafroller. |
Raspberry Sawfly, Monophadnoides geniculatus (Htg.)
This is not a common pest in Ohio, but it does occur at times in low numbers. The adult is a small, thick-bodied black sawfly, little more than 6 mm (1/4 inch) in length, which lays its eggs in the leaf tissue of the host in May and June. Larvae are light green and marked by conspicuous bristles, which arise from small swellings on the body. These larvae may be as much as 12 mm (1/2 inch) in length. In the course of their development, they consume the leaf tissue, and a heavy infestation may result in loss of the crop. The larvae complete their feeding in less than two weeks and then estivate in cocoons, which they construct in the ground. Larvae remain in these cocoons through the winter and pupate in early spring.
Blackberry Gallmaker, Diastrophus nebulosis (O-S.) and Related Species
The blackberry gallmaker causes the formation of large knot galls on the stems of brambles (Figure 38). The galls are first green and later red or brown. The causal agent is a tiny wasp in the family Cynipidae. If control measures are necessary, remove the galls by pruning and destroy them.
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| Figure 38. A knot gall caused by the blackberry gallmaker. |
Stalk Borer, Papaiperma nebris (Guen.)
This insect is almost a universal plant feeder, attacking stems of any plant large enough to shelter it and soft enough so that it can bore into them. The primary symptoms in a raspberry field are the wilted tips and the large hole in the side of the cane some 15 to 20 mm (6 to 8 inches) back from the tip. Damage is done primarily by boring and tunneling in the stems (Figure 39). Bramble plantings adjacent to weedy areas of the favored host, such as giant ragweed, are most often attacked.
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| Figure 39. The stalk borer attacks brambles as well as many other plants. |
Blackberry Psyllid, Trioza tripunctata Fitch
The blackberry psyllid curls and stunts the growth of new rapidly growing shoots and leaves of cultivated and wild brambles (Figure 40). Early in the season the injured tissue, particularly the leaves, is much darker green in color than normal tissue. The early stunting and malformation of the shoots and leaves are due entirely to adult females. Often by the time the malformations are seen, there are no insects easily visible on the leaves. Thus, such damage is often mistaken for other maladies such as virus. In Ohio, more curled, marked leaves are seen in the southern portion of the state than in other areas. However, this insect has not been seen causing much injury anywhere in the state.
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| Figure 40. Curled and misshapen leaves of bramble crops are often a sign that blackberry psyllid has been present. |
Raspberry Cane Maggot, Pegomya rubivora (COQ.)
The adult cane maggot is a small, grayish fly about a third smaller than a housefly. The first symptom, as in the case of several other bramble pests, is a wilted cane tip or a tip that has been cut off almost as cleanly as if it were cut with a sharp blade. The larvae or maggots tunnel around the inside of the stem, girdling it. A gall-like swelling forms where canes were girdled. It is an easy operation to cut off the infested portion a few inches below the girdle and destroy it by burning.
For More Current Information
For current information on control of insect pests of brambles, growers should
consult current pesticide recommendations in Ohio State University Extension
Bulletin 506-B, Commercial Small Fruit Spray Guide. It is available for
Ohio citizens from their county Ohio State University Extension office. For
citizens outside of Ohio, contact:
Media Distribution
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385 Kottman Hall
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Columbus, OH 43210-1044
Fruit Newsletter
The Ohio Fruit Integrated Crop Management Newsletter is available free
by e-mail to growers who send their request and e-mail address to:
gastier.1@osu.edu
Mail subscriptions are $45 for 12 months. Send your mail subscription requests to: Ted Gastier, Ohio State University Extension, Huron County, 180 Milan Avenue, Norwalk, OH 44857. Checks should be made out to Ohio State University Extension.
Midwest Small Fruit and Grape Net
This is your source for information on management, commercial production, and
harvesting of small fruits and grapes. The web address is:
http:/www.ag.ohio-state.edu/~sfgnet