Jack Pine Budworm

NA-FR-01-94 USDA Forest Service Northeastern Area State & Private Forestry HOW to Manage Jack Pine to Reduce Damage From Jack Pine Budworm Deborah G. McCullough, Steven Katovich, Robert L. Heyd, and Shane Weber Introduction part in perpetuating jack pine ecosystems. Tree mortality and top-kill resulting from Jack pine budworm, Choristoneura pinus budworm defoliation creates fuel for intense pinus Freeman, is a needle feeding caterpillar wildfires. Dense stands of jack pine typically that is generally considered the most regenerate after fire, eventually serving as significant pest of jack pine. Vigorous food for future generations young jack pine stands are rarely damaged of jack pine budworm. Harvesting and during outbreaks. The most vigorous stands other management activities can avoid are well-stocked, evenly spaced, fairly budworm caused tree mortality and reduce uniform in height, and less than 45 years old. the threat of damaging wildfires yet still Stands older than 45 years that provide suitable conditions for jack pine are growing on very sandy sites and suffering regeneration. from drought or other stresses are very vulnerable to damage. Tree mortality Jack pine provides valuable timber, and top-kill are more likely to occur in these recreation and wildlife values, and concerns stands. about jack pine budworm should not discourage its management. However, land Jack pine budworm is native to North managers should be aware that jack pine America and has evolved to play an integral budworm outbreaks will occur on a regular cycle. Several management strategies can be used Figure 3. Jack to reduce the risk of significant tree mortality pine budworm and top-kill resulting from periodic budworm moth. outbreaks. These are discussed in the sections titled “Management Strategies” and “Forest Management Recommendations”. Insect Description Young jack pine budworm caterpillars are yellowish-brown and less than ½ inch long Figure 4. Egg (Figure 1). Older caterpillars are reddish- mass of about 40 brown with cream-colored spots along the eggs on a jack pine sides (Figure 2). They have a characteristic needle. black head and a black plate immediately behind the head. Full-grown caterpillars are about 1 inch long. Adult moths are 3/4 inch in length and reddish-brown in color, with white markings Insect Life Cycle on the front wings (Figure 3). Eggs are green and laid in masses of about 40 eggs on The jack pine budworm has one generation needles. The eggs remain on needles per year. Moths are present for only a few following hatch, becoming translucent white days in midsummer during the mating and in color (Figure 4). egg laying period. Eggs hatch within 10-14 days. Newly emerged caterpillars do not feed. The young caterpillars spin silk Figure 1. cocoons for overwintering in protected spots Young budworm such as under bark scales or in needle caterpillar scars. They become active the following feeding in a male spring, usually between mid-May and early jack pine flower. June. Initially, caterpillars feed on pollen in male flowers (Figure 1). Eventually, the caterpillars migrate to the new expanding shoots and web new needles and shoots together to form feeding shelters. Budworm Figure 2. caterpillars will feed on old needles after new Older jack pine needles are consumed. Feeding is budworm completed in about 6 weeks, usually by early caterpillar. July. Pupation occurs on infested needles and shoots. Adult moths emerge from pupae in 6-10 days. Damage Symptoms 1. Maintain healthy, vigorous trees. Tree vigor is affected by several factors By mid-summer, clipped needles become including: reddish as they dry (Figure 5). The more brilliant the red within the crown the more Age - Jack pine is a relatively short-lived severe the defoliation. Defoliation intensity species that reaches maturity at an age of and the red color is often greatest in the 40-55 years. Overmature trees are less upper canopy. Close inspection of infested capable of surviving stressful events trees reveals partially eaten needles, frass, such as defoliation. shed skins and pupal cases webbed to needles and shoots (Figure 6). Heavy rain Stand Density - High stand density and wind eventually remove the red, dry creates competition for limited light, needles and webbing. Defoliated trees are water and nutrients. Overstocked stands left with thin crowns. Severely damaged can suffer high mortality from the trees appear grayish due to the absence of additional stress of defoliation. needles. Evidence of previous outbreaks includes the presence of dead and top-killed Site Quality - Growth and survival of trees. jack pine is better on high quality sites. Jack pine does best on well drained Figure 5. loamy sands. Poorer quality sites are Characteristic excessively sandy and dry. reddish color of foliage following 2. Minimize male flower production. budworm Low numbers of male flowers limit outbreaks in July survival of budworm caterpillars during and August. outbreaks. Factors that affect male flower production include: Stand Density - Low stand density Figure 6. Clipped produces trees with large crowns called needles, frass and “orchard” or “wolf” trees (Figure 7). pupal cases These “orchard” trees produce abundant collected in silk male flowers throughout full crowns webbing. which often extend to the ground. Stand Structure - Multi-storied or uneven-aged stands will sustain heavy damage during outbreaks because they have a high percentage of overstory Management Strategies “wolf” trees and many suppressed trees. Both wolf trees and suppressed Management of jack pine stands to reduce trees produce male flowers in growth loss and mortality from budworm abundance. defoliation is based on two principles: Edge Effect - Trees growing along forest edges produce abundant male 3. Large, contiguous blocks of mature flowers and support large numbers of and overmature jack pine (50 years budworm caterpillars. old) should be avoided. A mosaic of younger stands of varying ages should be encouraged. A minimum stand size of 40 acres is suggested to reduce the ratio of edge to stand area. Forest Management Recommendations 4. Minimize the amount of edge created in jack pine stands. Avoid leaving or Pre-outbreak Stands: The amount of planting narrow strips or islands of damage and the intensity of an outbreak can jack pine when regenerating a stand. often be reduced by following the recommendations listed below. 5. Avoid creating uneven-aged or multi-storied jack pine stands. Regenerate jack pine by clearcutting. 1. Most jack pine stands in the Lake States Standing dead trees and scattered are on poor quality sites and should not hardwoods or white pine can be left to be held past maturity (45-50 years). Site enhance diversity. When deciding on index is a measure of site productivity the number or density of living trees to which can be used to determine when to leave, keep in mind that jack pine is very harvest jack pine stands. Tree height shade intolerant. after 50 years of normal growth is a measure of site index for that tree 6. Conversion of jack pine stands to species. Thus, if a tree grows 55 feet in less susceptible tree species, or to 50 years, it has a site index of 55. A prairie or savannah may be good rule-of-thumb is to harvest jack appropriate in areas which experience pine when stand age is equal to the repeated, severe jack pine budworm site index minus five years. For outbreaks. Discuss any conversion example, a stand with a site index of 50 plan with a professional resource should be harvested at 45 years of age. manager. Management options for conversion are greatly influenced by site productivity, and by existing and surrounding vegetation. 2. Maintain basal area between 70 and 110 ft2/acre. Basal area is a measure of Outbreak and Postoutbreak Stands: stand density. The greater the number, Generally, tree mortality and topkill occur the higher the stand density. Higher only after severe defoliation. To evaluate basal area (110-130 ft2/acre) may be defoliation, wait until the red needles have appropriate on very good sites. Stands fallen from infested trees. If at that time, few with basal area below 70 ft2/acre are at green needles are visible in the upper crowns risk of severe budworm damage because of the majority of trees in a stand, consider they tend to have trees with large crowns the following: producing many male flowers. 1. Salvage sales should be initiated Authors quickly in mature and overmature stands following severe defoliation Deborah G. McCullough, if trees appear gray and have little or no Assistant Professor and Extension foliage in the upper canopy. Trees killed Forest Entomologist, Dept. of Entomology by budworm are no longer merchantable and Dept. of Forestry, Michigan State within 18-20 months after death and are University also a fire risk. Evaluating the condition of any mature jack pine stand defoliated Steven Katovich, by the jack pine budworm is an Entomologist, important part of protecting your timber USDA Forest Service, Northeastern Area resource investment. State and Private Forestry 2. Insecticide treatments are rarely Robert L. Heyd, justified economically. Exceptions Forest Health Specialist, Michigan Dept. of include individual high value trees in Natural Resources recreation areas or in ornamental settings. Occasionally, if timber values Shane Weber, are heavily emphasized and outbreaks District Entomologist/Silviculturist, are unusually intense, insecticide Wisconsin Dept. of Natural Resources applications may be economically justifiable for stands that are 25-30 years old. A DNR, Forest Service or Extension entomologist should be For more information contact your State consulted prior to any insecticide Department of Natural Resources or the applications. USDA Forest Service, State and Private Forestry. In Michigan, you may also contact your MSU Extension agent..

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