The warm and dry summer weather in Michigan has raised concerns about potential insect problems in field crops. The dry conditions, which are expected to persist, have created a favorable environment for piercing-sucking pests. Chris DiFonzo, field crops entomologist for Michigan State University Extension, highlights several pests that farmers should be vigilant about.
• Tarnished Plant Bug and Related Species: These insects are commonly found in field crops in Michigan. They suck juices from leaves and may later pierce beans. The characteristic bright yellow or brown discoloration on sugarbeet leaves indicates their presence. Effective management of plant bugs can be challenging since the damage is often observed after the bugs have already left the plants.
• Thrips: These small, torpedo-shaped insects feed by puncturing plant cells and sucking their contents. Heavy thrip populations can cause silvery patches and the death of entire leaves. While thrips are usually controlled by natural predators, outbreaks may occur in bean fields adjacent to wheat during dry spells.
• Potato Leafhopper: These pests arrived from the south in May and have been reproducing on crops and weeds. Their feeding leads to leaf yellowing, known as hopperburn, primarily affecting sensitive crops like alfalfa, dry beans, and vegetables. Early detection and regular scouting can help manage potato leafhopper populations effectively.
• Soybean Aphid: While soybean aphids have not been a major issue in recent years, the current season is different. Early-planted fields without seed treatments have shown aphid infestations. Fields planted later, with or without seed treatments, are less likely to be affected. Monitoring aphid populations and considering spraying options should be done cautiously, as beneficial predators are already present in the fields.
• Spider Mite: The most concerning pest for farmers is the spider mite, particularly due to its challenging management. Infestations usually start on field edges near ditch banks or dirt roads and can rapidly increase in hot and dry weather. Using insecticides to control other pests can inadvertently worsen spider mite infestations by eliminating natural predators. Selective miticides can be expensive, and poor coverage or the wrong choice of product can lead to ineffective control.
The warm and dry conditions during summer have several implications for these pests:
- Faster development: Insects and mites go through more generations and develop faster in increasing temperatures. Elevated day and night temperatures can further accelerate their development.
- Improved diet: Drought-stressed plants offer higher concentrations of nitrogen-type compounds, which are ideal for sucking pests. The enhanced nitrogen content provides better nutrition for these insects.
- Worsened injury: Feeding by piercing-sucking pests under dry conditions can exacerbate plant injury. The loss of water from punctured cells in low humidity can quickly lead to cell collapse and plant damage.
- Reduced biocontrol: Insects and mites that act as natural predators and control pests may be less effective in dry weather and low humidity. Dust particles on leaves hinder the activity of entomopathogenic fungi, reducing their ability to control pest populations.
- Limitations of insecticides: Some insecticides, like pyrethroids, work better under cool conditions. Pesticides also degrade more rapidly under sunny conditions, reducing their effectiveness. Additionally, insecticides can harm beneficial insects, causing pest populations to rebound quickly.
Before considering insecticide applications, farmers should carefully evaluate the situation. Spraying too early or as a precautionary measure can have negative consequences, such as promoting mite outbreaks or higher aphid populations later on. It is essential to consider the potential impact of spraying on beneficial insects and the long-term consequences for the fields in case of continued dry conditions.
If insecticide application is necessary, farmers are advised to choose the right product. Opt for options with a lower chance of flaring mite populations, such as dimethoate, orthene/acephate, Lannate, or bifenthrin. Ensure that the chosen product is labeled for use on the specific crop. Good coverage is crucial to effectively manage surviving aphids, mites, and thrips, as these pests can reproduce rapidly and rebound.
By closely monitoring insect populations, exercising caution in insecticide use, and considering the broader implications of pest management strategies, farmers can mitigate the challenges posed by piercing-sucking pests and safeguard their field crops during this warm and dry period.
Photo Credit: gettyimages-oticki
Categories: Michigan, Crops, Weather