Beneficial Nematodes and Fungi for Managing Plum Curculio

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Beneficial Nematodes and Fungi for Managing Plum
Curculio
Percent Larva Emergence from Fruit
1st spray
2nd spray
3rd spray
0
Degree Days (Base 50F)
Figure 2. Simplified Enviroweather phenology
model. The model will incorporate recommended
nematode application timings based on predicted
plum curculio larva emergence in Michigan. Apple
and cherry will have slightly different models.
Plum curculio adult and oviposition scar on apple
Plum Curculio Larvae Dark Infected with
Nematodes, Light Healthy
Figure 1. Average number of adult plum curculios
emerging from pathgogen-treated soil. Soils were
treated with the fungus Beauveria bassiana (Bb)
or the nematodes Heterorhabditis bacteriophora or
Steinernema riobrave at a low or high rate (Hb
Low, Hb High, Sr Low, Sr High). Larvae were
placed on soil either -10, -5, 0, 5,10, 15, or 20
days from pathogen application. Bars with an
asterisk () denote significantly lower means.
Note Hb Low and High were not included for the
-10, 10, or 20 day treatments.
Strategies, tactics, and tools for Biointensive
IPM and Organic Growers
Investigators Mark Whalon, Renee
Pereault Michigan State University Pesticide
Alternatives Laboratory http//whalonlab.msu.edu
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Results for Larvae 2008 field trials in 5
orchards, testing the efficacy of insecticidal
fungi and nematodes, indicated that the nematode
Steinernema riobrave was most efficacious against
PC larvae (Figure 1). The nematode performed best
in sandy soil. Application of Steinernema
riobrave in conjunction with irrigation is a
successful tactic in citrus root weevil
management in southern US. Results for Adults
The fungi B. bassiana and M. anisopliae cause
75-100 mortality of adult PC in the lab. The
fungi B. bassiana and M. anisopliae in granular
formulation applied to soil were not effective
against PC adults overwintering in field cages.
historical method with potential benefits in tune
with organic objectives, currently being studied
at Almar Orchards. 4) Insect pathogenic fungi
and insect pathogenic nematodes may be augmented
in an orchard to attack previously untargeted PC
life stages. These stages are soil-occupying last
instar larvae, pupae and emerging adults in the
summer as well as overwintering adults in the
winter spring.
Plum Curculio
Organic tree fruit production is on the rise in
the Upper Mid-West. While certification presents
one set of challenges, actual production of
saleable fruit is THE challenge. At least two key
pests, the plum curculio and apple scab, become
extreme challenges for many organic growers. Plum
curculio (PC) is a native weevil associated with
a range of cultivated fruit crops. In spring,
adults feed on foliage and buds and lay eggs in
new fruit, causing fruit scarring and
malformation. Larvae feed and produce frass while
developing within fruit and exit into the soil
under the tree canopy where they pupate. They
emerge as 2nd (summer) generation adults 35 days
later, continuing fruit feeding until they are
forced to overwinter in duff within and
surrounding the orchard. Untreated PC
populations can result in total crop loss. For
instance, PC damage increased from 2 to 82
within 3 years at Michigan State Universitys
Clarksville Horticulture Experiment Station
Organic Apple block. In processed cherry, where
there is a USDA zero tolerance for PC larvae in
fruit, even a 1 infestation can be economically
catastrophic. Therefore, Organic apple, cherry,
peach and plum growers will have to manage PCs
intensively. MSU is pursuing four main
approaches to PC management in organic
systems 1)Kaolin clay (Surround), the white
particle film, reduces oviposition by at least
30 with maintained coverage by repeated
sprays. 2)Push-Pull Strategy works by pushing PC
out of the interior rows with Surround while
pulling PC into the border rows with plum essence
and benzaldehyde scents, where aggregating PC can
be trapped with screen traps or pyramid traps or
sprayed with an organic insecticide. 3)Integrating
livestock such as hogs for rotational grazing of
PC larva-infested dropped apples is a
Beneficial Fungi Nematodes
Insect pathogenic fungi can penetrate the
bodies of some insects and cause death. Spray
formulations of Beauveria bassiana (Mycotrol-O
or Naturalis-L) in oil carriers are currently
EPA-registered and OMRI-approved for food crops.
Metarhizium anisopliae (Taenure) as a granule
for nursery greenhouse crops may become
registered for food crops with OMRI-approval in
the near future. Nematodes are microscopic,
colorless, unsegmented roundworms which can be
beneficial or pests depending on the species
feeding habits. Beneficial insect pathogenic
nematodes release bacteria into insect bodies on
which they feed and reproduce in the insects
body. Unlike the fungi, they are exempt from EPA
registration, but formulations must be cleared
through organic certifier. Strains of fungi or
nematodes within species may have differing
characteristics such as insect host range,
virulence, tolerance to environmental conditions,
and soil persistence. Unknown or poorly
understood impacts could result in some harm to
beneficial predator, pollinator and detritovore
insects. Repeated applications are likely needed
since persistence of these microorganisms varies
within the wide range of organic orchard ground
cover management systems. Insect life stages
(larva, pupa, adult) are often differentially
susceptible to different strains of these
beneficial organisms, as studies on PC in Georgia
and Utah suggest.
How to time applications?
A phenology model estimates the fraction of a
population residing in each life stage as a
function of time and environmental conditions.
Insects and mites, which are cold-blooded
animals, are dramatically influenced by
temperature. Temperature explains 75-80 of
variation in development whereas photoperiod,
moisture and other edaphic factors can explain
20. Therefore, using degree day units (a
predictor of temperature accumulation), growers
can predict when PC are in a vulnerable stage for
biopesticide treatments. As we refine the
phenology of PC by studying the development of
larvae in growers fruit through 2009, we will be
able to better pinpoint applications, which is
critical to the successful and economical use of
biopesticides just as with other reduced risk and
Organophosphate-Alternative pesticides in
conventional orchards. We are planning to make
visual treatment timing models available by fall
2009 to growers and scouts at growers meetings
and on the web at http//www.enviroweather.msu.edu
. A simplified example is given in Figure 2.