Tree Pest Alert - SDSU Extension SDSU Extension

Tree Pest AlertApril 21Volume 19, Number 10In This IssuePlant development for the growingseasonPlant Development . 1Treatments to begin now. 1Timely topic . 1Emerald ash borer update . 2Sweating bare-root hackberries and oaks . 3E-samples . 3Frost injury on new foliage. 3Pine needle scale . 3Samples received/site visits . 4Davison County (pinewood nematode) . 4Lake County (Dothistroma needle blight) . 4Lincoln County (declining Austrian pine) . 4Lyman County (Zimmerman pine moth) . 5The cold weather persisted through last week with briefsnow flurries common in late afternoons and evening.The growing degree days (GDD) base 50 is about 95 forthe Sioux Falls area and only 50 for Rapid City.However, this is close to where we were last year (andremember we had a few May flurries!).SamplesJohn Ball, Professor, SDSU Extension Forestry Specialist & SouthDakota Department of Agriculture and Natural Resources ForestHealth SpecialistEmail: john.ball@sdstate.eduPhone: 605-688-4737 (office), 605-695-2503 (cell)Samples sent to: John BallAgronomy, Horticulture and Plant Science DepartmentRm 314, Berg Agricultural Hall, Box 2207ASouth Dakota State UniversityBrookings, SD 57007-0996Note: samples containing living tissue may only be accepted fromSouth Dakota. Please do not send samples of plants or insects fromother states. If you live outside of South Dakota and have a question,please send a digital picture of the pest or problem.Cherries, as with many stone fruits, are among ourearliest blooming trees. This is a picture of a purpleleafsandcherry (Prunus x cistena) in full bloom. I have alsoseen apricots and a few peach trees blooming and if wehave a hard frost in the next few days, it may meananother year of poor apricot and peach production inSouth Dakota.Any treatment recommendations, including those identifying specificpesticides, are for the convenience of the reader. Pesticides mentionedin this publication are generally those that are most commonlyavailable to the public in South Dakota and the inclusion of a productshall not be taken as an endorsement or the exclusion a criticismregarding effectiveness. Please read and follow all label instructions asthe label is the final authority for a product’s use on a pest or plant.Products requiring a commercial pesticide license are occasionallymentioned if there are limited options available. These products will beidentified as such, but it is the reader’s responsibility to determine ifthey can legally apply any products identified in this publication.Treatments to Begin NowReviewed by Master Gardeners: Bess Pallares, Carrie Moore, andDawnee LebeauDiplodia tip blightThe South Dakota Department of Agriculture and South Dakota StateUniversity are recipients of Federal funds. In accordance with Federallaw and U.S. Department of Agriculture policy, this institution isprohibited from discriminating on the basis of race, color, nationalorigin, sex, age, or disability (Not all prohibited bases apply to allprograms.) To file a complaint of discrimination, write USDA, Director,Office of Civil Rights, Room 326-W, Whitten Building, 1400Independence Avenue, SW Washington, DC 20250-9410, or call (202)720-5964 (voice and TDD). USDA is an equal opportunity provider andemployer.Diplodia tip blight (Diplodia pinea) is one of the mostcommon disfiguring diseases of 2- and 3-needled pinesin South Dakota. It is a common disease son Austrian(Pinus nigra) and ponderosa (P. ponderosa) pines.The most common means of managing the disease iswith fungicides. The treatment are foliage applicationswith a fungicide containing Thiophanate-methyl,Propiconazole, or Chlorothalonil (and labeled fortreatment of this disease). The first application is appliedjust before the bud sheaths have opened.This publication made possible through a grant from the USDA ForestService.1

Timing is critical. Once the bud sheaths have openedand the candle begins to form, it is a little late to start thefirst application and this is the one that provides most ofthe protection. A second application is made about twoweeks later.We have three different species of tent caterpillar inSouth Dakota: forest tent, eastern tent, and western tent.They have similar life cycles and treatments are thesame so identification is not critical to management.Regardless of which “worm” is in a tree, now is the besttime for treatment as the insects are venturing outside oftheir nests and beginning to feed on foliage. Thecaterpillars are less than 1/4-inch long, so it does nottake a lot of insecticide to kill them right now. There aremany insecticides labelled for their control.Spruce needleminerThe spruce needleminer (Endothenia albolineana) larvaeare moving from their webbed nest and resuming theirfeeding. This is a picture of a larva in its nest of webbedneedles. A spray of high-pressure water right now willknock them off the tree but be sure to rake up the fallenneedles and larvae after the water spray.But the simplest and best treatment now is to tear openthe nests. The nests help protect the young larvae fromthe environment and their natural enemies. Kicking themout the house now is certain death. Just tear the nestsopen. Do not burn the nests. While that is entertaining, itcan lead to ‘fire blight’ on much of the tree!Zimmerman pine mothSee information under Lyman County in the SamplesReceived/Site Visit section of this Pest Alert.Timely TopicsEmerald ash borer updateWe are continuing to monitor insect development thisspring. While there are a few larvae still in the J-shapedstage (which they entered last fall), most are now in theprepupal and pupal stage.The other approach is pesticide treatments, mostcommonly insecticides labelled for the needleminer andcontaining Carbaryl, Malathion, or Spinosad as theactive ingredient. A spray into the canopy will kill thelarvae as they begin moving out onto the foliage.Remember to spray inside the canopy, not just theexterior. Actually “power washing” the lower canopy ofthe spruce is a good way of cleaning off all the dead anddying needles as well as some insects. However, beaware the tree will appear a little open afterwards!Tent caterpillarsTent caterpillar nests are expanding and becoming morenoticeable as hatch continues. Tent caterpillars begin tohatch and start spinning webs at about 95 GDD and weare or above this threshold in the southeastern part ofthe state.This means the insects are no longer curled and now arestraight but shrunken. They will soon develop into pupaeand a few are already beginning this process. This stagebegins as the insect takes a white, cylindrical shape,nondescript form that gradually takes the appearanceand form of an adult.This process will take several weeks. Once the insecttransforms into an adult, it may remain just beneath thebark for a few days to a week or more before chewing aD-shaped hole and emerging.Based on the current development of the insect and thelong-range weather forecast, emergence is expected tobegin around June 1 in Sioux Falls.2

This means the ideal time to begin sweating bare-rootsseedlings in much of the state is about mid-May. Thedanger of hard frosts will be over by the time the budsare expanding.A reminder to sweat bare-root hackberriesand oaksSoil temperatures are in the high 40s to near 60oF in theupper 4-inches for almost all the state. This is a greattime to begin bare-root tree planting. The soils are warmenough to promote fast root growth, yet the airtemperatures are still cool.E-samplesFrost injury on new foliageWe have seen enough brief periods of sunny, warmweather than some trees have been ‘fooled’ into leafingout a little too early. Peach trees are very gullible andnever seem to learn that warm spring weather is quicklyfollowing by freezing winter-like weather.The cool air temperatures will help slow leaf expansionand transpiration until the roots are able to replenish thiswater loss. A little more rain will help as well as rootdevelopment depends on two basic ingredients, warmsoils and moisture. It will probably be necessary to waternewly planted seedling going into windbreaks this year.Every seedling should receive about a pint of water atplanting.But some plants need a little more than water. Theyneed to work up a sweat first! Two tree speciescommonly planted in South Dakota – hackberry (Celtisoccidentalis) and bur oak (Quercus macrocarpa) – willeither not break bud or do so very slowly if not sweatedbefore planting.Sweating is only necessary for bare-root trees that werein cold storage for the winter. Since most bare-root stockis harvested in the fall and held in coolers at nearfreezing temperatures for the winter, assume that anybare-root bur oak or hackberry will need to be sweated.This poor peach leafed out in Yankton and was injuredby the hard frost. The most common symptoms of frostinjury are shriveling and blackening of the leaf margins.Severely damaged leaves will begin falling in a week ortwo. Fortunately, the trees will produce new leaves thisspring.Sweating is a simple process. The bare-root treeseedlings are laid on a warm surface (soil or flooring)and in a building. The air temperatures should bebetween 45 to 70oF.Pine needle scaleCover the roots with moist material - wet straw or woodchips – water, and then cover the plants, roots, and topswith plastic. Be sure this “mini-greenhouse” is in shadeand not exposed to direct sunlight as the temperatureswill become too high. The waxed boxes the trees comein from the Big Sioux Nursery work well for sweating.The flocking on pine trees, the small white bumps on theneedles, are an insect known as the pine needle scale(Chionaspis pinifoliae) as can be seen in this recentlysent picture. Pine needle scale is an armored scale, onethat forms a hard shell and armored scales do notproduce honeydew, the sticky material excreted byaphids and soft scales.After three days to a week, the buds on the seedlingswill begin to expand. Once this occurs, take theseedlings and plant them as soon as possible. Since theseedlings are going to leaf out quickly, planting needs tobe done after hard frosts are common (which candamage the tender leaves).Pine needle scale is very common insect on Austrianand mugo pines (pictured here). Right now, you can findeggs beneath the teardrop shaped scales and these willhatch about the time common lilacs are in bloom, lateMay or early June. Managing this insect is difficult asmost pesticides do a better job at killing the predators3