Pasture Damage Control By CRICKETS Methods

New Zealand Journal of Agriculture, Volume 98, Issue 3, 16 March 1959, Page 217

Pasture Damage Control By CRICKETS Methods

By

C. M. BUCK,

Fields Instructor, Department of Agriculture, Warkworth

PERIODICALLY when seasons are favourable the population of crickets builds up to immense hordes which cause widespread damage to pastures in certain areas of the North Island. Severe infestations during the past two seasons have caused tremendous damage and heavy financial loss and have resulted in greatly intensified interest in this pest. The development of new insecticides and techniques for their application has also served to stimulate interest, as it is now possible to eradicate crickets economically from large areas. /CRICKET damage usually occurs during dry autumns, when pasture plants have little power of recovery, and continues until the cooler ■ weather, when again the plants lack vigour required to repair damage. Consequently the effects of the ravages of the cricket are felt long after the pest has disappeared. The cricket has been a pest in New Zealand for many years. Extensive damage was caused in the Hauraki Plains by this pest in 1911. The first reference in “The New Zealand Journal of Agriculture” occurred in the March 1916 issue, where it is stated: “In certain northern districts of New Zealand the black cricket ' (Gryllus commodus) often commits considerable depredations during summer.” The cricket is not therefore a new pest, but as a result of research there are available new methods of control which have been welcomed by many farmers. The mature cricket is black and about an inch long and has long hind legs which when used in combination with its wings enable rapid movement. A thorough investigation of the life history of the cricket has not been made in New Zealand, but observations have established the position fairly well. From February onward the light-coloured, cigar-shaped eggs about 1/10 in. long are deposited by the female into the turf or just below the soil surface. Some of these eggs could possibly hatch in the following few weeks if conditions were satisfactory, but hatching does not generally begin until early October. From the egg emerges a nymph, which is very similar to the adult but which is wingless and very small. The

nymph begins to feed immediately and as it feeds passes through a succession of moults until after several months it becomes a winged adult. The■ cricket is usually near the adult stage before damage is noticed.. The main effect of the cricket is felt in the Auckland Province and in particular in the Hauraki Plains and North Auckland peninsula, where soils and climate are ideal for this pest. Recently severe damage has been caused in Hawke’s Bay Province, mainly in Waipukurau and Patangata Counties. In these areas many thousands of acres of pasture were eaten out by crickets last season. Crickets have also been reported in small localised areas in northern parts of the South Island, where, however, they appear to be of little consequence. The occurrence of this pest is invariably associated with heavy soils which crack during dry . periods, the cracks providing excellent shelter. Heavy cricket infestation is most unusual on a soil which does not crack, though small populations sometimes occur on such soils. The indication is then that these cracks are most necessary for the survival of this pest. , , Soils which are subject to cracking have a high proportion of clay particles and the expansion and contraction of this clay as it is first wet and then dries cause cracking. Most severe > cracking occurs during dry summers and autumns which follow wet winters and under these conditions most severe cricket infestations occur. Severe damage has also occurred in a dry autumn after a fairly dry‘winter when soils were not completely wetted and cracks 'of the previous summer were not healed. The cricket population also increases after a succession of two or more seasons favourable to them. An example of this occurred in North Auckland recently. The 1956-57 season was favourable to the crickets and considerable damage was caused, and in the following season, which was again suitable, the numbers were built up to such an extent that severe widespread damage resulted. Dry clay knobs and ridges crack readily and are usually the first to be attacked and damage moves progressively from such areas if suitable weather persists. The difficulty which is often experienced in establishing and holding good pasture in such places can often be traced to an annual defoliation by crickets. When the pasture on these dry areas becomes brown and parched in summer the cause is often considered to be lack of moisture unless a careful inspection is made. It is possible

even to walk over such areas where there is a heavy cricket infestation and not see a cricket. Crickets in advance of the path taken quickly retire to refuge in cracks and do not appear until the disturbance has passed.

Types of pasture and pasture management also influence the degree of infestation. Any form of management which will encourage ground cover and minimise cracking will result in a pasture with greater resistance to the depredations.

Paspalum has considerable resistance to the cricket as well as appearing to lack attractiveness. It also tends to hold the soil against cracking, so that strong paspalum pastures are seldom severely damaged. Management should be aimed at encouraging paspalum in young pastures.

Cocksfoot, though readily eaten by the cricket, has strong powers of recovery from severe damage. Cricket damage has often resulted in complete cocksfoot dominance of pastures where previously this grass was a minor constituent.

Ryegrass of all types is undoubtedly the most favoured of our pasture species and is greedily eaten by crickets. Heavy infestations of crickets will quickly eliminate ryegrass from pastures. On the other hand white clover appears to be much less attractive and is usually left until ryegrass has been eliminated. As a result of this preferential feeding well balanced

swards which recover from cricket damage are often completely clover dominant and consequently produce much less than good mixed swards. The cricket is directly responsible for this loss of production and also for

the costs involved in correcting the unbalanced pasture. It is therefore good economy to take precautions against cricket damage and ensure against loss of production and later heavy expenditure. Pattern of Damage The pattern of damage begins with the plants adjacent to the cracks being eaten out and as these are eliminated so the damage radiates out until it adjoins that from a nearby crack and large areas are therefore completely devastated. The cricket is a surface feeder. The plants it relishes are

closely cropped to the. ground and, as damage is associated with dry weather, they have little hope of recovery. The crickets will also consume any seed which has been shed, so that there is often little hope of recovery of the pasture from self seeding. Damage continues if unchecked and will spread over large areas until rain fills the cracks and drowns the pest or cold weather partially immobilises and eventually kills them. The latter usually happens in late April or early May, but damage may continue, as it did last season, into early June. Temperatures which are low enough to affect the cricket will also cause a reduction in growth rate of the pasture, so that by the time the cricket has disappeared the pasture has little power of recovery. Badly damaged pastures often remain completely bare for months after the cricket has gone and unless endeavour is made to re-establish pasture, weeds such as thistles, dock, buttercup, rushes, pennyroyal, and many others will quickly establish. On fertile soils much of the buttercup and pennyroyal infestation results from the pastures being bared by crickets. Minimising Damage There are several means of limiting the cricket damage in addition to the use of chemicals. Mention has been made of the resistance of paspalum and every encouragement should be given to the establishment of this plant. Spring sowing of paspalum to hasten establishment should be considered. Paspalum is very slow to establish from autumn sowing, but when it is spring sown quite good cover can be obtained in 2 or 3 years.

The paspalum may be sown alone or with a crop of turnips in spring; then the ground is harrowed or lightly disced in autumn and the balance of the pasture mixture sown.

Any other form of management which is aimed at increasing the vigour of the pasture will help to minimise damage. Wet soils which pug in winter are more likely to crack in summer and drainage of these areas would be helpful. Pastures with a good cover are not likely to dry out so quickly; hence hard grazing will encourage the cricket. Crickets are not usually found in numbers in cultivated fields, so that new sown grass is seldom damaged except where cultivated areas are adjacent to pasture or scrub which is infested with crickets. Severe damage has been found under such conditions, so it is always advisable to eradicate crickets from areas adjacent to new grass. Small populations have caused severe damage to seedling pastures. Chemical Control Little effort was made to control crickets with insecticides until the advent of DDT and. BHC. In 1947 Banfield and Cottier, working in the Thames district, evolved a bait which has since been used extensively with excellent results. In these experiments the two insecticides were also used as dusts at rates up to 60 lb. per acre but without success. Fortunately when . the chemicals were administered as sprays or in bait form good results were obtained, but because of the ease of application baits became most popular. The baits consisted of 24 lb. of bran and 4 lb. of molasses per acre with DDT or BHC added. Since then it has been found that costs may be reduced by substituting sawdust for half of the bran. When bran is not available materials such as poultry mash may be used. The DDT and BHC were added at the rate of 1/10 lb. of 100 per cent active ingredient. These baits have been used extensively over a number of years and excellent results have been obtained. Recently a new insecticide — dieldrin— become available and has been in use for two seasons. This material appears much more toxic ,to the cricket than previously available materials and will probably supersede DDT and BHC. Dieldrin has proved very efficient as a spray and it is fortunate that the development of tractor spraying equipment and the use of the aircraft in farming have made it possible to spray large areas for reasonable cost. An added advantage is that dieldrin has also given good results when applied as a dust. At the rate of 4 oz. per acre of 100 per cent material dieldrin as a spray has given excellent

kills and appears to be effective for a month or more. Evidence of its effectiveness as a dust at the 4 oz. per acre rate is insufficient, but it appears that this rate may be satisfactory. However, a dieldrin-superphosphate mix is available containing 8 oz. of 100 per cent dieldrin in 2 cwt. of superphosphate and this is the recommended rate of application in the meantime. Method of Application Baits are normally hand sown and if prepared without excessive moisture may be sown through a topdressing machine. Dieldrin has been applied as a spray by aeroplane, tractor mounted booms, and by hand machine with good results in all cases. Aerial application of dieldrin-superphosphate mix has also given good kills. A dieldrin-lime mixture made by spraying dieldrin into the lime gave a good kill after the mixture had been applied by spinner topdressing. Time of Application The correct timing of the application of insecticide is most important but often difficult to achieve. Very often farmers are not aware that crickets are going to be a problem until damage is observed and even if the crickets are killed immediately, recovery of the pasture is often slow, particularly if hot, dry weather prevails. Therefore those wishing to prevent this trouble should keep a careful check on pastures during December and January and judging on numbers present anticipate the possibility of damage and apply the insecticide before severe damage occurs. Applications under such conditions would normally be made in early

February, but this would be varied according to the season. If the application is made too early, however,. a second spraying may be necessary to eliminate later crickets. In the Hauraki Plains G. L. Banfield has determined that it is preferable to delay treatment until damage is starting to show up around the cracks, though spraying should be done before the crickets reach full maturity, when they would be capable of laying, eggs. If treatment is delayed to late February, it is possible to get away with one spray application without accepting too much cricket damage. Repair of Damage When a cricket infestation is allowed to run its course the crickets persist until cold weather eventually reduces their activity and they ultimately die. Repair of damage is then difficult because the colder conditions prevent rapid development of new sown pasture seed. Weeds are therefore permitted room for development. It is a fact also that many of the soils which are likely to be damaged by crickets are unsuitable for spring sowing of grass seed. Cricket damage should therefore be repaired while growing conditions are still favourable in autumn. This entails killing off the crickets if they have not already been drowned by autumn rains and sowing of seed. Some of the best results from undersowing and sod seeding, have been obtained after severe cricket damage. Competition from the damaged pasture is negligible and undersown species have every chance. Where undersowing is not possible light discing or

harrowing and oversowing usually give good results. On hill country the seed may be covered by moving a flock of sheep several times across the damaged area. Where autumn sowing has failed or not been possible the feeding of hay containing viable seed of desirable pasture plants during winter will be of some assistance. To reduce the chance of cricket damage every endeavour should be

made to produce vigorous pastures and manage them well. Paspalum and cocksfoot should be encouraged and close, continuous grazing should be avoided. Wet soils should be drained and wherever possible the management of the farm should be arranged to avoid pugging.

It is of great importance to anticipate the damage or at least identify it early so that the cricket can be eradicated and the pasture allowed to recover before damage is too severe. Control measures should consist of DDT or BHC applied in bait form or dieldrin as a spray or dust. Repair of damaged pasture should be done during autumn before cold weather prevents a rapid cover of the bare ground. Precautions with Insectides Dieldrin is a dangerous insecticide which is poisonous to humans, animals, and bees, but it is not often realised that DDT and BHC are also poisons. These two have been in use for some time and many farmers have had experience with them and often this familiarity has bred carelessness.

Contractors and farmers are therefore warned not to take risks when using any of these materials. Even though there are not usually any ill effects after excessive contamination, there is always the possibility that residues will remain in the body and eventually build up to toxic levels. Similarly farm animals should not be unnecessarily exposed to these insecticides. It is desirable for treated fields to be kept free of stock for a week or two or until heavy rain occurs so that the intake of insecticide is limited. Apart from the safety of the stock there is also to be considered, with milking cows, the tendency for insecticide to concentrate in the milk, through which a house cow or milking herd could pass on further contamination. Bees are particularly susceptible to these chemicals, so care should be taken when they are used near flowering plants. Acknowledgment Acknowledgment is made to the article “Success of Poison Baits in Eradicating Crickets” by G. L. Banfield and W. Cottier, Journal of Agriculture”, vol. 77, p. 569, which has been drawn on freely; also to G. L. Banfield, Instructor in Agriculture, Department of Agriculture, Thames, for his advice.

Management of New Pastures

IN the late winter-early spring period new pasture is potentially capable of producing more and better feed than any other pasture on the farm. For this reason autumn management of newly sown grass should be designed to take advantage of this potential production. There are two main points to consider. First, stocking in autumn is essential to achieve sufficient consolidation to allow stocking of the pasture under the wetter conditions usual in early spring. Secondly, grazing in late autumn must be carried out early enough to allow the pasture to recover before winter. The most satisfactory way of obtaining both consolidation and autumn recovery is by mob stocking. Heavy stock concentrations consolidate the ground with minimum damage to the pasture and grazing is completed early enough to allow adequate recovery. In the colder districts correct timing of the autumn grazing is the critical factor in the successful spring utilisation of new pasture, and though in the warmer districts there can be more latitude in autumn grazing, it is still essential to allow the pasture to make a good recovery before growth ceases.

—M. L. CAMERON,

Instructor in Agriculture, Department of Agriculture, Timaru