Managing Insect Pests of Pecan Ted Cottrell USDA, Agricultural Research Service SE Fruit and Tree Nut Research Laboratory Bryon, GA Ted.Cottrell@ars.usda.gov
1) Invasive brown marmorated stink bug (BMSB) 2) Nut fumigation to control pecan weevil 3) Obscure scale
The Brown Marmorated Stink Bug: An exotic species now in Georgia Brown Marmorated SB Brown SB Green SB Southern Green SB Dusky SB
Identifying the BMSB Bugwood: Susan Ellis Bugwood: Susan Ellis Bugwood: Steven Valley Bugwood: Steven Valley
Invasion History of the BMSB • From east Asia • Detected as early as 1996 • 2004 – found on farms and in forests. • 2010 – “catastrophic” damage in many mid- Atlantic states. • Commonly overwinter in buildings. • Known to be moved to new areas when overwintering in RVs.
Some of the known host plants of the BMSB: • Corn • Cotton • Peach • Okra • Black Cherry • Soybean • Tree of Heaven • Beans • Pear • Catalpa • Sweet corn • Redbud • English Holly • Pepper • Pecan • Southern Magnolia • Sunflower • Shagbark • Apple Hickory • Egg Plant • Crab Apple • Maples • Tomato • Mimosa • Privet • Paulownia
Stink Bug Capture in Pheromone-baited Traps Byron, GA Fall 2015 40 35 Avg. Stink Bugs per Trap 30 25 20 Brown Marmorated 15 Brown 10 Dusky 5 0 Found on peach at Byron, GA during Aug. 2015
Can we control BMSB on pecan? • Yes. • We know it’s here. • Attraction pheromone has been developed. • Insecticide options • Similar as for the brown stink bug. • Past research has identified products providing best results. • We don’t know how large the population will be this season or when the peak population(s) will occur.
7DAT 24hr 7 DAT 24hrs 100 A % Dead + Moribund A 100 % Moribund + Dead 80 80 60 60 40 40 20 B B B B B B 0 20 B 0 Control Brigade 32oz Treatment Treatment 7DAT 48hr 100 A % Moribund + Dead 80 60 40 B B 20 B B B B 0 Treatment 7DAT 72hr A 100 % Moribund + Dead 80 60 40 B B 20 B B B B 0 Treatment
In-Shell Fumigation for Control of Pecan Weevil Larvae? • Collaborators: Dr. Ellen Thoms Douglas Products Dr. Thomas Phillips Kansas State Univ.
(with ProFume)
Can larval pecan weevil be controlled in-shell? • Test Objective: • Expose weevil-infested pecans to different concentrations of sulfuryl fluoride to calculate an LD 99 .
Putting weevil larvae into pecans…..we must be nuts! Cotton plug Weevil Agar
Fumigation • Five concentration x time dosages: • 150, 300, 450, 600, and 750 g- h/cm 3 • Pecans exposed to SF gas for 24 h. • Weevil mortality examined 10 DAT.
Sulfuryl fluoride lethal dose against pecan weevil: • An LD 99 was calculated at 1080 g-h/cm 3 . • Confirmatory assays found 100% mortality at 1300 g- h/cm 3 . • This information will be used to develop a treatment schedule based on a target dose of 1300 g-h/cm 3 . • Bottom line: Sulfuryl fluoride is active against pecan weevil larvae in nuts.
Some pecan insects receive more attention than others…..
Scale Insects on Pecan • A large group of minute and highly specialized herbivorous insects • do not look like insects • many are inconspicuous on plants • infestations can be highly damaging • > 20 species of scale insects attack pecan • Most species found ‘occasionally’ but some found ‘commonly’ on pecan • Obscure scale is usually the most damaging. • Giant pecan scale is the most striking; common but rarely seen.
Scale Insects Attacking Pecan • If you spray pecan with pyrethroid insecticides you should expect to see scale. • If you spray pecan with pyrethroid insecticides, you should be aware of what to look for regarding scale insects.
Armored Scale Insects Protective scale covering • Armored scale insects live under a protective ‘scale’ made from wax Live insect secreted by the insect • The protective scale covering is free from the insect • Immobile insects - only newly hatched nymphs (crawlers) and adult males are mobile • Dispersal: crawlers move to new sites on same host plant, birds may carry some, wind may move some
Obscure Scale • Attacks hickory, chestnut and oak species: • Chinese chestnut Photographer: J.A.Davidson • Pecan • Hickory • Oaks (black, blackjack, chestnut, English, live, pin, post, red, scarlet, Spanish, swamp white, water, white, willow) • Reservoirs for infestations are many!
Obscure Scale • Known as a pest of pecan for many years “Pecan trees, on which large branches were completely killed, have been frequently observed, and in a few instances the trees were so badly infested that they were completely incrusted with this scale from top to bottom.” H.L. Dozier. 1925. The obscure scale attacking pecan trees. The Quarterly Bulletin, State Plant Board of Florida, v. IX, no. 4. “… a serious pest on both seedling and improved varieties in Texas, Louisiana , Arkansas, Mississippi, and Alabama.” H. Baker. 1933. The obscure scale on the pecan and its control. USDA Circular No. 295.
Damage • Immature scale and adult females use piercing/sucking mouthparts to feed on plant sap (adult males do not feed) • Infestations typically start on the lower, inner portions of the tree, spreading toward terminals • Severe infestations can weaken and kill limbs
Obscure Scale: Biology • Life cycle • One generation per year Eggs – Summer (July to early Sept.) Immature stages – Summer, Fall, Winter* Adults – Spring/Summer *Must overwinter on living tissue; not found on leaves and nuts
Obscure Scale: Biology • Life cycle on pin oak at Auburn, AL • Eggs laid from June through early September (most laid in June and July) • Crawlers: mid-June through mid-Sept. (most occurred from mid-June through July)
Monitoring Scale on Pecans • What to monitor: • Search for scale on bark (not on leaves or nuts) • A hand lens is needed! • Older Trees: search smoother bark on limbs and terminals • Younger Trees: search bark on trunk and limbs
Monitoring Scale on Pecans • Finding scale is just the beginning….. • Although the insect may be dead, the scale covering will continue to adhere to bark • Must be able to differentiate live vs. dead scale • Accurate scouting pays: Don’t spray dead scale! • The hand lens will help to determine live vs. dead scale
Scale Management Monitoring for crawlers: Use black electrical tape, sticky side out, wrapped around infested limbs. A degree day model was developed for obscure scale on pin oak in Kentucky. Byron, GA: Adult male emergence - April 11, 2014 Crawler emergence – June 5/6, 2014
Scale Management • Biological Control • predators (certain species of lady beetles, predatory mites) • parasites (several species of parasitic wasps) • pathogens (pink scale fungus [ Nectria diploa ] )
Scale Management - Oils • Dormant oil application • Typically applied to approach runoff using 2% oil with a repeat application 10- 14 days later **Death is by suffocation • Thorough coverage is required • Typical coverage by airblast for scab or aphids is not enough • Scale covering can protect the insect from the treatment • live scale can be covered by one or more layers of dead scale.
Precautions for applying dormant oil • Do not apply oils during freezing weather. This can cause the emulsion to break down and produce uneven coverage. • Do not apply oils if plant tissues are wet or rain is likely. These conditions inhibit oil evaporation. High humidity (above 90 percent) also may contribute to plant injury risk, while low humidity generally reduces plant injury risk. • Do not spray when shoots are growing. • Avoid treating plants during the fall until after winter hardening has occurred. Fall treatments have sometimes caused increased susceptibility to winter injury. • Do not apply oils in combination with sulfur or sulfur-containing pesticides; they can react with oils to form phytotoxic compounds. • Follow label directions; hickories can be sensitive to oil applications.
Scale Management - Insecticides • Chemical Insecticides: Timing sprays against the vulnerable crawler stage can be effective. • Various insecticides are effective against the crawlers (e.g., dimethoate, chlorpyrifos, diazinon, malathion, acephate and carbaryl – read the label). • Movento is good against San Jose Scale. In apples, peaches, etc. it is applied to expanding foliage using a penetrative, spreading surfactant for maximum systemic activity. • Insect Growth Regulator • pyriproxifen
Acknowledgments: • Georgia Agricultural Commodity Commission for Pecan – funding for stink bug research. • Collaborators: Bill Ree (Texas A&M), Ellen Thoms (Douglas Products), Tom Phillips (Kansas State Univ.). • Technical Assistance: Ann Amis, Merry Bacon, Shannon Day, Emily Kemp, Saleah Starks.
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