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Gorse Control Tactics and Strategy for Jughandle State Reserve
Note: Preliminary Draft
This is preliminary. Ive presented information that is correct to the best of my knowledge, but in some cases Ive presented information without expressing doubts where Im not sure. I am depending upon others to correct my errors. The recommendations at the end are also tentative and made in order to elicit responses and opinions.
The purposes of this document are:
Approaches to Gorse Control
A. Control of Established Stands of Gorse
3-R Follow-up Methods
To prevent substantial flowering and seed production, mowing must be done at least annually. A previously rototilled and mowed area that is left unmowed for three years will generally become a solid gorse patch of 3 5 plants.
Parks has used rototilling for control in a number areas. One previously rototilled area near Gibney Lane was re-rototilled in 1994. No significant gorse grew there for five years. Discouragingly, however, a visit in December 1999 showed a high density of new sprouts throughout the treated area. Apparently, the seeds lay dormant in the ground for five years, until conditions for germination were especially favorable (perhaps due to the heavy rains of the preceding two winters). Thus, a number of years without the appearance of gorse is no sign that gorse has been eliminated.
Grazing only works if mature plants have been removed first. Animals will eat seedlings but not mature plants. Fields must be fenced to contain the animals. Grazing is not suitable for areas where there are tender plants that one desires to allow to grow.
Local residents experience is that herbicides are generally effective against seedlings; they will not immediately kill re-sprouts from roots, but will keep the plants from vigorous growth and eventually kill them. Yearly applications are required to prevent re-establishment of gorse patches.
Parks pesticide application included treating resprouts at the edge of edge of tractor-piled gorse patches. Moderately infested areas which had been previously had removed and had vigorously resprouted were treated, and medium-size plans at the edge of a disked area were sprayed. The rest of the headlands was walked in transects to catch scattered individual plants. [Tina, would you comment on the effectiveness of the treatment in the different situation.]
Burning of large gorse patches has been used in the past in Jughandle, at least in
the 1980s and perhaps (?) earlier. A large gorse field off Caspar Point Road also
caught fire and burned quite completely in 1988. According to Guil Dye, a Caspar Point
homeowner, burning of gorse patches that become established in pastures is standard
procedure in Scotland.
Several experiments have been tried using black plastic to cover areas where tops have been removed manually or by mowing.
Jughandle farms has had several areas covered with black plastic for over a year. According to Tina Fabula, who visited the test recently, there is still living gorse under the plastic (perhaps new sprouts?).
I have used plastic on two occasions, once to cover the crown a mature plant that had been cut back many times and mowed over regularly but still survived. I covered it with a 10 square of black polyethylene for about six months. The plant died. A second time, I put down two overlapping six-foot wide strips of woven nursery cloth on a field that had an extremely dense gorse infestation (which had been bushhogged). The length was about fifty feet. I left this for several years, during which time the adjacent gorse grew back up and flowered. By the end of the second year, much debris had accumulated on the cloth, and gorse seeds had sprouted and sent roots through the cloth. At that point, I removed the cloth. There were no living older plants and very few seedlings emerged in the first year. More have now appeared, perhaps because of seeding from the adjacent plants, but the level of infestation is much less than in the adjoining, untreated field.
There are various parasites of gorse that can be of assistance in a long-term control effort, but they will be of little immediate help in dealing with the crisis at hand.
Tasmania is undertaking a major effort to establish biological control species as an aid in an overall control program. A contact for this program is Dr. John Ireson, Senior Entomologist, Tasmanian Institute of Agricultural Research (I have written to him and asked him to join our egroup). A description of this program is at
Collecting more information on biological control should be an important part of developing a long-term control program.
Throughout Jughandle, individual plants and small patches are widely dispersed around the major gorse patches. Much of the southern half of the headlands area south of Jughandle Creek and all major solid patches are surrounded by this type of gorse infestation.
Treatment alternatives that have been tried are:
Manual removal generally is done using mattocks to attempt to dig out as much of the plant and roots as possible Special "weed wrenches" are also sometimes used, but are much slower and difficult to use. Manual removal been used repeatedly in Jughandle Reserve south of Jughandle Creek. Inmate crews and volunteers have worked there (I believe) every year since systematic control efforts were halted. This effort has proven completely ineffective. Gorse infestation has increased every year. I believe that this has occurred for several reasons: First, some part of the root is left in the ground, especially on larger plants (over 1). Second, the earth is disturbed, effectively planting gorse seeds in the soil. The following year, there will be more sprouts.
My own experience in controlling gorse spreading across a neighbors small field (approx 50 by 50) toward my property line has been much better than this. I have gone into the field each spring and mattocked out all of the plants that I could see, generally only 10 to 20 plants, none over 18" tall. Ive done this for 10 years, and during that time, no solid gorse patches have developed. Possible reasons may be: 1) the field is covered with tall grass that is never mowed, perhaps shading out some sprouts; 2) there are some trees to the south, providing additional shade; 3) perhaps this field has never had solid infestation and thus has a limited seed inventory.
Parks Department carried out a pesticide spray in September, 1994. Garlon 4 (chosen because it is not toxic to grasses) was applied to in a number of ways, including treatment of individual plants scattered throughout the Reserve. My own observation of south Jughandle was that the spray was effective at killing the top growth of the plants that I saw, some of which were several feet tall. I did not inspect the plants carefully; so I dont know whether all were killed or resprouted from the base. The next year there were fresh gorse plants growing in the treated area, but this would be expected even if sprayed plants were killed. Many seedlings would not be spotted because of high grass. These would become significant plants in the following year.
Cut and paint on isolated plants has not been tried in Jughandle to my knowledge. It would be more time consuming, but according to Peter Warner, is feasible and effective.
Short-term Gorse Control in Jughandle
Gorse is so rampant within Jughandle that immediate action is needed to contain its spread. A long-term, sustained program of control is essential to long-term success, but effort now should concentrate on short-term measures.
Some tentative conclusions emerge from reviewing the results of all of the approaches that have been tried so far:
In areas previously rototilled, rototilling again will not do further damage to the ecology, but there still remain questions about its effectiveness. Although it will kill existing small sprouts, it also tills the earth and places new seeds into conditions favorable for germination. Experience is that gorse still abounds in fields that have been rototilled numerous times.
If the above methods are ruled out as major measures for controlling established gorse stands, we are left with two short-term measures: herbicides and bushhogging. Hand removal of small plants also can play a role in the overall control program.
Attacking Established Gorse Stands and Mature Plants
The most hopeful control method for mature gorse plants, whether individual, in clusters, or in stands is "cut and paint" of herbicide (glyphosate and triclopyr), or stem injection of imazapyr, if this can be found to be effective on gorse.
As compared to spraying on foliage, direct application to the stem greatly reduces the amount of herbicide used and essentially eliminates possible concerns about aerosols, ground and water contamination, and ancillary killing of desirable plants. Unless there were significant technical or economic advantages to foliar spray, direct stem application would clearly preferable. There appear to be no technical advantages to foliar spray; if anything, direct stem application is more effective. And, the economic advantages do not seem sufficient to outweigh its other advantages in most situations.
Peter Warners experience suggest that the cost of using direct stem application as the primary control method in Jughandle would fit within Parks control budget. As shown in a note at the end, a very rough estimate of treating all of Jughandle west of Hwy 1 is $60,000. This is less than half of the $140,000 that Parks has been allocated for exotic plant control in Jughandle. It needs to be noted, though, that this allocation is for three years and is to cover Park personnel costs as well as contract costs. Given this, $60,000 may not may not fit within the current allocation. Still, it seems in the range of an acceptable cost. Given sufficient public concern, the legislature seems likely to be willing to budget additional money in coming years.
Recommendation: Given the potential advantages of direct-stem herbicide treatment over other methods, Parks should make direct-stem treatment its primary method of attacking gorse in Jughandle. It should move as quickly as possible to apply this control method on a major scale.
What should be done first?
The first priority in the direct-stem control effort should be treating isolated plants and small clusters. Each of these is a source of "infection" that will spread gorse and add to the treatment burden next year. Gorse is flowering now and will soon begin setting seeds. Removing these plants now will lessen next years problems.
Scattered and isolated plants are only a small percentage of the total gorse population of Jughandle, and because they are smaller and more easily accessible that those in solid stands, they can be treated with much less effort. There is no doubt that the benefit/cost ratio of treating the small clusters and isolated plants makes them the preferred first target of the control effort.
Is there a place for foliar pesticide spray?
Direct-stem treatment is clearly superior environmentally. Its costs seem within reason. The only reason I can think of for using foliar spray is that it can be done much more quickly than direct-stem application. This is not compelling, unless Parks cannot get its direct-stem program underway quickly. Then, rather than letting clusters spread without treatment, foliar spray should be considered as a one-time emergency measure. The herbicides involved are used routinely by private landowners around Jughandle, with less knowledge and care than a professional person. Scientific evidence indicates that these pesticides are essentially non-toxic to mammals, birds, and fish. There are, of course, uncertainties with all chemicals, but most of us use more toxic chemicals routinely (gasoline, bleach, detergents, for example). Hopefully, though, Parks will be able to act quickly enough so that foliar spray need not even be considered.
A First Cut at Estimating the Cost of Direct Stem Application of Herbicide in Jughandle
Peter Warner worked alone about 100 hours to treat approximately two acres of heavily infested land near Bodega Bay. He cut and treated about 1000 plants. Jughandles infested land is much larger -- how much larger, I dont know. But, just to get a rough idea of the possible cost, assume that it there are sixty acres of equivalently infested land in Jughandle (30,000 plants). There should be some economies relative to Warner in treating Jughandle (because of learning over time and possible division of labor), but assume that it takes the same amount of time per acre. The total hours worked to treat 60 acres would be 3,000 hours. Given labor rates in this area, it seems feasible to hire this done for $20 per hour, or a total of $60,000.
Gorse a Prohibited Plant
In parts of Australia: " Land owners in areas where furze is Regionally Prohibited must eradicate or control it on their land. Landholders in areas where furze is Regionally Prohibited must take all reasonable steps to control it and prevent its spread on land and the roadsides which adjoin their land." Similar policies exist in New Zealand.
January 14, 2000