Gadenin日本語Get the appSquirrels take the crop, and they take it early
Every other hazelnut problem is a nuisance. Squirrels are the crop. A gray squirrel will strip a mature bush of several pounds of nuts in under a week, and it starts before the husks have yellowed, while the shells are still pale and the kernels are only three quarters filled. Growers who lose the lot almost always lost it in the window between the shells hardening and the husks turning, which is precisely the window in which the nuts look not quite ready to a human eye.
You will know it is happening from the litter under the bush: neatly split shell halves, chewed green husks, and small piles of shell fragments on a fence post or a low branch where the animal sat to eat. Once you see split shells you are already in the raid, and the crop is measured in days.
There is no spray and no repellent that works for long. What works is either physical exclusion, a genuine barrier the animal cannot cross, or taking the crop before the squirrels commit to it. In practice most home growers succeed by combining the two: pick early, and net or trap the bushes they care about most.
| Approach | How it works | Realistic result | Effort |
|---|---|---|---|
| Pick early | Harvest at first husk color change, dry off the bush | Most reliable single tactic | Low, needs weekly checking |
| Netting over the whole bush | Small-mesh net taken right to the ground and pegged | Good on bushes under 8 ft (2.4 m) | High, and useless if left with gaps |
| Trapping | Live or lethal traps set from midsummer, checked daily | Effective, but new animals move in | High, and legally restricted in many places |
| Smooth trunk baffles | Metal collar on a single-stemmed tree | Fails on suckering bushes and where branches touch a fence | Low, rarely applicable |
| Scarers and repellents | Noise, movement, scent | Days at best, animals habituate | Low, and not worth relying on |
Check the law where you live before trapping or relocating squirrels. In several countries releasing a trapped gray squirrel is an offense, and the rules differ between species. Exclusion and early picking are legal everywhere.
Nut weevil: the neat round hole
If you crack a nut and find a fat, legless, cream-colored grub curled in a hollowed kernel, that is nut weevil. The adult is a small brown beetle with a long curved snout. In early summer she drills through the soft shell of a developing nut and lays a single egg inside. The grub eats the kernel through the rest of the summer, then chews a clean round exit hole about an eighth of an inch (3 mm) across, drops to the ground and spends the winter in the soil as a pupa.
The tell is the exit hole: perfectly circular, sharp-edged, and always in a nut that feels light for its size. Squirrel damage is a ragged split, and rot is a soft brown patch. A round hole is always a weevil. Damage runs from a few percent of the crop in a garden with one bush to a third or more where hazels have been growing untreated for years.
The whole life cycle passes through the soil under the bush, so that is where you break it. Clear and destroy every fallen nut at harvest instead of leaving them, since each infested nut on the ground is next year's adult. Light cultivation of the soil surface under the bush in late autumn exposes the pupae to frost and to birds. A float test at harvest also removes hollowed nuts before they reach the store, where the emerging grubs would otherwise contaminate the batch.
Big bud mite and the other regulars
In late winter, when the bush is bare, look along the twigs. Healthy buds are small, pointed and tight against the wood. Buds infested with hazel big bud mite are swollen to the size of a small pea, round and soft. Inside are thousands of microscopic mites. Those buds never produce a shoot or a flower, so a heavily infested bush loses a slice of next season's growth and crop, though it does not kill the plant.
The control is simply picking. Go over the bush in late winter while the swollen buds are easy to see against bare wood, snap each one off, and burn or bin them rather than composting. On a small bush this takes twenty minutes and dramatically reduces the population the following year. The mites move to new buds in late spring when the old buds break down, so anything you remove before then is a generation prevented.
The rest of the list is minor. Aphids colonise soft shoot tips in spring and are dealt with by ladybirds and hoverflies if you leave them alone. Caterpillars chew leaves in early summer without affecting the nuts. A fungal canker disease of hazel exists in some regions and shows as sunken, dead patches of bark with rows of small black bumps on two- and three-year-old wood; where that is present locally, cut out affected branches well below the visible canker, disinfect the saw between cuts, and burn the prunings.
| Symptom | Likely cause | When you see it | What to do |
|---|---|---|---|
| Split shells and chewed husks under the bush | Squirrels | Late summer, before you think it is ripe | Harvest immediately, net or trap next year |
| Neat round hole in a light nut | Nut weevil grub | At harvest and in store | Float test, clear fallen nuts, cultivate soil in autumn |
| Swollen round buds on bare twigs | Big bud mite | Late winter | Pick off and destroy the swollen buds |
| Plenty of shells, shriveled or absent kernels | Poor pollination, not a pest | At harvest | Add a partner bush that flowers at the same time |
| Sunken dead bark with black bumps | Fungal canker of hazel | Spring and summer on older wood | Prune out well below the canker in dry weather and burn it |
| Nuts drop small and green in midsummer | Drought stress or natural thinning | High summer | Water deeply in dry spells; a light drop is normal |
Blank nuts are a pollination fault
A common complaint is a bush loaded with normal-looking nuts that turn out to be empty or contain a shriveled scrap of kernel. Growers reach for fertilizer, then a fungicide, and neither helps, because nothing has attacked the nut. The shell formed and the kernel never did, which is what happens when the flower was fertilized poorly or not at all.
Hazels flower in the depths of winter and are pollinated by wind, not insects. The pollen has to travel from a catkin on a different, compatible bush and reach a tiny red female flower at exactly the time it is receptive. If your only partner bush finishes shedding pollen a fortnight before your main bush opens its female flowers, you get shells and no kernels, year after year, regardless of feeding.
So treat blanks as a diagnosis rather than a disease. Record the proportion of empty nuts, note when catkins shed and when the red flowers appeared on each bush, and if the two do not overlap, plant a partner that flowers at the same time. The pollination guide covers the timing in detail.
A young bush cropping for the first time often produces a proportion of blanks regardless of pollination. Judge the problem on a bush that has cropped for at least three seasons before you plant anything new.