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| Honeybees & Garden SpraysAgdex 481
Number 136/00
28/9/2000
Honeybees are of a great benefit to the home gardener. The hairy nature of bees enables them to carry great numbers of pollen grains as they go about their foraging duties. This makes bees more effective than other insects as pollinators. As they brush against the reproductive parts of the blossoms or flowers, the pollen grains are picked up or deposited. By maximising the pollination of the crop you also maximise the seed or fruit set of that crop. Many fruit trees require cross-pollination to set a crop of fruit. Some plants have separate male and female flowers therefore the pollen must be transferred by some mechanical agency. Plants in this category include pumpkins, zucchinis, cucumbers, melons and kiwi fruit. When pollinated effectively crops ripen more evenly and yields increase.
 Unfortunately bees may be killed when using chemicals and wetting agents around the garden. Wetting agents reduce the surface tension present in the solution being sprayed. This tends to make it adhere to the surface on which it is being sprayed instead of beading and running off. This includes any foraging bees with which the solution may have direct or indirect contact.
Wetting agents make it difficult for the bee to fly, as the wings of the insect cannot get up to speed when soaked with water. It also allows any harmful solution to remain on the bee for longer periods increasing the chance of contamination of other bees if the bee can make its way back to the hive.
Bees possess breathing pores, called spiracles, which are designed to repel water. When a wetting agent is used it may allow the liquid to enter the breathing pores thus effectively suffocating the bee.
Pesticides and herbicides can have a very harmful effect on bees. The particular chemical used and the method by which it is applied can reduce the chance of bee kills.
You can reduce the chances of bees becoming affected by the use of sprays or wetting agents in your garden by following these simple rules:
- Spray before or after plants are in bloom. This includes shade trees and weeds. Prior to spraying mow your lawns and weeds to remove any blooms.
- Apply sprays in the late afternoon when bees are less likely to be foraging. Damage to bees can be minimised by using a spray with a low residual toxicity as these break down more rapidly.
- Apply sprays when there is little or no wind. This decreases the chance of any spray drifting onto an area that is not intended to be sprayed.
- Do not allow spray to drip and form puddles.
- Contact any beekeepers you know in your neighbourhood and inform them of the time you intend to spray and with what chemical. They may be able to close or relocate their hive, or take some other precaution.
- Use the chemical that is specifically made for the problem you are trying to rectify. If you have a choice of chemicals opt for the one that will be the least harmful to bees. Dusts present more of a hazard to bees than sprays. Wettable powders are usually more harmful than either emulsifiable concentrates or water soluble solutions.
- Always check the product labels for specific bee hazards. Take notice of the mixing rates and never exceed the recommended level. Pay particular attention to any safety instructions. Only apply sprays if you have the necessary safety equipment as recommended on the label. These may include gloves, respirators, waterproof clothing, gumboots, etc.
- Always dispose of any waste chemicals or used containers in the recommended manner.
 Below is a chart showing the toxicity of some commonly used garden pesticides to bees foraging in the field:
| Common Name | Toxicity Rating | Residual Toxicity | Use Class | | Bacillus thuringiensis | low | nil | 3 | | Carbaryl | high | 7-12 days | 1 | | Chlorpyrifos | very high | 2-3 days | 1 | | Copper compound | low | nil | 3 | | Diazinon | very high | 2 days | 1 | | Dicamba | low | unknown | 4 | | Dicofol | low | nil | 3 | | Dimethoaete | very high | 3 days | 1 | | Fenitrothion | high | 1-5 days | 1 | | Fenthion | very high | 2-3 days | 1 | | Fenvalerate | high | unknown | 1 | | Lime Sulphur | moderate | unknown | 2 | | Maldison | very high | 1-7 days | 1 | | MCPA | low | unknown | 4 | | Methiocarb | high | unknown | 1 | | Pyrethrum | low | 3 hours | 3 | | Rotenone | low | unknown | 4 | | Sulphur | low | unknown | 4 | | Thiram | low | nil | 3 | | Trichlorfon | moderate | 2-5 hours | 2 |
Use class:
1. Severe losses may be expected if used when bees are present at the time of application. Losses may continue until the residual effect on bees has dissipated. Cannot be applied safely to flowering crops at any time.
2. Can be used near bees if dosage, timing and method of application are correct, but should not be applied directly to bees in the field or on plants while bees are foraging.
3. Can be used near bees with a minimum of injury to them, non-foraging times preferred.
4. Low toxicity rating. Please refer to the label and observe any warnings regarding hazards to bees.
Photograph: A honey bee (Apis Mellifera Spp.) gathering pollen from a Wattle tree in Devonport.
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