Hi fruit growers! Hopefully the season is going well for all of you. I am hearing from several folks that fruit development is ahead of where it was this time last year, and maybe that’s why I’m also getting a lot of questions about ‘unusual’ damage to the leaves and fruits of caneberries, apples, and peaches, which I believe to be caused by sap-feeding insects like leafhoppers and plant bugs. So, here’s a quick overview of signs and symptoms you can be on the lookout for in your orchard/berry patch!
Figure 1. Adult potato leafhopper (A) Photo: J. Obermeyer, and symptoms of leafhopper feeding on apple leaves (B) Photo: Mid-Atlantic Orchard Monitoring Guide
Many of you are likely familiar with leafhoppers – there are many different kinds of these insects that differ in size and color. Some common ones in the orchard include the white apple leafhopper and potato leafhopper (Figure 1A). They have a characteristic jumping or hopping behavior, and if you happen to disturb leaves where many adults are resting, they will seem to “burst” out and fly away – a key sign of hopper activity. As with most insects though, only the adults have wings, so nymphs (immature stage) will often stay on the leaves/plant crawling about quickly and trying to avoid your eye. The nymphs can be very small though and blend in well with the leaves, so you’ve got to look carefully and closely. Some planthoppers inject toxins into plants when they feed with their straw-like mouthparts, and this may cause yellowing, shriveling, or curling of the foliage (Figure 1B). For most, this is the key symptom of planthopper injury that you will spot in the orchard. Some may also see “hopper burn” which presents as yellowing on just the tips of foliage. In my experience, these yellowing symptoms are often most apparent along the edges of the fruit plantings or your orchard, especially when populations are high. However, some of you may see this injury but find no insects present! Well, that’s because leafhoppers are very mobile insects that can fly well, and given their small size, they can also be assisted in their movement by the wind. So, boiling all this down to what you need to know: we often see symptoms of planthopper injury after the insects have already moved through. This means, by the time you notice injury, the planthoppers may be long gone. Although the foliage may look rough and leaves may even be dropped, the good news is that most healthy, established plants and trees will recover from this feeding injury.
Figure 2. Adult tarnished plant bug (A) Photo: John Obermeyer, symptoms of “funnel” feeding damage on apple (B) Photo: Celeste Welty, and “corky” scar damage on peach (C) Photo: New York State Ag Experiment Station.
Another insect group that I’m hearing a bit about this season are plant bugs, and similar to the leafhoppers, there are many different kinds of these insects and they feed on lots of different plants. One plant bug that many of you are likely familiar with in the orchard is the tarnished plant bug (Figure 2A). Although these insects also feed on buds and woody tissue, most of the questions I’ve received this season are about injury to developing fruits. Key symptoms of plant bug feeding on fruit are funnel-like depressions (Figure 2B) or “cat-facing” injury on pome fruit, and “corky” scars (Figure 2C) on stone fruit. It can be tricky to diagnose plant bug injury though because there are other insects with similar feeding strategies that many of us think of first, like stink bugs! However, you may be more likely to spot plant bugs than leafhoppers, as they are larger and don’t move quite as quickly. Although it’s too late to act now if you see this injury, hopefully you’ll be more confident in guessing who the responsible insect might be in the future, based on the symptoms of injury.
Whether it’s leafhoppers, plant bugs, or another sap-feeding insect entirely, you can always submit photos and physical samples of foliage, stems, and fruits to the Purdue Plant and Pest Diagnostic Lab for help with identification, and I’ll be ready to take a look when you do!