New and Increasing Pests in Turf and Alfalfa
Crane fly larvae (bottom) and pupae are found below ground and leave noticeable adult emergence holes. Heavy damage is seen as brown spotting (top).
In 2014, the common crane fly, Tipula oleracea, an introduced fly from Europe, was detected for the first time in Utah turf, in Salt Lake and Tooele Counties by Adam Van Dyke of Professional Turfgrass Solutions, LLC. This crane fly has been an occasional pest in turf in the cool, moist habitats of the Pacific Northwest and the Northeast since the late 1990’s. This new find is surprising given that arid habitats are not favorable for this insect. There are many other species of crane fly that are associated with streams and other bodies of water that do not harm turf.
In general, adult common crane fly resembles a very large mosquito that bumbles around in flight. These flies do not bite humans, and although one of their common names is “mosquito hawk,” they do not feed on mosquitoes. The adults do not feed on turf; it is their larvae that cause the damage. Also known as “leather jackets,” the larvae feed on turf roots, and when the microclimate is humid, they will also feed on blades of grass.
The turf damage seen in Utah has been minimal and isolated to a few spots. It is unclear how extensive the effect of this insect will be in coming years, given its occasional pest status in other areas of the U.S. where it is well established. Soapy water flushes or taking soil cores to investigate larval numbers in the soil are two ways to monitor larvae. In the Pacific Northwest, 25 larvae per square foot can be tolerated in healthy turf. Management consists of healthy plant maintenance and good drainage, beneficial nematodes, and pesticides are also available.
The blue alfalfa aphid is not a new pest to alfalfa in Utah; however, in some areas of the state, particularly in southern Utah, it has become difficult to manage. Other areas, including southern and central California and Arizona, have also had issues in dealing with this pest. It turns out that blue alfalfa aphid populations are increasing earlier in the season than previously thought, but it is not clear why this is happening. Some of the possible factors may include:
- Changes in predator and parasitoid abundance
- Changes in weather patterns (during the winter and growing season); cooler temperatures during the season favor blue alfalfa aphid but not beneficial insects
- Changes in pesticide efficacy against aphids
- More pesticide use for weevil that may reduce beneficial insects
Blue alfalfa aphids reproduce rapidly and honeydew or aphid excrement can lead to mold issues.
Research surrounding this issue is currently being organized and conducted in areas with high aphid pressure.
Blue alfalfa aphids are phloem-feeding insects that feed on young alfalfa leaves and new stems. Moderate to high infestations may result in yellow leaves, leaf curl and wilt, defoliation, and slow green-up after cutting. Generally, low to moderate aphid populations can be tolerated, but identification is important. Pea aphid and blue alfalfa aphid can be differentiated by their antennae. Pea aphid has 3 to 4 bands along the antennae while blue alfalfa aphid antennae are not banded and uniformly brown.
The primary strategies to reduce aphid infestations are to:
- Maintain the beneficial insects that provide natural pest control and keep aphids in check. Pest Control Advisers (PCA) in California have observed very low parasitism of aphids by parasitoids and low abundance of lady beetles in problem areas.
- Use alfalfa varieties with resistance to blue alfalfa aphid.
- PCA’s have observed that green chop with quick alfalfa removal aids in aphid suppression because they do not build up well in windrows.
- Use insecticides judiciously. In California, where blue alfalfa aphid has become a problem, PCA’s found that Lannate, dimethoate, and Lorsban can be effective, with more options being considered.
-Ricardo Ramirez, Entomologist