FO-6703-C MI NESOTA EXTENSION SERVICE 1996 U NIVER SIT Y OF MINNES OTA C OLLEGE OI· A GRICULTURAL. Fooo. AND E NV I RONMENTAL S CIENCES Sawflies of Trees and Shrubs Robert P. Wawrzynski Sawflies are a group of insects related to wasps and tree for a new host once all previous-season needles have bees. Their name is derived from the saw-like ovipositor been eaten. Larvae never eat new needles, but may feed on the adult female uses to lay eggs. Adult sawflies are the bark of new shoots. European pine sawfly seldom kills inconspicuous trees since new fo liage is never eaten; however, repeated wasp-like insects defoliations can slow growth. Feeding on bark of new that do not sting. shoots may cause twig mortality but it is rarely serious. The larval or Life History and Habits: Overwinter as eggs in the immature stage of previous season's needles. Larvae begin feeding around sawflies are plant mid-May and continue through June. After feeding, larvae feeders and look pupate in the soil or on the tree and adults begin appear­ like hairless ing in early September through late fall. Adults lay eggs in caterpillars (the the current season's needles near the ends of branches immature stage of where they overwinter. There is one generation per year. butterflies and moths). The most Introduced Pine Sawfly, Dip rion similis (Fig. 3) distinguishing Figure 1 : Caterpillar showing Appearance: Larvae have black heads, a yellow-green character between prolegs. body with a black double stripe and many yellow and sawflies and black spots; they are 20-25 mm (3 / 4 - 1") when full grown. caterpillars is the number of prolegs (fleshy, leg-like Hosts: White pine is preferred, but they will also feed on projections) on the abdomen. Caterpillars have 2-5 prolegs Scot's, jack, and red pines. on the abdomen (Fig. 1), while sawflies have 6 or more (Figs. 5, 11). Sawflies often feed in groups and can quickly Damage: First generation larvae eat the previous year's defoliate portions of their host plant. There are many needles; second generation larvae feed on both new and different species of sawflies and each prefers specific old needles. Young larvae feed in groups and eat only the plants or groups of related plants. Some of the more outer, tender parts common sawflies that feed on trees and shrubs in Minne­ of the needle while sota are described in this publication. older larvae feed singly and eat Evergreen Plants entire needles and European Pine Sawfly, Neodiprion sertifer(Fig. 2) bark if foliage is Appearance: Larvae are gray-green with a black head and absent. Defoliation legs. They have a single, light longitudinal stripe down the is usually most back, two light green stripes and one dark green or black severe in the upper stripe on each side, half of trees, but and are 18-25 mm entire trees can be (3 / 4-1") when fu ll defoliated if grown. populations are Figure 3: Introduced pine sawfly. high. Hosts: Mugo, Scot's, red, and jack Life History and Habits: Overwinter as prepupae in the pines are preferred; soil. First generation larvae begin feeding from late May/ eastern white, early June to early July; second generation larvae feed Austrian, and from late July through early September. ponderosa pines Redheaded Pine Sawfly, Neodiprion lecontei (Fig. 4) may also be fed on Appearance: Full-grown larvae have reddish brown heads Figure 2: European pine sawflies if they occur near a and yellow bodies, with six rows of irregular black spots on mugo pine. preferred host. and are 20-30 mm (3 / 4 - 1") long. D amage: Larvae Hosts: Many species of pines; however, red and jack pines feed in groups on the previous year's needles and eat all that are less than 15 feet tall are preferred. previous-season needles on a single branch before moving to another branch to continue feeding. They will vacate a D amage: Larvae feed in groups and can completely defoliate a tree repeated, heavy feeding can cause thin foliage and re­ from the top down. duced growth. Young trees are Life History and Habits: Winter is spent in the soil as a preferred and prepupa. Adults emerge and lay eggs on currently elon­ stressed trees are gating shoots on branches. Larvae then move to feed on especially vulner­ tufts of needles (beginning around early June) found on able to damage. short shoots of older twigs; they feed for about three Life History and weeks. All stages of this insect may be found at once due Habits: Winter is to the long period of emergence by the adults; larval spent as a pupa in feeding may continue into September. There is one genera­ Figure 4: Redheaded pine the soil. First tion per year. sawflies. generation larvae Yellowheaded Spruce Sawfly, Pikonema alaskensis feed between mid­ (Fig. 7) June and late July; second generation larvae feed between mid-August and late September. Appearance: Full­ grown larvae have White Pine Sawfly, Neodiprion pinetum (Fig. 5) yellow or reddish Appearance: Larvae are pale yellow with black heads and brown heads and have four rows of black spots from the head to their olive-green bodies posterior end; they are about 25 mm (1 ") when full grown. with six gray-green Hosts: Eastern stripes. They are 18 white pine is mm (3/4") in preferred, but length. they will also Hosts: Isolated feed on red pine. !! white, black, and (1. Figure 7: Yellowheaded spruce <( C blue spruce such as Damage: Larvae <I) ::, those found in sawfly and damage. feed in groups on both new and old most landscapes needles, gener­ are preferred. ally defoliating Damage: Larvae prefer new needles, but older larvae will one branch eat previous season's needles when new foliage is scarce. before moving to Figure 5: White pine sawfly. Three or four years of consecutive defoliations can kill a another. Larvae tree. attack trees of all Life History and Habits: Overwinter as prepupae in the sizes and because they feed on both new and old needles, soil. Adult females deposit eggs in the current year's trees can be completely defoliated. needles and larvae appear and begin feeding in late May Life History and Habits: Overwinter as prepupae in the to mid-June; larvae feed from four to six weeks and soil. Adult females lay eggs in needles in the spring. complete development by late July. There is one genera­ Larvae feed from late June to early August. After feeding, tion per year. Yellowheaded spruce sawfly should not be larvae drop to the ground and pupate. There is usually confused with the spruce budworm caterpillar that also one generation per year. feeds on white spruce in the spring. Spruce budworm Larch Sawfly, Pristiphora erichsonii (Fig. 6) occurs very early in the spring feeding on newly emerging foliage. Webbed foliage is also common with spruce Appearance: Larvae have black heads, gray-green bodies budworm. with white undersides, and are 16 mm (1 /2") long when full grown. Deciduous Plants Hosts: Tamarack Blackheaded Ash Sawfly, Tethida cordigera (Fig. 8) and various larch Brownheaded Ash Sawfly, Tomostethus multicinctus species. Appearance: Blackheaded larvae have black heads and Damage: Adult legs, are white/ egg-laying activity yellow and about in new shoots can 18 mm (3/4") when cause shoots to full grown. become curved or Brownheaded curled as they larvae are green/ grow. These yellow-white, have curved shoots are a brown head Figure 6: Larch sawflies. an indicator of capsule, and are impending larval 14-20 mm (1/2 - feeding. Larvae feed in groups on tufts of needles found 3/4") in length. on short shoots of older twigs. Because larvae don't feed Hosts: Ash. on the single needles of elongating shoots, 100% defolia­ Figure 8: Blackheaded ash tion seldom takes place. Trees usually refoliate but sawflies and damage. Damage: Larvae are voracious feeders. They consume Life History and entire leaves, and heavily infested trees may be completely Habits: Overwinter defoliated in a very short time. as prepupae in the Life History and Habits: Overwinter as prepupae in the soil. Larvae first soil. Adults emerge, lay eggs in leaves, and larvae begin appear in May and feeding in early May through June. There is one genera­ feed through June. tion per year. A second genera­ tion occurs in July, Dusky Birch Sawfly, Croesus latitarsus (Fig. 9) feeding until the Appearance: end of the summer. Larvae are yellow­ Willow sawfly may Figure 11: Willow sawfly. green with black be confused with blotches on their the imported sides and have a willow leaf beetle which also defoliates willows (see Leaf black head; they Beetles in Urban Landscapes FS-6342-A). are about 24 mm Pear Sawfly (Pear Slug), Caliroa cerasi (Fig. 12) (1 ") long when full grown. Appearance: Larvae are slimy and slug-like, and shiny olive green in color. They are 12 mm (1 /2") when full Hosts: Birch. grown. Damage: Larvae feed in groups Figure 9: Dusky birch sawflies. Hosts: Plum, cherry, cotoneaster, pear, mountain ash, and hawthorn. around the edges of leaves. Heavy defoliation by this insect is rare. Damage: Larvae feed on the upper leaf surface, leaving only the leaf veins. Heavy defoliation gives the tree a Life History and Habits: Overwinter as prepupae in the scorched appearance and leaves may drop prematurely. soil. First generation larvae feed from May to early July. A Severe defoliation second, overlapping generation may occur and feed can adversely through September. affect tree health. Mountain Ash Sawfly, Pristiphora geniculata (Fig. 10) Life History and Appearance: Habits: Overwinter Larvae are a pale as prepupae in the green-yellow with soil.