Aphids are among the most common of garden pests. They’re relatively soft, squishy and destructive. There are thousands of species, and their reproductive strategies are varied and creative. They can be hard to spot as the insects often feed on varieties that are similar in color, but they don’t let color stop them from feeding on succulent sap.
What’s that in the shadows?
I’ve seen them approach 1cm, but most in my garden are several millimeters long.
Depending on the severity of the infestation, control practices can range from blasting the insects with a hose to topical oils and pesticides to systemics. More environmentally friendly approaches include the release of aphid predators like the ladybug.
As aphids grow, they shed, leaving behind pale exoskeletons.
Ants commonly “farm” aphids for their honeydew, the sticky-sweet liquid aphids secrete when they feed. When you see ants on bonsai, look closely for aphids as the two are often found together.
Although I tend to associate aphids with the more succulent foliage of deciduous varieties, aphids can attack conifers too. The give away is uneven foliage color.
Aphids on pine
Aphids often focus on weak foliage, and they further weaken any foliage upon which the feed.
Aphid damage on last year’s needles
Given enough time to feed on pine foliage, they can cause needles to yellow and die. Unchecked infestation can do the same to entire trees.
The branch on the left lost its needles due to aphid damage
Treating aphids on pine is the same as treating them on broadleaf trees. Avoid aphids as much as possible by providing enough light and fresh air in the tree’s interior. Keeping plants overly full and crowded next to each other on the bench creates ideal conditions for aphids. Just say no – give your trees the space and sunlight they deserve!
The pine needle scale can be tricky to spot. Small, white spots are the giveaway.
Uh-oh, white spots
If it’s fall or early spring where I live, it’s always what I think it is – pine needle scale. Here’s why they can be tricky to spot. When they grow on the inside surface of a pair of pine needles, they’re all but invisible.
A sliver of white is the giveaway
Peeling the needles apart reveals the insect – small white spot with even smaller yellow dot at one end.
Pine needle scale
If I’ve spotted them early enough, I’ll find singles or pairs of them on a limited number of needles. If I do nothing about it, a few days later I might find far more.
Yuck – more pine needle scales!
The reason I’m not a fan – they can be hard to control. Many of the weaker pesticides have trouble killing scale. I usually start with light-touch approaches and mount increasingly potent assaults as need be. My general approach is the same as it is for any scale:
- If there are only a few I’ll scrape them off with my fingernail
- If I have to spray, I’ll start with oils
- If oils don’t get them under control, I’ll using something more toxic, though I typically avoid this last step as I don’t like using pesticides.
What’s the most important thing to know about treating scale? If at all possible, avoid getting it in the first place. How might one go about reducing the potency and number of infestations?
- Keep your trees healthy. This includes lots of sunshine, appropriate water and fertilizer and well-draining soil.
- Don’t give them space to hide. Leaving old leaves or needles in place prevents light and air from reaching the tree’s interior – that’s how scale like it.
- Use oils on a regular basis. Oil sprays are the least toxic treatment for scale.
- If you know there are lots of scale in the area or have fought infestations in the past, systemic pesticides are a good bet.
Uncontrolled scale infestations can greatly weaken and even kill bonsai. Be on the lookout for them!
Fall, in moderate climates, is a key time to look out for pests on bonsai. In colder climates, many insects are killed by cold weather. Not where I live. Within the past week I’ve found all varieties of unwanted guests in the garden. This week I’ll focus on scale.
Healthy looking olive foliage
What’s this – a small black dot. Could it be?
Yes, it’s scale
Scale come in thousands of shapes and sizes, and just about all varieties of bonsai are susceptible to some scale or other. Closely inspecting your trees on a regular basis is the best way to stave off bad infestations.
Scale on olive foliage
The crafty creatures on this olive grew between the wire and the branch making them very hard to spot. It was when I de-wired this olive that I realized I had scale. It was the first time I’d seen scale on the tree.
How do scale get around? Once you see them on your trees, they likely don’t. Newly hatched “crawlers” find a good spot to latch on and rarely move after that, relying instead on their typically hard shells for protection. Scale can also move from plant to plant via the wind and can be carried around by other insects like ants.
What did I do when I found them? I picked them off with tweezers. The next step is to spray prophylactic oil. This works well for minor infestations – nastier infestations and tricky-to-treat scale like the pine needle scale require a stronger plan of attack – more on that Friday.
The Golden State Bonsai Federation’s 37th Convention was host to the 2014 Joshua Roth New Talent Bonsai Competition. The event has become one of the better venues for recognizing new bonsai talent in North America. From the ABS website:
The Joshua Roth New Talent Bonsai Competition is an annual competition to recognize and promote new bonsai talent in North America. First prize is no more than $1,000 toward an exclusive course of instruction with an approved bonsai teacher. The first stage of the competition is a judging of photographs of previously designed trees by the entrant. The second stage will be the actual production of a bonsai during the GSBF/ABS Convention, Oct. 30, 2014 at the Double Tree Hotel Sacramento CA. Joshua Roth and the American Bonsai Society are sponsoring this contest.
This year’s contest featured junipers. By the time I arrived at the convention, the work was complete. Top honors – and congratulations – go to Ryan Nichols of Back to the Roots Bonsai for his winning entry.
Ryan Nichol’s winning entry
Ryan at work
Congratulations to each of the entrants for accomplishing so much with their trees in a limited period of time – well done!
Tree #8 by Ron Anderson
Tree #8 before – trunk detail