Current issues in landscape IPM

1
Current issues in landscape IPM
Dr. Vera Krischik, Department of Entomology,
University of Minnesota
2
New course ENT 4015, Ornamental and turf
entomology, 3 credits, S2001, S2002also offered
as a workshop for UMES
3
CUES website receives 250,000 requests/year
www.entomology.umn.edu/cues
4
Japanese beetle is no longer a quarantine pest in
Minnesota
New UMES/MDA bulletin on managing Japanese beetle
5
UMES bulletin and poster Restore your backyard
and shoreland with native vegetation
before
one year later
6
Effects of urban ecosystems on elm resistance

• Dr. Vera Krischik, Department of Entomology,
• University of Minnesota, St Paul, MN 55108

7
Elm is a common street tree in the Midwest.
8
Elm leaf beetle was introduced from Europe.
Xanthogaleruca luteola is a specialist on elms,
and adult beetles and larvae feed on elm leaves.
Beetle defoliation stresses trees and predisposes
elms to bark beetle attack. Elm bark beetles
vector a fungus, that causes Dutch elm disease,
which kills elm trees.
9
Elm leaf beetle larvae crawl down the tree and
pupate in mass at the base of the tree. In MN,
there are two generations of elm leaf beetle a
year.
10
A soil-inhabiting fungus, Beauveria bassiana,
kills pupating beetles. In Italy, natural
epizootics of this fungus control beetle
populations.
11
Forest trees have little defoliation by elm leaf
beetle.
12
Street trees have high defoliation by elm leaf
beetle.
13
Outbreaks of ELB on street trees

• Bottom up factors Leaf quality
• Increased plant stress and mobilization of
  nitrogen, facilitates insect outbreaks in urban
  areas.
• Leaves with higher nitrogen levels and young
  shoots are a better quality to herbivores and
  encourage insect population growth (Herms and
  Mattson 1997).
• Little is known on the effects of urban compared
  to forested habitats on plant stress, leaf
  ontogeny, and leaf quality (Fostad and Pedersen
  1997, Percival and Dixon 1997).

14
Outbreaks of ELB on street trees

• Top down factors Predation and disease
• Insect outbreaks in urban areas may be related to
  decreased numbers of predators, parasitoids, and
  diseases, as a result of fragmented landscapes,
  reduction of natural ground cover, and widespread
  use of insecticides (Paine et al. 1997).
• Insect outbreaks in urban areas may be reduced by
  insect pathogens. Elm leaf beetle is managed in
  Italy by outbreaks of the fungus Beauveria
  bassiana.

15
Bottom up factors Leaf quality

• Leaf nitrogen
• Measure total nitrogen TN and
• total Kjedahl nitrogen (TKN)
• Plant stress
• Measure levels of defoliation
• Measure leaf chlorophyll flourescence and
• leaf photosynthesis
• Evaluate leaf quality on herbivore fitness
• Performance bioassays Raise females
  beetles for entire life on leaves from street
  and forest trees.

16
Bottom up factors Leaf quality

• Do urban ecosystems alter plant resistance?
• We can evaluate whether street trees have more
  nitrogen than trees in urban forests, although
  presently we may not know the mechanism.
• Nitrogen enrichment can be from
• 1. lawn fertilizers being absorbed by tree
  roots
• 2. tree roots invading sewers
• 3. nitrous oxide deposition from pollution
• stress ? nitrogen ? defense
• nitrogen enrichment ? nitrogen ? defense

17
Bottom up factors Leaf quality

• Defoliation levels LICOR leaf area meter
• 2000 Def F 0.5 0.09 Pgt0.05
• Def S 1.0 0.07
• Epizootics of Beauveria bassiana reduced
  beetle population size in 2000.
• 1998 Def F 7.8 2.31 P0.0006
• Def S 32.2 12.05
• 1997 Def F 3.2 2.66 P0.0102
• Def S 54.65 16.06
• Street trees consistently receive higher
  levels of defoliation.

18
Bottom up factors Leaf quality

• Nitrogen Entire shoot
• 1998 TKN F (6) 1.47 0.08 P0.0053
• S (7) 1.96 0.09
• TN F (6) 1.67 0.08
  P0.0220
• S (7) 2.19 0.08
• Street trees have significantly higher
  nitrogen per shoot than forest trees for both
  nitrogen parameters.

19
Bottom up factors Leaf quality

• Nitrogen Terminal leaves
• 1999 TKN F (7) 1.79 0.17 P0.0157
• S (10) 2.66 0.24
• TN F (8) 2.07 0.35
  P0.0216
• S (10) 2.81 0.70
• Terminal leaves of street trees have
  significantly higher nitrogen than terminal
  leaves of forest trees.

20
Bottom up factors Leaf quality

• Nitrogen Basal leaves
• 1999 TKN F (9) 1.08 0.17 P0.0070
• S (10) 2.06 0.16
• TN F (9) 1.44 0.16
  P0.0012
• S (10) 2.34 0.15
• Basal leaves of street trees have
  significantly higher nitrogen than basal leaves
  of forest trees.

21
Bottom up factors Leaf quality

• Nitrogen differences within a shoot
• 1999 TKN F 0.9538 P0.0462
• TKN S 0.2248 P0.4495
• 1999 TN F 0.9991 P0.0180
• TN S 0.8731 P0.2538
• Forest trees show the normal pattern of
  higher nitrogen in terminal leaves compared to
  basal leaves. Street trees have higher amounts
  of nitrogen and no difference in nitrogen between
  terminal and basal leaves.

22
Bottom up factors Leaf quality

• ELB preference
• Long term bioassays Number of eggs
  
  
  
  
• 2000 F (15) 38 10 Plt0.001
• S (18) 116 9
• Elm leaf beetles produce more eggs when fed
  leaves from street trees.

23
Bottom up factors Leaf quality

• Nitrogen differences within a shoot
• Street trees have higher amounts of nitrogen
  and have no difference in nitrogen between
  terminal and basal leaves. Consequently, these
  nitrogen enriched leaves are a better resource to
  herbivores. Field data demonstrate that herbivore
  defoliation is higher on street trees. Lab
  bioassays demonstrate that female beetles have
  twice the egg production on leaves from street
  trees compared to forest trees.

24
Bottom up factors Leaf quality

• Photosynthesis LICOR photo system
• Not corrected for herbivory
• 1999 F (6) 10.30 0.45 P0.0079
• S (6) 5.65 0.63
• Corrected for herbivory
• 1999 F(6) 10.95 0.27 P0.5590
• S (6) 9.74 1.16
• Street trees fix less carbon from
  photosynthesis and therefore store less carbon.

25
Bottom up factors Leaf quality

• Chloroplast function Fluorometer
• FV/FM and MRT F ratio P value
  7.93 0.001
• street high def a street low def b
• forest high def b forest low def b
• Street trees are stressed. Street trees have
  higher nitrogen leaves and greater amounts of
  defoliation by elm leaf beetle.

26
Managing elm leaf beetle
It is difficult to spray large elm trees with
conventional pesticides to control elm leaf
beetle. In addition, urban residents usually do
not want pesticide sprays around their homes.
However, elm leaf beetles pupate on the ground,
which offers the opportunity to use commercial
formulations of the fungus Beauveria bassiana and
the nematode Heterorhabditis bacteriophora.
These microbial pesticides are not toxic to
mammals, are safe for use in urban communities,
and do not offer the same risks as conventional
pesticides. We tested whether these microbial
pesticides were affective against elm leaf beetle
larvae and pupae.
27
(No Transcript)
28
Field bioassay The nematode Heterorhabditis bacte
riophora sprayed on beetles offers good control.
29
Managing elm leaf beetle
Elm leaf beetle can be managed by spraying the
beetles as they pupate on the ground with
commercial formulations of the fungus Beauveria
bassiana or the nematode Heterorhabditis
bacteriophora.
30
Summary Comparison of street and forest elms

• Street elms have higher levels of defoliation.
• Street elms have higher nitrogen levels.
• Elm leaf beetle females lay more eggs when fed
  leaves from street elms.
• Street elms are heavily defoliated and do not
  compensate for defoliation with increased
  photosynthesis. Therefore, street elms fix less
  carbon.
• As measured by leaf flourescence, street elms are
  stressed.
• Elm leaf beetle can be managed by spraying the
  larvae and pupae as they pupate on the ground
  with commercial microbial formulations of the
  fungus Beauveria bassiana or the nematode
  Heterorhabditis bacteriophora. Use of microbial
  pesticides decrease risks associated with
  conventional pesticide use in crowded urban areas.