Unlike diseases, it can be much easier to identify any insect pests because they are usually more visible. That doesn't necessarily make them easier to combat but at least you can see what you are after. Many insects are not more than an inconvenience and will not kill your plant or completely destroy your berry harvest. Regardless of the specific threat, you should know your insects and take care to watch for their signs before they cause your garden any real harm.
Pesticides are always an option though you have to make sure to limit their use during the blooming season, or you can risk killing off your pollinators (the bees). If that happens, you will have no berries for the year.
These do tend to go after cranberries the most, but they are also a major pest for blueberry crops as well. Like with most pests, it is the caterpillar stage of a moth that is the problem rather than the adult moth itself. The small larva chew into the ripening berries and will ruin them. You will seldom see the worms themselves but watch for berries that are stuck together with fine webbing, and chewed bits of stem that look like sawdust will be around the base of each berry.
Cranberry fruitworm moths are very nondescript with a brown and gray mottled color, and they lay small white eggs right at the base of the flower just as it is losing its petals. You can use netting to keep the moths off, as long as you time it just right so as not to prevent the bees from pollinating your flowers.
If you see signs of the worms, cut out the affected berries right away. They will move from one berry to the next if left undisturbed. Destroy the berries so that the larvae don't develop into more moths to continue the cycle.
Like the above-mentioned fruitworm, the Blueberry maggot is the larva stage of a fly that will feed on your berries. These are flies rather than moths though. They are quite small but have a clear black and white pattern on their wings. Unlike the fruitworms, these flies lay their eggs a little later in the season, usually after your berries have already started to develop into fruit.
Unless you actually see the flies, their worms can be hard to detect. There aren't a lot of signs of their presence. The eggs are oblong and white, and will be laid on the outside of each berry. You'll have to look closely to see.
Because Blueberry maggot flies are laying eggs after the pollination season, you can be a little more aggressive in their treatment. Pesticides can work and you can also hang sticky traps in your bushes designed to capture fruit flies. This is also the best way to know you even have flies in the first place.
These insects attack the new flower buds, so you will have to be on the look out much earlier than with the other pests. The beetle is very small and is a reddish black color with a long “nose”. The female makes a hole in the new flower buds to lay her eggs, which kills the flower. If too many flowers are killed, your bushes will have a reduced fruit crop.
Any dead buds that fall to the ground will likely have a larvae in it, and it will eventually hatch into more weevils so you should try to clean up any debris from around the base of your plants. Pesticides can be used as long as you stop their application once the flowers have opened up and you need bees to pollinate your plants.
Scale refers to a number of different species of tiny insect that creates a waxy shell over itself when it latches onto the stem of a plant. So it looks like a bump or scale on the bark. They will only be a problem in great numbers, and even then a healthy bush can still produce a good crop of berries. The insects drink the sap out of the stems, so large numbers of them will slowly cause the plant to suffer. If they start to settle on your fruit, then you will have a bigger problem.
Because of their waxy covering, they can be very difficult to get rid of. Most pesticides won't work. If you only have a few bushes to treat, a direct application of rubbing alcohol can work. Some oil-based sprays can be used for larger outbreaks, and they work by smothering the little bugs so they are not a poisonous pesticide.