^^^ RESEARCH Figure 1. Mole cricket damage is often quite severe and effective control can often times be a frustrating and expensive endeavor. While fire ants present their own spe- vantage. We don't know where the pest Practical Use of New cial challenges, just not in terms of effec- is concentrated, its developmental stage, tive control, but also from the health risk or even its general abundance prior to Research for Effective they produce, in this article we will re- serious damage to the turfgrass. strict our comments to mole crickets. Secondly, the soil and associated or- Mole Cricket Control The underground nature of this insect, ganic matter (such as thatch) work BY RICK L. BRANDENBURG, PH.D. its presence near water, and several be- against our efforts to deliver the insec- North Carolina State University havioral characteristics of this pest make ticide or other control agent directly to he southeastern United States, it a particular challenge {Fig. 1). the insect pest. Many insecticides are and Florida in particular, seem to The majority of this article will focus bound tightly to organic matter in the Tbe blessed (or cursed) with an on recent research that helps us better soil and this results in less availability abundance of turfgrass insect pests. The understand what the mole cricket does of the product to the insect. The soil list ranges from cutworms to mole crick- under the soil and how this information itself somewhat buffers the insects from ets, fire ants to sod webworms, chinch ma be useful in helping us manage this any application of an insecticide. As a bugs to white grubs. Many of these pests pest. result, control of soil insects such as are troublesome every year and often The first advantage that mole crickets mole crickets is a great challenge that persist for long periods of time during have working in their favor is the very often requires a significant investment the warmer months. In addition, several fact that they are a soil insect. This works in time and money. of the pests such as fire ants and mole to their advantage in two ways. These challenges in mole cricket man- crickets offer special challenges as we at- First, we can't see what the insect is agement have resulted in a number of tempt to control them in an environmen- doing when its below the soil surface. research projects through the years to tally and economically sound manner. This obviously works to the insect's ad- help us better understand the biology liest hatching southern mole crickets do consume a few of the later hatching tawny mole cricket. When we consider the management implications of this difference, the length of egg hatch is going to be considerably longer in areas where the two species coexist. This makes good control more difficult since the timing and residual activity of the insecticide must cover a longer period of time than the situation where only one species is present. The combination of the two species in one location usually gives us a bit more of a problem in our efforts to obtain maxi- mum control. In addition to the fact that we can have two different species present in one location, we are finding that there are some rather significant regional differ- ences in mole crickets. Figure 2. The southern (left) and tawny mole crickets are similar in appearance, but differ in For example, in a particular year, a their biology and ecology. mole cricket population in north Florida may enter into the winter months with about 80% of the nymphs having com- and ecology of this pest. Our program at ets, their biology gives them a leg up on pleted their development to the adult North Carolina State University has been the southern mole cricket. Tawny mole stage. In North Carolina we may see as studying this pest for about 15 years and cricket adults typically lay eggs earlier high as 90% of the population overwin- a very significant effort has been under than the southern mole cricket and as a ter as adults. way for the past 10 years. A portion of result the tawny mole crickets are often a We don't know why we see advanced this work in collaboration with Dr. Mike little larger, offering them a level of pro- development in an area with cooler spring Villani at Cornell University has been tection from the southern mole crickets. and fall temperatures and where the eggs funded for seven years by the United It is quite possible that some of the ear- may hatch a month later. There also States Golf Association. The major focus of our research has been studying the biology and behavior MEAN NO. OF EGGS PER FEMALE of mole crickets and how this affects our efforts to manage this pest. We have AT DAYS 28 & 32 -1997 studied both the southern and tawny mole crickets (Fig. 2). While there are many similarities between the two spe- cies, there are also some distinct differ- ences. The southern mole cricket is more of a predator feeding on soil organisms and the tawny mole cricket feeds more on the root systems of the turf. Each will modify its feeding behavior somewhat under unusual or less than optimal conditions. However, the very predatory nature of the southern mole crickets actually al- lows them to attack and feed upon tawny mole crickets that are the same size or smaller. Figure 3. Effect of soil moisture on the egg laying of mole crickets in a greenhouse study (North Fortunately for the tawny mole crick- Carolina). appear to be some differences in the susceptibility of mole crickets to par- ticular insecticides from various parts of the Southeast. Are all of these differences a reflection of different environments (i.e. soil types, rainfall, temperature), the result of years of exposure to different insecticides, or is it that the various populations of mole crickets that found their way to the U. S. came from different points of origin in South America? I don't think we have a clear answer for this yet, but it does caution us in accepting data from far removed loca- tions as the gospel. The way a product stacks up in North or South Carolina may or may not be the same as it per- Figure 5. Indications of avoid behavior by forms in south Florida. Local testing and Figure 4. Typical "Y" shaped tunnel of a tawny mole crickets to the presence of an on-site trials are critical with this pest. tawny mole cricket in the soil as observed insecticide in the soil as observed through an One aspect of mole cricket ecology through an X-ray image. X-ray image. that does appear to be consistent across its range is that it is a creature of habit. By eggs a little bit earlier if a good rainfall applied in a timely manner, but under this, I mean that the mole cricket popu- occurs and a little bit later if the soil is dry soil conditions. Time passes and it lation generally finds an area that it is dry. remains dry. During this dry period suitable and populations tend to occur I believe the effect of soil moisture is the mole crickets are still feeding and there year after year. one reason why we have not been able growing larger, but there is little evi- Much of this is the result of the fact to accurately predict egg hatch based dence of surface damage. that the adult male mole cricket seeks upon soil degree days. This desire for Then we enter a period where we sites that are suitable for making attrac- higher moisture area to initially de- receive some good soaking rains and tive calling chambers to attract the fe- posit the eggs may well explain the suddenly mole cricket damage appears males for mating in the spring. These reason for the consistency in the sites everywhere, including the treat areas same sites are often good for egg laying, in which they show up each year. Once (regardless of the insecticide used). Im- which the females frequently utilize soon hatched, the nymphs may migrate to mediately we feel that the treatment after mating. In effect, the signs of adult drier areas as we often see them around has failed. activity in the spring are actually a very bunkers and on mounds. What has most likely happened is good indicator of where significant egg Under drier soil conditions, the that with the rains, the crickets moved laying will occur and represents a site mole crickets also have a tendency to to the surface and it's the first time the where monitoring of egg hatch should be a little deeper in the soil. This is why crickets have actually been exposed to be focused. it is more difficult to use the soap flush the insecticide. If the insecticide has This is not to say mole crickets don't to get them to the surface when it is sufficient residual activity it will then spread to new areas because they cer- dry. begin to control the crickets. One must tainly can and do. By mapping and moni- Dry conditions also make it more remember, however, that the crickets toring these sites of springtime adult difficult to control mole crickets. The are larger and it may take up to several activity, superintendents can use their dry soil and organic matter make it weeks before the damage begins to sub- time most effectively and feel confident more likely that much of the pesticide side and the mole crickets die.