Looking for bugs isn’t a nerdy middle school hobby – not if you’re an orchardist. It’s essential for tree fruit growers, no matter what spray program you use.
Blanketing the orchard with sprays as a preventive may be someone’s idea of pest control, but a more cost-effective, rational and effective approach is best. Using integrated pest management means going beyond one-size-fits-all spray routines.
Proactive pest protection
Your best defense is a good offense – but not in the form of unwarranted spraying. Proper soil fertility, water availability, tree fruit nutrition, site selection, the use of mulches or cover crops, picking up drops and fallen leaves and proper pruning techniques are good for starters. Increasing habitat for beneficial insects – such as hoverflies, mason bees and tachinid flies – by adding diversity with native plants and by providing nesting blocks or osmia tubes, can help keep pest pressures in check.
These cultural aspects come first, C.J. Walke, tree fruit specialist with Maine Organic Farmers and Gardeners Association said during a presentation at the 2017 Maine Agricultural Trades Show. When these techniques aren’t enough, then it’s time to apply materials.
“In most situations, pest levels can get pretty high,” Walke said. “Find that point of vulnerability in the insect life cycle.”
Scout it out
Monitoring for pest pressures, using traps and visually inspecting plants for signs of infestation are all about timing.
Interrupting the pest life cycle means understanding it. Know what signs to look for in the orchard, use a variety of traps to attract bugs and provide an indication of the pressure, and do so at the correct time.
Thirty days after bloom is when major pests tend to materialize. Along with the June drop, any pest in the fruit will drop to the soil where it can propagate. Cleaning up these drops immediately, as well as having a strong predatory insect presence, can help keep pest pressures from escalating.
Red sticky balls, pheromone traps and sticky cards are all used to attract pests and monitor pressure. Different products attract different insects. These need to be placed out at the appropriate time to identify the pressure and catch the pest at a vulnerable life cycle stage. Traps work using various combinations of a sticky substance, color, odors and food to attract insects and trap them.
Degree-day tracking is a tool that can be effective in interrupting insect life cycles. For many insects, researchers have calculated the time between the first and the second hatch. Using this information to determine when the next wave of larvae will emerge will help to time your spray applications for efficacy and to alert you to prime times for scouting and seeking evidence of ongoing concerns.
Degree days are cumulative, using a base temperature threshold needed for the insect to emerge and the time it takes to complete its life cycle. Although there are several ways of determining degree days, the basic premise is the same. By determining the actual daily temperature in relation to this, and adding these up, the time to the next life cycle stage can be calculated with accuracy. The insect life cycle is dependent on temperature. For more information, search “growing degree days” for the article “Using Growing Degree Days for Insect Pest Management.”
Common pest concerns
Walke shared an overview of some common orchard pests, how to scout for them, when they are vulnerable to intervention and how to combat them. Here are some of his recommendations:
European Apple Sawfly: Adults emerge at bloom and larvae will hatch out of the fruitlets, leaving a surface scar. Ultimately they will again burrow into fruits, and these damaged fruitlets will drop from the tree. When thinning, any damaged fruitlets should be removed. Using a white sticky card at bloom will indicate pest pressure levels. Clay-based deterrents at pink stages or an insecticide such as Spinosad are recommended after bloom if needed.
Plum Curculio: A small weevil affecting apples and plums, which damages fruit. Adults feed on fruitlets and lay eggs in fruit. Pyramid traps can be used to estimate pressure, and designating an untreated trap tree may remove pressure from the rest of the orchard block. Kaolin clay sprays (Surround) can provide protection. Cleaning up dropped fruit – even placing tarps on the soil to prevent the larvae from entering soils – can help keep this pest from becoming established.
Coddling Moth: Adults emerge at bloom, infecting pear and apples. Kaolin sprays repel adults, who lay eggs on fruit, which larvae eat. The larvae travel down the tree to pupate in the trunk. Cardboard bands can prevent them from doing so. Scout traps for males, and count the first male moth as day one for degree-day tracking. Degree-day tracking to determine when to apply Bacillus thuringiensis (Bt) sprays is recommended.
Round-headed Apple Tree Borer: An important pest in the Northeast, this has to be attacked in the larval stage. Adults lay eggs at the soil line of trees, and the larvae feed at the cambium layer for several years. They will girdle the tree and get into the roots. Use screens around the trunks and keep the soil line visible. Orange frass at the soil line indicates infestation. Borers need to be cut out using a knife to cut through the clean tissue until the borer is located and killed.
Apple Maggot Fly: This insect emerges in late June, and the larvae move into the fruit. During the late fruit drop, they will emerge from dropped fruit and pupate in the soil. Red sticky balls, set out prior to adult emergence, are key to determining pest pressures. Spinosad can be used as an insecticide when adults are found in traps.
Determining if actual conditions present in the orchard indicate that pest pressures are approaching a threshold level requires some knowledge of entomology.
Be prepared and put on your best defense by looking for those bugs, properly identifying them and knowing their life cycle stages. Then, any treatments you apply will be most effective, giving you the best return on your investment.