What’s going on with ‘June drop’ on fruit trees?
Q: My peach tree is dropping lots of young fruits. Is it stressed in some way?
A: This phenomenon is called June drop, and is a well-known trait for peaches, though it also occurs to a lesser extent with other fruit trees. This is the tree thinning its own fruits to reduce competition for the tree’s resources and ensure there is enough energy to produce viable seed to reproduce itself. Crowded fruits are small when mature and are more vulnerable to diseases and pests. Fruits shading each other can also hamper good skin coloration when they ripen. (You can’t circumvent this limitation by irrigating and fertilizing more, because the tree must photosynthesize the sugars that go into fruit development. Plus, over-watering and over-fertilizing can easily be detrimental to plant and soil health.)
Ideally, fruits are thinned by the gardener before the tree takes matters into its own hands, so to speak. It’s a bit like thinning-out surplus seedlings when you sow several in a pot or row. By whittling-down the surplus, you ensure the remaining seedlings (or fruits in this case) get the nourishment they need to develop well and, for our purposes, be as tasty and rewarding as possible. As a general guideline, pinch off baby fruits so the individuals remaining are about as far from their neighbors as the width of your hand.
Tree stress can influence the degree of fruit drop. Contributing factors include disease, insect feeding, or environmental conditions. If pollination is poor, either fewer fruits will form in the first place, or the tree may shed more young fruits than normal because infertile fruits will not fully develop. Either way, remove and discard (or hot compost) the fallen or plucked fruits.
Q: Bagworms were an issue on my shrubs last year. When might they reappear and what can I do? A:
Quite soon if they haven’t hatched already during the past
couple of weeks. As with all insect development, egg hatch is temperature-dependent, but central Maryland typically sees bagworms hatch around late May to early June.
Monitor the plants you’ve seen bagworms on before (or plants they prefer) and look for tiny, well-camouflaged bags appearing on the foliage. Sunny branch extremities are typical feeding grounds. Needled evergreens (conifers such as spruce, juniper, leyland cypress, arborvitae) seem to be favorite host plants, but they can also feed on a wide array of deciduous shrubs and trees.
If you see any full-size bags left over from last year, pluck them off and squish them. Females lay their eggs in these shelters and dispatching them this way is the simplest chemical-free approach for management. While a few missed and scattered individuals won’t cause serious damage to a plant, a large population can strip a conifer pretty thoroughly, and few plants will be able to replace those lost needles, causing permanent damage.
If you can’t reach most of the old bags or you find later that you missed a bunch of juveniles, you can treat plants with a reducedrisk insecticide containing Bacillus
thuringiensis (Bt). Select strains of this naturally-occurring soil bacterium affect only caterpillars, and the bagworm larvae will ingest treated foliage and cease feeding shortly thereafter.
You can’t effectively spray the larvae directly with a contact pesticide like neem oil because they shelter their bodies in those bags, like a sleeping bag they never fully crawl out of. By thoroughly treating the foliage, you’ll expose them to this natural toxin through their food source instead.
When treating plants, do so early in the bagworm’s development, because older larvae aren’t
as vulnerable to Bt and different pesticides may be needed. Bt breaks down quickly in sunlight, so don’t apply it as a preventative measure — wait until you see live juveniles first. Use the services of a certified pesticide applicator for plants too large to spray yourself, such as evergreens well over your head. More information can be found on our Bagworms on Trees and Shrubs page.