[Image: 1]A phenology research garden was planted in fall 2007 at the LSU AgCenter Hammond Research Station in Hammond, La. The garden is located in a full-sun area and away from a heat source or sink. The garden comprises a pest-monitoring plot surrounded by four-indicator plant plots. Flowering woody ornamental plants were planted as indicator plants with four replications in each of the indicator plots. Host plants also are planted in the pest plot to monitor targeted pests, including lace bug, euonymus scale and whiteflies.
During 2008, indicator plants were monitored daily so phenological events can be identified with precision: dates of bud break, first bloom and full bloom.
- Bud break: leaf tip grows out but not unfolded
- First bloom: date of the first flower bud on the plant open, revealing pistils or stamens
- Full bloom: date 95% of the flower buds open (i.e., 1 bud out of 20 has yet to open)
We did not inoculate pests to the host plants to avoid stress during plant establishment. Natural population of whiteflies were observed and identified as Bemisia tabaci in spring 2008. Meteorology data were collected by an on-site weather station at the LSU AgCenter Hammond Research Station. Degree days (DD) were calculated using January 1 as the start date and a 50-degree F lower temperature threshold for general pest development.
Fifteen ornamental species were recorded with phenological event that can be identified with precision, including bud break and first bloom (Table 1). The event close to the presence of first adult whitefly was the bud break of the red buckeye. Based on a reference DD for azalea lace bug egg hatch, this event may possibly occur following the bud break of Indian hawthorn Snow White. Reference DD for euonymus scale egg suggests that the first bloom of Chinese Snowball viburnum may be a signal for this event. These two pests need to be inoculated to the pest plots to obtain pest development DDs for more accurate prediction because reference DDs from other regions could be several days off from what we are experiencing in the Gulf States. From current observations, a sequence of phonological events in advance of pest activities can be identified from these ornamental indicator plants to assist pest monitoring in the southern landscape.
Table 1. Sequences of ornamental plant phenological events and pest activities during spring 2008.The degree days were calculated by sine-wave method with lower threshold set at 50 degrees F and a start date of January 1.
|
Ornamental Plant |
Phenology Event |
Calendar Date |
Day of Year |
Accumulated Degree Days |
|
Jap. magnolia 'Alexandria' |
First Bloom |
1/26/08 |
26 |
104.7 |
|
Indian Hawthorn ‘Snow White’ |
Bud Break |
2/5/08 |
36 |
189.4 |
|
Azalea lace bug |
Egg hatch |
- |
- |
206* |
|
Red Buckeye |
Bud Break |
2/20/08 |
51 |
299.2 |
|
Whitefly |
Adult emergence |
2/22/08 |
53 |
314.3 |
|
Ligustrum |
Bud Break |
2/23/08 |
54 |
326.1 |
|
Azalea 'G.G. Gerbing' |
First Bloom |
2/25/08 |
56 |
334.0 |
|
Arrowwood Viburnum 'Autumn Jazz' |
Bud Break |
2/26/08 |
57 |
336.5 |
|
Purple Leaf Plum |
Bud Break |
2/28/08 |
59 |
354.2 |
|
Azalea 'White Moon' |
First Bloom |
3/4/08 |
64 |
390.8 |
|
Euonymus 'Manhattan' |
Bud Break |
3/4/08 |
64 |
390.8 |
|
Chinese Snowball Viburnum |
First Bloom |
3/8/08 |
68 |
404.3 |
|
Euonymus scale |
Egg hatch |
|
|
406* |
|
Spirea 'Anthony Waters' |
First Bloom |
3/13/08 |
73 |
465.1 |
|
Althea 'Morning Star' |
Bud Break |
3/14/08 |
74 |
477.6 |
|
Purple Leaf Plum |
First Bloom |
3/14/08 |
74 |
477.6 |
|
Red Buckeye |
First Bloom |
3/19/08 |
79 |
536.1 |
|
Indian Hawthorn |
First Bloom |
3/21/08 |
81 |
554.5 |
|
Red Maple 'Brandy Wine' |
Bud Break |
3/21/08 |
81 |
554.5 |
|
Bottlebrush |
First Bloom |
3/31/08 |
91 |
692.0 |
|
Althea 'Morning Star' |
First Bloom |
5/18/08 |
139 |
1505.9 |
|
Crape Myrtle 'Natchez White' |
First Bloom |
5/29/08 |
150 |
1766.9 |