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Four orchard measurement tools

Below are the four orchard measurement tools developed by our team. Visit our references section to view additional measurement tools from other resources.

1) Mite diversity as an ecological indicator of orchard sustainability.
2) Measuring orchard sustainability with lepidopteran insect diversity.
3) Primary producer stress indicator: carbon storage and water use efficiency.
4) Amplification of soil microbiology and soil nutrient potential measured through duff diagnostics.

1
Mite diversity as an ecological indicator of orchard sustainability.

We have developed a system using mite predator/prey ratios and population dynamics, which has proven to be a reliable functional ecology indicator (Strickler et al. 1987). Leaf feeding mites, unlike other tree fruit pests, not only affect fruit quality and yield but also stress trees. Mites are also very sensitive integrators of plant health, environmental disruptors (pesticides) and tree nutrient status. Predator mites can be very effective at regulating pest mite populations, but are often highly sensitive to orchard operations such as mowing, irrigation, fertilization, and chemical application (Whalon and Croft 1984). Because of their environmental sensitivity, high numbers of seasonal generations, seasonal movement between the ground cover and the tree, local area dispersal and intimate association with the leaf surface, mites are perhaps the best overall arthropod indicator of the overall health of a tree-fruit ecosystem.

Our premise, which is based on intensive studies in 17 orchards representing a range of pesticide, nutrient and water inputs from intensive to long-abandoned (Strickler et al 1987) and extensive experience in hundreds of orchards around the world (Whalon and Croft 1986, Perry et al. 1996, Flore et al. 1992, Whalon and Penman 1991), is that if plant-feeding mites are not being regulated by predators, the orchard system is not functioning properly. We have developed a tabular indexing system, which provides a site-specific rating based on mite interspecies dynamics that is an accurate assessor of whether horticulture and pest management input decisions are moving an orchard ecosystem toward or away from sustainability.

Two species of predatory mites that feed on pest mites in fruit.

In addition to the pest and predator mites found in the orchard, the total indexing system incorporates fungus, pollen and generalist feeding mites. These groups of mites are also important in giving a clearer picture of orchard disturbance and inferring information about orchard ecosystem processes. In using this indexing system in Michigan apple orchards, we have seen a clear demarcation between long-term abandoned, short-term abandoned, organic, bio-intensive IPM and conventional IPM apple orchards. This system has been extrapolated and is being reworked for use in cherry and peach orchards, with the expectation that it will eventually be applicable to any tree fruit production system.

The sample process requires a 3X/year assessment (500-700, 1400-1700 and after 2400 degree days base 50 ºF). In each sample, 5 leaves from 20 trees are selected from the interior to the terminal end of a randomly selected major scaffold limb. A diagonal transect across the orchard (6 exterior and 14 interior trees) provides the total 100 leaf sample which can be observed directly or transported to the lab. The sample results are then fed into the index, which incorporates time of the sample season timing with mite species and abundance. The result is a number, the index value, which falls in a continuum ranging from highly disturbed to highly sustainable. From here, the grower can make decisions about their pesticide spray program and overall land management depending on the index value.

Possible mite index values range from -100 to 100.  These values fall along an orchard ecology continuum. Negative values represent orchards that are disrupted while positive values are reported for more sustainable orchards. (back to top)

2
Measuring orchard sustainability with lepidoperan insect diversity.

Lepidoptera are the most abundant group of insects that feed on the fruit and foliage of apples, cherries and peaches. Over 50 species of Lepidoptera have been reported to inhabit Michigan apple orchards (Strickler and Whalon 1985, Howitt 1993). The most abundant and widely distributed species are in the family Tortricidae. These include leafrollers, budworms and a group of species that feed within the fruit (e.g., codling moth, oriental fruit moth and lesser apple worm). The kinds and relative abundance of tortricids is known to vary greatly depending on horticultural and pesticide management practices. Insecticide susceptibility differences can account for major tortricid diversity differences (Chapman and Lienk 1971, Reissig 1978). Tortricid parasitoids population dynamics are also impacted in a similar manner providing greater richness to assess functional ecology using interspecies diversity measurement index. Although it is the larvae of Lepidoptera that feed in fruit orchards, the adults are the easiest to sample. Thus, pheromone-baited sticky traps will be used to determine the kinds and abundance of tortricid moths in the study orchards. Pheromone monitoring technology has already been widely adopted in Michigan orchards (Battenfield et al. 1984). Therefore, pheromone traps are a quick, economic and grower-friendly assessment tool. The sex pheromones of most tortricids collected in Michigan fruit orchards have been identified (Mayer and McLaughlin 1991).
	Above, codling moth larva damage. Below, adult eyespotted bud moth.

Although each species uses a unique blend of attractant chemicals, many species share the same major component. To assess the diversity of the 30 to 40 species of tortricids that may occur in our study, orchards will only require placing 12 to 15 traps, each baited with different, commercially available pheromones. The drawing range of tortricid attractants is large, thus only a single trap of each kind will need to be placed in the center of each block, visited biweekly and the sticky liner removed, covered with plastic wrap and returned to the lab where moths will be identified and counted.  (back to top)

3
Primary producer stress indicator: carbon storage and water use efficiency.

Carbon assimilation, storage and partitioning are the standard currency by which plant health and performance are determined. Since the leaf is the primary photosynthesis organ of most plants, any damage (biotic and/or abiotic) could compromise the health of the tree. We hypothesize that the health of a tree can be determined by observing the balance between vegetative and reproductive development, which can be validated by using storage of carbon just before bud break in the spring and carbon isotope discrimination (an emerging, reliable means of assessing assimilation stress which shows great promise to provide economic, efficient and precise stress metrics) as indicators of plant stress and therefore wellbeing.  One full year of analysis has been completed and a second is in progress (spring 2006).  Data are still being analyzed. Vegetative/reproduction balance is an easy indicator of overall tree health, but can be a subjective measure.  Data acquisition and analysis are proceeding to inferences about the use of starch, or carbon isotope discrimination as an assessment tool with perhaps a reliable and inexpensive indicator of plant health.   (back to top)

4
Amplification of soil microbiology and soil nutrient potential measured through duff diagnostics.

Each orchard will be divided into 24 quadrants and the center of each quadrant geo-positioned. In the fall of 2003, a 100 cm3 sample of litter (duff) will be taken from the center of each quadrant. The samples will be bulked and a 500 cm3 sub-sample taken and submitted to MSU Diagnostic Services for nematode community structure assessment. A fall 2003 Baseline Duff Diagnostics Ratio based on the population density of bacterial and fungal feeding nematodes/plant feeding nematodes will be calculated for each of the 18 orchards, and converted to a qualitative index (1-5, poor-excellent). Population densities of mycorrhizal fungi spores and micro-oligocheates will also be recorded.

The process will be repeated in the spring and fall of 2004 and 2005. For comparative purposes, 100 cm3 soil samples will be taken at a depth of 1 to 4 inches in the fall of 2003, in each of the 24 sampling locations in each of the 18 orchards. Three of the orchards (one organic apple, one conventional peach and one abandoned cherry) will be selected for determination of the variance among the sampling sites. In each case, the samples from all 24 sampling sites will be analyzed separately. For calibration of the Duff Diagnostics Protocol with the soil microbiology, six samples from each of the three orchards will be selected at random and analyzed for total soil food web status (recovered and active bacterial and fungal biomass, and population densities of flagellates, ciliates and amoebae).Similar calibration analyzes have already been completed for eight Michigan commercial cherry orchards and one organic research apple orchard and assembled into an index assessing soil health. We will modify this index as needed.

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